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  • 101. Fiameni, S.
    et al.
    Famengo, A.
    Agresti, F.
    Boldrini, S.
    Battiston, S.
    Saleemi, Mohsin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Johnsson, M.
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Fabrizio, M.
    Effect of Synthesis and Sintering Conditions on the Thermoelectric Properties of n-Doped Mg2Si2014Ingår i: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 43, nr 6, s. 2301-2306Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Magnesium silicide (Mg2Si)-based alloys are promising candidates for thermoelectric (TE) energy conversion in the middle-high temperature range. The detrimental effect of the presence of MgO on the TE properties of Mg2Si based materials is widely known. For this reason, the conditions used for synthesis and sintering were optimized to limit oxygen contamination. The effect of Bi doping on the TE performance of dense Mg2Si materials was also investigated. Synthesis was performed by ball milling in an inert atmosphere starting from commercial Mg2Si powder and Bi powder. The samples were consolidated, by spark plasma sintering, to a density > 95%. The morphology, and the composition and crystal structure of samples were characterized by field-emission scanning electronic microscopy and x-ray diffraction, respectively. Moreover, determination of Seebeck coefficients and measurement of electrical and thermal conductivity were performed for all the samples. Mg2Si with 0.1 mol% Bi doping had a ZT value of 0.81, indicative of the potential of this method for fabrication of n-type bulk material with good TE performance.

  • 102.
    Filipovic, Mirjana
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Evolution of artificial defects during shape rolling2007Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Very often defects are present in rolled products. For wire rods, defects are very deleterious since the wire rods are generally used directly in various applications. For this reason, the market nowadays requires wire rods to be completely defect-free. Any wire with defects must be rejected as scrap which is very costly for the production mill. Thus, it is very important to study the formation and evolution of defects during wire rod rolling in order to better understand and minimize the problem, at the same time improving quality of the wire rods and reducing production costs.

    The present work is focused on the evolution of artificial defects during rolling. Longitudinal surface defects are studied during shape rolling of an AISI M2 high speed steel and a longitudinal central inner defect is studied in an AISI 304L austenitic stainless steel during ultra-high-speed wire rod rolling. Experimental studies are carried out by rolling short rods prepared with arteficial defects. The evolution of the defects is characterised and compared to numerical analyses. The comparison shows that surface defects generally reduce quicker in the experiments than predicted by the simulations whereas a good agreement is generally obtained for the central defect.

  • 103.
    Filipovic, Mirjana
    et al.
    National Post Gradual School in Metal Forming, Dalarna University.
    Eriksson, Conny
    Fsgersta Stainless AB.
    Overstam, Henrik
    Mechanical Engineering, Department of Technology, Örebro University .
    Behaviour of surface defects in wire rod rolling.2006Ingår i: STEEL RES INT, ISSN 1611-3683, Vol. 77, nr 6, s. 439-444Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Defects are often present in rolled products, such as wire rod. The market demand for wire rod without any defects has increased. In the final wire rod products, defects originating from steel making, casting, pre-rolling of billets and during wire rod rolling can appear. In this work, artificial V-shaped longitudinal surface cracks have been analysed experimentally and by means of FEM. The results indicate that the experiments and FEM calculations show the same tendency except in two cases, where instability due to fairly "round" false round bars disturbed the experiment. FE studies in combination with practical experiments are necessary in order to understand the behaviour of the material flows in the groove and to explain whether the crack will open up as a V-shape or if it will be closed as an I-shape.

  • 104.
    Filipovic, Mirjana
    et al.
    National Post Gradual School in Metal Forming, Dalarna University.
    Jonsson, Stefan
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Experimental and Numerical study of the Evolution of Artifical Inner Defects in Stainless Steel rolled in a Wire Rod Block.Manuskript (preprint) (Övrigt vetenskapligt)
  • 105.
    Floresjö, Robert
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Slipning och tillämpning av pulverstålvalsar vid kallvalsning av tunna rostfria band2011Självständigt arbete på avancerad nivå (magisterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Kallvalsning av rostfria band har, historiskt sett, ständigt utmanats med högre ytkrav och tjocklekstoleranser, samtidigt som bredare och tunnare band efterfrågas. Detta innebär en utmaning inom valsteknik när produktiviteten samtidigt skall bibehållas. En viktig faktor vid dessa förändringar är valsmaterialet, som bl.a. behöver bli mer nötningsbeständigt och hårdare, utan att segheten och slipbarheten försämras. På Outokumpu Thin Strip Kloster i Långshyttan används arbetsvalsar av materialet RT60 ERS vid kallvalsning. Ett alternativ till dessa valsar, som kan uppfylla de hårdare kraven, är pulverstålvalsar.

     

    Syftet med examensarbetet är, att utreda hur effektivt pulverstålvalsar av materialen ASP 2005, ASP 2023 och Vancron 40 kan slipas med CBN slipskiva och användas i produktion. Detta utan att försämra leveransytan jämfört med dagens valsar.

     

    Resultaten visade, att pulverstålvalsarna har ett mycket bra motstånd mot slitage vid valsning, och kan ur denna aspekt med fördel användas ur produktionssynpunkt. Banden, som valsades med pulverstålvalsar, erhöll grövre textur jämfört med konventionella valsarna. Detta berodde på att dagens skärputrustning ej kunde ge tillräckligt fin textur på CBN slipskivan, vilken därför gav för grov yta på valsarna. Band valsade med pulverstålvalsar i jämförelse med konventionella valsar påvisade fler extremtoppar med högre amplitud, men även att ytan var mindre diffus p.g.a. valsslitage. Produktiviteten för slipning av pulverstålvalsar är densamma som för slipning av konventionella valsar.

  • 106.
    Folmerz, Marcus
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Cut edge condition and its effect on resistance to hydrogen embrittlement in martensitic steel grades2014Självständigt arbete på avancerad nivå (magisterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Hydrogen embrittlement (HE) occurs for ultra-high strength steels (UHS) in combination with corrosion protection by electro galvanizing. The purpose of the project has been investigating the impact of the cut edge condition to HE. Several different cut edges were investigated including cutting with shear parallel blades with different cutting clearance, punching, grinding (grinded edge) and laser cutting. A method of charging hydrogen into the steel specimens during static tensile testing at 80 % of the ultimate tensile strength (UTS) was set up, called constant load testing. Also U-bend testing, static load testing and slow strain rate testing (SSRT) was performed.

    The materials used in this project were all cold rolled martensitic steels with different alloying and with UTS exceeding 1300 MPa.

    The results show that the cut edge condition has a big impact on the sensitivity for HE. The laser cut and grinded specimens passed the constant load test and showed no sensitivity for HE in that test. The laser cut samples also passed the U-bend test and the grinded samples managed the U-bend test significantly better than the cut edges with different cutting clearances. The cut samples show the same HE sensitivity regardless which cutting clearance were used.

