| 1. |
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| 2. |
- Karlström, Anders, 1977, et al.
(författare)
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An extended analytical model including a layered
- 2005
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Ingår i: Environmental Vibrations, ISEV2005. - 0415390354 ; , s. 303-310
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Ground vibrations are investigated with an analytical approach. The ground is modelled as a layered half-space on which a layered embankment is placed. Situated on top of the embankment, the sleepers are modelled with an anisotropic Kirchhoff plate and the rails as Euler-Bernoulli beams. In the equation for the rails, propagating wheel loads with constant velocity are accounted for. The analyzing method is based on Fourier transforms in time and along the space coordinate parallel with the track. In the transverse direction Fourier transforms are adopted in the ground, whereas Fourier cosine and Fourier sine series are used in the embankment layers. The numerical scheme is very efficient. In particular the beam-like rectangular elastic region (embankment) is compared with the Euler-Bernoulli beam, both supported on a layered ground. With the same bending stiffness, the two solutions are seen to differ already from 0 Hz.
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| 3. |
- Karlström, Anders, 1977, et al.
(författare)
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Efficiency of trenches along railways for trains moving at sub- or supersonic speeds
- 2007
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Ingår i: Soil Dynamics and Earthquake Engineering. ; 27, s. 625-641
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Tidskriftsartikel (refereegranskat)abstract
- A full 3D analytical approach is adopted to account for trenches on one or both sides close to a railroad. Low-frequency ground vibrations are investigated due to passing trains, and open trenches are used as wave barriers. The modelling technique is based on Fourier transforms and Fourier series. The ground is modelled as a layered semi-infinite domain and the embankment with finite layers. The trenches are obtained by simulating the upper surface layer with two or three finite rectangular regions with appropriate widths. A particular boundary condition is adopted on the vertical sides of all finite regions to enable the solution procedure. Rails and sleepers are accounted for with Euler-Bernoulli beams and an anisotropic plate with transversal isotropy. The wheel loads from the boggie wheel pairs of the train are simulated as moving forces. Hence, no irregularities in rails or wheels are accounted for.
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| 4. |
- Lindberg, Gustav, et al.
(författare)
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Determination of thermodynamic properties of Na2S using solid-state EMF measurements
- 2007
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Ingår i: Journal of Chemical Thermodynamics. - : Elsevier. - 0021-9614 .- 1096-3626. ; 39:1, s. 44-48
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Tidskriftsartikel (refereegranskat)abstract
- To obtain reliable thermodynamic data for Na2S(s), solid-state EMF measurements of the cell Pd(s)|O2(g)|Na2S(s), Na2SO4(s)|YSZ| Fe(s), FeO(s)|O2(g)ref| Pd(s) were carried out in the temperature range 870 < T/K < 1000 with yttria stabilized zirconia as the solid electrolyte. The measured EMF values were fitted according to the equation Efit/V (±0.00047) = 0.63650 − 0.00584732(T/K) + 0.00073190(T/K) ln (T/K). From the experimental results and the available literature data on Na2SO4(s), the equilibrium constant of formation for Na2S(s) was determined to be lg Kf(Na2S(s)) (±0.05) = 216.28 − 4750(T/K)−1 − 28.28878 ln (T/K). Gibbs energy of formation for Na2S(s) was obtained as ΔfG(Na2S(s))/(kJ · mol−1) (±1.0) = 90.9 − 4.1407(T/K) + 0.5415849(T/K) ln (T/K). By applying third law analysis of the experimental data, the standard enthalpy of formation of Na2S(s) was evaluated to be ΔfH(Na2S(s), 298.15 K)/(kJ · mol−1) (±1.0) = −369.0. Using the literature data for Cp and the calculated ΔfH, the standard entropy was evaluated to S(Na2S(s), 298.15 K)/(J · mol−1 · K−1) (±2.0) = 97.0.
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| 5. |
- Boström, Anders E, 1951, et al.
(författare)
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Elastic SH wave propagation in a layered anisotropic plate with interface damage modelled by spring boundary conditions
- 2009
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Ingår i: Quarterly Journal of Mechanics and Applied Mathematics. - : Oxford University Press (OUP). - 0033-5614 .- 1464-3855. ; 62:1, s. 39-52
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Tidskriftsartikel (refereegranskat)abstract
- Elastic SH wave propagation in a layered anisotropic plate withinterface damage is modelled in several steps. A single interfacecrack between two half-spaces is first studied and an explicitsolution for the crack-opening displacement is obtained at lowfrequencies. This is then generalized to a random distribution ofcracks at the interface and the result is reformulated as a springboundary condition. As an example of its usefulness,this boundary condition is then used in thederivation of a plate equation by expanding the displacements inpower series in the thickness coordinate.
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| 6. |
- Boström, Anders E, 1951, et al.
(författare)
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In-plane P-SV waves from a piezoelectric strip actuator: exact versus effective boundary condition solutions
- 2005
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Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control. - 0885-3010. ; 52:9, s. 1594-1600
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Tidskriftsartikel (refereegranskat)abstract
- A piezoelectric strip of finite width and thickness is placed on top of anisotropic elastic half-space. It operates in actuator mode and a timeharmonic voltage is thus applied across it. The piezoelectric material isof type $6mm$ oriented so that a 2D inplane (P-SV) problem results.By Fourier series expansions the problem is solved exactly and thisresult is compared to the case when the piezoelectric strip is replaced byan effective boundary condition, which is derived by series expansionsin the thickness coordinate in the piezoelectric strip. At low frequenciesthe results agree very well and this corresponds to the situation oftenmet in practice. In general, the effective boundary condition should bemuch easier to apply, for example when a FEM program is used.
