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  • 3051.
    Akbarnejad, Shahin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Investigation on static strength of welded joints2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Although high strength steels represent yield strength up to 1300 MPa, welded structures reveal lowerstrength values. The strongest commercially available electrode provides the yield strength of about900 MPa. Therefore, in welded steels with strength above this type of filler metal, achieving anacceptable global strength is a crucial issue.

    In this master thesis, affects of different welding procedures on static strength of welded jointsof Weldox 960 and Weldox 1100 steels, were studied. These steels are produced by SSAB inOxelösund. Meanwhile, finite element method analyses were applied in order to investigatethe static strength behavior of such weldments under uniaxial tension.

    The welding parameters which were selected as variables are:

    •  Heat input
    • Weld joint geometry
    • Filler metal

    When weld metal is undermatching in strength levels than the base material, by applyingtension the soft weld metal begins to deform before parent metal. At that point thedeformation of resulted soft zone, including the weld metal and the heat affected zone, ishindered by high strength parent metal. Thus, uniaxial stress caused by uniaxial load isconverted to multiaxial stress. This conversion in tension results in increase in the staticstrength of weldment. The increase in strength is emphasized by increase in the width of thewelded joint while the thickness of the plate is kept as constant.

    After experiments and performing FEM studies, it was revealed that the static strength ofWeldox 960 welded joints approaches towards the tensile strength of parent metal by increasein the width of the weldment. In Weldox 1100 joints; a slight increase in tensile properties ofthe weldments, when the width of the sample increases, was observed.

  • 3052.
    Akbarnejad, Shahin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Lage
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Kennedy, M. W.
    Aune, R. E.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Analysis on Experimental Investigation and Mathematical Modelling of Incompressible Flow through Ceramic Foam FiltersManuscript (preprint) (Other academic)
  • 3053.
    Akbarnejad, Shahin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jonsson, Lage Tord Ingemar
    Kennedy, Mark William
    Aune, Ragnhild Elizabeth
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Analysis on Experimental Investigation and Mathematical Modeling of Incompressible Flow Through Ceramic Foam Filters2016In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 47, no 4, p. 2229-2243Article in journal (Refereed)
    Abstract [en]

    This paper presents experimental results of pressure drop measurements on 30, 50, and 80 pores per inch (PPI) commercial alumina ceramic foam filters (CFF) and compares the obtained pressure drop profiles to numerically modeled values. In addition, it is aimed at investigating the adequacy of the mathematical correlations used in the analytical and the computational fluid dynamics (CFD) simulations. It is shown that the widely used correlations for predicting pressure drop in porous media continuously under-predict the experimentally obtained pressure drop profiles. For analytical predictions, the negative deviations from the experimentally obtained pressure drop using the unmodified Ergun and Dietrich equations could be as high as 95 and 74 pct, respectively. For the CFD predictions, the deviation to experimental results is in the range of 84.3 to 88.5 pct depending on filter PPI. Better results can be achieved by applying the Forchheimer second-order drag term instead of the Brinkman-Forchheimer drag term. Thus, the final deviation of the CFD model estimates lie in the range of 0.3 to 5.5 pct compared to the measured values.

  • 3054.
    Akbarnejad, Shahin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Kennedy, M. W.
    Fritzsch, R.
    Aune, R. E.
    An investigation on permeability of ceramic foam filters (CFF)2015In: TMS Light Metals, 2015, p. 949-954Conference paper (Refereed)
    Abstract [en]

    CFFs are used to filter liquid metal in the aluminum industry. CFFs are classified in grades or pores per inch (PPI), ranging from 10-100 PPI. Their properties vary in everything from pore and strut size to window size. CFFs of 80-100 PPI are generally not practical for use by industry, as priming of the filters by gravitational forces requires an excessive metal head. Recently, co-authors have invented a method to prime such filters using electromagnetic Lorentz forces, thus allowing filters to be primed with a low metal head. In the continuation of this research work, an improved experimental setup was developed in the present study to validate previous results and to measure the permeability of different filters, as well as a stack of filters. The study of permeability facilitates estimation of the required pressure drop to prime the filters and the head required to generate a given casting rate.

  • 3055.
    Akbarnejad, Shahin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Saffari Pour, Mohsen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Lage
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Significance of Fluid Bypassing Effect on Darcy and Non-Darcy Permeability Parameters of Ceramic Foam FiltersManuscript (preprint) (Other academic)
  • 3056.
    Akbarnejad, Shahin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Saffari Pour, Mohsen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jonsson, Lage Tord Ingemar
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pӓr Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Effect of Fluid Bypassing on the Experimentally Obtained Darcy and Non-Darcy Permeability Parameters of Ceramic Foam Filters2017In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 48, no 1, p. 197-207Article in journal (Refereed)
    Abstract [en]

    Ceramic foam filters (CFFs) are used to remove solid particles and inclusions from molten metal. In general, molten metal which is poured on the top of a CFF needs to reach a certain height to build the required pressure (metal head) to prime the filter. To estimate the required metal head, it is necessary to obtain permeability coefficients using permeametry experiments. It has been mentioned in the literature that to avoid fluid bypassing, during permeametry, samples need to be sealed. However, the effect of fluid bypassing on the experimentally obtained pressure gradients seems not to be explored. Therefore, in this research, the focus was on studying the effect of fluid bypassing on the experimentally obtained pressure gradients as well as the empirically obtained Darcy and non-Darcy permeability coefficients. Specifically, the aim of the research was to investigate the effect of fluid bypassing on the liquid permeability of 30, 50, and 80 pores per inch (PPI) commercial alumina CFFs. In addition, the experimental data were compared to the numerically modeled findings. Both studies showed that no sealing results in extremely poor estimates of the pressure gradients and Darcy and non-Darcy permeability coefficients for all studied filters. The average deviations between the pressure gradients of the sealed and unsealed 30, 50, and 80 PPI samples were calculated to be 57.2, 56.8, and 61.3 pct. The deviations between the Darcy coefficients of the sealed and unsealed 30, 50, and 80 PPI samples found to be 9, 20, and 31 pct. The deviations between the non-Darcy coefficients of the sealed and unsealed 30, 50, and 80 PPI samples were calculated to be 59, 58, and 63 pct.

  • 3057.
    Akbarpour, S.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Hallström, S.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Metal reinforcement around fastener holes in composites2016In: ECCM 2016 - Proceeding of the 17th European Conference on Composite Materials, European Conference on Composite Materials, ECCM , 2016Conference paper (Refereed)
    Abstract [en]

    One way of improving the load capacity of bolted joints in composite components is to use metal inserts locally at the holes in order to reduce the bearing stress. In this paper an innovative local reinforcement concept is introduced where metal inserts are implemented in the form of stacked patches at the holes in order to improve the bearing strength of the composite. After doing some initial tests and a parameter study, some specimens with optimized stacked patch inserts were designed and tested. The specimens with optimized inserts show 50-60% improved bearing strength in pin-loaded tests which corresponds to a potential weight reduction of about 30%. These very promising results indicates that the efficiency of joints in composites can be improved significantly.

  • 3058.
    Akbarpour, Sahar
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Hallström, Stefan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Reinforcement around holes in composite materials by use of patched metal inserts2019In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 225, article id 111084Article in journal (Refereed)
    Abstract [en]

    Metal inserts are sometimes used to improve the load carrying capacity of bolted joints in composite materials. In this paper a new concept is introduced where inserts are built during composite manufacturing by integrating stacked metal patches at locations where holes are to be made after consolidation. Initial tests and a parameter study enable more informed design, and specimens with improved stacked inserts are then produced and tested. The specimens with inserts show up to 60% strength improvement in pin-loaded tests. In addition to the experimental work, finite element analysis is performed to investigate the stress fields and the failure mechanisms. The model indicates that the singular stresses at the multi-material corner points are governing for the strength and give indications of the failure mechanisms. Some basic analytical estimates are also presented.