    Since the grinded and laser cut samples shows great improvement in these tests, there is reason to believe that these edges either equalize stresses from the edge, prevents hydrogen absorption or both. However, the different cutting clearances do not seem to affect the sensitivity for HE. Punching or cutting is equal considering sensitivity for HE.

  • 107. Franz, Yohann
    et al.
    Ren, Haonan
    Healy, Noel
    Ignatyev, K
    Jones, Maxwell
    Hawkins, Thomas
    Ballate, John
    Gibson, Ursula
    Norwegian Univ of Science and Technol..
    Peacock, Anna
    Material properties of tapered crystalline silicon core fibers2017Ingår i: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 7, nr 6, s. 2055-2061Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Crystalline silicon optical fibers are emerging as a promising platform for a wide range of optoelectronic applications. Here we report a crystallographic study of the material properties within silicon fibers that have been post-processed via a tapering procedure to obtain small, few micron-sized core diameters. Our results reveal that the tapering process can improve the polysilicon quality of the core through the formation of large, centimeter long crystal grains, thus significantly reducing the optical losses.

  • 108.
    Fredriksson, Per
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    A strain gradient plasticity analysis of size effects in thin films2005Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 109. García, A.
    et al.
    Norambuena-Contreras, J.
    Bueno, M.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. Empa, Swiss Federal Laboratories for Materials Science and Technology, Duebendorf, Switzerland .
    Influence of steel wool fibers on the mechanical, termal, and healing properties of dense asphalt concrete2014Ingår i: Journal of Testing and Evaluation, ISSN 0090-3973, E-ISSN 1945-7553, Vol. 42, nr 5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper summarizes the main results of experimental research on the induction healing of dense asphalt concrete with steel wool fibers. Different physical properties of dense asphalt concrete, as the steel wool fibers distribution, mechanical properties, thermal conductivity, and healing via induction heating have been analysed. The main results show that short and thick fibers disperse very well in the mixture, while long and thin fibers produce clusters. It was also observed that fibers can be damaged during the mixing and compaction processes. In addition, it was found that steel wool fibers do not significantly improve the mechanical properties and damage resistance of dense asphalt concrete. Moreover, steel wool fibers slightly increase the thermal conductivity of dense asphalt concrete. Furthermore, the temperature reached due to induction heating increases with the number of fibers in the mixture and with their diameter. Finally, it was found that dense asphalt concrete heals through the increase of temperature and that the type and diameter of fibers do not influence the healing properties of dense asphalt concrete.

  • 110.
    Ghafoori Roozbahany, Ehsan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. VTI Swedish National road and transport research institute, Olaus Magnus väg 35, Linköping, 583 30, Sweden.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Elaguine, Denis
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Modelling the flow of asphalt under simulated compaction using discrete element2019Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 227, artikel-id 116432Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The flow differences between the particles of asphalt mixtures compacted in the laboratory and in the field have been identified as one of the reasons for the discrepancies between laboratory and field results. In previous studies, the authors developed a simplified test method, the so-called compaction flow test (CFT), for roughly simulating the flow of particles in asphalt mixtures under compacting loads in laboratory. The CFT was used in different studies to examine its capability of revealing the differences between the flow behavior of different asphalt mixtures under various loading modes. The promising results encouraged further development of the CFT by investigating the possible impacts of simplifications and boundary conditions on the results of this test. For this reason, discrete element method (DEM) was utilized to investigate possible impacts of the mold size, geometry of the loading strip as well as the loading rate on the results of the CFT. The results of the simulation indicate that in case of wearing course layers with nominal maximum aggregate size of 11 mm, the length of the CFT mold can be increased from 150 mm to 200–250 mm for reducing flow disturbances from the mold walls. However, since the majority of the flow of asphalt mixture particles is expected to take place within the first 100–150 mm length of the mold, reasonable results can still be obtained even without changing the size of the CFT mold. Moreover, comparing results with different loading strip geometries and loading rates indicates that the current CFT setup still appears to provide consistent results.

  • 111.
    Ghazian Tafrishi, Babak
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Study of Argon Shrouding in Ingot Casting, with Focus on Improving the Operation at Scana Björneborg Steel Plant2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This thesis has been carried out as a development project at Scana Steel Björneborg with the purpose to study the influential parameters in argon shrouded ingot casting during the manufacturing of low-alloy steels.

    In the first stage, a literature study was conducted in order to investigate the theoretical background of the procedure and the importance of protecting the melt during ingot casting.

    Next, a computer model of the shield was designed using COMSOL Multiphysics® with regard to the process conditions at Scana Steel Björneborg. The effect of various parameters on the process was examined through simulations of the argon gas flow pattern, heat transfer between the gas and the melt stream, and the chemical species transport in the gas around the melt stream.

    Based on the simulation results, two different shapes of shield were proposed for the argon shrouding operation. A set of implementation tests was executed in order to check the installation and usage conditions of the two new shields.

    After deciding the proper shape of the shield, a full-scale ingot-casting test was performed with the selected shield to investigate the protection behavior. Moreover, the impact of the new casting-protection shield on the nitrogen and oxygen contents of steel was examined through sampling and analyzing the steel before and after casting.

    It was found that the use of the new shield during the uphill ingot casting is an effective way to reduce the final nitrogen and oxygen contents of the casted ingot. Therefore, the new design of the shield can be used as a developed substitute for the protection of the melt stream in the ingot casting operation.

  • 112.
    Gibson, Ursula
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik. Norwegian Univ of Science and Technol..
    Group IV Semiconductor fibers2017Konferensbidrag (Övrigt vetenskapligt)
  • 113.
    Gibson, Ursula
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik. Norwegian Univ of Science and Technol..
    Optical materials – unusual films, particles and fibers2017Konferensbidrag (Övrigt vetenskapligt)
  • 114.
    Gibson, Ursula
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik. Norwegian Univ of Science and Technol..
    Semiconductor-core fibers2017Konferensbidrag (Övrigt vetenskapligt)
  • 115.
    Gibson, Ursula
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik. Norwegian Univ of Science and Technol..
    Ballato, John
    Peacock, Anna
    Semiconductor core glass fiber2017Konferensbidrag (Övrigt vetenskapligt)
  • 116.
    Gibson, Ursula
    et al.
    Norwegian Univ of Science and Technol..
    Ballato, John
    Peacock, Anna
    Semiconductor core optical fibers2017Konferensbidrag (Övrigt vetenskapligt)
  • 117.
    Gong, Yuze
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Wear Studies on Silicon Carbide  Whisker Reinforced Alumina2011Självständigt arbete på avancerad nivå (masterexamen), 30 poäng / 45 hpStudentuppsats (Examensarbete)
    Abstract [en]

      Wear and biological response to wear debrisof artificial joints remain the major concerns in total hip arthroplasty (THA) [1].Silicon carbide reinforced alumina, Al2O3-SiCw,can be considered as a candidate for hip implants due to its high hardnessand toughness, aswell as chemical inertness. In this study, thewear and friction properties of Al2O3-SiCw areinvestigated by pin-on-disc experiments, with Hank’s Buffered Salt Solution(HBSS) as lubricant. Comparisons with BIOLOX®delta,the most commonly used ceramic in THA, under the same test conditions are made as well.

