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  • 122901. Zane, Silvia
    et al.
    Winter, Berend
    Theobald, Craig
    Theodorou, Theodorus
    Pinchera, Michele
    Muleri, Fabio
    Spada, Francesca
    Sgro, Carmelo
    Zanetti, Davide
    Feng, Hua
    del Monte, Ettore
    Rubini, Alda
    Soffitta, Paolo
    Bellazzini, Ronaldo
    Bozzo, Enrico
    Burwitz, Vadim
    Castro Tirado, Alberto J.
    Costa, Enrico
    Gburek, Szymon
    Goosmann, Rene
    Karas, Vladimir
    Matt, Giorgio
    Nandra, Kirpal
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Poutanen, Juri
    Reglero, Victor
    Dolores Sabau, Maria
    Santangelo, Andrea
    Tagliaferri, Giampiero
    Tenzer, Christopher
    Vink, Jacco
    Weisskopf, Martin
    The on-board calibration system of the X-ray Imaging Polarimetry Explorer (XIPE)2016Inngår i: SPACE TELESCOPES AND INSTRUMENTATION 2016: ULTRAVIOLET TO GAMMA RAY, SPIE - International Society for Optical Engineering, 2016, artikkel-id UNSP 99054HKonferansepaper (Fagfellevurdert)
    Abstract [en]

    The calibration system for XIPE is aimed at providing a way to check and correct possible variations of performance of the Gas Pixel Detector during the three years of operation in orbit (plus two years of possible extended operation), while facilitating the observation of the celestial sources. This will be performed by using a filter wheel with a large heritage having a set of positions for the calibration and the observation systems. In particular, it will allow for correcting possible gain variation, for measuring the modulation factor using a polarized source, for removing non interesting bright sources in the field of view and for observing very bright celestial sources. The on-board calibration system is composed of three filter wheels, one for each detector and it is expected to operate for a small number of times during the year. Moreover, since it operates once at a time, within the observation mode, it allows for simultaneous calibration and acquisition from celestial sources on different detectors. In this paper we present the scope and the requirements of the on-board calibration system, its design, and a description of its possible use in space.

  • 122902. Zanella, F.
    et al.
    Varagnolo, Damiano
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Cenedese, A.
    Pillonetto, G.
    Schenato, L.
    Asynchronous Newton-Raphson Consensus for distributed convex optimization2012Inngår i: Estimation and Control of Networked Systems: Volume 3, Part 1, 2012, s. 133-138Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We consider the distributed unconstrained minimization of separable convex cost functions, where the global cost is given by the sum of several local and private costs, each associated to a specific agent of a given communication network. We specifically address an asynchronous distributed optimization technique called Newton-Raphson Consensus. Beside having low computational complexity, low communication requirements and being interpretable as a distributed Newton-Raphson algorithm, the technique has also the beneficial properties of requiring very little coordination and naturally supporting time-varying topologies. In this work we analytically prove that under some assumptions it shows either local or global convergence properties, and corroborate this result by the means of numerical simulations.

  • 122903.
    Zanello, Fabrizio
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.).
    Improving the bounds of the multiplicity conjecture: The codimension 3 level case2007Inngår i: Journal of Pure and Applied Algebra, ISSN 0022-4049, E-ISSN 1873-1376, Vol. 209, nr 1, s. 79-89Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Multiplicity Conjecture (MC) of Huneke and Srinivasan provides upper and lower bounds for the multiplicity of a Cohen-Macaulay algebra A in terms of the shifts appearing in the modules of the minimal free resolution (MFR) of A. All the examples studied so far have lead to conjecture (see [J. Herzog, X. Zheng, Notes on the multiplicity conjecture. Collect. Math. 57 (2006) 211-226] and [J. Mighore, U. Nagel, T. Romer, Extensions of the multiplicity conjecture, Trans. Amer. Math. Soc. (preprint: math. AC/0505229) (in press)]) that, moreover, the bounds of the MC are sharp if and only if A has a pure MFR. Therefore, it seems a reasonable - and useful - idea to seek better, if possibly ad hoc, bounds for particular classes of Cohen-Macaulay algebras. In this work we will only consider the codimension 3 case. In the first part we will stick to the bounds of the MC, and show that they hold for those algebras whose h-vector is that of a compressed algebra. In the second part, we will (mainly) focus on the level case: we will construct new conjectural upper and lower bounds for the multiplicity of a codimension 3 level algebra A, which can be expressed exclusively in terms of the h-vector of A, and which are better than (or equal to) those provided by the MC. Also, our bounds can be sharp even when the MFR of A is not pure. Even though proving our bounds still appears too difficult a task in general, we are already able to show them for some interesting classes of codimension 3 level algebras A: namely, when A is compressed, or when its h-vector h(A) ends with (.., 3, 2). Also, we will prove our lower bound when h(A) begins with (1, 3, h,), where h(2) : 4, and our upper bound when h (A) ends with (.... h(c-1), h(c)), where h(c-1) < h(c) + 1.

  • 122904.
    Zanello, Fabrizio
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.).
    The h-vector of a relatively compressed level algebra2007Inngår i: Communications in Algebra, ISSN 0092-7872, E-ISSN 1532-4125, Vol. 35, nr 4, s. 1087-1091Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The purpose of this note is to supply an upper and a lower bound (which are in general sharp) for the h-vector of a level algebra which is relatively compressed with respect to any arbitrary level algebra A. The useful concept of relatively compressed algebra was recently introduced in Migliore et al. (2005) (whose investigations mainly focused on the particular case of A a complete intersection). The key idea of this note is the simple observation that the level algebras which are relatively compressed with respect to A coincide (after an obvious isomorphism) with the generic level quotients of suitable truncations of A. Therefore, we are able to apply to relatively compressed algebras the main result of our recent work, Zanello (2007).

  • 122905. Zanette, I.
    et al.
    Zdora, M. -C
    Zhou, Tunhe
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Burvall, Anna
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Larsson, Daniel H.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Thibault, P.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Pfeiffer, F.
    X-ray microtomography using correlation of near-field speckles for material characterization2015Inngår i: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 112, nr 41, s. 12569-12573Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nondestructive microscale investigation of objects is an invaluable tool in life and materials sciences. Currently, such investigation is mainly performed with X-ray laboratory systems, which are based on absorption-contrast imaging and cannot access the information carried by the phase of the X-ray waves. The phase signal is, nevertheless, of great value in X-ray imaging as it is complementary to the absorption information and in general more sensitive to visualize features with small density differences. Synchrotron facilities, which deliver a beam of high brilliance and high coherence, provide the ideal condition to develop such advanced phase-sensitive methods, but their access is limited. Here we show how a small modification of a laboratory setup yields simultaneously quantitative and 3D absorption and phase images of the object. This single-shot method is based on correlation of X-ray near-field speckles and represents a significant broadening of the capabilities of laboratory- based X-ray tomography.

  • 122906. Zanette, I.
    et al.
    Zhou, Tunhe
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Burvall, Anna
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lundström, Ulf
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Larsson, Daniel H.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Zdora, M.
    Thibault, P.
    Pfeiffer, F.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Speckle-Based X-Ray Phase-Contrast and Dark-Field Imaging with a Laboratory Source2014Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 112, nr 25, s. 253903-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the observation and application of near-field speckles with a laboratory x-ray source. The detection of speckles is possible thanks to the enhanced brilliance properties of the used liquid-metal-jet source, and opens the way to a range of new applications in laboratory-based coherent x-ray imaging. Here, we use the speckle pattern for multimodal imaging of demonstrator objects. Moreover, we introduce algorithms for phase and dark-field imaging using speckle tracking, and we show that they yield superior results with respect to existing methods.