  • 3059.
    Akbary, Amir
    et al.
    Univ Lethbridge, Dept Math & Comp Sci, 4401 Univ Dr, Lethbridge, AB T1K 3M4, Canada..
    Parks, James
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.). Univ Lethbridge, Dept Math & Comp Sci, 4401 Univ Dr, Lethbridge, AB T1K 3M4, Canada.
    On the Lang-Trotter conjecture for two elliptic curves2019In: Ramanujan Journal, ISSN 1382-4090, Vol. 49, no 3, p. 585-623Article in journal (Refereed)
    Abstract [en]

    Following Lang and Trotter, we describe a probabilistic model that predicts the distribution of primes p with given Frobenius traces at p for two fixed elliptic curves over Q. In addition, we propose explicit Euler product representations for the constant in the predicted asymptotic formula and describe in detail the universal component of this constant. A new feature is that in some cases the l-adic limits determining the l-factors of the universal constant, unlike the Lang-Trotter conjecture for a single elliptic curve, do not stabilize. We also prove the conjecture on average over a family of elliptic curves, which extends the main results of Fouvry and Murty (Supersingular primes common to two elliptic curves, number theory (Paris, 1992), London Mathematical Society Lecture Note Series, vol 215, Cambridge University Press, Cambridge, 1995) and Akbary et al. (Acta Arith 111(3):239-268, 2004), following the work of David et al. (Math Ann 368(1-2):685-752, 2017).

  • 3060. Akbarzadeh, Sara
    et al.
    Combes, Richard
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Altman, Zwi
    Self-organizing femtocell offloading at the flow level2013In: International Journal of Network Management, ISSN 1055-7148, E-ISSN 1099-1190, Vol. 23, no 4, p. 259-271Article in journal (Refereed)
    Abstract [en]

    Femtocell technology is expected to be fully self-managed, empowered by self-organizing network functionalities. This paper proposes a solution for self-optimized offloading of macrocell traffic towards open/hybrid-access femtocells. A heterogeneous network comprising macro- and femtocells is modeled as parallel queues. The coverage area of the femtocells is self-optimized by dynamically adapting their pilot powers. A simple update equation for the pilot power is given and its convergence is studied using stochastic approximation techniques. The algorithm balances the load among the cells to improve network capacity. Simulation results illustrate the important performance gains brought about by the proposed scheme, using a dynamic network simulator.

  • 3061. Akcay, H.
    et al.
    Hjalmarsson, Håkan
    Department of Electrical Engineering, Linköping University.
    Ljung, Lennart
    Department of Electrical Engineering, Linköping University.
    On the choice of norms in system identification1996In: IEEE Transactions on Automatic Control, ISSN 00189286 (ISSN), Vol. 41, no 9, p. 1367-1372Article in journal (Refereed)
    Abstract [en]

    In this paper we discuss smooth and sensitive norms for prediction error system identification when the disturbances are magnitude bounded. Formal conditions for sensitive norms, which give an order of magnitude faster convergence of the parameter estimate variance, are developed. However, it also is shown that the parameter estimate variance convergence rate of sensitive norms is arbitrarily bad for certain distributions. A necessary condition for a norm to be statistically robust with respect to the family F(C) of distributions with support [-C, C] for some arbitrary C > 0 is that its second derivative does not vanish on the support. A direct consequence of this observation is that the quadratic norm is statistically robust among all ℓp-norms, p ≀ 2 < ∞ for F(C). ©1996 IEEE.

  • 3062.
    Akdis, M
    et al.
    SIAF, Switzerland.
    Verhagen, J
    SIAF, Switzerland.
    Taylor, A
    SIAF, Switzerland.
    Karamloo, F
    SIAF, Switzerland.
    Karagiannidis, C
    SIAF, Switzerland.
    Crameri, R
    SIAF, Switzerland.
    Thunberg, Sarah
    Karolinska Institutet.
    Deniz, G
    SIAF, Switzerland.
    Valenta, R
    SIAF, Switzerland.
    Fiebig, H
    SIAF, Switzerland.
    Kegel, C
    SIAF, Switzerland.
    Disch, R
    SIAF, Switzerland.
    Schmidt-Weber, C B
    SIAF, Switzerland.
    Blaser, K
    SIAF, Switzerland.
    Akdis, C A
    SIAF, Switzerland.
    Immune responses in healthy and allergic individuals are characterized by a fine balance between allergen-specific T regulatory 1 and T helper 2 cells2004In: Journal of Experimental Medicine, ISSN 0022-1007, E-ISSN 1540-9538, Vol. 199, no 11, p. 1567-1575Article in journal (Refereed)
    Abstract [en]

    The mechanisms by which immune responses to nonpathogenic environmental antigens lead to either allergy or nonharmful immunity are unknown. Single allergen-specific T cells constitute a very small fraction of the whole CD4(+) T cell repertoire and can be isolated from the peripheral blood of humans according to their cytokine profile. Freshly purified interferon-gamma-, interleukin (IL)-4-, and IL-10-producing allergen-specific CD4(+) T cells display characteristics of T helper cell (Th)1-, Th2, and T regulatory (Tr)1-like cells, respectively. Tr1 cells consistently represent the dominant subset specific for common environmental allergens in healthy individuals; in contrast, there is a high frequency of allergen-specific IL-4-secreting T cells in allergic individuals. Tr1 cells use multiple suppressive mechanisms, IL-10 and TGF-beta as secreted cytokines, and cytotoxic T lymphocyte antigen 4 and programmed death 1 as surface molecules. Healthy and allergic individuals exhibit all three allergen-specific subsets in different proportions, indicating that a change in the dominant subset may lead to allergy development or recovery. Accordingly, blocking the suppressor activity of Tr1 cells or increasing Th2 cell frequency enhances allergen-specific Th2 cell activation ex vivo. These results indicate that the balance between allergen-specific Tr1 cells and Th2 cells may be decisive in the development of allergy.

  • 3063.
    Akdogan, Mariam
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Baghdo, Gabriella
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Utvärdering och effektivisering av byggprocessen på Projektgaranti AB2012Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The ame of this examination thesis is to evaluate the operation system at the company Projektgaranti AB and find different approaches and solutions on how to streamline the construction process. The purpose of evaluating the operational system is to get an understanding of Projektgaranti ABs way to work and investigate the use of the system.To carry out this study, we determined three different methods of evaluation that must be done in order to get a broad perspective at the opportunities that the system has to develop. This took the form of sample survey based on five selected projects from the company server. After that a questionnaire was sent out to all employees of the company in Stockholm and Gothenburg. Based on the answers we received we selected two employees from each office to be interviewed.The evaluation result shows the employees' opinions about the system, various improvement and development.To make the construction process more efficient is based on various research techniques. The one which we found to be most profitable for the company's development was the Lean Production, which includes showing different types of waste that can be avoided, how to create value and better planning. If you do it visually and include teamwork and commitment it will lead to a more efficient construction.

  • 3064. Akerman, J. J.
    et al.
    Venturini, E. L.
    Siegal, M. P.
    Yun, S. H.
    Karlsson, U. O.
    Rao, K. V.
    KTH, Superseded Departments, Materials Science and Engineering.
    Two-stage crossover from thermal to quantum flux creep of dilute vortex ensembles in various high-T-c superconducting thin films2001In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 64, no 9Article in journal (Refereed)
    Abstract [en]

    The thermal-to-quantum flux creep crossover at low vortex densities has been studied in YBa2Cu3O7, TlBa2CaCu2O7-delta, and HgBa2CaCu2O6+delta thin films using ac susceptibility. The crossover temperatures T-cr are 10-11, 17, and 30 K, respectively. Both thermal and quantum flux creep is suppressed as the vortex density is decreased. We observe a two-stage nature in the crossover behavior which appears to be a general property of all the three materials studied.