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| 7. |
- Boström, Anders E, 1951
(författare)
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Ultrasonic benchmarking with UTDefect
- 2005
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Ingår i: Review of progress in Quantitative Nondestructive Evaluation. - 0735402450 ; 24B, s. 1859-1863
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Konferensbidrag (refereegranskat)
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| 8. |
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| 9. |
- Boström, Katrin, 1955-
(författare)
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Living with deteriorating and hereditary disease : experiences over ten years of persons with muscular dystrophy and their next of kin
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overall aim of this thesis was to elucidate haw persona with muscular dystrophy (MD) and their next of kin experience and describe their daily lives over the last ten years. MD is a group of inherited disorders characterised by muscular weakness caused by muscle wasting. Both qualitative and quantitative methods were used. Forty-isx individuals with MD and 36 next of kin were interviewed (Studies I, III, IV). Both groups completed the questionnaire Subjective Quality of Life (SQoL), (Study V). Persons with MD also completed the questionnaires Sickness Impact Profile and Self-report ADL (Study II). The interviews were subjected to qualitative content analysis. The persons with MD described the change from being independent to being an individual in need of assistive devices and/or personal support to manage activities of every day life (StudyI). Besides muscular weakness persons with MD have hte strain it means to have a hereditary disease, which also affects the family (Study III). The deterioration during a decennium was primarily with regard to ambulation. The number of persons walking without assistive devices has decreased from 40 to 23 and that of those working has almost been halved, from 21 to 11 (Study II). Next of kin have a special vulnerability in form of an emotional and practical lonliness in addition to actual and anticipatory losses. The relationship was described as related to obligation and/or love. To have an orientation towards tasks (obligation) was linked to a feeling of being weighed down by demands, while having an orientation towards relationship (love) was linked to a feeling of quality in life (Study IV). The persons with MD scored lower on most items in the SQoL than the next of kin (Study V). Patients without a partner scored lower on QoL as a whole than those with a partner. Those with an early onset of disease scored lower on personal economy. Next of kin who gave daily help assessed their relationships to friends lower than those who gave weekly help (Study V). This thesis provides knowledge of the trajectory with MD over time on the basis of a ten-year follow up. It also broadens the knowledge of how the hereditary aspect is experienced both by those with MD and their next of kin. How the next of kin of adult persons with MD experience their situation is an issue that has been overlooked in previous research.
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| 10. |
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| 11. |
- De Geyter, Sigrid, et al.
(författare)
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Effects of non-quartz minerals in natural bed sand on agglomeration characteristics during fluidized bed combustion of biomass fuels
- 2007
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 21:5, s. 2663-2668
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Tidskriftsartikel (refereegranskat)abstract
- Most of the previous literature on fluidized bed agglomeration during biomass combustion is based on quartz as a bed material. Full-scale installations however often use natural sand, which apart from quartz may contain a high fraction of non-quartz minerals such as potassium feldspar and plagioclase. The objective of the present study was therefore to elucidate the effects of non-quartz minerals occurring in natural sand on the agglomeration behavior during fluidized bed combustion of biomass fuels. Three fuels typical for previously determined agglomeration mechanisms were chosen as model fuels: calcium-rich bark, potassium-rich olive residues, and silica- and potassium-rich wheat straw. Two different feldspar minerals were used: a potassium feldspar and a plagioclase, labradorite, which both occur in many commercial bed materials. Furthermore, olivine was used as a bed material as this mineral represents another type of bed material used in some full-scale installations. Quartz was used as a reference bed material. The effects of non-quartz minerals in natural sand on initial defluidization temperature were assessed during carefully controlled, bench-scale fluidized bed agglomeration experiments. Bed material samples and agglomerates were analyzed using scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) in order to explore the occurrence and chemical composition of coating and attack layers on the bed particles and necks between agglomerated particles. Significant differences in agglomeration characteristics were found for the different minerals when bark and olive residue were combusted. Potassium-feldspar was shown to lower the initial defluidization temperature for combustion of bark and olive residues. Plagioclase and olivine on the other hand were found to increase the initial defluidization temperature as compared to quartz for the combustion of olive residue, but for bark combustion, they did not differ significantly from quartz. During combustion of wheat straw, all bed materials agglomerated shortly after the startup of the experiment. For bark and olive residue samples, attack layers were found on all bed materials and the composition of the inner attack layer and agglomerate necks differed significantly with the fuel/bed material combination. For wheat straw however, no continuous attack layers were found, and the bed material composition was concluded not to influence the agglomeration characteristics for this biomass. The results were used to suggest possible mechanisms involved in layer formation for the different minerals.
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| 12. |
- De Geyter, Sigrid, et al.
(författare)
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Skillnader i bäddagglomereringstendens mellan alternativa bäddmaterial och olika mineraler i natursand
- 2005
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Projektets resultat visar på skillnaderna i bäddagglomereringstendens mellan olika mineraler i natursand och ett antal alternativa bäddmaterial, t.ex. olivinsand, gjuterisand och hyttsand. Vid förbränning av ett bränsle med hög andel kalium, olivkross, visar försöken att K-fältspater har en högre benägenhet till bäddagglomerering. Detta kan även förklara skillnaden mellan ren kvartssand och Rådasand vilket innehåller en förhållandevis hög andel fältspater.
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| 13. |
- Dorn, Michael, et al.
(författare)
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Logistik 2015-2020 : En framtidsstudie om logistiksimulering: FoT 19 logistik
- 2006
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Rapport (populärvet., debatt m.m.)abstract
- In this study an attempt is made to put forward ideas about how logistic support to the Armed Forces of the future will be dealt with, based on a survey of current social, military and economic trends. The aim is to identify those logistic matters, which it would be relevant to simulate within a 10 to 15-year period. The study has been carried out with the aid of NATO logistic doctrine and a qualitative method, which is closely comparable to idea analysis.One of the findings of the study is that the Swedish Armed Forces could be one module, amongst many (e.g. police, rescue services and aid organisations), tailor-made for a particular peace support operation, led by a national HQ. It can also be taken that civilian actors, to a much greater extent than today, will be part of the logistics system and that this system could resemble the “IKEA model”, i.e. small stores of equipment that can quickly be put together to meet different needs. All this will require a greater degree of specialisation and coordination, both in Sweden and in other countries.Those logistic matters identified as being relevant for simulation within a 10 to15-year period have been brought together in a summary. The main conclusion of the study indicates that it is of the utmost importance to simulate a model of the complete logistic chain. In the meantime, in order to carry out the simulation, the collection of experiences and lessons learned must be systemised and recorded. If this does not happen, it is doubtful that the simulation can be used as a system to support decision-making.