  • 122907. Zang, A.
    et al.
    Stephansson, Ove
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630). GFZ German Research Centre for Geosciences, Telegrafenberg, Germany .
    Stress field of the earth's crust2010Bok (Fagfellevurdert)
    Abstract [en]

    This book about rock stress is suitable for students in geosciences and rock engineering, who need to broaden their horizons about the Stress Field of the Earth?s Crust. The book covers the topic so that geosciences students will be able to grasp the Cauchy Stress Principle without fear of matrix transformations in an exercise. Students interested in mathematics, physics and engineering will learn how strain gauges are used to obtain in-situ stress by the overcoring method. Leading edge technology in determining rock stress like quadruple packer and the Kaiser effect are presented together with classical methods like hydraulic fracturing. Borehole techniques (breakouts) and core-based methods (anelastic strain recovery) are illustrated. With respect to stress data, we choose to present the scientific ultra-deep drilling project KTB (Germany), the excavation for nuclear waste disposal at Olkiluoto (Finland) and the drilling into a seismic active fault zone at SAFOD (USA). Stress compilations viewed by the World Stress Map project are presented and interpreted in terms of plate tectonics.

  • 122908. Zang, A.
    et al.
    Stephansson, Ove
    Dresen, G.
    Rock damage and fluid transport: Part 22006Inngår i: Pure and Applied Geophysics, ISSN 0033-4553, E-ISSN 1420-9136, Vol. 163, nr 10, s. 2049-2050Artikkel i tidsskrift (Fagfellevurdert)
  • 122909.
    Zang, Kristina
    KTH, Skolan för industriell teknik och management (ITM), Industriell ekologi.
    Analys av miljöaspekter för en planerad svensk fabrik i Kina2006Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    A Swedish company, company F, will establish a new factory in China. Company F is adivision within Company F. The factory in China will manufacture wire products. Thepurpose of this final thesis is to analyse which legal and practical measures the company hasto undertake during the process of localization to get approval from the Chineseenvironmental legislation.An analysis of the influencing factors on the environment from the production in theconstruction in Sweden was carried through. A material-balance was analysed according tothe flowchart of the production. Since China is still considered a developing country, it is alsostill a lot different from Sweden, but it is changing rapidly. Most of the environmental lawsthat were studied are parts of the legal framework, which means that no exact limits ordetailed guidelines are given. The company brings its cutting-edge technology, which still isnew and unknown to the industrial park in China. Therefore it is too early to decide whethercompany F complies with the local jurisdiction in China. The company will make a thoroughreport on its future production to EPA, the Environmental Protection Agency, when theyapply for a license for the factory. In the report they can describe the production in Swedenand compare it to its possible production in China. By presenting the demands andrequirements of the EPA in Sweden given to company F by regard to its Swedish business, itcan help the EPA in China getting a better idea about the production and to what extentdischarge and contamination from the factory will affect the environment. To be able to planfor the long run and make the production meet the environmental standards in China, thefactory must use Swedish standards from the beginning.Two industrial parks in China were visited, one in Suzhou and the other in Wuxi. From anenvironmental perspective, both of the locations are good options for company F since bothare high-qualitative industrial parks that already exist. Suzhou is closer to Shanghai and hasits own Customs, which will benefit the company. There are companies, approved by theindustrial park and the EPA, that take care of waste. They collect the waste from the factory,and send some parts to a recycling factory. After the process of recycling, it is once againdelivered to the factories to produce e.g. new paper- or plastic-products. The rest of the toxicwaste is sent to other places for storage, disposal and destruction. Some toxic waste collectedfrom the factory undergoes a special process.When company F establishes its factory in China they should pay extra attention to whichlocation to choose and also which material of construction to use in order to avoid the hazardof fire. The lay-out must be thoroughly planned – e.g. where the fire exits should be. It isimperative that education about processing and environment be given continuously. Theinformation must reach the staff on all levels. The company must improve the technique allthe time, and look for the best possible technique available. Discharge in air or water must bemeasured regularly, according to the standards of the local authorities. The inspections of theplant must also take place regularly.

  • 122910. Zang, W.
    et al.
    Gudmundson, Peter
    KTH, Tidigare Institutioner, Hållfasthetslära.
    Damage Evolution and Thermoelastic Properties of Composite Laminates1993Inngår i: International journal of damage mechanics, ISSN 1056-7895, E-ISSN 1530-7921, Vol. 2, s. 290-308Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An analytic model for the prediction of the thermoelastic properties of micro cracked composite laminates is presented. The expression for the calculation of en ergy release rates due to growth of micro cracks is also provided. Numerical results are presented that show that the present method, to a very good accuracy, can predict ther moelastic properties of micro cracked laminates at varying crack densities and layup con figurations. In addition, a resistance curve behavior of the energy release rate is observed for both carbon/epoxy and glass/epoxy composite laminates. The reasons for this R-curve behavior are discussed. Criteria that govern the initiation and growth of micro cracks in composite laminates are discussed and compared to experimental data.

  • 122911.
    Zang, Weilin
    et al.
    KTH, Tidigare Institutioner                               , Hållfasthetslära.
    Gudmundson, Peter
    KTH, Tidigare Institutioner                               , Hållfasthetslära.
    A Boundary Integral Method For Internal Piece-Wise Smooth Crack Problems1988Inngår i: International Journal of Fracture, ISSN 0376-9429, E-ISSN 1573-2673, Vol. 38, nr 4, s. 275-294Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new boundary integral method for plane elasticity problems with internal piece-wise smooth cracksis presented. The method can be applied to both infinite and finite geometries. A numerical technique which combines a collocation method for the cracks and the standard BEM technique for the outer boundary is used to solve the integral equations. Numerical examples are presented and compared either to existing solutions or to FEM calculations. All of the results provided by the present method are shown to be very accurate for both smooth and kinked cracks in both finite and infinite geometries.

  • 122912.
    Zang, Weilin
    et al.
    KTH, Tidigare Institutioner                               , Hållfasthetslära.
    Gudmundson, Peter
    KTH, Tidigare Institutioner                               , Hållfasthetslära.
    An Integral-Equation Method For Piece-Wise Smooth Cracks In An Elastic Half-Plane.1989Inngår i: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 32, nr 6, s. 889-897Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A boundary integral equation method for piece-wise smooth cracks in an elastic half-plane is presented. Both internal and surface cracks have been considered. The numerical formulation is based on an element description of the unknown dislocation densities along the crack line. Crack line kinks are treated by an introduction of double nodes at each kink. Numerical test examples are presented and compared, either to existing solutions, or to own finite element calculations. Excellent agreements were obtained for all cases.

  • 122913. Zang, W.L.
    et al.
    Gudmundson, Peter
    KTH, Tidigare Institutioner, Hållfasthetslära.
    An integral equation method based on resultant forces on a piece-wise smooth crack in a finite plate1989Inngår i: Proceedings of the 7th International Conference on Fracture (ICF7), Houston, Texas, 1989, s. 2127-2134Konferansepaper (Fagfellevurdert)
  • 122914.
    Zang, W.L.
    et al.
    KTH, Tidigare Institutioner                               , Hållfasthetslära.
    Gudmundson, Peter
    KTH, Tidigare Institutioner                               , Hållfasthetslära.
    Contact Problems Of Kinked Cracks Modeled By A Boundary Integral Method1990Inngår i: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 29, nr 4, s. 847-860Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Based on the integral equation for the resultant forces along a crack, a numerical method is developed for the solution of two dimensional kinked crack problems taking crack contact into account. The method is demonstrated by a consideration of an elastic half-plane containing a piece-wise straight line crack. Two numerical examples are presented and compared to finite element calculations. The numerical results indicate that the present method can be an effective and reliable tool for investigations of kinked crack problems associated with crack contact.

  • 122915. Zang, W.L.
    et al.
    Gudmundson, Peter
    SICOMP, Swedish Institute of Compositie.
    Frictional Contact Problems Of Kinked Cracks Modeled By A Boundary Integral Method1991Inngår i: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 31, nr 3, s. 427-446Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A numerical method is presented for the solution of two dimensional crack problems including the effects of crack kinks and frictional contact between crack faces. The method is based on an integral equation for the resultant forces along a crack. Coulomb friction between contacting crack surfaces is taken into account. The numerical implementation is demonstrated by considerations of surface and sub-surface piece-wise straight line cracks in a half-plane. Numerical results are presented to illustrate the efficiency and the reliability of the presented method.