  • 3065. Akerman, J. J.
    et al.
    Yun, S. H.
    Karlsson, U. O.
    Rao, K. V.
    KTH, Superseded Departments, Materials Science and Engineering.
    Dislocation-mediated creep of highly separated vortices in a-axis-oriented HgBa2CaCu2O6+delta thin films2001In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 64, no 2Article in journal (Refereed)
    Abstract [en]

    Using ac susceptibility, we determine the critical current density J(c) and the flux creep activation energy U of an a-axis-oriented HgBa2CaCu2O6+delta thin film. The critical current density at helium temperatures is found to be 4.6 x 10(4) A/cm(2), i.e., about two orders of magnitude smaller than for corresponding films with c-axis orientation. The temperature and ac field dependent activation energy is consistent with dislocation-mediated flux creep and well described by U(T,H-ac)=U-o(1-t(4))H-ac(-1/2) with t=T/T-c, T-c=120K, and U-o = 0.77 eV Oe(1/2) for temperatures T>45 K and in the field range studied. The activation energy is of the same order as that found in c-axis-oriented films. Below T = 45 K the activation energy is observed to decrease as thermally assisted quantum creep becomes increasingly important.

  • 3066. Akesson, M.
    et al.
    Gustafsson, E.
    Johansson, Karl Henrik
    Control design for a helicopter lab process1996Conference paper (Refereed)
  • 3067.
    Akeyo Forsman, Prisca
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    A Study of Construction Project Stakeholders’ Management Methods and the Critical Success Factors Essential for Successful Management in Stockholm Region.2017Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
  • 3068.
    Akfidan, Johny
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Sadek, Rafed
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Dimensionering och utförande av bottenplattor utsatta för upptryck2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    När en konstruktion byggs på det viset att dess bottenplatta hamnar under grundvattenytan, skapas ett grundvattentryck upp mot bottenplattan och konstruktionen, som kan åstadkomma stora problem. Grundvattnet, som tryckts undan av konstruktionen, vill nå upp till sin ursprungliga nivå och därmed trycka med sig konstruktionen upp. Detta fenomen kallas hydraulisk bottenupptryckning. Fenomenet kan motverkas på olika sätt, där rapporten beaktar två olika sätt att motverka hydraulisk bottenupptryckning på: genom en bottenplatta som är tyngre än grundvattentrycket eller förankra bottenplattan mot ett fast underlag.

    Genom att uppmärksamma och sammanställa projekt (huvudsakligen konstruerade av Tyréns) som tagit hänsyn till ovan nämnda fenomen vid dimensioneringen av bottenplattan, har en rapport skapats. Denna rapport ska finnas för att åstadkomma kunskapsåterföring av de problem som uppstått i projekten och deras lösningar.

    Utöver att skapa en rapport där de berörda projekten sammanställs ska en bottenplatta optimeras, huvudsakligen med hänseende till bottenplattans tjocklek och dess bärförmåga mot genomstansning för olika förankringstyper. Optimeringen ska ske i enlighet med, huvudsakligen Eurokod 2 kapitlen 6.4 och 7.3. Det har bestämts att tre tjocklekar på bottenplattan ska beaktas, och dessa är 400, 550 och 800 mm. Genom diskussioner med våra handledare, sakkunnig personal på Tyréns och representanter inom branschen, valdes ett antal förankringstyper som skulle jämföras. För att kunna jämföra kombinationerna av de olika tjocklekarna på bottenplattan och de olika förankringstyperna, har Tyréns projekt Biomedicum med dess förutsättningar, utnyttjats som referensobjekt.

    Att ta fram de inre krafterna i bottenplattan via handberäkningar är mycket komplicerat och tidskrävande för att rymmas inom ramen för denna studie. Därför används programmet FEM Plate (Strusoft) för att ta fram dessa krafter. De inre krafter som tas fram från FEM Plate utnyttjas sedan för att med hjälp av handberäkningar, i enlighet Eurokod 2, dimensionera Biomedicums bottenplatta enligt de moment som krävs.

    Jämförelsen av de olika kombinationerna visar på att bottenplattan 400 mm med förankringstypen stålkärna av diameter 80 mm från Inexa Profil är den optimala lösningen för Biomedicums bottenplatta. Denna förankringstyp (för bottenplattan 400 mm) är den enda som får en tillräcklig bärförmåga mot genomstansning av bottenplattan, endast med åtgärden skjuvarmering runtomkring förankringen.

    En föreslagen lösning på hur förankringstypen bör monteras i bottenplattan har tagits fram. Diskussioner med sakkunnig personal från Minova (tillverkare av MAI-förankringen) har lett till övertygelsen om att föreslagen lösning fungerar utan några kapacitetsförsämringar på förankringen. En modellering av bottenplattan 400 mm med föreslagen lösning på MAIförankringen och efterföljande handberäkningar, visar att lösningen optimerar bottenplattan än mer. föreslagen lösning på monteringen i bottenplattan bör dessutom kunna tillämpas på de andra förankringstyperna, men har endast beaktats för MAI-förankringen.

    Eftersom fokus endast är på att den optimala bottenplattan är 400 mm och ingen hänsyn tas till kostnaderna, är föreslagen lösning på MAI-staget den optimala lösningen. Det är den enda förankringen som har en tillräcklig bärförmåga mot genomstansning för bottenplattan 400 mm, utan några som helst extra åtgärder.

    En bottenplatta med vot under förankringen bör undvikas, eftersom förtjockningen av bottenplattan under förankringen kräver mycket extra tid i utförande. Därför rekommenderas det att en jämntjock bottenplatta dimensioneras med eventuell skjuvarmering, om bottenplattans bärförmåga mot genomstansning inte är tillräcklig utan skjuvarmering.

    Den optimering som tagits fram är en generalisering av Biomedicums bottenplatta. Detta leder till att de modeller och beräkningar som gjorts, enkelt kan implementeras på andra bottenplattor med samma problem genom att justera indata.

  • 3069.
    Akhand, Victoria
    KTH, School of Chemical Science and Engineering (CHE).
    Mass Balance Model of Impurities for the WoodRoll Process2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The depletion time for fossil fuels calculated from 2009 is 35 years for oil, 37 years for gas

    and 107 years for coal. Hence, it has become essential to reduce the dependence on fossil

    fuels by switching over to renewable resources. This in turn will also help in combating the

    negative effects on the environment like global warming. Thermochemical processes such as

    pyrolysis and gasification of biomass are considered the most efficient technology for

    converting biomass to useful energy carriers. Cortus Energy AB is a Swedish company that

    has developed a patented gasification technology called WoodRoll

    ® for gasification of fuels derived from biomass. However, ash in a thermochemical conversion process can cause

    corrosion, sintering, slag and poisoning of catalysts, which leads to operational problems. In

    addition, heavy metals such as Zn, Pb and Cd are environmentally problematic. These metals

    contribute to environmental pollution by contaminating the soil, which in turn can harm

    humans and the ecosystem via the food chain. The undesired elements should therefore be

    identified to minimize their impact on the overall thermochemical process and to reduce the

    emission of these harmful substances.

    The objective of this master thesis project, on behalf of Cortus Energy AB, was to investigate

    possible key numbers that can be used to describe and predict how the ash behaves in their

    patented WoodRoll® process. The key numbers that have been identified are empirically

    developed based on experience of coal combustion. These key numbers are regularly used for

    fuel derived from biomass by companies specializing in analyzing, although knowledge about

    whether they can actually be used on biomass is limited. In order to ensure that the use of

    these for biomass is correct, they must be experimentally verified in the future. In addition, a

    theoretical investigation is conducted to study which species can form and in what phase this

    occurs. The investigation reveals that there are no clear trends for how the inorganic elements

    behave since contradicting results from different studies have been reported. Formation of

    species and their phase depends on several parameters such as temperature, heating rate,

    particle size, volatility, quantity and interaction between the elements in the biomass. The

    thesis project ends with a mass balance model on selected inorganic elements for wood

    residues, as well as for bark. The model could be a tool for Cortus Energy AB to identify

    approximately how much of each element is present in each stream in the WoodRoll® process.