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| 14. |
- Ekblad, Alf, et al.
(författare)
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Forest soil respiration rate and d13C is regulated by recent above ground weather conditions
- 2005
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 143:1, s. 136-142
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Tidskriftsartikel (refereegranskat)abstract
- Soil respiration, a key component of the global carbon cycle, is a major source of uncertainty when estimating terrestrial carbon budgets at ecosystem and higher levels. Rates of soil and root respiration are assumed to be dependent on soil temperature and soil moisture yet these factors often barely explain half the seasonal variation in soil respiration. We here found that soil moisture (range 16.5-27.6% of dry weight) and soil temperature (range 8-17.5 degrees C) together explained 55% of the variance (cross-validated explained variance; Q2) in soil respiration rate (range 1.0-3.4 micromol C m(-2) s(-1)) in a Norway spruce (Picea abies) forest. We hypothesised that this was due to that the two components of soil respiration, root respiration and decomposition, are governed by different factors. We therefore applied PLS (partial least squares regression) multivariate modelling in which we, together with below ground temperature and soil moisture, used the recent above ground air temperature and air humidity (vapour pressure deficit, VPD) conditions as x-variables. We found that air temperature and VPD data collected 1-4 days before respiration measurements explained 86% of the seasonal variation in the rate of soil respiration. The addition of soil moisture and soil temperature to the PLS-models increased the Q2 to 93%. delta13C analysis of soil respiration supported the hypotheses that there was a fast flux of photosynthates to root respiration and a dependence on recent above ground weather conditions. Taken together, our results suggest that shoot activities the preceding 1-6 days influence, to a large degree, the rate of root and soil respiration. We propose this above ground influence on soil respiration to be proportionally largest in the middle of the growing season and in situations when there is large day-to-day shifts in the above ground weather conditions. During such conditions soil temperature may not exert the major control on root respiration.
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| 15. |
- Eriksson, Anders, et al.
(författare)
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RPC-LAP : The Rosetta Langmuir probe instrument
- 2007
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Ingår i: Space Science Reviews. - : Springer Science and Business Media LLC. - 0038-6308 .- 1572-9672. ; 128:04-jan, s. 729-744
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Forskningsöversikt (refereegranskat)abstract
- The Rosetta dual Langmuir probe instrument, LAP, utilizes the multiple powers of a pair of spherical Langmuir probes for measurements of basic plasma parameters with the aim of providing detailed knowledge of the outgassing, ionization, and subsequent plasma processes around the Rosetta target comet. The fundamental plasma properties to be studied are the plasma density, the electron temperature, and the plasma flow velocity. However, study of electric fields up to 8 kHz, plasma density fluctuations, spacecraft potential, integrated UV flux, and dust impacts is also possible. LAP is fully integrated in the Rosetta Plasma Consortium (RPC), the instruments of which together provide a comprehensive characterization of the cometary plasma.
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| 16. |
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| 17. |
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| 18. |
- Henricsson, Anna, et al.
(författare)
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Bottenfauna i Stockholms län 2008 : En undersökning av bottenfaunan vid 9 lokaler i rinnande vattenoch 11 lokaler i sjölitoral
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- På uppdrag av Länsstyrelsen i Stockholms län har Medins Biologi AB utfört bottenfauna undersökningarpå 11 lokaler i sjöars litoralzon samt 9 lokaler i rinnande vatten. Lokalerna provtogs med sparkprovtagning (SS-EN 27 828). Provtagningarna utfördes under maj 2008.Den sammanvägda statusen med avseende på bottenfaunan klassificerades som god eller hög vid samtliga lokaler utom två, enligt Naturvårdsverkets bedömningsgrunder (Tabell 2). Vid 9 Bränningeån och 16 Märstaån klassades statusen som måttlig med avseende på eutrofiering. Vår expertbedömning är dessutom att bottenfaunan vid ytterligare en lokal (5 Åbyån) var betydligt påverkad av näringsämnen/organiskt material (Tabell 3).Bottenfaunan bedömdes hysa mycket höga naturvärden vid tre lokaler (1 Långsjön, 4 Sillen och 13 Bysjön), och höga naturvärden vid sex lokaler (2 och 3 Långsjön, 9 Bränningeån, 14 Öran, 20 Ullnasjön och 23 Messormen) (Figur 2). Vid årets undersökning påträffades tio arter som betecknas som ovanliga i södra och mellersta Sverige (Tabell 5), däremot påträffades inga rödlistade arter.
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| 19. |
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| 20. |
- Jansson, Per-Åke, 1949, et al.
(författare)
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Simulation of the 2008 Ultrasonic Benchmark Problems Using UTDefect
- 2009
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Ingår i: AIP Conference Proceedings. - : AIP. - 0094-243X .- 1551-7616. - 9780735406292 ; 28B, s. 1968-1972
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Konferensbidrag (refereegranskat)abstract
- The computer program UTDefect is used to solve some of the 2008 ultrasonic benchmark problems. UTDefect is a program for simulation of ultrasonic testing with applications within the nuclear industry in mind. Scattering from various types of defects, like a side-drilled hole and a flat-bottom hole, is modelled using solutions that are essentially exact. For the benchmark problems the results obtained from UTDefect are in fairly good agreement with the experimental data from CEA.
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| 21. |
- Krasnova, Tatiana, 1967, et al.