  • 122916.
    Zang, W.L.
    et al.
    KTH, Tidigare Institutioner                               , Hållfasthetslära.
    Gudmundson, Peter
    SICOMP, Swedish Institute of Composites.
    Kinked Cracks In An Anisotropic Plane Modeled By An Integral-Equation Method.1991Inngår i: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 27, nr 14, s. 1855-1865Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A boundary integral method for cracks in an anisotropic material is presented. The method is based on the integral equation for the resultant forces along the cracks. The integral kernels contain only a weak logarithmic singularity, which simplifies the numerical implementation. Crack closure is also taken into account in the numerical formulation. Numerical tests are presented to illustrate the efficiency and the reliability of the proposed method.

  • 122917.
    Zang, W.L.
    et al.
    KTH, Tidigare Institutioner, Hållfasthetslära.
    Gudmundson, Peter
    KTH, Tidigare Institutioner, Hållfasthetslära.
    Kinked cracks in bonded half-planes modeled by an integral equation method1992Inngår i: International Journal of Fracture, ISSN 0376-9429, E-ISSN 1573-2673, Vol. 54, nr 1, s. 65-78Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Based on the integral equation for resultant forces along a crack, a boundary integral equation method for the solution of kinked cracks in bonded half-planes is presented. The equation only contains a weak logarithmic singularity and is valid for every point along the crack lines. Numerical results are presented to illustrate the efficiency and reliability of the method.

  • 122918. Zang, W.L.
    et al.
    Gudmundson, Peter
    KTH, Tidigare Institutioner, Hållfasthetslära.
    On integral equation methods for kinked cracks1990Konferansepaper (Fagfellevurdert)
  • 122919. Zangenah, S.
    et al.
    Andersson, Anders F.
    KTH, Skolan för bioteknologi (BIO), Genteknologi. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Ozenci, V.
    Bergman, P.
    Genomic analysis reveals the presence of a class D beta-lactamase with broad substrate specificity in animal bite associated Capnocytophaga species2017Inngår i: European Journal of Clinical Microbiology and Infectious Diseases, ISSN 0934-9723, E-ISSN 1435-4373, Vol. 36, nr 4, s. 657-662Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Capnocytophga canimorsus and Capnocytophga cynodegmi can be transmitted from cats and dogs to humans, and can cause a wide range of infections including wound infections, sepsis, or endocarditis. We and others recently discovered two new Capnocytophaga species, C. canis and C. stomatis, mainly associated with wound infections. The first-line treatment of animal bite related infections is penicillin, and in case of allergy, doxycycline and trimethoprim/sulfamethoxazole. However, there is a lack of antibiotic susceptibility patterns for animal bite associated Capnocytophaga species. Thus, we i >> inverted question markset out to study the antibiotic profiles against animal bite associated Capnocytophaga species isolated from wound and blood cultures after cat and dog bites and coupled the findings to whole genome sequencing data. A total of 24 strains were included in the study. Phenotypic analysis of antibiotic resistance was performed with E-tests. The web-based tool 'Resfinder' was used to identify resistance genes in the whole genome dataset. Two strains of C. cynodegmi and two strains of the recently discovered C. stomatis were resistant to penicillin (MIC 24 mgi >> inverted question mark/L) and cephalosporins (MIC 24 mg/i >> inverted question markL), and three out of these strains also exhibited resistance to imipenem (MIC = 32 mg/i >> inverted question markL). Genomic analysis revealed that these strains carried a class D beta-lactamase gene, which has not previously been found in Capnocytophaga spp. A class D beta lactamase with broad substrate specificity was found in animal bite associated Capnocytophaga species, which could have important implications when treating wound infections after cat and dog bites. It also suggests that pet animal bacteria can harbour resistance genes with relevance for human infections.

  • 122920. Zangenah, Salah
    et al.
    Abbasi, Nasir
    Univ Miguel Hernandez,Spain.
    Andersson, Anders F.
    KTH, Centra, Science for Life Laboratory, SciLifeLab. KTH, Skolan för bioteknologi (BIO), Genteknologi.
    Bergman, Peter
    Whole genome sequencing identifies a novel species of the genus Capnocytophaga isolated from dog and cat bite wounds in humans2016Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, artikkel-id 22919Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    C. canimorsus and C. cynodegmi are dog and cat commensals which can be transmitted to humans via bites or scratches and can cause sepsis, meningitis, endocarditis, and eye- or wound infections. Recently an additional Capnocytophaga species was identified as part of the oral flora of healthy dogs and was given the name "C. canis". We previously identified a Capnocytophaga isolate that could not be typed with available diagnostic tests including MALDI-TOF, 16S rRNA sequencing or species-specific PCR. This strain and 21 other Capnocytophaga spp isolated in Sweden from clinical blood- or wound-cultures were subjected to whole genome sequencing using the Illumina platform. Phylogenetic analysis revealed that the previously non-typable isolate belongs to the putative new species "C. canis". Since this strain was isolated from a wound it also shows that members of "C. canis" have the potential to be pathogenic. In addition, our phylogenetic analysis uncovered an additional species of Capnocytophaga, which can be transmitted from dogs and cats to humans, suggesting a speciation within the Capnocytophaga family that has not been observed before. We propose the name of "C. stomatis" for this putative novel species.

  • 122921.
    Zangeneh, Abbas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad. ELU Konsult AB.
    Battini, Jean-Marc
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Pacoste, Costin
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Karoumi, Raid
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Fundamental Modal Properties of Simply Supported Railway Bridges Considering Soil-Structure Interaction Effects2019Inngår i: Soil Dynamics and Earthquake Engineering, ISSN 0267-7261, E-ISSN 1879-341X, Vol. 121, s. 212-218Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, a simplified discrete model for calculating the modal parameters of the fundamental vertical mode of a simple beam on viscoelastic supports is proposed. Exact closed-form expressions for the fundamental natural frequency and modal damping ratio of the aforementioned coupled system are derived, as a function of the beam geometry and the foundation impedances. Using this model, the effect of the dynamic stiffness and dissipation capacity of the foundation-soil system on the modal characteristics of the fundamental vertical mode of the railway beam bridges is investigated and discussed. The proposed closed-form expressions, in combination with the impedance functions of different foundation-soil systems, can clarify the main features of dynamic SSI analysis of the railway beam bridges and lead to review the recommended modal damping ratios in the code provisions and design manuals.

  • 122922.
    Zangeneh, Abbas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad. ELU Consulting Engineeeirng, Sweden.
    Svedholm, Christoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad. ELU Consulting Engineeeirng, Sweden.
    Andersson, Andreas
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad. Swedish Transport Administration, Sweden.
    Pacoste, Costin
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad. ELU Consulting Engineeeirng, Sweden.
    Karoumi, Raid
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Dynamic Stiffness Identification of Portal Frame Bridge-Soil System using Controlled Dynamic Testing2017Inngår i: X International Conference on Structural Dynamics, EURODYN 2017, Elsevier, 2017, Vol. 199, s. 1062-1067Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Short-span portal frame bridges are predominant in Swedish railway lines. Although it is well known that the dynamic response of these partially-buried rigid structures is governed by the surrounding soil, the effect of the soil is usually neglected in the train-induced vibration analysis due to the expensive computational costs. This paper focuses on studying the effect of the surrounding soil conditions on the dynamic response of portal frame railway bridges. The study aims to validate the accuracy of simplified numerical models in evaluating the dynamic stiffness and modal properties of the bridge-soil system. To achieve this aim, a model updating method was used for FE model calibration of a full-scale portal frame bridge using measured frequency response functions. Both measured and computed responses identify the substantial contribution of the surrounding soil on the global damping of the system and highlight the importance of the soil-structure interaction on the dynamic response of these structures.