    The models are verified with analysis results. Inorganic elements that affect the

    overall process and its equipment have been selected for modelling. The volume percent of

    H2, CO, CO2 and CH4 in the models agree well with the values obtained by Cortus Energy

    AB. This shows that the thermodynamic equilibrium calculations performed are reasonable.

  • 3070.
    Akhand, Victoria
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Celsi, Adrian
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Lagerberg, Tove
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Sångberg, Oscar
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Plastfilm från rapshalm2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of this project is to extract hemicellulose from the rape straw by using alkali- and water extraction, and thereafter to produce a film with these polymers. The intention with this film is to eventually replace the present oxygen barrier made of aluminium in applications such as food packaging made of cardboard, among other things. The film is composed of hemicellulose and additives, either the CMC or sorbitol molecules. Many analyses were conducted on the extracts and the films in order to draw conclusions about the structure and properties. The NMR analysis showed that the extracts contained the expected sugars and that the main deacetylation of O-acetyl groups happened during the extraction with low alkali. The SEC analysis gave low values of Đ. The tensile testing gave exceptional results, namely elongations of 10-60%, depending on the composition of the films. Two of the most significant analyses are the ion chromatography and the oxygen permeability test, which could not be implemented because of technical difficulties. Low alkali is to be preferred as solvent, used to extract the polymers, with respect to the environment, the economy and the mechanical properties. Furthermore, high addition of CMC is preferred when producing films because low CMC and sorbitol resulted in sticky films. For future work it would be recommended to analyse the films by conducting the ion chromatography and the oxygen permeability test. Additionally, it would be desirable to find the optimal addition amount of the CMC.

  • 3071. Akhi, Ramin
    et al.
    Wang, Chunguang
    Kyrklund, Mikael
    Kummu, Outi
    Turunen, Sini Pauliina
    Hyvärinen, Kati
    Kullaa, Arja
    Salo, Tuula
    Pussinen, Pirkko J
    Hörkkö, Sohvi
    Cross-reactive saliva IgA antibodies to oxidized LDL and periodontal pathogens in humans.2017In: Journal of Clinical Periodontology, ISSN 0303-6979, E-ISSN 1600-051X, Vol. 44, no 7, p. 682-691Article in journal (Refereed)
    Abstract [en]

    AIM: Oxidized low-density lipoproteins (oxLDL) are formed as a result of lipid peroxidation and are highly immunogenic and proatherogenic. In this study, saliva antibodies binding to oxLDL, Porphyromonas gingivalis (Pg) and Aggregatibacter actinomycetemcomitans (Aa) were characterized and their cross-reactivity was evaluated.

    MATERIALS AND METHODS: Resting and stimulated saliva samples were collected from 36 healthy adults (mean age 26 years). Saliva IgA, IgG and IgM autoantibody levels to copper oxidized LDL (CuOx-LDL) and malondialdehyde acetaldehyde-modified LDL (MAA-LDL) were determined with chemiluminescence immunoassay.

    RESULTS: Saliva IgA and IgG antibodies binding to MAA-LDL and CuOx-LDL were detected in all samples and they were associated with the saliva levels of IgA and IgG to P. gingivalis and A. actinomycetemcomitans. Competitive immunoassay showed that saliva antibodies to MAA-LDL cross-reacted specifically with P. gingivalis. The autoantibody levels to oxLDL in saliva were not associated with the autoantibody levels to oxLDL in plasma or with saliva apolipoprotein B 100 levels.

    CONCLUSIONS: Saliva contains IgA and IgG binding to oxLDL, which showed cross-reactive properties with the periodontal pathogens Porphyromonas gingivalis (P.g). The data suggest that secretory IgA to P.g may participate in immune reactions involved in LDL oxidation through molecular mimicry.

  • 3072.
    Akhlaghi, Shahin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Degradation of acrylonitrile butadiene rubber and fluoroelastomers in rapeseed biodiesel and hydrogenated vegetable oil2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Biodiesel and hydrotreated vegetable oil (HVO) are currently viewed by the transportation sector as the most viable alternative fuels to replace petroleum-based fuels. The use of biodiesel has, however, been limited by the deteriorative effect of biodiesel on rubber parts in automobile fuel systems. This work therefore aimed at investigating the degradation of acrylonitrile butadiene rubber (NBR) and fluoroelastomers (FKM) on exposure to biodiesel and HVO at different temperatures and oxygen concentrations in an automated ageing equipment and a high-pressure autoclave. The oxidation of biodiesel at 80 °C was promoted by an increase in the oxygen partial pressure, resulting in the formation of larger amounts of hydroperoxides and acids in the fuel. The fatty acid methyl esters of the biodiesel oxidized less at 150 °C on autoclave aging, because the termination reactions between alkyl and alkylperoxyl radicals dominated over the initiation reactions. HVO consists of saturated hydrocarbons, and remained intact during the exposure. The NBR absorbed a large amount of biodiesel due to fuel-driven internal cavitation in the rubber, and the uptake increased with increasing oxygen partial pressure due to the increase in concentration of oxidation products of the biodiesel. The absence of a tan δ peak (dynamical mechanical measurements) of the bound rubber and the appearance of carbon black particles devoid of rubber suggested that the cavitation was caused by the detachment of bound rubber from particle surfaces. A significant decrease in the strain-at-break and in the Payne-effect amplitude of NBR exposed to biodiesel was explained as being due to the damage caused by biodiesel to the rubber-carbon-black network. During the high-temperature autoclave ageing, the NBR swelled less in biodiesel, and showed a small decrease in the strain-at-break due to the cleavage of rubber chains. The degradation of NBR in the absence of carbon black was due only to biodiesel-promoted oxidative crosslinking. The zinc cations released by the dissolution of zinc oxide particles in biodiesel promoted reduction reactions in the acrylonitrile part of the NBR. Heat-treated star-shaped ZnO particles dissolved more slowly in biodiesel than the commercial ZnO nanoparticles due to the elimination of inter-particle porosity by heat treatment. The fuel sorption was hindered in HVO-exposed NBR by the steric constraints of the bulky HVO molecules. The extensibility of NBR decreased only slightly after exposure to HVO, due to the migration of plasticizer from the rubber. The bisphenol-cured FKM co- and terpolymer swelled more than the peroxide-cured GFLT-type FKM in biodiesel due to the chain cleavage caused by the attack of biodiesel on the double bonds formed during the bisphenol curing. The FKM rubbers absorbed biodiesel faster, and to a greater extent, with increasing oxygen concentration. It is suggested that the extensive biodiesel uptake and the decrease in the strain-at-break and Young’s modulus of the FKM terpolymer was due to dehydrofluorination of the rubber by the coordination complexes of biodiesel and magnesium oxide and calcium hydroxide particles. An increase in the CH2-concentration of the extracted FKM rubbers suggested that biodiesel was grafted onto the FKM at the unsaturated sites resulting from dehydrofluorination.