(författare)
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Ultrasonic wave propagation in an anisotropic cladding with a wavy interface
- 2005
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Ingår i: Wave Motion. - : Elsevier BV. - 0165-2125. ; 41:2, s. 163-177
-
Tidskriftsartikel (refereegranskat)abstract
- The propagation of ultrasonic waves in a thick plate with a cladding is investigated in the two-dimensional case. The surfaces of the plate are traction-free except where an ultrasonic probe is attached and emits waves into the plate. The plate is made of two different materials, the base material and the cladding, and these are both allowed to be anisotropic. The interface between the base material and the cladding is assumed to be wavy (sinusoidal) and this is common in practice for welded claddings. The null field approach is used to solve the wave propagation problem. Thus the starting point is the (surface) integral representations in the two materials. The Green’s tensors are chosen as the half space Green’s tensors as only the integrals along the interface then remain. The Green’s functions are expanded in Fourier transforms along the interface and the surface fields are likewise expanded. Applying the periodicity of the interface a discretized set of equations remains. For the sinusoidal interface all integrals can be computed analytically which leads to an efficient numerical scheme. Some numerical results show the influence of the anisotropy and the wavy interface.
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| 22. |
- Kunets, Y. I., et al.
(författare)
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Scattering of a SH-wave by an elastic fiber of nonclassical cross section with an interface crack
- 2008
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Ingår i: Mechanics of Composite Materials. - : Springer Science and Business Media LLC. - 0191-5665 .- 1573-8922. ; 44:2, s. 165-172
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Tidskriftsartikel (refereegranskat)abstract
- The problem of interaction of a plane time-harmonic SH-wave with an elastic fiber of quasi-square or quasi-triangular cross section, when an interface crack is present between an infinite elastic matrix and the fiber, is considered. The modified null-field method taking into account the asymptotic behavior of the solution at crack tips is exploited for obtaining numerical results. The effects of fiber shape, fiber/matrix material combination, debonding (crack size), and direction of wave incidence on the scattering amplitude in the far field are analyzed.
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| 23. |
- Lind, Per, et al.
(författare)
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Structural, photophysical, and nonlinear absorption properties of trans-di-arylalkynyl Platinum(II) Complexes with Phenyl and Thiophenyl Groups
- 2007
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 111:9, s. 1598-1609
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Tidskriftsartikel (refereegranskat)abstract
- Optical power limiting and luminescence properties of two Pt(II) complexes with thiophenyl and phenyl groups in the ligands, trans-Pt(P(n-Bu)3)2(C[triple bond]C-Ar)2, where Ar = -C4H2S-C[triple bond]C-p-C6H4-n-C5H11 (1) and -p-C6H4-C[triple bond]C-C4H3S (2), have been investigated. The fluorescence lifetimes were found to be on the sub-nanosecond time scale, and the quantum yields were low, in accord with fast intersystem crossing from the excited singlet to triplet manifold. The phosphorescence lifetimes of 1 and 2 were shorter than that of a Pt(II) complex having two phenyl groups in the ligands. In order to elucidate the C-Pt bonding nature in the ground state, the 13C NMR chemical shift of the carbon directly bonded to Pt, the coupling constants 1JPtC, 2JPtC, and 1JPtP, and IR νC[triple bond]C wavenumbers were obtained for 1, 2, and three other trans-diarylalkynyl Pt(II) complexes. X-ray diffraction data of 1 and 2 and density functional theory calculated geometries of models of 1, 2, and trans-Pt(P(n-Bu)3)2(C[triple bond]C-p-C6H4-C[triple bond]C-C6H5)2 (3) show that 1 preferably exists in a different conformation from that of 2 and 3. The variations in photophysical, NMR, and IR data can be rationalized by differences in geometry and pi-backbonding from Pt to the alkynyl ligand.
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| 24. |
- Liss, Per, et al.
(författare)
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Renal effects of CO2 and iodinated contrast media in patients undergoing renovascular intervention : a prospective, randomized study
- 2005
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Ingår i: Journal of Vascular and Interventional Radiology. - 1051-0443 .- 1535-7732. ; 16:1, s. 57-65
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: CO2 gas has been proposed for use instead of iodinated contrast media in angiographic examinations in patients at risk of developing renal failure from contrast media. The influence of intraarterial injection of CO2 with small added amounts of ioxaglate (200 mgI/mL) or ioxaglate alone on renal function in patients with suspected renal artery stenosis was studied in a prospective, randomized study. MATERIALS AND METHODS: One hundred twenty-three patients underwent renovascular intervention (n = 83) and/or renal angiography (n = 40) for suspected renal artery stenosis. Patients with a serum creatinine concentration less than 200 micromol/L (n = 82) were randomized prospectively to receive CO2 with small added amounts of ioxaglate (n = 37) or only ioxaglate (n = 45). Patients with serum creatinine levels greater than 200 micromol/L (n = 41) were not randomized and initially received CO2. Serum creatinine concentrations were measured within 1 day before and 1 day, 2 days, and 2-3 weeks after the procedure. RESULTS: The amount of injected CO2 did not relate to an increase in serum creatinine level. In the randomized groups, and also when the whole patient sample was considered, the amount of injected iodine was significantly correlated (P = .011) with an increase in serum creatinine level and a decrease in estimated creatinine clearance after 2 days. Among the randomized patients, one in the CO2 group and three in the ioxaglate group had a more than 25% increase in serum creatinine level within the first 2 days after the intervention. CONCLUSION: The risk of impairment of renal function is lower after injection of CO2 with small amounts of added ioxaglate compared with injection of a larger amount of ioxaglate alone. The larger the amount of administered iodinated contrast medium, the greater the risk of development of renal failure.
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| 25. |
- Liu, Wei, et al.