  • 118. Gorbatov, O. I.
    et al.
    Ruban, Andrei V.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Gornostyrev, Yu.N.
    Effect of magnetism on precipitation of Cu in bcc Fe: Ab-initio based modeling2009Ingår i: Scientific basis for nuclear waste management XXXIII, Materials Research Society, 2009, s. 469-476Konferensbidrag (Refereegranskat)
    Abstract [en]

    Theoretical modeling of the decomposition in bcc Fe-Cu alloys has been performed using a combined approach which includes ab-initio calculations of the effective cluster interactions and statistical-mechanical (Monte Carlo) simulations. We showed that the effective Cu-Cu and Cu-vacancy interactions in the bcc Fe matrix have a strong dependence on the global magnetic state of iron. As a result, all the related thermodynamic properties of the alloys (such as solubility limit and diffusivity) are expected to have a pronounced non-Arrhenius temperature behavior, originated from variation of the global magnetization with temperature. We find that strong Cu-vacancy interactions in the bcc Fe matrix lead to a remarkable effect of vacancies on the Cu precipitation and significantly modify the alloy decomposition kinetics under irradiation.

  • 119.
    Gram, Annika
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad (byte av engelskt namn 20110630).
    Numerical Modelling of Self-Compacting Concrete Flow: Discrete and Continuous Approach2009Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Med uppkomsten av självkompakterande betong (SKB) och dess möjligheter att flyta ut under inverkan av endast gravitation uppstod ett behov av att kunna förutsäga och kontrollera även mer komplicerade gjutningar. Numerisk simulering av SKBs flöde kan kommma att utgöra ett kraftfullt verktyg för att optimera gjutprocessen, ge möjlighet att förutsäga nödbvändig arbetbarhet och säkerställa kompatibilitet mellan den armerade formen och betongens reologi. I föreliggande avhandling undersöks betongens flöde med både diskreta och kontinuumbaserade simuleringsmetoder. Den diskreta partikelmodellen används för att simulera detaljer och fenomen hos t.ex. ballast i betong. I de här presenterade simuleringarna används sfäriska partiklar, men det är även möjligt att skapa ballastkorn av olika form. Ballastens ytråhet och storlek kan modelleras med parametrar för friktion och storlek medan sammanfogning av ett flertal partiklar kan ge ekvivalent form. Den kontinuumbaserade ansatsen används för att simulera större flödesmängder. Betongen modelleras som ett homogent material, eventuella effekter av ballastens inverkan, till exempel blockering eller separation, ingår ej. God överensstämmelse har uppnåtts med Binghams materialmodell som applicerats på några av SKBs provningsmetoder (bl a flytsättmått och L-låda) liksom även för större gjutningar. Formfyllnad av en hårt armerad sektion av ett STT-element, liksom två pumpade betongleveranser till en hög vägg, har framgångsrikt simulerats. En kvantitativ övergripande analys av betongflödet i formen kan göras med den kontinuumbaserade ansatsen för att upptäcka zoner med eventuella svårigheter. En högupplöst detaljstudie kompletterar sedan analysen på valda delar av och kring dessa zoner för att fånga partikelfenomen kvalitativt med hjälv av den diskreta modellen. Då datorkapaciteten ökar kommer även större volymer med högre detaljrikedom att kunna simuleras. En framtida modell simulerar med stor sannolikhet partiklar i flöde, vilket till fullo kan fånga betongens egenskaper som suspension. Som ett första steg på vägen har en fallande ellipsoid i en newtonsk vätska simulerats.

  • 120.
    Gram, Annika
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Farhang, Ali
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Silfwerbrand, Johan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Computer-aided modelling and simulation of self-compacting concrete flow2007Ingår i: Proceedings pro054: Self-Compacting Concrete - SCC 2007 / [ed] G. De Schutter and V. Boel, RILEM Publications SARL , 2007, s. 455-460Konferensbidrag (Refereegranskat)
    Abstract [en]

     The flow behaviour of SCC is currently being investigated as an ongoing PhD project. This paper presents a development of the Distinct Element Method using the commercial software PFC3D to model the flow of SCC. A good correspondence was obtained between laboratory test and numerical result for the slump flow test.

  • 121.
    Gram, Annika
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Silfwerbrand, Johan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Computer simulation of SCC flow2007Ingår i: Betonwerk und Fertigteil-Technik/Concrete Plant and Precast Technology, ISSN 0373-4331, Vol. 73, nr 8, s. 40-48Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Starting in 1993, Sweden was, inspired by Japanese research in the concrete field, the first European country to develop the revolutionary material called Self Compacting Concrete (SCC). The Swedish Cement and Concrete Research Institute (CBI) was one of the pioneer research environments on SCC in Europe; f. i. the first European SCC bridges were cast in Sweden in 1998. Furthermore, an SCC flow a simulation project was started; in 2000 at CBI. The used particle based software is icalled Particle Flow Code (PFC) and is based on the Distinct Element Method (DEM).

  • 122.
    Gravoille, Pauline
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    CASE STUDY OF ACTIVE FREE COOLING WITH THERMAL ENERGY STORAGE TECHNOLOGY2011Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    May 25, 2011, Reuters’ headline read: "New York State is prepared for summerelectricity demand". The NY operator forecasts for next summer a peak of 33GW, close to therecord ever reached. With soaring cooling demands, the electricity peak load represents a substantialconcern to the energy system. In the goal of peak shaving, research on alternative solutions based onThermal Energy Storage (TES), for both cooling and heating applications, has been largely performed.This thesis addresses thermal comfort applications with use of active free cooling through implementationof latent heat based TES. Active free cooling is based on the use of the freshness of a source, the outsideair for example, to cool down buildings. This work conceptualizes the implementation of TES basedcooling system with use of Phase Change Material in an in-house-built model. The principle of PhaseChange Material, or Latent Heat TES (LHTES), lies on latent energy which is the energy required for thematerial to change phase. In order to properly size this cooling system, a multi-objective optimization isadopted. This optimization, based on minimization of multi-objective functions, led to optimal designconfigurations. In parallel, the electrical consumption of the system and the volume uptake of the systemwere also considered. Through the obtained optimization studies, we identified non-linearinterdependency between the two objective functions: the cost of the system and the acceptable remainingcooling needs. By remaining cooling needs, we mean the cooling needs that the system cannot meet. As amatter of fact, sizing the system according to these cooling needs would imply a very high cost. It wasfound that for a certain amount of remaining cooling needs, the PCM-based cooling system reveals to bean interesting solution compared to conventional air conditioning in terms of electrical consumption andoverall system cost.