  • 3073.
    Akhlaghi, Shahin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Amir Masoud, Pourrahimi
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Christian, Sjöstedt
    Martin, Bellander
    Mikael S., Hedenqvist
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Ulf W., Gedde
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Degradation of fluoroelastomers in rapeseed biodiesel at different oxygen concentrations2017In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 136, p. 10-19Article in journal (Refereed)
    Abstract [en]

    The degradation of fluoroelastomers (FKM) based on different monomers, additives and curing systems was studied after exposure to rapeseed biodiesel at 100 °C and different oxygen partial pressures. The sorption of fuel in the carbon black-filled FKM terpolymer was promoted by the fuel-driven cavitation in the rubber. The bisphenol-cured rubbers swelled more in biodiesel than the peroxide-cured FKM, presumably due to the chain cleavage caused by the attack of biodiesel on the double bonds formed during the bisphenol curing. With any of the selected types of monomer, the FKM rubbers absorbed biodiesel faster and to a greater extent with increasing oxygen partial pressure due to the increase in concentration of the oxidation products of biodiesel. Water-assisted complexation of biodiesel on magnesium oxide and calcium hydroxide particles led to dehydrofluorination of FKM, resulting in an extensive fuel uptake and a decrease in the strain-at-break and the Young's modulus of the rubbers. An increase in the CH2-concentration determined by infrared spectroscopy, and the appearance of biodiesel flakes in scanning electron micrographs of the extracted rubbers, were explained as being due to the presence of insoluble biodiesel grafted onto FKM on the unsaturated sites resulting from dehydrofluorination. The extensibility of the GFLT-type FKM was the least affected on exposure to biodiesel because this rubber contained less unsaturation and metal oxide/hydroxide particles.

  • 3074.
    Akhlaghi, Shahin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. Scania CV AB, Sweden.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Brana, Maria T. Conde
    Bellander, Martin
    Deterioration of automotive rubbers in liquid biofuels: A review2015In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 43, p. 1238-1248Article, review/survey (Refereed)
    Abstract [en]

    Concerns over the fast depletion of fossil fuels, environmental issues and stringent legislation associated with petroleum-based fuels have triggered a shift to bio-based fuels, as an alternative to meet the growing energy demand in the transportation sector. However, since conventional automobile fuel systems are adapted to petroleum-based fuels, switching to biofuels causes a severe deterioration in the performance of currently used rubber components. The degradation of the rubber materials in biofuels is complicated by the presence of different additives in biofuels and rubber compounds, by oxidation of biofuels and by the effects of thermomechanical loadings in the engine. This paper presents a comprehensive review of the effects of different types of biofuels, particularly biodiesel and bioethanol, on the physical, mechanical, morphological and thermal properties of elastomers under different exposure conditions. In addition, the literature data available on the variation of rubbers' resistance to biofuels with the changes in their monomer type and composition, cure system and additives content was also studied. The review essentially focuses on the compatibility of biofuels with acrylonitrile butadiene rubber, fluoroelastomers, polychloroprene rubber and silicon rubber, as the most commonly used automotive rubbers coming into contact with fuels during their service. The knowledge summarized in this study can help to develop a guideline on the selection of rubber for automotive parts designed to withstand biofuels.

  • 3075.
    Akhlaghi, Shahin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Brana, M. T. Conde
    Bellander, M.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Deterioration of acrylonitrile butadiene rubber in rapeseed biodiesel2015In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 111, p. 211-222Article in journal (Refereed)
    Abstract [en]

    The deterioration of acrylonitrile butadiene rubber (NBR) exposed to rapeseed biodiesel at 90 degrees C was studied. The oxidation of biodiesel and NBR during ageing was monitored by H-1 NMR and infrared spectroscopy, HPLC and titration methods. The oxidation of biodiesel was impeded in the presence of NBR, but promoted in biodiesel-exposed rubber. This was explained as being due to the migration of stabilizer from the rubber to biodiesel, the diffusion of dissolved oxygen from biodiesel into NBR and the absorption of oxidation precursors of biodiesel by the rubber. The resemblance between the anomalous sorption kinetics of biodiesel in NBR and the equilibrium benzene uptake by the aged rubbers revealed that biodiesel caused a network defect in NBR, resulting in a gradual increase in the equilibrium swelling. The cleavage of crosslinks was implausible since the Young's modulus of the rubber at low strains, disregarding an initial decrease, increased with increasing exposure time. The appearance of 'naked' carbon black particles in the scanning electron micrographs of the aged rubbers and a drastic decrease in the strain-at-break of NBR after exposure to biodiesel suggests that internal cavitation was caused by the attack of biodiesel on the acrylonitrile units of NBR.

  • 3076.
    Akhlaghi, Shahin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Pourrahimi, A. M.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Christian, Sjöstedt
    Martin, Bellander
    Mikael S., Hedenqvist
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Ulf W., Gedde
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Effects of ageing conditions on degradation of acrylonitrile butadiene rubber filled with heat-treated ZnO star-shaped particles in rapeseed biodiesel2017In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321Article in journal (Refereed)
    Abstract [en]

    The degradation of acrylonitrile butadiene rubber (NBR) after exposure to biodiesel at different oxygen partial pressures in an automated ageing equipment at 80 °C, and in a high-pressure autoclave at 150 °C was studied. The oxidation of biodiesel was promoted by an increase in oxygen concentration, resulting in a larger uptake of fuel in the rubber due to internal cavitation, a greater decrease in the strain-at-break of NBR due to the coalescence of cavity, and a faster increase in the crosslinking density and carbonyl index due to the promotion of the oxidation of NBR. During the high-temperature autoclave ageing, less fuel was absorbed in the rubber, because the formation of hydroperoxides and acids was impeded. The extensibility of NBR aged in the autoclave decreased only slightly due to the cleavage of rubber chains by the biodiesel attack. The degradation of NBR in the absence of carbon black was explained as being due to oxidative crosslinking. The dissolution of ZnO crystals in the acidic components of biodiesel was retarded by removing the inter-particle porosity and surface defects through heat treating star-shaped ZnO particles. The rubber containing heat-treated ZnO particles swelled less in biodiesel than a NBR filled with commercial ZnO nanoparticles, and showed a smaller decrease in the strain-at-break and less oxidative crosslinking.

  • 3077.
    Akhlaghi, Shahin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Pourrahimi, Amir Masoud
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Sjöstedt, C.
    Bellander, M.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Degradation of carbon-black-filled acrylonitrile butadiene rubber in alternative fuels: Transesterified and hydrotreated vegetable oils2016In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 123, p. 69-79Article in journal (Refereed)
    Abstract [en]

    The deterioration of acrylonitrile butadiene rubber (NBR), a common sealing material in automobile fuel systems, when exposed to rapeseed biodiesel and hydrotreated vegetable oil (HVO) was studied. The fuel sorption was hindered in HVO-exposed rubber by the steric constraints of bulky HVO molecules, but it was promoted in biodiesel-exposed rubber by fuel-driven cavitation in the NBR and by the increase in diffusivity of biodiesel after oxidation. The absence of a tan δ peak of the bound rubber and the appearance of carbon black particles devoid of rubber suggested that the cavitation was made possible in biodiesel-aged rubber by the detachment of bound rubber from particle surfaces. The HVO-exposed NBR showed a small decrease in strain-at-break due to the migration of plasticizer from the rubber, and a small increase in the Young’s modulus due to oxidative crosslinking. A drastic decrease in extensibility and Payne-effect amplitude of NBR on exposure to biodiesel was explained as being due to the damage caused by biodiesel to the continuous network of bound rubber-carbon black. A decrease in the ZnO crystal size with increasing exposure time suggested that the particles are gradually dissolved in the acidic components of oxidized biodiesel. The Zn2+ cations released from the dissolution of ZnO particles in biodiesel promoted the hydrolysis of the nitrile groups of NBR.

  • 3078. Akhmadaliev, S.
    et al.
    Albiol, F.
    Amaral, P.
    Berglund, S.
    Lund-Jensen, Bengt
    KTH, Superseded Departments, Physics.
    Lundquist, J.
    Sellden, B.
    Soderqvist, J.
    Zolnierowski, Y. P.
    et al,
    Results from a new combined test of an electromagnetic liquid argon calorimeter with a hadronic scintillating-tile calorimeter2000In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 449, no 3, p. 461-477Article in journal (Refereed)
    Abstract [en]

    A new combined test of an electromagnetic liquid argon accordion calorimeter and a hadronic scintillating-tile calorimeter was carried out at the CERN SPS. These devices are prototypes of the barrel calorimeter of the future ATLAS experiment at the LHC. The energy resolution of pions in the energy range from 10 to 300 GeV at an incident angle a of about 12 degrees is well described by the expression sigma/E = ((41.9 +/- 1.6)%/root E + (1.8 +/- 0.1)%)circle plus(1.8 +/- 0.1)/E, where E is in GeV. The response to electrons and muons was evaluated. Shower profiles, shower leakage and the angular resolution of hadronic showers were also studied. Results are compared with those from the previous beam test.