(författare)
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Unique expression of connexins in the human cochlea
- 2009
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Ingår i: Hearing Research. - : Elsevier BV. - 0378-5955 .- 1878-5891. ; 250:1-2, s. 55-62
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Tidskriftsartikel (refereegranskat)abstract
- Mutations in the genes GJB2 and GJB6, which encode the proteins Connexin 26 (Cx26) and Connexin 30 (Cx30), have been linked to nonsyndromic prelingual deafness in humans. These proteins may form so-called gap junctions (GJ) or transcellular pathways between cells. The pathogenesis of deafness due to GJ Connexin mutations remains unclear partly because examinations performed in the human ear are infrequent. Here we analysed the expression and distribution of Cx26 and Cx30 in five fresh normal human cochleae taken out at occasional surgery. Immunohistochemistry including confocal microscopy in decalcified specimen showed that these proteins are widely expressed in the human cochlea. In the lateral wall there was strong antibody co-labeling for Cx26 and Cx30 that support the existence of channels comprising heteromeric Cx26/Cx30 connexons. In the organ of Corti there were some co-labeling in the supporting cell area including mainly the Claudius cells and Deiter cells of these two Cxs, apart from isolated Cx26 and Cx30 labeling in the same area, suggestive of both homomeric/homotypic pattern and hybrid pattern (heteromeric or heterotypic). Cx30, Cx26 and Connexin 36 (Cx36) immunoreactivity was also associated with spiral ganglion type I neurons, the latter being a gap junction protein specific to neurons. Gap-junction-based electrical synapses are not known to occur in mammalian auditory system other than in bats where they may play a role for fast electrical nerve transmission useful for echolocation. Their potential role in the processing of human auditory nerve signaling as well as non-GJ roles of the connexins in human cochlea is discussed.
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| 26. |
- Lundholm, Karin, et al.
(författare)
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Fate of Cu, Cr and As during combustion of impregnated wood with and without peat additive
- 2007
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Ingår i: Environmental Science and Technology. - : American Chemical Society. - 0013-936X .- 1520-5851. ; 41:18, s. 6534-6540
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Tidskriftsartikel (refereegranskat)abstract
- The EU Directive on incineration of waste regulates the harmful emissions of particles and twelve toxic elements, including copper, chromium, and arsenic. More information is critically needed on the speciation and behavior of these trace elements during combustion, including the effects of different process variables, as well as of different fuels and fuel mixtures. Using a 15 kW pellets-fueled grate burner, experiments were performed to determine the fate of copper, chromium, and arsenic during combustion of chromate copper arsenate (CCA) preservative wood. The effects of co-combustion of CCA-wood with peat were also studied since peat fuels previously have proved to generally reduce ash related problems. The fate and speciation of copper, chromium, and arsenic were determined from analysis of the flue gas particles and the bottom ash using SEM-EDS, XRD, XPS, and ICP-AES. In addition, chemical equilibrium model calculations were performed to interpret the experimental findings. The results revealed that about 5% copper, 15% chromium, and 60% arsenic were volatilized during combustion of pure CCA-wood, which is lower than predicted volatilization from the individual arsenic, chromium, and copper oxides. This is explained by the formation of more stable refractory complex oxide phases for which the stability trends and patterns are presented. When co-combusted with peat, an additional stabilization of these phases was obtained and thus a small but noteworthy decrease in volatilization of all three elements was observed. The major identified phases for all fuels were CuCrO2(s), (Fe,Mg,Cu)(Cr,Fe,Al)O4(s), Cr2O3(s), and Ca3(AsO4)2(s). Arsenic was also identified in the fine particles as KH2AsO4(s) and As2O3(s). A strong indication of hexavalent chromium in the form of K2CrO4 or as a solid solution between K3Na(CrO4)2 and K3Na(SO4)2 was found in the fine particles. Good qualitative agreement was observed between experimental data and chemical equilibrium model calculations.
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| 27. |
- Lundholm, Karin, et al.
(författare)
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Reduced bed agglomeration by co-combustion biomass with peat fuels in a fluidized bed
- 2005
-
Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 19:6, s. 2273-2278
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Tidskriftsartikel (refereegranskat)abstract
- Fluidized bed combustion is an energy conversion technology that is very suitable for biomass combustion because of its fuel flexibility and low process temperatures. However, agglomeration of bed material may cause severe operating problems. To prevent or at least reduce this, peat has been suggested as an additive to the main fuels. Nevertheless, the characteristics of peat fuels vary and there is limited information of the effect of different peat fuels and of the mechanisms behind the agglomeration prevention. The objectives of the present work were therefore to: (i) quantify the potential positive effect by co-combustion peat with forest fuels in terms of initial agglomeration temperatures; (ii) determine the amount of peat fuel that is needed to significantly reduce the agglomeration tendencies; and, if possible, (iii) elucidate the governing mechanisms. The results showed that all peat fuels prevented agglomeration in the studied interval of 760-1020 °C and even as little as 5% peat fuel was found to have significant effects. The results also indicated that the mechanism of the agglomeration prevention varies between different peat fuels. Possible mechanisms are the minerals in the peat fuel retain alkali, which then is either elutriated up from the bed or captured in the bed; calcium and other refractory elements increase the melting temperature and thereby counteract the melting of alkali; and sulfur reacts with alkali metals and the alkali sulfates is either elutriated up from the bed or prevents agglomeration by increased melting temperature and lowered viscosity. Results from elemental analysis of the coating on bed particles showed that all mixtures with peat fuel resulted in a decreased or unchanged fraction of potassium and an increased fraction of aluminum in the coatings. The results also indicated a complex relationship between the fuel inorganic contents and the agglomeration process.
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| 28. |
- Matus, V. V., et al.
(författare)
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Wave propagation in 2D elastic composites with partially debonded fibres by the null field appraoch
- 2009
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Ingår i: Waves in Random and Complex Media. - : Informa UK Limited. - 1745-5030 .- 1745-5049. ; 19:4, s. 654-669
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Tidskriftsartikel (refereegranskat)abstract
- Time-harmonic plane wave propagation in a two-dimensional (2D) elastic matrix with partially debonded elastic fibres of nonclassical cross-section is investigated. The modified null field approach, taking into account the asymptotic behaviour of the solution at the interface crack-tips, is exploited to obtain the numerical results for a single scatterer. The effective medium approach based on Foldy's approximation is applied to estimate the average dynamic parameters of the composites containing randomly distributed partially debonded fibres of dilute concentration. Numerical results concern the longitudinal wave dispersion and attenuation owing to scattering by both randomly oriented and aligned fibres. The effects of the fibre shape, debonding (interface crack) size and direction of wave incidence on the effective P-wave velocity and attenuation coefficient are analysed.