  • 122923.
    Zangeneh, Abbas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad. ELU Konsult AB, Stockholm, Sweden.
    Svedholm, Christoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad. ELU Konsult AB, Stockholm, Sweden.
    Andersson, Andreas
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad. Swedish Transport Adm, Solna, Sweden.
    Pacoste, Costin
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad. ELU Konsult AB, Stockholm, Sweden.
    Karoumi, Raid
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Identification of soil-structure interaction effect in a portal frame railway bridge through full-scale dynamic testing2018Inngår i: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 159, s. 299-309Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper is devoted to identify the effect of soil-structure interaction on the dynamic response of,a portal frame railway bridge. The study aims to validate the accuracy of numerical models in evaluating the dynamic stiffness and modal properties of the bridge-soil system. To achieve this aim, a controlled vibration test has been performed on a full-scale portal frame bridge to determine the modal properties of the system through measuring Frequency Response Functions. The results of the dynamic test provide reference data for FE model calibration as well as valuable information about the dynamic behavior of this type of bridges. Using the experimental data, an FRF-based model updating procedure was used to calibrate a full 3D solid model involving the entire bridge track-soil system. Both measured and computed responses identify the substantial contribution of the surrounding soil on the global damping of the system and highlight the importance of the soil-structure interaction on the dynamic response of this type of bridges. The identified modal damping ratio corresponding to the fundamental bending mode of the studied bridge was nearly 5 times higher than the recommended design values. A simplified model for the surrounding soil was also proposed in order to attain a less complicated model appropriate for practical design purposes.

  • 122924.
    Zangeneh Kamali, Abbas
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad. ELU Konsult AB.
    Dynamic Soil-Structure Interaction Analysis of Railway Bridges: Numerical and Experimental Results2018Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The work reported in this thesis presents a general overview of the dynamic response of short-span railway bridges considering soil-structure interaction. The study aims to identify the effect of the surrounding and underlying soil on the global stiffness and damping of the structural system. This may lead to better assumptions and more efficient numerical models for design.A simple discrete model for calculating the dynamic characteristics of the fundamental bending mode of single span beam bridges on viscoelastic supports was proposed. This model was used to study the effect of the dynamic stiffness of the foundation on the modal parameters (e.g. natural frequency and damping ratio) of railway beam bridges. It was shown that the variation in the underlying soil profiles leads to a different dynamic response of the system. This effect depends on the ratio between the flexural stiffness of the bridge and the dynamic stiffness of the foundation-soil system but also on the ratio between the resonant frequency of the soil layer and the fundamental frequency of the bridge.

    The effect of the surrounding soil conditions on the vertical dynamic response of portal frame bridges was also investigated both numerically and experimentally. To this end, different numerical models (i.e. full FE models and coupled FE-BE models) have been developed. Controlled vibration tests have been performed on two full-scale portal frame bridges to determine the modal properties of the bridge-soil system and calibrate the numerical models. Both experimental and numerical results identified the substantial contribution of the surrounding soil on the global damping of short-span portal frame bridges. A simplified model for the surrounding soil was also proposed in order to define a less complicated model appropriate for practical design purposes.

  • 122925.
    Zangeneh Kamali, Abbas
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Shear Strength of Reinforced Concrete Beams subjected to Blast Loading: Non-linear Dynamic Analysis2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The experimental investigations performed on the behaviour of reinforce concrete elements subjected to blast loading have revealed that the shear mechanisms and ductility play important roles in the overall response and failure mode of such structures.

    The main aim of this master thesis is to study the possibility of using finite element method as a tool for predicting the dynamic response of blast loaded reinforced concrete beams and evaluation of their shear strength. In this study, the commercial software, ABAQUS/Explicit has been used by implementing appropriate constitutive material models in order to consider the material nonlinearity, stiffness degradation and strain rate effects. The results of some blast loaded tested beams have been used for verification and calibration of the model. As a secondary objective, the calibrated model used to study the influence of some important factors on the shear strength of reinforced concrete beams and investigate their effects on the failure mode. The results used as a reference and compared with the calculations according to some design codes for blast resistance design.

    The results of the present research show that the implemented nonlinear finite element model successfully simulates the dynamic responses including displacement/reaction force time histories and induced damage patterns of blast tested beams with reasonable accuracy.

    The results of performed parametric study confirm that the ductility play important role in the failure behaviour of studied beams. The numerical simulations show that dynamic response of a soft element is more ductile than the stiffer one and the shear forces are thereby limited. Thus, although a soft element fails by large deformations in flexure, a stiff element may experience a brittle shear failure mode for the same load intensity.

    The comparison between the results of numerical analysis and design codes calculation show that the American approach in shear design of reinforced concrete elements subjected to blast loading is relatively conservative, similar to static design approach and do not consider the effect of ductility in the shear design procedure. On the contrary, the procedure that Swedish guideline implemented somehow considers the effect of ductility on the shear strength of reinforced concrete elements subjected to impulsive loads.

    Further research should involve the using the developed finite element model as a tool in order to theoretically study the dynamic response of blast loaded reinforced concrete elements and their failure modes. The results of numerical simulations can be used as a reference to derive simplified computational methods for practical design purposes.

  • 122926.
    Zangeneh Kamali, Abbas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Svedholm, Christoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Johansson, Morgan
    Chalmers.
    Effects of restrained thermal strains in transversal direction of concrete slab frame bridges2013Rapport (Annet vitenskapelig)
    Abstract [en]

    In the last few years the usage of 3D finite element analyses has increased substantially in the bridge design community. Such analyses provide the possibility for a more accurate study of the structure than what is possible by using more traditional design tools. However, in order to use the full strength of the finite element method in daily design practice a number of critical issues have to be addressed. These issues are related either to the FE-modelling itself (geometry, support conditions, mesh density, etc.) or to the post processing of the obtained results (stress concentrations, choice of critical sections, distribution widths and so on).  In the latter category, one problem of special significance refers to concrete structures subjected to restrained forces caused by temperature loading or shrinkage.

     

    In this context, the present report addresses the problem of crack width control in transversal direction for concrete slab frame bridges subjected to restrained thermal or shrinkage loading. The recommendations given herein are based not only on the existing literature but also on the authors own investigations using non-linear finite element analyses.

     

    The authors want to express their gratitude to the members of the reference group. Their comments and suggestions have been invaluable in shaping the report.

     

    This report is a part of a larger research project entitled “Recommendations for finite element analysis of structures whose coordinators are Costin Pacoste and Mario Plos. The work has been financially supported by Trafikverket and also ELU Konsult. This support is gratefully acknowledged.

  • 122927. Zangger Borch, D.
    et al.
    Sundberg, Johan
    KTH, Tidigare Institutioner, Tal, musik och hörsel.
    Lindestad, P.
    Thalén, M.
    Vocal fold vibration and voice source aperiodicity in "dist" tones: a study of a timbral ornament in rock singing2004Inngår i: Logopedics, Phoniatrics, Vocology, ISSN 1401-5439, E-ISSN 1651-2022, Vol. 29, nr 4, s. 147-153Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The acoustic characteristics of so-called 'dist' tones, commonly used in singing rock music, are analyzed in a case study. In an initial experiment a professional rock singer produced examples of 'dist' tones. The tones were found to contain aperiodicity, SPL at 0.3 m varied between 90 and 96 dB, and subglottal pressure varied in the range of 20-43 cm H2O, a doubling yielding, on average, an SPL increase of 2.3 dB. In a second experiment, the associated vocal fold vibration patterns were recorded by digital high-speed imaging of the same singer. Inverse filtering of the simultaneously recorded audio signal showed that the aperiodicity was caused by a low frequency modulation of the flow glottogram pulse amplitude. This modulation was produced by an aperiodic or periodic vibration of the supraglottic mucosa. This vibration reduced the pulse amplitude by obstructing the airway for some of the pulses produced by the apparently periodically vibrating vocal folds. The supraglottic mucosa vibration can be assumed to be driven by the high airflow produced by the elevated subglottal pressure.

  • 122928.
    Zanki Alujevic, Vlasta
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Energy use and environmental impact from hotels on Adriatic Coast in Croatia: current status and future possibilities for HVAC systems2006Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    This thesis analyses a specific type of energy usage system, “energy usage in hotels”, and how this system behaves. In order to evaluate the current state of energy use in hotels, an energy audit questionnaire was developed and conducted among 31,5% of hotels on the Adriatic coast. The energy audit was used as a tool to set a benchmark for energy consumption in hotels and to identify opportunities for increased energy efficiency measures in HVAC systems. The analysis has shown that the average energy consumption in hotels on the Adriatic coast is in the range of 159 to 180 kWh/m2 and 162 to 225 kWh/m2 for seasonal and non seasonal hotels respectively. In order to establish a relationship between different independent variables in the hotels (total floor area and number of rooms) and dependent variables, such as electricity and oil consumption, mathematical statistical methods, such as correlation and regression analysis, were implemented.