  • 3079. Akhmadaliev, S.
    et al.
    Amaral, P.
    Ambrosini, G.
    Amorim, A.
    Anderson, K.
    Johansson, E.
    Lund-Jensen, Bengt
    KTH, Superseded Departments, Physics.
    Soderqvist, J.
    Zolnierowski, Y. P.
    et al,
    Hadron energy reconstruction for the ATLAS calorimetry in the framework of the non-parametrical method2002In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 480, no 03-feb, p. 508-523Article in journal (Refereed)
    Abstract [en]

    This paper discusses hadron energy reconstruction for the ATLAS barrel prototype combined calorimeter (consisting of a lead-liquid argon electromagnetic part and an iron-scintillator hadronic part) in the framework of the non-parametrical method. The non-parametrical method utilizes only the known e/h ratios and the electron calibration constants and does not require the determination of any parameters by a minimization technique. Thus, this technique lends itself to an easy use in a first level trigger. The reconstructed mean values of the hadron energies are within +/-1% of the true values and the fractional energy resolution is [(58+/-3)%/rootE+(2.5+/-0.3)%]circle plus(1.7+/-0.2)/E. The value of the e/h ratio obtained for the electromagnetic compartment of the combined calorimeter is 1.74+/-0.04 and agrees with the prediction that e/h > 1.66 for this electromagnetic calorimeter. Results of a study of the longitudinal hadronic shower development are also presented. The data have been taken in the H8 beam line of the CERN SPS using pions of energies from 10 to 300 GeV.

  • 3080.
    Akhmedov, Evgeny
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Duality in left-right symmetric seesaw2007In: Nuclear physics B, Proceedings supplements, ISSN 0920-5632, E-ISSN 1873-3832, Vol. 168, p. 369-371Article in journal (Refereed)
    Abstract [en]

    A reconstruction of the mass matrix of heavy right-handed Majorana neutrinos is performed in the framework of the left-right symmetric type I+II seesaw mechanism. An intriguing pairwise duality relation between different solutions is shown to exist.

  • 3081.
    Akhmedov, Evgeny
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Neutrino oscillations: Theory and phenomenology2011In: Nuclear Physics B - Proceedings Supplements, ISSN 0920-5632, Vol. 221, p. 19-25Article in journal (Refereed)
    Abstract [en]

    A brief overview of selected topics in the theory and phenomenology of neutrino oscillations is given. These include: oscillations in vacuum and in matter; phenomenology of 3-flavour neutrino oscillations; CP and T violation in neutrino oscillations in vacuum and in matter; matter effects on ν μ↔ν τ oscillations; parametric resonance in neutrino oscillations inside the earth; oscillations below and above the MSW resonance; unsettled issues in the theory of neutrino oscillations.

  • 3082.
    Akhmedov, Evgeny
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Blennow, Mattias
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Hällgren, Tomas
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Konstandin, Thomas
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Stability and leptogenesis in the left-right symmetric seesaw mechanism2007In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 4, p. 022-1-022-25Article in journal (Refereed)
    Abstract [en]

    We analyze the left-right symmetric type I+II seesaw mechanism, where an eight-fold degeneracy among the mass matrices of heavy right-handed neutrinos M-R is known to exist. Using the stability property of the solutions and their ability to lead to successful baryogenesis via leptogenesis as additional criteria, we discriminate among these eight solutions and partially lift their eight-fold degeneracy. In particular, we find that viable leptogenesis is generically possible for four out of the eight solutions.

  • 3083.
    Akhmedov, Evgeny
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Frigerio, M.
    Duality in left-right symmetric seesaw2006In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T127, p. 59-61Article in journal (Refereed)
    Abstract [en]

    We perform a reconstruction of the mass matrix of heavy right-handed Majorana neutrinos in the framework of the left - right symmetric type I + II seesaw mechanism. An intriguing pairwise duality relation between different solutions is shown to exist.

  • 3084.
    Akhmedov, Evgeny
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Frigerio, Michele
    Interplay of type I and type II seesaw contributions to neutrino mass2007In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 1, p. 043-Article in journal (Refereed)
    Abstract [en]

    Type I and type II seesaw contributions to the mass matrix of light neutrinos are inherently related if left-right symmetry is realized at high energy scales. We investigate implications of such a relation for the interpretation of neutrino data. We proved recently that the left-right symmetric seesaw equation has eight solutions, related by a duality property, for the mass matrix of right-handed neutrinos M-R. In this paper the eight allowed structures of M-R are reconstructed analytically and analyzed numerically in a bottom-up approach. We study the dependence of right-handed neutrino masses on the mass spectrum of light neutrinos, mixing angle theta(13), leptonic CP violation, scale of left-right symmetry breaking and on the hierarchy in neutrino Yukawa couplings. The structure of the seesaw formula in several specific SO(10) models is explored in the light of the duality. The outcome of leptogenesis may depend crucially on the choice among the allowed structures of M-R and on the level crossing between right-handed neutrino masses.

  • 3085. Akhmedov, Evgeny
    et al.
    Huber, Patrick
    Lindner, Manfred
    Ohlsson, Tommy
    KTH, Superseded Departments, Physics.
    T violation in neutrino oscillations in matter2001In: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 608, no 02-jan, p. 394-422Article in journal (Refereed)
    Abstract [en]

    We consider the interplay of fundamental and matter-induced T violation effects in neutrino oscillations in matter. After discussing the general features of these effects we derive a simple approximate analytic expression for the T-violating probability asymmetry DeltaP(ab)(T) for three-flavour neutrino oscillations in a matter with an arbitrary density profile in terms of the two-flavour neutrino amplitudes. Explicit examples are given for the cases of a two-layer medium and for the adiabatic Emit in the general case. We then discuss implications of the obtained results for long baseline experiments. We show, in particular, that asymmetric matter effects cannot hinder the determination of the fundamental CP- and T-violating phase delta (CP) in the long baseline experiments as far as the error in this determination is larger than 1% at 99% CL. Since there are no T-violating effects in the two-flavour case, and in the limits of vanishing theta (13) or Deltam(21)(2) the three-flavour neutrino oscillations effectively reduce to the two-flavour ones, studying the T-violating asymmetries ApT ab can in principle provide us with a complementary means of measuring theta (13) and Deltam(21)(2).

  • 3086. Akhmedov, Evgeny K.
    et al.
    Johansson, Robert
    KTH, Superseded Departments, Physics.
    Lindner, Manfred
    Ohlsson, Tommy
    KTH, Superseded Departments, Physics.
    Schwetz, Thomas
    Series expansions for three-flavor neutrino oscillation probabilities in matter2004In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2004, no 04, p. 078-Article in journal (Refereed)
    Abstract [en]

    We present a number of complete sets of series expansion formulas for neutrino oscillation probabilities in matter of constant density for three flavors. In particular, we study expansions in the mass hierarchy parameter alpha = Deltam(21)(2)/Deltam(31)(2) and mixing parameter s(13) = sin theta(13) up to second order and expansions only in alpha and only in s(13) up to first order. For each type of expansion we also present the corresponding formulas for neutrino oscillations in vacuum. We perform a detailed analysis of the accuracy of the different sets of series expansion formulas and investigate which type of expansion is most accurate in different regions of the parameter space spanned by the neutrino energy E, the baseline length L, and the expansion parameters alpha and s(13). We also present the formulas for series expansions in alpha and in s(13) up to first order for the case of arbitrary matter density profiles. Furthermore, it is shown that in general all the 18 neutrino and antineutrino oscillation probabilities can be expressed through just two independent probabilities.