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| 29. |
- Mauritsson, Karl, 1980, et al.
(författare)
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Dynamic equations for a homogenous, fully anisotropic, elastic plate
- 2008
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Ingår i: Proceedings of the 6th International Conference on Computation of Shell & Spatial Structures. ; , s. 18-21
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Konferensbidrag (refereegranskat)abstract
- The derivation of plate equations for a homogenous, fully anisotropic, elastic plate is considered. Power series expansionsin the thickness coordinate for the displacements lead to recursion relations among the expansion functions.Using these in the boundary conditions a set of plate equations, which can be truncated to any order in the thickness,are obtained and it is believed that these equations are asymptotically correct. Numerical investigations for guidedwaves along the plate illustrate the accuracy.
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| 30. |
- Mauritsson, Karl, 1980, et al.
(författare)
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Modelling of thin piezoelectric layers on plates
- 2008
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Ingår i: Wave Motion. - : Elsevier BV. - 0165-2125. ; 45:5, s. 616-628
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Tidskriftsartikel (refereegranskat)abstract
- The derivation of plate equations for a plate consisting of twolayers, one anisotropic elastic and one piezoelectric, isconsidered. Power series expansions in the thickness coordinate forthe displacement components and the electric potential lead torecursion relations among the expansion functions. Using these inthe boundary and interface conditions, a set of equations areobtained for some of the lowest-order expansion functions. This setis reduced to six equations corresponding to the symmetric(in-plane) and antisymmetric (bending) motions of the elastic layer.These equations are given to linear (for the symmetric equations) orquadratic (for the antisymmetric equations) order in the thickness.It is noted that it is, in principle, possible to go to any order,and that it is believed that the corresponding equations areasymptotically correct. A few numerical results for guided wavesalong the plate and a 1D actuator case illustrate the accuracy.
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| 31. |
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| 32. |
- Pommer, Linda, et al.
(författare)
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Mechanisms behind the positive effects on bed agglomeration and deposit formation combusting forest residue with peat additives in fluidized beds
- 2009
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 23:9, s. 4245-4253
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Tidskriftsartikel (refereegranskat)abstract
- A compilation was made of the composition of peat from different areas in Sweden, of which a selected set was characterized and co-combusted with forest residue in controlled fluidized-bed agglomeration tests with extensive particle sampling. The variation in ash-forming elements in the different peat samples was large; thus, eight peat samples were selected from the compilation to represent the variation in peat composition in Sweden. These samples were characterized in terms of botanical composition, analyzed for ash-forming elements, and oxidized using a low-temperature ashing procedure, followed by characterization using scanning electron microscopy/electron-dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD). The selected peat samples had in common the presence of a small fraction of crystalline phases, such as quartz, microcline, albite, and calcium sulfate. The controlled fluidized-bed agglomeration tests that co-combusted forest residue with peat resulted in a significant increase in agglomeration temperatures compared to combusting forest residue alone. Plausible explanations for this were an increase of calcium, iron, or aluminum in the bed particle layers and/or the reaction of potassium with clay minerals, which prevented the formation of low-melting bed particle layers. The effects on particle and deposit formation during co-combustion were reduced amounts of fine particles and an increased number of coarse particles. The mechanisms for the positive effects were a transfer and/or removal of potassium in the gas phase to a less reactive particular form via sorption and/or a reaction with the reactive peat ash (SiO2 and CaO), which in most cases formed larger particles (>1 μm) containing calcium silicon and potassium.
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| 33. |
- Pommier, Thomas, et al.
(författare)
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Global patterns of diversity and community structure in marine bacterioplankton
- 2007
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Ingår i: Molecular Ecology. - : Blackwell Publishing Ltd. - 0962-1083 .- 1365-294X. ; 16:4, s. 867-880
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Tidskriftsartikel (refereegranskat)abstract
- Because of their small size, great abundance and easy dispersal, it is often assumed that marine planktonic microorganisms have a ubiquitous distribution that prevents any structured assembly into local communities. To challenge this view, marine bacterioplankton communities from coastal waters at nine locations distributed world-wide were examined through the use of comprehensive clone libraries of 16S ribosomal RNA genes, used as operational taxonomic units (OTU). Our survey and analyses show that there were marked differences in the composition and richness of OTUs between locations. Remarkably, the global marine bacterioplankton community showed a high degree of endemism, and conversely included few cosmopolitan OTUs. Our data were consistent with a latitudinal gradient of OTU richness. We observed a positive relationship between the relative OTU abundances and their range of occupation, i.e. cosmopolitans had the largest population sizes. Although OTU richness differed among locations, the distributions of the major taxonomic groups represented in the communities were analogous, and all local communities were similarly structured and dominated by a few OTUs showing variable taxonomic affiliations. The observed patterns of OTU richness indicate that similar evolutionary and ecological processes structured the communities. We conclude that marine bacterioplankton share many of the biogeographical and macroecological features of macroscopic organisms. The general processes behind those patterns are likely to be comparable across taxa and major global biomes.
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| 34. |
- Rask-Andersen, Helge, et al.