  • 123.
    Gren, Emil
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Optimering av stjärtändar på oklippta varmvalsade band genom att före värmning justera hörngeometrin på ämnen2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Detta projekt har genomförts för att studera möjligheterna med att justera ämnesgeometrin före valsning för att minimera tillväxten av tungor som bildar stjärtändar i bandets sistaände. Olika justeringar har utvärderats genom att ämnen har justerats med hjälp av gasskärning och sedan valsats i förpar och färdigverk. Ett delmål var att förenkla efterföljande behandlingar där långa stjärtändar är ett hinder.

     

    Resultaten visar att stora skillnader på längden hos tungorna kan åstadkommas med mindre justeringar hos ämnena. Längden på stjärtändarna minskade med upp till 70 % på band som valsats till en tjocklek av 15,02 mm och 75 % på band som valsats till en tjocklek av 12,02 mm. Effekten av att valsa ämnen med dessa justeringar var att en midja bildades i slutet av bandet där bredden linjärt avtog innan det att stjärtänden uppstod. Delmålet uppnåddes genom att alla uppmätta, justerade band i framtiden kan undvika ett processteg då längderna hos tungorna hade minskats tillräckligt mycket.

     

    Svårigheter under projektet var att kunna planera och genomföra omfattande försök med många ämnen vilket resulterade i ett begränsat antal fick genomföras. Ämnesgeometrin var även ett problem då inga exakta mått fanns att tillgå före valsningen vilket gjorde det svårt att förutse valsinställningar för specifika ämnen.

  • 124.
    Grytsan, Andrii
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Biomekanik.
    Abdominal aortic aneurysm inception and evolution - A computational model2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Bukaortaaneurysm (AAA) kännetecknas av en utbuktning hos aortaväggen i buken. Tillväxt av en AAA är oftast asymtomatisk, men en sådan utbuktning kan plö̈tsligt brista, vilket har hög dödlighet. Tyvärr finns det inga mediciner som kan förhindra AAA från att expandera eller brista. Patienter med upptä̈ckt AAA hålls därför under uppsikt tills operationskrav är uppnådda, såsom maximal AAA-diameter på 55 mm eller expansionstakt på 1 cm/år. Modeller för AAA-tillväxt kan bidra till att öka förståelsen för sjukdomsförloppet och till att förbättra beslutsunderlaget på en patientspecifik basis. AAA modeller för tillväxt och strukturförändring (G&R) är ganska komplicerade och innan man tar sig an denna utmaning krävs de god klinisk validering.

    I Artikel A har en befintlig tjockväggig modell för tillväxt av ett skikt av en AAA-skiva utö̈kats till en två-skiktsmodell. Denna modell återspeglar bättre den skiktade strukturen hos kärlväggen. Genom en parameterstudie undersö̈ktes påverkan av mekaniska egenskaper och G&R-parametrar hos en sådan modell för AAA-tillväxt.

    I Artikel B utvidgades modellen från Artikel A till en organnivå-modell för AAA-tillväxt. Vidare inkorporerades modellen i ett “Fluid–Solid–Growth” (FSG) ramverk. En patientspecifik geometri hos bukaortan användes för att illustrera möjligheterna med modellen.

    I Artikel C undersöktes utvecklingen av patientspecifika biomekaniska egenskaper hos AAA. Fyra patienter som skannats fem till åtta gånger med “Computed Tomography-Angiography” (CT-A) vid olika tillfällen analyserades. Flera icke triviala statistiska samband konstaterades mellan de analyserade parametrarna.

    I Artikel D undersöktes effekten av olika tillväxt-kinematik för AAA tillväxt. En modell med transversellt-isotrop-i-tjockleken-tillväxt var den bäst lämpade för AAA tillväxt, medans antagandet om fullt-isotrop-tillväxt och transversellt-isotrop-i-planet-tillväxt producerade orimliga resultat. Dessutom gav modellering av vävnadsvolymsförändring ett förbättrat väggtjockleks resultat men en fortsatt överskattning av väggförtunningen under AAA-expansionen.

  • 125.
    Guzman, Jonathan
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Process Design and Technical feasibility analysis of Catalytic fas tpyrolysis for biocrude production2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Efterfrågan om förnyelsebara bränslen ökar. Catalytic Fast Pyrolysis är en växande teknologisom skulle kunna förse med bio-crude av hög kvalité för att användas med dagensinfrastruktur. Den process som valdes för att implementera denna teknologi är in-situcirculating fluidized bed med sågspån som inmatning. Två fall blev utformade och sedanmodellerade i ASPEN Plus. Det första fallet använder sig av ånga som flödare och andrafallet använder sig av återvunnen pyrolysgas. Båda fallen var självförsörjande med endastbiomassa som energikälla. Enligt parameterstudien stämmer detta endast för biomassa medmindre än 40% fuktinnehåll.

  • 126.
    Gärdsback, Mattias
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Rotation-free shell elements for thin-film structures and simulations of centrifugally deployed spece webs2007Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 127.
    Gärdsback, Mattias
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Tibert, Gunnar
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Space webs2006Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report presents a study of the controlled deployment of a large web in space. The study is composed of three major parts:1. The design of the space web starts with a study of different geometries, i.e. threeor four corners. For each geometry, three different mesh topologies are investigated,i.e. triangular, square or hexagonal meshes. An analysis by the force method showedt hat only the web with a square mesh could be prestressed by a centrifugal forcefield. The triangular mesh had a too high degree of static indeterminacy, whichresulted in compressed elements. The hexagonal mesh had a too high degree ofkinematic indeterminacy and became too distorted under the centrifugal force field.The square mesh webs were subsequently analysed in terms of out-of-plane flexibilityand vibrational characteristics. Preliminary investigations on the choice of materialfor the web and the probability of web failure due to micro-meteoroid impact werealso performed. MATLAB routines that automatically generates the web with anarbitrary size, mesh width and sag-to-span ratio have been developed.2. A successful deployment requires an adequate folding pattern. A literature review identified the star-like folding pattern as a promising candidate. The folding is performedin two distinctive stages. First, the web is folded towards the central hub in a way so that three or four radial arms are formed, depending on the chosen geometry.Then, the radial arms can be either coiled around the central hub or folded ina zig-zag manner towards the hub. The MATLAB-generated web from part 1 is fed into new MATLAB routines, which folds the web according to the various pattern described above.3. The dynamic deployment of the space web is analysed by a two-dimensional analyticalmodel in MATLAB and a full three-dimensional model by the commercialfinite element software LS-DYNA. The developed analytical models can simulatethe deployment of the arms from a position coiled around the hub or reeled up onspools. A simple control strategy was found in literature and implemented in the analyticalmodel with successful results. The MATLAB-generated model of the foldedweb was inserted into the software LS-DYNA. For an uncontrolled deployment, thefinite element model yields the expected coiling off-coiling on oscillating behaviour.The control law with the drooping characteristics is not implemented in the finite element model, but analyses with a simplified control law shows good agreement between the analytical and the finite element results for the deployment of the stararms.