    The objective of this thesis was also to develop - from an energy, environmental and economical points of view - a methodology for the design and retrofit of HVAC systems in the hotels on the Adriatic coast. The methodology named HOTECO is based on a system thinking approach. With respect to the technological aspects, the first step was to analyse conventional HVAC system designs and to compare it with the three most promising alternative HVAC systems utilizing renewable energy sources for a typical hotel. Computer modelling in TRNSYS was used to assess energy consumption. TRNSYS software has been used for simulations for a number of years, is internationally recognized, and has been validated and verified.

    It was concluded that energy and environmental savings in hotels on the Adriatic coast could be achieved using readily available technologies. The HOTECO methodology also demonstrated a framework that supports decision making iv regarding system selection and operational strategies to limit environmental impact from HVAC systems in hotels. Four scenarios for energy consumption in hotels on the Adriatic coast with regards to current state of energy systems and improved retrofit solutions utilizing renewable energy source were given.

  • 122929.
    Zanni-Merk, Cecilia
    et al.
    Natl Inst Appl Sci Rouen Normandie, LITIS Lab, Normandy, France.;Natl Inst Appl Sci Rouen Normandie, MIND Team, Normandy, France..
    Frydman, Claudia
    Aix Marseille Univ, Marseille, France..
    Håkansson, Anne
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Programvaruteknik och datorsystem, SCS.
    Special Issue: Advances in Knowledge-Based and Intelligent Engineering and Information Systems Preface2018Inngår i: DATA TECHNOLOGIES AND APPLICATIONS, ISSN 2514-9288, Vol. 52, nr 4, s. 462-462Artikkel i tidsskrift (Annet vitenskapelig)
  • 122930. Zanonato, Pier Luigi
    et al.
    Di Bernardo, Plinio
    Fischer, Andreas
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Grenthe, Ingmar
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Chemical equilibria in the UO22+-H2O2-F-/OH(-)systems and possible solution precursors for the formation of [Na-6(OH2)(8)]@[UO2(O-2) F](24)(18-)and [Na-6(OH2)(8)]@ [UO2(O-2) OH](24)(18-)clusters2013Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 42, nr 28, s. 10129-10137Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The focus of this study is on the relationship between uranyl(VI) poly-peroxo clusters in the solid state and their possible precursors in solution. For this purpose, the complex formation in the ternary U(VI)-H2O2-F-system has been studied by potentiometric titrations, measuring p[H+] and p[F-], revealing that significant amounts of ternary uranyl(VI)-peroxide-fluoride complexes are formed. Based on the analysis of these data we find that there are two models consistent with structure data and previous speciation in the uranyl(VI)peroxide- carbonate system (Dalton. Trans., 2012, 41, 11635-11641). One model contains ternary complexes (UO2)(4)(O-2)(4)F- and (UO2)(4)(O-2)(4)F-2(2-) and the other (UO2)(4)(O-2) (F-)(4) and (UO2)(5)(O-2)(5)F-3(3-); we have chosen the second model as the one most consistent with available information. We suggest that (UO2)(4)(O-2)(4)(F-) is a building block in the U-24 cluster, [Na-6(OH2)(8)]@[UO2(O-2)F](24)(18-) identified in a single-crystal X-ray diffraction study of the solid phase that slowly precipitates from the slightly acidic test solutions. At p[H+] approximate to 9.5, a new solid phase is formed that contains the cluster [Na-6(OH2)(8)]@[UO2(O-2)OH](24)(18-), also identified from an X-ray structure. Both structures contain. 2-. 2 bridging peroxide and. 2 bridging fluoride or hydroxide ions, respectively. As fluoride bridges are unknown in solution coordination chemistry, it is unlikely that the U-24 fluoride cluster is formed in solution. We suggest that both the solid state fluoride and hydroxide clusters are formed in the crystallization from smaller precursors identified in solution. The study illustrates the importance of accurate control of the solution chemistry when preparing poly-peroxo-metallate clusters and also that the mechanism of their formation is still an open field of research.

  • 122931. Zanonato, Pier Luigi
    et al.
    Di Bernardo, Plinio
    Grenthe, Ingmar
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    A calorimetric study of the hydrolysis and peroxide complex formation of the uranyl(VI) ion2014Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 43, nr 6, s. 2378-2383Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The enthalpies of reaction for the formation of uranyl(VI) hydroxide {[(UO2)(2)(OH)(2)](2+), [(UO2)(3)(OH)(4)](2+), [(UO2)(3)(OH)(5)](+), [(UO2)(3)(OH)(6)]((aq)), [(UO2)(3)(OH)(7)](-), [(UO2)(3)(OH)(8)](2-), [(UO2)(OH)(3)](-), [(UO2)(OH)(4)](2-)} and peroxide complexes {[UO2(O-2)(OH)](-) and [(UO2)(2)(O-2)(2)(OH)](-)} have been determined from calorimetric titrations at 25 degrees C in a 0.100 M tetramethyl ammonium nitrate ionic medium. The hydroxide data have been used to test the consistency of the extensive thermodynamic database published by the Nuclear Energy Agency (I. Grenthe, J. Fuger, R. J. M. Konings, R. J. Lemire, A. B. Mueller, C. Nguyen-Trung and H. Wanner, Chemical Thermodynamics of Uranium, North-Holland, Amsterdam, 1992 and R. Guillaumont, T. Fanghanel, J. Fuger, I. Grenthe, V. Neck, D. J. Palmer and M. R. Rand, Update on the Chemical Thermodynamics of Uranium, Neptunium, Plutonium, Americium and Technetium, Elsevier, Amsterdam, 2003). A brief discussion is given about a possible structural relationship between the trinuclear complexes [(UO2)(3)(OH)(n)](6-n), n = 4-8.

  • 122932. Zanonato, Pier Luigi
    et al.
    Di Bernardo, Plinio
    Grenthe, Ingmar
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Chemical equilibria in the binary and ternary uranyl(VI)-hydroxide-peroxide systems2012Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, nr 12, s. 3380-3386Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The composition and equilibrium constants of the complexes formed in the binary U(VI)-hydroxide and the ternary U(VI)-hydroxide-peroxide systems have been studied using potentiometric and spectrophotometric data at 25 degrees C in a 0.100 M tetramethylammonium nitrate medium. The data for the binary U(VI) hydroxide complexes were in good agreement with previous studies. In the ternary system two complexes were identified, [UO2(OH)(O-2)](-) and [(UO2)(2)(OH)(O-2)(2)](-). Under our experimental conditions the former is predominant over a broad p[H+] region from 9.5 to 11.5, while the second is found in significant amounts at p[H+] < 10.5. The formation of the ternary peroxide complexes results in a strong increase in the molar absorptivity of the test solutions. The absorption spectrum for [(UO2)(2)(OH) (O-2)(2)](-) was resolved into two components with peaks at 353 and 308 nm with molar absorptivity of 16200 and 20300 M-1 cm(-1), respectively, suggesting that the electronic transitions are dipole allowed. The molar absorptivity of [(UO2)(OH)(O-2)](-) at the same wave lengths are significantly lower, but still about one to two orders of magnitude larger than the values for UO22+(aq) and the binary uranyl(VI) hydroxide complexes. It is of interest to note that [(UO2)(OH)(O-2)](-) might be the building block in cluster compounds such as [UO2(OH)(O-2)](60)(60-) studied by Burns et al. (P. C. Burns, K. A. Kubatko, G. Sigmon, B. J. Fryer, J. E. Gagnon, M. R. Antonio and L. Soderholm, Angew. Chem. 2005, 117, 2173-2177). Speciation calculations using the known equilibrium constants for the U(VI) hydroxide and peroxide complexes show that the latter are important in alkaline solutions even at very low total concentrations of peroxide, suggesting that they may be involved when the uranium minerals Studtite and meta-Studtite are formed by alpha-radiolysis of water. Radiolysis will be much larger in repositories for spent nuclear fuel where hydrogen peroxide might contribute both to the corrosion of the fuel and to transport of uranium in a ground water system.