  • 3087.
    Akhmedov, Evgeny Kh
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Neutrino oscillations: Theory and phenomenology2006In: NEUTRINO - Proc. Int. Conf. Neutrino Phys. Astrophys., 2006, p. 16-22Conference paper (Refereed)
    Abstract [en]

    A brief overview of selected topics in the theory and phenomenology of neutrino oscillations is given. These include: oscillations in vacuum and in matter; phenomenology of 3-flavour neutrino oscillations; CP and T violation in neutrino oscillations in vacuum and in matter; matter effects on νμ ↔ ντ oscillations; parametric resonance in neutrino oscillations inside the earth; oscillations below and above the MSW resonance; unsettled issues in the theory of neutrino oscillations.

  • 3088.
    Akhmedov, Evgeny
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Maltoni, Michele
    Smirnov, Alexei Yu.
    1-3 leptonic mixing and the neutrino oscillograms of the Earth2007In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 5, p. 077-Article in journal (Refereed)
    Abstract [en]

    We develop a detailed and comprehensive description of neutrino oscillations driven by the 1-3 mixing in the matter of the Earth. The description is valid for the realistic (PREM) Earth density profile in the whole range of nadir angles and for neutrino energies above 1 GeV. It can be applied to oscillations of atmospheric and accelerator neutrinos. The results are presented in the form of neutrino oscillograms of the Earth, i.e. the contours of equal oscillation probabilities in the neutrino energy-nadir angle plane. A detailed physics interpretation of the oscilligrams, which includes the MSW peaks, parametric ridges, local maxima, zeros and saddle points, is given in terms of the amplitude and phase conditions. Precise analytic formulas for the probabilities are obtained. We study the dependence of the oscillation pattern on theta(13) and find, in particular, that the survival probability P-ee < 1/2 appears for sin(2) 2 theta(13) as small as similar to 0.009. We consider the dependence of the oscillation pattern on the matter density profile and comment on the possibility of the oscillation tomography of the Earth.

  • 3089. Akhmetova, D.
    et al.
    Kestor, G.
    Gioiosa, R.
    Markidis, Stefano
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    Laure, Erwin
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    On the application task granularity and the interplay with the scheduling overhead in many-core shared memory systems2015In: Proceedings - IEEE International Conference on Cluster Computing, ICCC, IEEE , 2015, p. 428-437Conference paper (Refereed)
    Abstract [en]

    Task-based programming models are considered one of the most promising programming model approaches for exascale supercomputers because of their ability to dynamically react to changing conditions and reassign work to processing elements. One question, however, remains unsolved: what should the task granularity of task-based applications be? Fine-grained tasks offer more opportunities to balance the system and generally result in higher system utilization. However, they also induce in large scheduling overhead. The impact of scheduling overhead on coarse-grained tasks is lower, but large systems may result imbalanced and underutilized. In this work we propose a methodology to analyze the interplay between application task granularity and scheduling overhead. Our methodology is based on three main points: 1) a novel task algorithm that analyzes an application directed acyclic graph (DAG) and aggregates tasks, 2) a fast and precise emulator to analyze the application behavior on systems with up to 1,024 cores, 3) a comprehensive sensitivity analysis of application performance and scheduling overhead breakdown. Our results show that there is an optimal task granularity between 1.2x10^4 and 10x10^4 cycles for the representative schedulers. Moreover, our analysis indicates that a suitable scheduler for exascale task-based applications should employ a best-effort local scheduler and a sophisticated remote scheduler to move tasks across worker threads.

  • 3090.
    Akhmetova, Dana
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Computational Science and Technology (CST).
    Cebamanos, L.
    Iakymchuk, Roman
    KTH, School of Electrical Engineering and Computer Science (EECS), Computational Science and Technology (CST).
    Rotaru, T.
    Rahn, M.
    Markidis, Stefano
    KTH, School of Electrical Engineering and Computer Science (EECS), Computational Science and Technology (CST).
    Laure, Erwin
    KTH, School of Electrical Engineering and Computer Science (EECS), Computational Science and Technology (CST).
    Bartsch, V.
    Simmendinger, C.
    Interoperability of GASPI and MPI in large scale scientific applications2018In: 12th International Conference on Parallel Processing and Applied Mathematics, PPAM 2017, Springer Verlag , 2018, p. 277-287Conference paper (Refereed)
    Abstract [en]

    One of the main hurdles of a broad distribution of PGAS approaches is the prevalence of MPI, which as a de-facto standard appears in the code basis of many applications. To take advantage of the PGAS APIs like GASPI without a major change in the code basis, interoperability between MPI and PGAS approaches needs to be ensured. In this article, we address this challenge by providing our study and preliminary performance results regarding interoperating GASPI and MPI on the performance crucial parts of the Ludwig and iPIC3D applications. In addition, we draw a strategy for better coupling of both APIs. 

  • 3091.
    Akhmetova, Dana
    et al.
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    Iakymchuk, Roman
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    Ekeberg, Örjan
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    Laure, Erwin
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    Performance study of multithreaded MPI and Openmp tasking in a large scientific code2017In: Proceedings - 2017 IEEE 31st International Parallel and Distributed Processing Symposium Workshops, IPDPSW 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 756-765, article id 7965119Conference paper (Refereed)
    Abstract [en]

    With a large variety and complexity of existing HPC machines and uncertainty regarding exact future Exascale hardware, it is not clear whether existing parallel scientific codes will perform well on future Exascale systems: they can be largely modified or even completely rewritten from scratch. Therefore, now it is important to ensure that software is ready for Exascale computing and will utilize all Exascale resources well. Many parallel programming models try to take into account all possible hardware features and nuances. However, the HPC community does not yet have a precise answer whether, for Exascale computing, there should be a natural evolution of existing models interoperable with each other or it should be a disruptive approach. Here, we focus on the first option, particularly on a practical assessment of how some parallel programming models can coexist with each other. This work describes two API combination scenarios on the example of iPIC3D [26], an implicit Particle-in-Cell code for space weather applications written in C++ and MPI plus OpenMP. The first scenario is to enable multiple OpenMP threads call MPI functions simultaneously, with no restrictions, using an MPI THREAD MULTIPLE thread safety level. The second scenario is to utilize the OpenMP tasking model on top of the first scenario. The paper reports a step-by-step methodology and experience with these API combinations in iPIC3D; provides the scaling tests for these implementations with up to 2048 physical cores; discusses occurred interoperability issues; and provides suggestions to programmers and scientists who may adopt these API combinations in their own codes.

  • 3092.
    Akhondi, Mehdi
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Pelletäppan, tennishall med bristfällig konstruktion: En fallstudie av massiv limträkonstruktion2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Detta arbete bygger på en jämförelse mellan Boverkets Byggregler och Eurokoder för en befintlig limträkonstruktion. Referensobjektet är en tennishall belägen i Botkyrka kommun. Objektet byggdes under början på 90-talet i form av en treledsram med taktäckning av PVC duk som vilar direkt på limträbalkarna, inklusive en inre duk med mellanliggande isolering och luftspalt. Under de senaste åren har konstruktionen uppvisat tecken på svagheter med bl.a. stora sprickor i limträbalkarna, dessa skador kulminerade i att på begäran av kommunen stänga av anläggningen för fortsatta spel.