  • 128. Gårdstam, Johannes
    Simulation and verification of pierce nut in high strength sheet steels2005Rapport (Övrigt vetenskapligt)
  • 129.
    Gårdstam, Johannes
    KTH, Tidigare Institutioner                               , Mekanik.
    Simulation and verification self pierced rivet joints of stainless sheet steels2004Rapport (Övrigt vetenskapligt)
  • 130.
    Gårdstam, Johannes
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Simulation of mechanical joining for automotive applications2006Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Regarding the use of material, modern lightweight car bodies are becoming more and more complex than previous constructions. The materials nowadays are used for a more specific field of application and more high strength steels are used and also other materials like aluminium, stainless steel, reinforced polymers are used more frequent. The joining of these materials often requires new or modified joining processes. The aim with this thesis is concerned with the development of simulation models of the joining process as well as mechanical properties of self piercing riveted (SPR) joints and pierce nut joints. In both of these joining methods problems occur when introducing more high strength steel sheets. For SPR, fractures occur in the rivet, and for pierce nut the thread will be damaged.

    Since both the SPR process and the pierce nut process expose the material for plastic deformation up to 150%, correct material properties for very large strain and a simulation program that could handle this was required. With the commercial finite element program Deform2D an axi-symmetric model has been built for the SPR process and the pierce nut process. Because of the computational time, 3D simulations were only used where it was necessary. The developed 3D models use the commercial finite element program ABAQUS-Explicit. All simulation models have been verified with satisfactory agreement to experimental results.

    For SPR, an axi-symmetric simulation model was used for evaluating and optimising the setting process in the stainless steel sheets EN1.4301, HyTens 800 and HyTens 1200. Subsequently, 3D models were used for predicting the mechanical properties of new SPR joints that have showed reduced risk for rivet cracking. In pierce nut simulations, nuts with hardness 8 and 10 have been set in the high strength steel sheet DP600. An axi-symmetric simulation model was used for centred nut setting and two different simulation models in 3D were used to evaluate eccentric nut setting and torque resistance.

    This work resulted in more knowledge about the fracture risk in the rivet and how to reduce it. The strain and stress, which was used as fracture indicators, were reduced to the half with modifications of the rivet and the die geometry. Mechanical property simulations in shear and peel load resulted in satisfactory results for new SPR joints that have showed reduced fracture risk during rivet setting. New die and rivet designs can be developed effectively by combining the process and mechanical property simulations.

    For a pierce nut joint in high strength steel sheets (1.5mm DP600), the simulations show that the cutting of the sheet in combination with eccentric setting over the die causes the thread damage. The thread damage can be avoided by changing the dimension of the nut or by increasing the strength of the nut material. The simulation models can also be used to develop new nut and die geometries for future applications.

  • 131.
    Gårdstam, Johannes
    KTH, Tidigare Institutioner                               , Mekanik.
    Simulation of self piercing riveting of high strength austenitic stainless steel in 1 and 2 mm sheet thickness2004Rapport (Övrigt vetenskapligt)
  • 132.
    Gårdstam, Johannes
    et al.
    KTH, Tidigare Institutioner                               , Mekanik.
    Melander, A.
    Self-piercing rivetin of stainless sheet steels-simultation and verification2004Ingår i: 11th Paderborner Symposium Fügetechnik, Mechanishes Fügen und Kleben, 2004, s. 135-143Konferensbidrag (Refereegranskat)
  • 133.
    halsteen, Tanja
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Potentiella möjligheter att minska koksförbrukningen vid Befesa ScanDust: Användning av alternativa kolkällor och förbränningsgaser2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Befesa ScanDust AB reducerar knappt 65 000 ton metallstoft per år och använder koks som reduktionsmedel. Koks utgör idag en stor del av produktionskostnaden samtidigt som det bidrar till ökade koldioxidutsläpp och det finns därför ett intresse i att minska förbrukningen i processen.För att minska koksförbrukningen gjordes ett försök med att använda kvävgas istället för luft som injektionsgas. Dessutom så planerades ett försök med tillsats av olja göras. Dock genomfördes inget sådant på grund av tidsbrist och försöket fick skjutas fram. En beräkning baserat på stökiometriska förhållanden gjordes för att se hur lågt koksförbrukningen kan sänkas. Prover togs även under hela produktionslinjen för att se hur kolet fördelar sig i processen idag.Kvävgasförsöket visade lovande resultat. Det vill säga en minskning av koksförbrukningen kunde urskiljas i mätningarna. Dock höjdes vätgashalten i emissionsgasen, vilket inte är önskvärt. Emissionsgasen återanvänds i plasmageneratorer och en hög vätgashalt påverkar konduktiviteten, vilket kan störa ljusbågen i dessa.Beräkningarna visar att ca 20 % mer koks än nödvändigt tillsätts i produktionen för att erhålla en fullständig reduktion. En fortsatt utredning gällande hur förbrukningen kan sänkas bör därför göras. Ett oljeförsök skulle vara av intresse för att se om en flytande kolkälla skulle kunna göra reduktionen mer effektiv.

  • 134.
    Hannes, Dave
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Alfredsson, Bo
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Modelling of surface initiated rolling contact fatigue damage2013Ingår i: Fatigue Design 2013, International Conference Proceedings, Elsevier, 2013, s. 766-774Konferensbidrag (Refereegranskat)
    Abstract [en]

    A parametric study was performed to investigate the contribution of surface roughness, friction and a constant residual surface stress to the rolling contact fatigue damage process. The effects on initiation, crack path and fatigue life were examined for a gear application. The asperity point load model could predict effects on rolling contact fatigue that are observed with experiments. The study of a ring/cone crack subjected to a rolling contact fatigue load allowed to explain the v-shaped cracks typical for surface initiated spalling. The results further support the asperity point load mechanism as a source behind surface initiated rolling contact fatigue.