  • 122933. Zanonato, Pier Luigi
    et al.
    Di Bernardo, Plinio
    Szabo, Zoltan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Grenthe, Ingmar
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Chemical equilibria in the uranyl(VI)-peroxide-carbonate system: identification of precursors for the formation of poly-peroxometallates2012Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, nr 38, s. 11635-11641Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The focus of this study is on the identification of precursors in solution that might act as building blocks when solid uranyl(VI) poly-peroxometallate clusters containing peroxide and hydroxide bridges are formed. The precursors could be identified by using carbonate as an auxiliary ligand that prevented the formation of large clusters, such as the ones found in solids of fullerene type. Using data from potentiometric and NMR (O-17 and C-13) experiments we identified the following complexes and determined their equilibrium constants: (UO2)(2)(O-2)(CO3)(4)(6-), UO2(O-2)CO32-, UO2(O-2)(CO3)(2)(4-), (UO2)(2)(O-2)(CO3)(2)(2-), (UO2)(2)(O-2)(2)(CO3)(2-) and [UO2(O-2)(CO3)(5)(10-). The NMR spectra of the pentamer show that all uranyl and carbonate sites are equivalent, which is only consistent with a ring structure built from uranyl units linked by peroxide bridges with the carbonate coordinated "outside" the ring; this proposed structure is very similar to [UO2(O-2)(oxalate)](5)(10-) identified by Burns et al. (J. Am. Chem. Soc., 2009, 131, 16648; Inorg. Chem., 2012, 51, 2403) in K-10[UO2(O-2)(oxalate)](5)center dot(H2O)(13); similar ring structures where oxalate or carbonate has been replaced by hydroxide are important structure elements in solid poly-peroxometallate complexes. The equivalent uranyl sites in (UO2)(2)(O-2)(2)(CO3)(2-) suggest that the uranyl-units are linked by the carbonate ion and not by peroxide.

  • 122934. Zanonato, Pier Luigi
    et al.
    Di Bernardo, Plinio
    Vallet, Valerie
    Szabo, Zoltan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Grenthe, Ingmar
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Alkali-metal ion coordination in uranyl(VI) poly-peroxide complexes in solution. Part 1: the Li+, Na+ and K+ - peroxide-hydroxide systems2015Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 44, nr 4, s. 1549-1556Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The alkali metal ions Li+, Na+ and K+ have a profound influence on the stoichiometry of the complexes formed in uranyl(VI)-peroxide-hydroxide systems, presumably as a result of a templating effect, resulting in the formation of two complexes, M[(UO2)(O-2)(OH)](2)(-) where the uranyl units are linked by one peroxide bridge, mu-eta(2)-eta(2), with the second peroxide coordinated "end-on", eta(2), to one of the uranyl groups, and M[(UO2)(O-2)(OH)](4)(3-), with a four-membered ring of uranyl ions linked by mu-eta(2)-eta(2) peroxide bridges. The stoichiometry and equilibrium constants for the reactions: M+ + 2UO(2)(2+) + 2HO(2)(-) + 2H(2)O -> M[(UO2)(O-2)(OH)] 2 - + 4H(+) (1) and M+ + 4UO(2)(2+) + 4HO(2)(-) + 4H(2)O -> M[(UO2)(O-2)(OH)](4)(3-) + 8H(+) (2) have been measured at 25 degrees C in 0.10 M (tetramethyl ammonium/M+)NO3 ionic media using reaction calorimetry. Both reactions are strongly enthalpy driven with large negative entropies of reaction; the observation that Delta H(2) approximate to 2 Delta H(1) suggests that the enthalpy of reaction is approximately the same when peroxide is added in bridging and "end-on" positions. The thermodynamic driving force in the reactions is the formation of strong peroxide bridges and the role of M+ cations is to provide a pathway with a low activation barrier between the reactants and in this way "guide" them to form peroxide bridged complexes; they play a similar role as in the synthesis of crown-ethers. Quantum chemical (QC) methods were used to determine the structure of the complexes, and to demonstrate how the size of the M+-ions affects their coordination geometry. There are several isomers of Na[(UO2)(O-2)(OH)](2)(-) and QC energy calculations show that the ones with a peroxide bridge are substantially more stable than the ones with hydroxide bridges. There are isomers with different coordination sites for Na+ and the one with coordination to the peroxide bridge and two uranyl oxygen atoms is the most stable one.

  • 122935. Zanonato, P.L.
    et al.
    Szabó, Zoltan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Vallet, V.
    Di Bernardo, P.
    Grenthe, Ingmar
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Alkali-metal ion coordination in uranyl(VI) poly-peroxo complexes in solution, inorganic analogues to crown-ethers. Part 2. Complex formation in the tetramethyl ammonium-, Li+-, Na+- and K+-uranyl(VI)-peroxide-carbonate systems2015Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 44, nr 37, s. 16565-16572Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The constitution and equilibrium constants of ternary uranyl(VI) peroxide carbonate complexes [(UO2)(p)(O-2)(q)(CO3)(r)](2(p-q-r)) have been determined at 0 degrees C in 0.50 M MNO3, M = Li, K, and TMA (tetramethyl ammonium), ionic media using potentiometric and spectrophotometric data; O-17 NMR data were used to determine the number of complexes present. The formation of cyclic oligomers, "[(UO2)(O-2)(CO3)](n)", n = 4, 5, 6, with different stoichiometries depending on the ionic medium used, suggests that Li+, Na+, K+ and TMA ions act as templates for the formation of uranyl peroxide rings where the uranyl-units are linked by mu-eta(2)-eta(2) bridged peroxide-ions. The templating effect is due to the coordination of the M+-ions to the uranyl oxygen atoms, where the coordination of Li+ results in the formation of Li[(UO2)(O-2)(CO3)](4)(7-), Na+ and K+ in the formation of Na/K[(UO2)(O-2)(CO3)](5)(9-) complexes, while the large tetramethyl ammonium ion promotes the formation of two oligomers, TMA[(UO2)(O-2)(CO3)] 5 9-and TMA[(UO2)(O-2)(CO3)](6)(11-). The NMR spectra demonstrate that the coordination of Na+ in the five-and six-membered oligomers is significantly stronger than that of TMA(+); these observations suggest that the templating effect is similar to the one observed in the synthesis of crown-ethers. The NMR experiments also demonstrate that the exchange between TMA[(UO2)(O-2)(CO3)](5)(9-) and TMA[(UO2)(O-2)(CO3)](6)(11-) is slow on the O-17 chemical shift time-scale, while the exchange between TMA[(UO2)(O-2)(CO3)](6)(11-)and Na[(UO2)(O-2)(CO3)](6)(11-) is fast. There was no indication of the presence of large clusters of the type identified by Burns and Nyman (M. Nyman and P. C. Burns, Chem. Soc. Rev., 2012, 41, 7314-7367) and possible reasons for this and the implications for the synthesis of large clusters are briefly discussed.

  • 122936.
    Zanotelli, Pietro
    KTH, Skolan för industriell teknik och management (ITM), Industriell ekonomi och organisation (Inst.), Industriell Management.
    MANAGING PRODUCT VARIETY: How to reduce complexity and increase product portfolios’ profitability2013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This paper describes a new approach to the management of product variety that

    should help manufacturing companies to improve the profitability of their product

    portfolios. The scientific research is conducted in different ways. After a short

    introduction of basic concepts relevant for the research, a broad review of the

    existing academic knowledge is proposed in form of a literature review. As a

    conclusion of the review, gap analysis shows the limitations of existing methods of

    variety management and sets the requirements for a new methodology. A

    methodology is hence developed by the author to analyze variety of product

    portfolios. The methodology includes the analysis of customer requirements, the

    calculation of complexity costs and the mapping of physical variety. Furthermore,

    clear guidelines are presented with the aim of improving the overall profitability of the

    chosen product portfolio; these mainly refer to changes in product architectural

    aspects or complete elimination of certain product variants.

    Subsequently, empirical evidence has been gathered from a case study at a

    manufacturing company, which has been a valuable source of data to confirm the

    applicability and the validity of such a methodology. The benefits of using the

    proposed methodology are proved, comparing the achieved results to the ones

    gathered after the application of other methodologies.