(författare)
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Regeneration of human auditory nerve. In vitro/in video demonstration of neural progenitor cells in adult human and guinea pig spiral ganglion
- 2005
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Ingår i: Hearing Research. - : Elsevier BV. - 0378-5955 .- 1878-5891. ; 203:1-2, s. 180-191
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Tidskriftsartikel (refereegranskat)abstract
- Time lapse video recordings of cultured adult human and guinea pig spiral ganglion (hSG and gpSG) show that mitogen responsive progenitor/stem cells develop in the form of spheres that proliferate and differentiate into mature neurons and glia cells. Neurospheres, cultured with EGF and bFGF showed expression of nestin and incorporation of 5'-Bromo-2-deoxyuridine (BrdU). Newly formed BrdU labelled cells were positive for beta-tubulin, and also for GFAP demonstrating that neuronal cells were derived from a dividing population of progenitor cells. Dissociated spheres cultured either with glia cell line-derived neurotrophic factor (GDNF) or brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3), induced differentiation of the progenitor cells. Video microscopy showed that neurons develop from subcultured spheres maintained for up to four weeks. Neurons showed fasciculation and migration with a speed of 10-30 microm/h, and some cells had up to 6 mm long neurites coexpressing TrkB and TrkC receptors. Precise dissection suggests that the neurons formed are cochlea-specific. The results suggest that the mammalian auditory nerve has the capability for self-renewal and replacement. Transplantation of progenitor cells together with established means to induce neural differentiation and fiber growth may facilitate strategies for better repair and treatment of auditory neuronal damage.
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| 35. |
- Råberg, Mathias, 1977-
(författare)
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Black liquor gasification : experimental stability studies of smelt components and refractory lining
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Black liquors are presently combusted in recovery boilers where the inorganic cooking chemicals are recovered and the energy in the organic material is converted to steam and electricity. A new technology, developed by Chemrec AB, is black liquor gasification (BLG). BLG has more to offer compared to the recovery boiler process, in terms of on-site generation of electric power, liquid fuel and process chemicals. A prerequisite for both optimization of existing processes and the commercialization of BLG is better understanding of the physical and chemical processes involved including interactions with the refractory lining. The chemistry in the BLG process is very complex and to minimize extensive and expensive time-consuming studies otherwise required accurate and reliable model descriptions are needed for a full understanding of most chemical and physical processes as well as for up-scaling of the new BLG processes. However, by using these calculated model results in practice, the errors in the state of the art thermochemical data have to be considered. An extensive literature review was therefore performed to update the data needed for unary, binary and higher order systems. The results from the review reviled that there is a significant range of uncertainty for several condensed phases and a few gas species. This resulted in experimental re-determinations of the binary phase diagrams sodium carbonate-sodium sulfide (Na2CO3-Na2S) and sodium sulfate-sodium sulfide (Na2SO4-Na2S) using High Temperature Microscopy (HTM), High Temperature X-ray Diffraction (HT-XRD) and Differential Thermal Analysis (DTA). For the Na2CO3-Na2S system, measurements were carried out in dry inert atmosphere at temperatures from 25 to 1200 °C. To examine the influence of pure CO2 atmosphere on the melting behavior, HTM experiments in the same temperature interval were made. The results include re-determination of liquidus curves, in the Na2CO3 rich area, melting points of the pure components as well as determination of the extent of the solid solution, Na2CO3(ss), area. The thermal stability of Na2SO3 was studied and the binary phase diagram Na2SO4-Na2S was re-determined. The results indicate that Na2SO3 can exist for a short time up to 750 °C, before it melts. It was also proved that a solid/solid transformation, not reported earlier, occurs at 675 ± 10 °C. At around 700 °C, Na2SO3 gradually breaks down within a few hours, to finally form the solid phases Na2SO4 and Na2S. From HTM measurements a metastable phase diagram including Na2SO3, as well as an equilibrium phase diagram have been constructed for the binary system Na2SO4-Na2S. Improved data on Na2S was experimentally obtained by using solid-state EMF measurements. The equilibrium constant for Na2S(s) was determined to be log Kf(Na2S(s)) (± 0.05) = 216.28 – 4750(T/K)–1 – 28.28878 ln (T/K). Gibbs energy of formation for Na2S(s) was obtained as ΔfG°(Na2S(s))/(kJ mol–1) (± 1.0) = 90.9 – 4.1407(T/K) + 0.5415849(T/K) ln (T/K). The standard enthalpy of formation of Na2S(s) was evaluated to be ΔfH°(Na2S(s), 298.15 K)/(kJ mol–1) (± 1.0) = – 369.0. The standard entropy was evaluated to be S°(Na2S(s), 298.15 K)/(J mol–1 K–1) (± 2.0) = 97.0. Analyses of used refractory material from the Chemrec gasifier were also performed in order to elucidate the stability of the refractory lining. Scanning electron microscopy (SEM) analysis revealed that the chemical attack was limited to 250-300 μm, of the surface directly exposed to the gasification atmosphere and the smelt. From XRD analysis it was found that the phases in this surface layer of the refractory were dominated by sodiumaluminosilicates, mainly Na1.55Al1.55Si0.45O4.
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| 36. |
- Sandström, Malin, 1976-
(författare)
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Structural and solid state EMF studies of phases in the CaO–K2O–P2O5 system with relevance for biomass combustion
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fosfaters reaktioner i energiomvandlingsprocesser är kritisk för den generella processen som helhet, för askrelaterade problem, emissioner liksom för en effektiv och hållbar användning av askan.Denna avhandling är en sammanställning och diskussion med utgångspunkt i åtta artiklar som behandlar strukturella och termodynamiska studier på faser i CaO-K2O-P2O5-systemet, vilka är av relevans inom förbränning av biomassa. Målsättningen med denna avhandling var: i) att sammanställa och granska tillgängliga strukturella och termodynamiska data i CaO-K2O-P2O5-systemet samt att identifiera avsaknad av data, ii) att fylla i dessa luckor med grundläggande termodynamiska, strukturella och fasstabilitets studier samt iii) att visa på användning samt fördelarna med dessa nya data vid praktisk tillämpning.En initial litteraturundersökning i CaO-K2O-P2O5-systemet visade att det saknades både strukturella och termodynamiska data. När det gällde tillgängliga termodynamiska data var situationen särskilt otillfredsställande. Det fanns endast data för några kalcium– och kaliumfosfater med varierande tillförlitlighet. Situationen beträffande pulverröntgen för fasidentifiering var bättre, fast fördunklad av det faktum att strukturellt liknande fasövergångar ofta förekommer i det undersökta systemet. Däremot fattades det tillfredställande enkristallstrukturdata för ternära faser i det undersökta systemet.Enkristallröntgendiffraktion användes för att bestämma strukturerna för CaK2P2O7, CaKP3O9, Ca10K(PO4)7 och CaKPO4. Faserna CaK2P2O7 and CaKPO4 tillsammans med Ca3(PO4)2, KPO3 och K4P2O7 studerades med pulverröntgendiffraktion och termiska analysmetoder för att klargöra fasmodifikationer och övergångstemperaturer. Gibbs bildningsenergi bestämdes för Ca(PO3)2, Ca2P2O7, Ca3(PO4)2, Ca10K(PO4)7, CaK2P2O7, CaKPO4 och CaK4(PO4)2 med ems-metodik och yttriastabiliserad zirkonia som fast elektrolyt och Ni/Ni3P som hjälpsystem. Både de strukturella och termodynamiska data användes sedan vid analyser i ett förbrännningexperiment av olika sädesslag. Framtagna data användes både vid identifiering och även vid kvantifiering av bildade faser i biomassaresterna.