  • 135.
    Harlin, Kim
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Sandell, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Alternative Fuel for reheating furnace with aiming at CO2 mitigation2013Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This paper is researching different kinds of biomass based fuels and contains a case study of a reheating furnace, furnace 301, at SSAB. The purpose was to find out which type of bio fuel was best suited for the furnace application. An experiment at KTH in Sweden was observed to better understand the process of creating a gas fuel from pellets and a mass balance was done to show the difference between using a new kind of bio mass based fuel and the current use of liquid petroleum gas. Results from the experiment and mass balance show that syngas is the fuel best suited for furnace applications as well as a general idea of how to integrate it into the furnace design. Three enlarged gasifiers, with a fuel output of 32 MW, will be needed to meet the requirements in an industrial application. If furnace 301 at SSAB would be active all year around with no stops in the production, an amount of 153760 ton pellets will be needed per year which is equal to 367407 tons of wood per year.

  • 136.
    Hassan, Zahra
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Extensive investigations towards the development of a cupola furnace process model: A case study on the cupola furnace operations of Volvo Group Trucks Operations in Skövde, Sweden.2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 137.
    Hassanabadi, Massoud
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Grain Refinement of Commercial EC Grade 1070 Aluminium Alloy for Electrical Application2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The aluminium alloys for electrical conductivity applications are generally not grain refinedsince the addition of grain refiners drops the electrical conductivity by introducing impuritiesinto the melt. Non-grain refined aluminium may lead to bar fracture and cracks during themetalworking process.

    The present study focuses to find an optimum balance between the grain refiner addition andthe electrical conductivity of commercial EC grade 1070 aluminium alloy for electricalapplication. In order to reach this goal, the electrical conductivity and the macrostructure ofcommercial EC grade 1070 aluminium (commercial pure aluminium) have been studiedunder a series of controlled lab scale trails. Specific addition levels of different grain refiners(TiBloy, Al-5Ti-1B, Al-3Ti-0.15C, and Al-3Ti-1B) were added to the metal melt and sampleswere taken at specific time intervals. The collected samples were sectioned, ground andmacro-etched. Thereafter, the macrostructure was analysed by the use of a digital camera andthe electrical conductivity was measured at temperature. The obtained result was expressed asa percentage of the International Annealed Copper Standard (IACS %). The macro-structuralanalysis showed that TiBloy, Al-5Ti-1B, and Al-3Ti-1B, with the maximum addition level of0.1%, cannot grin refine commercial pure aluminium. However, at higher grain refiner levelsthe number of columnar grains increased and their size decreased.

    The Al-3Ti-0.15C master alloy, with the same addition level as the once chosen for the othergrain refiners (up to 0.1%), showed significantly better grain refining. By the addition of0.1% of this grain refiner the macrostructure became very equiaxed already after 30 minutesof grain refiner addition. The fading of the Al-3Ti-0.15 master alloy was, however, observedfor samples with a long holding time. Nevertheless, by maximum addition level (0.1%) and a90 minutes holding time the macrostructure remained as equiaxed grains.

    The electrical conductivity results showed that none of the applied grain refiners (TiBloy, Al-5Ti-1B, Al-3Ti-0.15C, and Al-3Ti-1B), with the maximum addition level of 0.1%, decreasedthe electrical conductivity of commercial pure aluminium.

  • 138. Hassel, B. I.
    et al.
    Modén, Carl S.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Berard, P.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Single cube apparatus - Shear properties determination and shear strain variation in natural density gradient materials2009Ingår i: ICCM-17 17th International Conference on Composite Materials, 2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    Transversal shear of softwoods was studied with the single cube apparatus (SCA). Full field strain data and FEA were used to validate the device. Once a close to pure shear strain region was confirmed, the relationship between shear strain and radial density gradient was obtained; finally an improved FE model was created.

  • 139. He, Z.
    et al.
    Stiewe, C.
    Li, Shen
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Platzek, D.
    Karpinski, G.
    Müller, E.
    Toprak, Muhammet
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Muhammed, Mamoun
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Processing and characterization of nano-structured ZrO2/ CoSb3 thermoelectric composites2006Konferensbidrag (Refereegranskat)
    Abstract [en]

    The addition of ceramic inclusion to a thermoelectric matrix could reduce the thermal conductivity of the composite, which is attributed to phonon scattering on the generated interfaces. The electrical conductivity of the composite, however, could also be reduced due to additional charge carrier scattering. The performance of the thermoelectric composite, therefore, depends on the resulting ratio of electrical conductivity to thermal conductivity, which results from the entire scattering effects on phonons and charge carriers. In the present work, nano-sized ZrO2 powders of different contents, which were expected to minimize their scattering impact on charge carriers, were dispersed into submicron-sized CoSb3 powders via ball milling. The as-milled powders were consolidated into dense compacts by hot pressing. The phase, the microstructure, and the thermoelectric properties of the prepared compacts were characterized. The correlation of phase purity, microstructure, and thermoelectric properties (electrical conductivity, thermal conductivity, and ratio of electrical conductivity to thermal conductivity), with the ceramic content and sintering temperature is presented. The results show how the performance of the investigated thermoelectric composites can be affected by the dispersion of nano-sized ceramic inclusions. It is noted that the selection of appropriate inclusion content is crucial to maintaining or improving the ratio of electrical conductivity to thermal conductivity.

  • 140.
    He, Zhangting
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    CALPHAD study of cubic carbide systems with Cr2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Cubic carbides (titanium, tantalum, niobium, and zirconium carbides) can constitute a significant proportion of so-called cubic and cermet grades, where it is added to substitute a portion of tungsten carbide. It is thus critical to understand and be able to thermodynamically model the cubic carbide systems. In order to do this, the thermodynamic descriptions of lower order systems, such as the Ti-Cr-C system, need to be well studied. To approach this goal, an extensive literature survey of thermodynamic data and phase diagram information on the Ti-Cr-C system, the Ta-Cr-C system, the Nb-Cr-C system and the Zr-Cr-C is presented in this work. Experiments are performed in the Ti-Cr-C system using powder metallurgy and heat treatments. The solubility of Cr in FCC_TiC phase was experimentally measured at 1773K and compared with previous studies showing that the solubility reported earlier is too large. Thereafter, a re-optimization of FCC_TiC and liquid interaction parameters of the Ti-Cr-C system was performed taking into account the experimental data obtained both from previous studies and this work. The Gibbs energy descriptions of the Cr-carbide end members were compared between the one from the in-house database [SandvikTDB] and from other studies. With the new description, the solubility of Cr in FCC_TiC is better described.

  • 141. Healy, Noel
    et al.
    Gibson, Ursula
    Norwegian Univ of Science and Technol..
    Peacock, Anna
    A review of materials engineering in silicon-based optical fibresIngår i: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Semiconductor optical fibre technologies have grown rapidly in the last decade and there are now a range of production and post-processing techniques that allow for a vast degree of control over the core material's optoelectronic properties. These methodologies and the unique optical fibre geometry provide an exciting platform for materials engineering and fibres can now be produced with single crystal cores, low optical losses, tunable strain, and inscribable phase composition. This review discusses the state-of-the-art regarding the production of silicon optical fibres in amorphous and crystalline form and then looks at the post-processing techniques
 and the improved material quality and new functionality that they afford.