    The purpose of this study was to develop a new methodology for supporting and

    enhancing decision related to variety in manufacturing companies. This methodology

    aims to find a way to link the cost of complexity to the product architecture, what

    represents a very important aspect that existing methodologies cannot fully perform.

    For this reason the study provides a valuable contribution to the empirical knowledge

    on variety management practices.

  • 122937.
    Zanoun, El-Sayed
    et al.
    BTU Cottbus Senftenberg, Dept Aerodynam & Fluid Mech, D-03046 Cottbus, Germany..
    Egbers, Christoph
    BTU Cottbus Senftenberg, Dept Aerodynam & Fluid Mech, D-03046 Cottbus, Germany..
    Örlü, Ramis
    KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Fiorini, Tommaso
    Univ Bologna, Dept Ind Engn, Forli, Italy..
    Bellani, Gabriele
    Univ Bologna, Dept Ind Engn, Forli, Italy..
    Talamelli, Alessandro
    Univ Bologna, Dept Ind Engn, Forli, Italy..
    Experimental evaluation of the mean momentum and kinetic energy balance equations in turbulent pipe flows at high Reynolds number2019Inngår i: Journal of turbulence, ISSN 1468-5248, E-ISSN 1468-5248, Vol. 20, nr 5, s. 285-299Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In light of recent data from hot-wire anemometry and laser Doppler velocimetry, this article explores experimentally the momentum balance and kinetic energy production in fully developed turbulent pipe flow for shear Reynolds numbers in the range from two pipe facilities. It has become common practice to indirectly deduce the Reynolds shear stress via the mean flow data and the mean-momentum balance whenever the simultaneous measurements of the streamwise and wall-normal velocity fluctuations can not be performed precisely. The current assessment underlines, however, the importance of measuring the Reynolds shear stress directly, and the friction velocity independently from the mean-velocity profile to ascertain the quality of the data when utilising the momentum balance. The present analysis also reinforces the universality of the viscous stress gradient to the Reynolds shear stress gradient in the wall vicinity up to the inner limit of the logarithmic layer. The new set of the experimental data shows that Panton's stress function reproduces the measured Reynolds shear stress and kinetic energy production in turbulent pipe flows over a wide Reynolds number range to a high degree.

  • 122938.
    Zanuso, G.
    et al.
    ABB Corporate Research.
    Peretti, Luca
    ABB Corporate Research, Västerås.
    Sandulescu, P.
    ABB Corporate Research.
    Model-based synchronous machine control with compensation of model inaccuracies and instantaneous flux weakening capabilities2016Inngår i: Proceedings of the 8th IET International Conference on Power Electronics, Machines and Drives (PEMD), Institution of Engineering and Technology, 2016, Vol. 2016, s. 1-6Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper proposes a model-based current/torque control strategy for synchronous machines, where the magnetic model mismatches are compensated in real time and the flux weakening operation is obtained without the need of an external voltage regulation loop. Starting from an initial (and potentially wrong) knowledge of the non-linear current-to-flux linkage relation in the form of a look-up-table, a combination of feedforward actions, compensating mechanisms and binary searches are used to achieve the target during real-time operation. The algorithm is implemented in a laboratory test bench and successfully verified with experiments on an 11-kW synchronous reluctance machine, proving the feasibility of the proposed approach.

  • 122939.
    Zanuso, G.
    et al.
    ABB Corporate Research.
    Peretti, Luca
    ABB Corporate Research.
    Sandulescu, P.
    ABB Corporate Research.
    Stator reference frame approach for DC injection-based stator resistance estimation in electric drives2015Inngår i: Proceedings of the 11th IEEE International Conference on Power Electronics and Drive Systems (PEDS), Institute of Electrical and Electronics Engineers (IEEE), 2015, s. 867-872, artikkel-id 7203391Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This work discusses an online stator resistance estimation method for synchronous machines. Multiple improvements are provided with respect to a similar method already been used for induction machines. The method is based on the temporary injection of a DC voltage in the machine phases during normal operation. The stator resistance estimation is obtained by means of the Ohm's law. The proposed scheme works entirely in the stator fixed reference frame, without the need of any machine parameter. The selection of the DC injection level is discussed, as well as the countermeasures for reducing the spurious harmonics appearing in the currents and the torque when the machine is speed- and current-regulated. In particular, minimum electric loss and minimum torque ripple due to the injection is achieved. Moreover, as an alternative to conventional low-pass filtering of the measured signals, it is shown that the resistance estimation can be obtained by averaging the signals over few electric periods. Experiments prove the validity of the proposed approach.

  • 122940.
    Zanuso, G.
    et al.
    ABB Corporate Research.
    Peretti, Luca
    ABB Corporate Research.
    Zigliotto, M.
    University of Padova.
    Permanent magnet synchronous machines flux linkage estimation with zero steady-state error and its field-programmable gate array implementation2015Inngår i: IET Electric Power Applications, ISSN 1751-8660, E-ISSN 1751-8679, Vol. 9, nr 4, s. 332-343Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The paper analyses a combined current model-voltage model estimator for flux linkages in permanent magnet synchronous machines, with the capability of converging to exact flux estimation even in presence of mismatches because of magnetic saturation. As a trend in next-generation electric drives, the whole algorithm, including both the flux estimator and the standard field-oriented control, has been implemented in a field-programmable gate array (FPGA) chip. Simulations and experimental tests, along with some figures for the FPGA selection, have been included in the study.

  • 122941.
    Zanuso, Giovanni
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Fodor, Viktória
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    Peretti, Luca
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Wallmark, Oskar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Networked electric drives in the Industry 4.02018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Industrial automation has been recently challenged by new initiatives such as Industry 4.0, which promises higher connectivity between the devices in an industrial plant. The goal of this work is to discuss how electric drives, widely employed in industry, could benefit from this increased connectivity. Specific applications, such as condition monitoring and multi drive systems, are considered to show the advantages of the industrial network presence, combined with the introduction of new data driven methods. Moreover, the status of industrial communication technologies is depicted, and their suitability for condition monitoring and multi-drive systems applications is described.

  • 122942.
    Zanuso, Giovanni
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Peretti, Luca
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Sandulescu, Paul
    ABB Oy, Finland.
    Model-based flux weakening strategy for synchronous machines without additional regulators2018Inngår i: IET Electric Power Applications, ISSN 1751-8660, E-ISSN 1751-8679, Vol. 12, nr 9, s. 1283-1290Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study proposes a model-based control strategy for flux weakening operation of a synchronous reluctance machine, with a methodology that is extendible to any synchronous machine. The strategy leverages in the presence of digital non-linear models that describe the relation between currents and flux linkages in the machine. Such models are usually needed for conventional maximum-torque-per-ampere control and sensorless control, but here they are exploited to achieve flux-weakening operation without the need of flux weakening regulators, ensuring a seamless transition between the operating regions of the machine. The external voltage regulation loop for flux weakening is thus eliminated and substituted by a combination of look-up tables and binary searches, which are executed within one digital control period and which generate the required current and voltage references that fulfil the drive limitations. The method can also be coupled with mechanisms to compensate for magnetic parameter inaccuracies, to achieve an accurate tracking of the reference torque. The proposed solution is simulated and validated in a laboratory test bench on an 11 kW synchronous reluctance machine.

  • 122943.
    Zanuy, Carrillo
    et al.
    TUB.
    Boysen, Hans
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Trafik och logistik.
    Mašek, J
    UNIZA.
    Buda, M
    UNIZA.
    Janíček, F
    TVP.
    Karabin, J
    TVP.
    VEL Wagon: State of the art and concept drafting2011Rapport (Annet vitenskapelig)
    Abstract [en]

    The present deliverable presents a general overview of the European rail freight system in terms of:

    Demand:

    Where the general characteristics and trends on freight transportation market are analysed, obtaining among other conclusions that more transport of processed high-valued goods with low density and higher space requirement is happening in contrast to transport of bulk cargo and heavy goods.

    Supply

    Where the freight railway system and its performance are analysed, being intermodal transportation and unit trains the business segments with major interest. The current wagon fleet characteristics together with their performance are discussed to produce guidelines for VEL-Wagon concepts, among which the multipurpose applications. 

    Infrastructure

    General overview of railway infrastructure characteristics paying especial attention to loading gauges and axle loads.