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| 37. |
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| 38. |
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| 39. |
- Wiinikka, Henrik, et al.
(författare)
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High-temperature aerosol formation in wood pellets flames : Spatially resolved measurements
- 2006
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Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180 .- 1556-2921. ; 147:4, s. 278-293
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Tidskriftsartikel (refereegranskat)abstract
- The formation and evolution of high-temperature aerosols during fixed bed combustion of wood pellets in a realistic combustion environment were investigated through spatially resolved experiments. The purpose of this work was to investigate the various stages of aerosol formation from the hot flame zone to the flue gas channel. The investigation is important both for elucidation of the formation mechanisms and as a basis for development and validation of particle formation models that can be used for design optimization. Experiments were conducted in an 8-kW-updraft fired-wood-pellets combustor. Particle samples were withdrawn from the centerline of the combustor through 10 sampling ports by a rapid dilution sampling probe. The corresponding temperatures at the sampling positions were in the range 200-1450 °C. The particle sample was size-segregated in a low-pressure impactor, allowing physical and chemical resolution of the fine particles. The chemical composition of the particles was investigated by SEM/EDS and XRD analysis. Furthermore, the experimental results were compared to theoretical models for aerosol formation processes. The experimental data show that the particle size distribution has two peaks, both of which are below an aerodynamic diameter of 2.5 μm (PM2.5). The mode diameters of the fine and coarse modes in the PM2.5 region were ∼0.1 and ∼ 0.8 μm, respectively. The shape of the particle size distribution function continuously changes with position in the reactor due to several mechanisms. Early, in the flame zone, both the fine mode and the coarse mode in the PM2.5 region were dominated by particles from incomplete combustion, indicated by a significant amount of carbon in the particles. The particle concentrations of both the fine and the coarse mode decrease rapidly in the hot oxygen-rich flame due to oxidation of the carbon-rich particles. After the hot flame, the fine mode concentration and particle diameter increase gradually when the temperature of the flue gas drops. The main contribution to this comes from condensation on preexisting particles in the gas of alkali sulfates, alkali chlorides, and Zn species formed from constituents vaporized in the fuel bed. The alkali sulfates were found to condense at a temperature of ∼ 950 ° C and alkali chlorides condensed later at ∼ 600 ° C. This agrees well with results of chemical equilibrium calculation of the gas-to-particle conversion temperature. After the hot flame the coarse mode concentration decreased very little when the flue gas was cooled. In addition to carbon, the coarse mode consists of refractory metals and also considerable amounts of alkali. © 2006 The Combustion Institute.
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| 40. |
- Zhang, B. X., et al.
(författare)
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Study of SH acoustic radiation field excited by a piezoelectric strip
- 2005
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Ingår i: Wuli Xuebao/Acta Physica Sinica. - 1000-3290. ; 54:5, s. 2111-2117
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Tidskriftsartikel (refereegranskat)abstract
- A piezoelectric strip of infinite length but with finite width and thickness is placed on top of an isotropic elastic half space. The piezoelectric strip is excited by an electrical signal and the acoustic field is generated. The piezoelectric strip is of type 6 mm crystal system oriented along its length direction. The SH wave is studied for the structure of this piezoelectric transducer. At first, the field is expanded as a Fourier series in the piezoelectric strip and as a Fourier integral in the half space. Then, the response of the solution inside the piezoelectric strip and in the half space is obtained by the boundary conditions. The acoustic field distribution is analyzed and compared to that obtained by the traditional method. Finally, the acoustic radiation field at the far field is investigated by the saddle point method and the directional factor is analyzed. It is found that the traditional method is valid only in the case where the product of the frequency with the width of the piezoelectric strip is less than 1 kHz · m. The stress and displacement in the piezoelectric strip are oscillatory distributions when the frequency increases. The greater the frequency, the greater the difference between the traditional method and the present method.
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| 41. |
- Öhman, Marcus, et al.
(författare)
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Minskade askrelaterade driftsproblem (beläggning, slaggning, högtemperaturkorrosion, bäddagglomerering) genom inblandning av torv i biobränslen
- 2006
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Projektet behandlar effekter av torvinblandning i problematiska biobränslen (grot, salix, halm) med avseende på uppkomsten av askrelaterade driftsproblem (beläggning, slaggning, högtemperatur-korrosion och bäddagglomerering). Studien visar att inblandning av torv i de problematiska biobränslen som studerats ger tydligt positiva effekter vad avser bäddagglomerering och beläggningsbildning/korrosion i pannans konvektionsdelar redan vid relativt låga inblandningsgrader (15-20 vikts-%) i salix och grot, samt vid inblandningsgrader upp mot 40 vikts-% i halm. Resultaten indikerar dock även att vissa torvslag i vissa bränslesammansättningar ger upphov till ökade slaggningstendenser på brännarrosters. De bakomliggande askkemiska och processmässiga mekanismerna till de observerade effekterna diskuteras i rapporten.
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