  • 142.
    Hedberg, Yolanda
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    Znidarsic, Monika
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap. Univ Ljubljana, Fac Chem & Chem Technol, Vecna Pot 113, SI-1000 Ljubljana, Slovenia.
    Herting, Gunilla
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    Milosev, Ingrid
    Odnevall Wallinder, Inger
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    Mechanistic insight on the combined effect of albumin and hydrogen peroxide on surface oxide composition and extent of metal release from Ti6Al4V2019Ingår i: Journal of Biomedical Materials Research - Part B Applied Biomaterials, ISSN 1552-4973, Vol. 107, nr 3, s. 858-867Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The titanium–aluminium (6 wt%)–vanadium (4 wt%) (Ti6Al4V) alloy is widely used as an orthopedic and dental implant material due to its high corrosion resistance in such environments. The corrosion resistance is usually determined by means of electrochemical methods, which may not be able to detect other chemical surface reactions. Literature findings report a synergistic effect of the combination of the abundant protein albumin and hydrogen peroxide (H 2 O 2 ) on the extent of metal release and corrosion of Ti6Al4V. The objectives of this study were to gain further mechanistic insight on the interplay of H 2 O 2 and albumin on the metal release process of Ti6Al4V with special focus on (1) kinetics and (2) H 2 O 2 and albumin concentrations. This was accomplished mainly by metal release and surface oxide composition investigations, which confirmed the combined effect of H 2 O 2 and albumin on the metal release process, although not detectable by electrochemical open circuit potential measurements. A concentration of 30 mM H 2 O 2 induced substantial changes in the surface oxide characteristics, an oxide which became thicker and enriched in aluminum. Bovine serum albumin (BSA) seemed to be able to deplete this aluminum content from the outermost surface or at least to delay its surface enrichment. This effect increased with increased BSA concentration, and for time periods longer than 24 h. This study hence suggests that short-term (accelerated) corrosion resistance measurements are not sufficient to predict potential health effects of Ti6Al4V alloys since also chemical dissolution mechanisms play a large role for metal release, possibly in a synergistic way.

  • 143. Hein, Hieronymus
    et al.
    Keim, Elisabeth
    Bechler, Eduoard
    Efsing, Pål
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Ganswind, Jens
    Knobel, René
    König, Günter
    Barriero, Pablo
    Widera, Martin
    de Jong, André
    CARINA: A program for experimental investigation of the irradiation behaviour of German Reactor Pressure Vessel materials2013Ingår i: ATW. Internationale Zeitschrift für Kernenergie, ISSN 1431-5254, Vol. 58, nr 5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The proof of a sufficient safety margin against brittle fracture of the reactor pressure vessel (RPV) is an important part of the operational safety of nuclear power plants. The RPV safety assessment procedure applicable in Germany is described in KTA 3201.2 of the Nuclear Safety Standard Commission (KTA). This deterministic assessment concept is based on the comparison of load curves with the material resistance curve in terms of fracture toughness. The fracture toughness curve can be determined either indirectly according to the RT-(NDT) concept based on Charpy tests or directly according to the more appropriate RTT0 approach based on Master Curve analysis of fracture toughness tests, respectively. In the recently completed research project CARINA the data base for pre-irradiated original RPV steels of German PWR construction lines was extended by comprehensive fracture toughness testing. The data obtained up to neutron fluences of 7.67 x 10(19) n/cm(2) (E > 1 MeV) are analysed and discussed particularly in terms of Master Curve applications. The experimental results show that optimized RPV manufacturing specifications and reactor designs are advantageous for a long-term plant operation in comparison to less optimized materials with lower toughness and to reactor designs with substantial higher neutron irradiation. With the obtained data, experiences and insights an essential contribution was also made to the integration of the Master Curve concept in German safety standards.

  • 144.
    Heintz, Sofia
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Muscular forces from static optimization2006Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    At every joint there is a redundant set of muscle activated during movement or loading of the system. Optimization techniques are needed to evaluate individual forces in every muscle. The objective in this thesis was to use static optimization techniques to calculate individual muscle forces in the human extremities.

    A cost function based on a performance criterion of the involved muscular forces was set to be minimized together with constraints on the muscle forces, restraining negative and excessive values. Load-sharing, load capacity and optimal forces of a system can be evaluated, based on a description of the muscle architectural properties, such as moment arm, physiological cross-sectional area, and peak isometric force.

    The upper and lower extremities were modelled in two separate studies. The upper extremity was modelled as a two link-segment with fixed configurations. Load-sharing properties in a simplified model were analyzed. In a more complex model of the elbow and shoulder joint system of muscular forces, the overall total loading capacity was evaluated.

    A lower limb model was then used and optimal forces during gait were evaluated. Gait analysis was performed with simultaneous electromyography (EMG). Gait kinematics and kinetics were used in the static optimization to evaluate of optimal individual muscle forces. EMG recordings measure muscle activation. The raw EMG data was processed and a linear envelope of the signal was used to view the activation profile. A method described as the EMG-to-force method which scales and transforms subject specific EMG data is used to compare the evaluated optimal forces.

    Reasonably good correlation between calculated muscle forces from static optimization and EMG profiles was shown. Also, the possibility to view load-sharing properties of a musculoskeletal system demonstrate a promising complement to traditional motion analysis techniques. However, validation of the accurate muscular forces are needed but not possible.

    Future work is focused on adding more accurate settings in the muscle architectural properties such as moment arms and physiological cross-sectional areas. Further perspectives with this mathematic modelling technique include analyzing pathological movement, such as cerebral palsy and rheumatoid arthritis where muscular weakness, pain and joint deformities are common. In these, better understanding of muscular action and function are needed for better treatment.

  • 145.
    Heintz, Sofia
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Gutierrez-Farewik, Elena
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Static optimization of muscle forces during gait in comparison to EMG-to-force processing approach2007Ingår i: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 26, nr 2, s. 279-288Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Individual muscle forces evaluated from experimental motion analysis may be useful in mathematical simulation, but require additional musculoskeletal and mathematical modelling. A numerical method of static optimization was used in this study to evaluate muscular forces during gait. The numerical algorithm used was built on the basis of traditional optimization techniques, i.e., constrained minimization technique using the Lagrange multiplier method to solve for constraints. Measuring exact muscle forces during gait analysis is not currently possible. The developed optimization method calculates optimal forces during gait, given a specific performance criterion, using kinematics and kinetics from gait analysis together with muscle architectural data. Experimental methods to validate mathematical methods to calculate forces are limited. Electromyography (EMG) is frequently used as a tool to determine muscle activation in experimental studies on human motion. A method of estimating force from the EMG signal, the EMG-to-force approach, was recently developed by Bogey et al. [Bogey RA, Perry J, Gitter AJ. An EMG-to-force processing approach for determining ankle muscle forcs during normal human gait. IEEE Trans Neural Syst Rehabil Eng 2005;13:302-10] and is based on normalization of activation during a maximum voluntary contraction to documented maximal muscle strength. This method was adapted in this study as a tool with which to compare static optimization during a gait cycle. Muscle forces from static optimization and from EMG-to-force muscle forces show reasonably good correlation in the plantarflexor and dorsiflexor muscles, but less correlation in the knee flexor and extensor muscles. Additional comparison of the mathematical muscle forces from static optimization to documented averaged EMG data reveals good overall correlation to patterns of evaluated muscular activation. This indicates that on an individual level, muscular force patterns from mathematical models can arguably be more accurate than from those obtained from surface EMG during gait, though magnitude must still be validated.