    Finally it presents rough concept definitions of VEL-Wagon based on partners evaluation.

  • 122944.
    Zanzi, Rolando
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Pyrolysis of biomass. Rapid pyrolysis at high temperature. Slow pyrolysis for active carbon preparation.2001Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Pyrolysis of biomass consists of heating solid biomass inthe absence of air to produce solid, liquid and gaseous fuels.In the first part of this thesis rapid pyrolysis of wood(birch) and some agricultural residues (olive waste, sugarcanebagasse and wheat straw in untreated and in pelletized form) athigh temperature (800ºC–1000ºC) is studied ina free fall reactor at pilot scale. These conditions are ofinterest for gasification in fluidized beds. Of main interestare the gas and char yields and compositions as well as thereactivity of the produced char in gasification.

    A higher temperature and smaller particles increase theheating rate resulting in a decreased char yield. The crackingof the hydrocarbons with an increase of the hydrogen content inthe gaseous product is favoured by a higher temperature and byusing smaller particles. Wood gives more volatiles and lesschar than straw and olive waste. The higher ash content inagricultural residues favours the charring reactions. Charsfrom olive waste and straw are more reactive in gasificationthan chars from birch because of the higher ash content. Thecomposition of the biomass influences the product distribution.Birch and bagasse give more volatiles and less char thanquebracho, straw and olive waste. Longer residence time inrapid pyrolysis increase the time for contact between tar andchar which makes the char less reactive. The secondary charproduced from tar not only covers the primary char but alsoprobably encapsulates the ash and hinders the catalytic effectof the ash. High char reactivity is favoured by conditionswherethe volatiles are rapidly removed from the particle, i.e.high heating rate, high temperature and small particles.

    The second part of this thesis deals with slow pyrolysis inpresence of steam for preparation of active carbon. Theinfluence of the type of biomass, the type of reactor and thetreatment conditions, mainly temperature and activation time,on the properties and the yield of active carbons are studied.The precursors used in the experiments are birch (wood) anddifferent types of agricultural residues such as sugarcanebagasse, olive waste, miscanthus pellets and straw in untreatedand pelletized form.

    The results from the pyrolysis of biomass in presence ofsteam are compared with those obtained in inert atmosphere ofnitrogen. The steam contributes to the formation of solidresidues with high surface area and good adsorption capacity.The yield of liquid products increases significantly at theexpense of the gaseous and solid products. Large amount ofsteam result in liquid products consisting predominantly ofwater-soluble polar compounds.

    In comparison to the stationary fixed bed reactor, therotary reactor increases the production of energy-rich gases atthe expense of liquid products.

    The raw materials have strong effect on the yields and theproperties of the pyrolysis products. At equal time oftreatment an increase of the temperature results in a decreaseof the yield of solid residue and improvement of the adsorptioncapacity until the highest surface area is reached. Furtherincrease of the temperature decreases the yield of solidproduct without any improvement in the adsorption capacity. Therate of steam flow influences the product distribution. Theyield of liquid products increases while the gas yielddecreases when the steam flow is increased.

    Keywords: rapid pyrolysis, pyrolysis, wood, agriculturalresidues,biomass, char, tar, gas, char reactivity,gasification, steam, active carbon

  • 122945.
    Zanzi, Rolando
    et al.
    KTH, Tidigare Institutioner, Kemiteknik. KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Sjöström, Krister
    KTH, Tidigare Institutioner, Kemiteknik. KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Björnbom, Emilia
    KTH, Tidigare Institutioner, Kemiteknik. KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk reaktionsteknik.
    Rapid pyrolysis of agricultural residues at high temperature2002Inngår i: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 23, nr 5, s. 357-366Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper deals with rapid pyrolysis of agricultural residues such as olive waste and straw at high temperature (800 -1000degreesC) in a free-fall reactor at pilot scale. The conditions are of interest for gasification in fluidized beds where rapid pyrolysis plays an important role as first stage. The objective of the work is to study the effect of the process conditions such as heating rate, temperature and particle size on the product distribution, gas composition and char reactivity. A higher temperature and smaller particles increase the heating rate resulting in a decreased char yield. The cracking of the hydrocarbons with an increase in the hydrogen content is favoured by a higher temperature and by using smaller particles. Wood gives more volatiles and less char than straw and olive waste. The higher ash content in agricultural residues favours the charring reactions. The higher lignin content in olive waste results in a higher char yield in comparison with straw. Chars from olive waste and straw are more reactive in gasification than chars from birch because of the higher ash content.

  • 122946.
    Zanzi Vigouroux, Rolando
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Producción de electricidad con gasificadores en contracorriente de biomasa2005Konferansepaper (Annet vitenskapelig)
  • 122947.
    Zanzi Vigouroux, Rolando
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Torrefaction as pre-treatment for improvement of the biomass properties prior combustion and gasification2010Konferansepaper (Annet vitenskapelig)
  • 122948.
    Zanzi Vigouroux, Rolando
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Birbas, Daniella
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Márquez Montesino, Francisco
    niversidad de Pinar del Río, Departamento de Quimica, Pinarde de Río, Cuba,.
    Preparation of Activated Carbon: Forest residues activated with Phosphoric Acid and ZincSulfate2011Inngår i: VII EDICIÓN DE LA CONFERENCIA CIENTÍFICA INTERNACIONAL MEDIOAMBIENTE SIGLO XXI, MAS XXI 2011, 2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper describes the preparation of activated carbon by chemical activation. The selected biomass used as precursor is sawdust from both Cuban and Swedish Pine tree. Phosphoric acid and Zinc Sulphate are the chemical reagents. The objective is to study the influence of acid concentration, impregnation ratio and activation temperature on adsorption performance of the obtained activated carbon.

    The experiments with phosphoric acid activation show that treatment with 40% acid concentration at 400 °C produce an activated carbon with good properties for ammonia adsorption and good iodine number. If a 30% phosphoric acid is used for activation, an activation temperature of 500 °C is recommended. With an impregnation ratio of 1, good adsorption was obtained in the activated carbon produced from Swedish pine while using Cuban pine a higher adsorption was obtained with an impregnation ratio of 2.

    The experiments with Zinc Sulphate activation show that activation conditions of 20% zinc sulphate concentration, 400 °C and impregnation ratio: 1 are enough to produce an activated carbon with good properties for ammonia adsorption. The adsorption of carbon tetrachloride was lower. Activated carbons produced with 10 % zinc sulphate concentration, 0.5 impregnation ratio and 400 °C activation temperature (the mildest studied conditions) show already good iodine number and BET surface area.    

  • 122949.
    Zanzi Vigouroux, Rolando
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Björnbom, Emilia
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk reaktionsteknik.
    Grimm, Alejandro
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk reaktionsteknik.
    Biosorbentes para la remoción de cobre (II) en soluciones acuosas2005Konferansepaper (Fagfellevurdert)
  • 122950.
    Zanzi Vigouroux, Rolando
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Björnbom, Emilia
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Soria, Santiago
    Dept. of Chemical and Environmental Engineering, Univ. of Zaragoza, Spain.
    Grimm, Alejandro
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    FIXED BED UPDRAFT GASIFICATION OF BIOMASS2005Inngår i: 14th European Biomass Conference and Exhibition, ETA-Florence, Italy and WIP-Munich, Germany , 2005Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The paper presents the initial work performed in a newly built updraft gasifier. Densified woody biomass, birch, in form of pellets with a diameter of 8 mm and a length between 5 and 15 mm has been used as a raw material for batch autothermal gasification using air as an oxidation agent. The main objectives were to study the effect of the treatment conditions on the distribution of the products and the composition of product gas to establish the suitability of the gasifier to produce combustible gas with sufficiently high calorific value.The amount of the biomass used in the experiments was varied between 1 and 4 kg and the flow rate of the oxidation agent, air, was varied from 1,1 to 2,6 m3/h. Increased airflow rates favored higher temperatures, however, excessively high airflow rates resulted in fast consumption of the biomass and it also favored combustion over gasification and thus formation of lower amounts of combustible products. High airflow rates caused also higher yields of liquid products, due to the shorter residence time of the tar-rich gas in the gasifier and thus unfavorable conditions for tar cracking.

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