  • 146.
    Heintz, Sofia
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Gutierrez-Farewik, Elena
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Eriksson, Anders
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Evaluation of load-sharing and load capacity in force-limited muscle systems2006Ingår i: Computer Methods in Biomechanics and Biomedical Engineering, ISSN 1025-5842, E-ISSN 1476-8259Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    This study had the objective to develop an algorithm for accurate force decomposition in a redundant musculoskeletal system. The hypothesis was that the calculated load-sharing is dependent on the optimality criterion adopted, but also on the magnitude of carried load. The developed algorithm emphasizes that several established optimization techniques can be unified, by identifying and separating the underlying optimization functions and the numerical methods to solve the resulting system. A numerically efficient and easily adaptable solution method is thereby created. In addition, individual capacity values are introduced for the muscles, allowing the evaluation of a magnitude-dependent load-sharing, and a load carrying capacity of the whole system. By modularizing the optimization method, the algorithm can be used as part of larger simulation systems. To illustrate the possibilities of the algorithm, a model of the upper limb is used in a set of demonstrative examples. The results from the examples show how the interactions between synergistic muscles is predicted in different configurations, and at different load levels.

  • 147.
    Hellberg, Per
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    A model of gas injection into a blast furnace tuyere2005Licentiatavhandling, monografi (Övrigt vetenskapligt)
  • 148.
    Hellström, Per-Erik
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Dentoni Litta, Eugenio
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Interfacial layer engineering using thulium silicate/germanate for high-k/metal gate MOSFETs2014Ingår i: ECS Transactions: Cancun, Mexico, October 5 – 9, 2014 2014 ECS and SMEQ Joint International Meeting, Electrochemical Society, 2014, nr 6, s. 249-260Konferensbidrag (Refereegranskat)
    Abstract [en]

    Thulium silicate (TmSiO) is considered as high-k interfacial layer in high-k/metal gate stacks, providing advantages in terms of EOT scalability and enhanced inversion layer mobility. In this work, we show that optimized annealing conditions for the TmSiO/HfO2/TiN gate stack provide competitive gate leakage current density, symmetric nFET and pFET threshold voltages, while retaining compatibility with CMOS processing and ∼20% higher electron and hole mobility than literature data on optimized SiOx/HfO2 stacks at EOT as low as 0.65 nm. We also evaluate cleaning procedures to facilitate thulium germanate formation on Ge channel materials and found that HF cleaning optimization is needed to allow thulium germanate formation while keeping surface roughness at an acceptable level.

  • 149.
    Heng, Piseth
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap. Université Européenne de Bretagne, France.
    Bud, M.
    Somja, H.
    Hjiaj, M.
    Battini, Jean-Marc
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggteknik och design.
    Residual stiffness and strength of shear connectors in steel-concrete composite beams after being subjected to a pull-out pre-damaging: An experimental investigation2017Ingår i: Structures, ISSN 2352-0124, Vol. 11, s. 189-205Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Horizontal stability of the medium rise steel frame structures is usually ensured by vertical bracings and diaphragm action of composite floors. Load transfer within the composite floor system is made through shear connectors, e.g. headed studs. In an event of explosion, such connectors must reserve sufficient residual stiffness and strength in order to avoid a sudden or delayed collapse of the building. These remaining capacities have not been experimentally studied yet in the literature. This paper presents large scale horizontal push out tests to determine the residual stiffness of the shear connectors after being initially damaged by explosion. The initial damaging is reproduced by a pull-out test using a quasi-static loading. Two types of numerical simulation have also been developed using ABAQUS/CAE software to provide a better understanding of the experimental results.

  • 150.
    Hermansson, Henry
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Arnelo, Albin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Salomonsson, Axel
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Recycling of E-waste using pyrolysis to enhance separation of important materials: A study on pyrolysis applicability at Rönnskärsverken, Boliden2018Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    I dagsläget genereras och slängs stora mängder elektroniskt avfall världen över. Detta har resulterat i ett globalt miljöproblem då elektroniskt avfall innehåller olika giftiga ämnen, vilka kan frigöras till omgivningen då det elektroniska avfallet behandlas. Därför är utvecklingen av gynnsamma metoder gällande återviningen av eletroniskt avfall nödvändig.

    Försök görs av Boliden för att studera nya sätt att skilja ut råvaror från elektronikskrot. I denna rapport har återvinningsvägen för elektroniskt avfall vid Boliden, Rönnskärsverken, studerats. Även pyrolysprocessen har undersökts specifikt för att identifiera de möjliga tekniska förbättringar som denna process kan bidra med till den nuvarande återvinningsvägen. Pyrolys är en metod för att termiskt sönderdela material i en syrefri miljö, vilket ger upphov till att de tre biprodukterna kol/ metallmassa, bioolja och en blandning av gaser kan utvinnas på ett kontrollerat sätt. Detta bidrar huvudsakligen till möjligheten att återvinna olika plastmaterial från elektronikskrot.

    Metoden för detta projekt bestod av flera laborationer av pyrolys, kombinerat med en rundtur på Rönnskärsverken och en litteraturstudie för att generera tillräckligt med information. Experimenten, utförda vid 300, 400 och 500 grader Celsius, visade det starka beroendet mellan mängden erhållna biprodukter och temperaturen. För att få en förståelse för de olika ämnena i biooljan och gasen gjordes även en teknisk analys av biprodukterna från pyrolysen.

    Sammanfattningsvis tillhandahåller pyrolysen förmågan att separera aluminium från koppar vid återvinning av elektronikskrot, vilket bidrar till att aluminium till större del kan utvinnas. Vidare bidrar även pyrolys till en hög återvinningsgrad av plaster då dessa kan erhållas som biprodukter på ett kontrollerat sätt.

    Ett förslag kan vara att använda pyrolys parallellt med den nuvarande återvinningsprocessen i Rönnskärsverken, för att skapa en större effektivitet vid återvinning av de önskade komponenterna i det elektroniska avfallet.

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