    Oavsett om beräkningarna utförs med BKR eller Eurokoder som är norm idag så har stommen inte tillräckligt bärighet för sin egentyngd och dagens snölast. Detta kan tyckas vara märkligt men förklaringen kan vara att man utförde byggnaden med tanke på att snön glider av hallen och inte ackumuleras. Med detta i åtanke skulle snön glida av om yttertaken hade hållits varm, mycket tyder på att så skulle ha varit fallet om fläktarna som luftar spalten i takkonstruktionen hade varit igång. Enligt Roger Vintemar, verksamhetschef för Idrott och Anläggning på Botkyrka kommun, har fläktaggregatets på/av knapp placerats lättillgängligt i spelargången och det finns anledning att misstänka att fläktaggregatet har varit avstängd vid långa perioder. Sprickorna i bågarna kan bero på överlast eftersom snön har ackumulerats och inte glidit av. Med avseende på hur konstruktionen är utformad och att det har blivit vattenansamlingar på spelbanan är det inte orimligt att ifrågasätta dragstagets rostskydd. Skulle dragstaget som håller ihop de två bågarna brista finns det en överhängande risk för s.k. sprött brott med ett snabbt ras till följd.

  • 3093.
    Akhras, Michael S.
    KTH, School of Biotechnology (BIO).
    Nucleic Acid Based Pathogen Diagnostics2008Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Pathogenic organisms are transmitted to the host organism through all possible connected pathways, and cause a myriad of diseases states. Commonly occurring curable infectious diseases still impose the greatest health impacts on a worldwide perspective. The Bill & Melinda Gates Foundation partnered with RAND Corporation to form the Global Health Diagnostics Forum, with the goal of establishing and interpreting mathematical models for what effects a newly introduced point-of-care pathogen diagnostic would have in developing countries. The results were astonishing, with potentially millions of lives to be saved on an annual basis.

    Golden standard for diagnostics of pathogenic bacteria has long been cultureable medias. Environmental biologists have estimated that less than 1% of all bacteria are cultureable. Genomic-based approaches offer the potential to identify all microbes from all the biological kingdoms. Nucleic acid based pathogen diagnostics has evolved significantly over the past decades. Novel technologies offer increased potential in sensitivity, specificity, decreased costs and parallel sample management. However, most methods are confined to core laboratory facilities. To construct an ultimate nucleic acid based diagnostic for use in areas of need, potential frontline techniques need to be identified and combined.

    The research focus of this doctoral thesis work has been to develop and apply nucleic acid based methods for pathogen diagnostics. Methods and assays were applied to the two distinct systems i) screening for antibiotic resistance mutations in the bacterial pathogen Neisseria gonorrhoeae, and ii) genotype determination of the cancer causative Human Papillomavirus (HPV). The first part of the study included development of rapid, direct and multiplex Pyrosequencing nucleic acid screenings. With improved methodology in the sample preparation process, we could detect an existence of multiple co-infecting HPV genotypes at greater sensitivities than previously described, when using the same type of methodology. The second part of the study focused on multiplex nucleic acid amplification strategies using Molecular Inversion Probes with end-step Pyrosequencing screening. The PathogenMip assay presents a complete detection schematic for virtually any known pathogenic organism. We also introduce the novel Connector Inversion Probe, a padlock probe capable of complete gap-fill reactions for multiplex nucleic acid amplifications.

  • 3094.
    Akhras, Michael
    et al.
    KTH, School of Biotechnology (BIO).
    Thiyagarajan, Sreedevi
    Stanford Univ, Stanford Genome Technol Ctr.
    Villablanca, Andrea C.
    Stanford Univ, Stanford Genome Technol Ctr.
    Davis, Ronald W.
    Stanford Univ, Stanford Genome Technol Ctr.
    Nyrén, Pål
    KTH, School of Biotechnology (BIO).
    Pourmand, Nader
    Stanford Univ, Stanford Genome Technol Ctr.
    PathogenMip Assay: A Multiplex Pathogen Detection Assay2007In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 2, no 2, p. e223-Article in journal (Refereed)
    Abstract [en]

    The Molecular Inversion Probe (MIP) assay has been previously applied to a large-scale human SNP detection. Here we describe the PathogenMip Assay, a complete protocol for probe production and applied approaches to pathogen detection. We have demonstrated the utility of this assay with an initial set of 24 probes targeting the most clinically relevant HPV genotypes associated with cervical cancer progression. Probe construction was based on a novel, cost-effective, ligase-based protocol. The assay was validated by performing pyrosequencing and Microarray chip detection in parallel experiments. HPV plasmids were used to validate sensitivity and selectivity of the assay. In addition, 20 genomic DNA extracts from primary tumors were genotyped with the PathogenMip Assay results and were in 100% agreement with conventional sequencing using an L1-based HPV genotyping protocol. The PathogenMip Assay is a widely accessible protocol for producing and using highly discriminating probes, with experimentally validated results in pathogen genotyping, which could potentially be applied to the detection and characterization of any microbe.

  • 3095.
    Akhras, Michael
    et al.
    KTH, School of Biotechnology (BIO).
    Unemo, Magnus
    Örebro Univ Hosp, Dept Clin Microbiol.
    Thiyagarajan, Sreedevi
    Stanford Univ, Stanford Genome Technol Ctr.
    Nyrén, Pål
    KTH, School of Biotechnology (BIO).
    Davis, Ronald W.
    Stanford Univ, Stanford Genome Technol Ctr.
    Fire, Andrew Z.
    Stanford Univ.
    Pourmand, Nader
    Univ Calif Santa Cruz.
    Connector Inversion Probe Technology: A Powerful One- Primer Multiplex DNA Amplification System for Numerous Scientific Applications2007In: PLoS ONE, ISSN 1932-6203, Vol. 2, no 9, p. e915-Article in journal (Refereed)
    Abstract [en]

    We combined components of a previous assay referred to as Molecular Inversion Probe (MIP) with a complete gap filling strategy, creating a versatile powerful one-primer multiplex amplification system. As a proof-of-concept, this novel method, which employs a Connector Inversion Probe (CIPer), was tested as a genetic tool for pathogen diagnosis, typing, and antibiotic resistance screening with two distinct systems: i) a conserved sequence primer system for genotyping Human Papillomavirus (HPV), a cancer-associated viral agent and ii) screening for antibiotic resistance mutations in the bacterial pathogen Neisseria gonorrhoeae. We also discuss future applications and advances of the CIPer technology such as integration with digital amplification and next-generation sequencing methods. Furthermore, we introduce the concept of two-dimension informational barcodes, i. e. "multiplex multiplexing padlocks'' (MMPs). For the readers' convenience, we also provide an on-line tutorial with user-interface software application CIP creator 1.0.1, for custom probe generation from virtually any new or established primer-pairs.

  • 3096.
    Akhtar, Faiza
    et al.
    UET, ACTSENA Res Grp, Taxila 47050, Pakistan..
    Naqvi, Syeda Iffat
    UET, ACTSENA Res Grp, Taxila 47050, Pakistan..
    Arshad, Farzana
    UET, ACTSENA Res Grp, Taxila 47050, Pakistan..
    Amin, Yasar
    KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK. UET, ACTSENA Res Grp, Taxila 47050, Pakistan.
    Tenhunen, Hannu
    KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK. Univ Turku, TUCS, FIN-20520 Turku, Finland..
    A Flexible and Compact Semicircular Antenna for Multiple Wireless Communication Applications2018In: Radioengineering, ISSN 1210-2512, E-ISSN 1805-9600, Vol. 27, no 3, p. 671-678Article in journal (Refereed)
    Abstract [en]

    This work presents a compact, quad-band planar antenna intended for assimilation into flexible and conformal devices. The CPW-fed semicircular shaped prototype with rake-shaped slots is designed, realized and characterized experimentally. The frequency bands covered by the proposed radiator are centered at 2.5, 3.7, 5.5 and 8 GHz with measured impedance bandwidths of 16%, 13.5%, 11.8% and 14.63%, respectively. The proposed antenna is thus enabled to support WLAN, ISM, Bluetooth, WiMAX LTE and X-band applications. The antenna exhibits a significant gain. The radiation characteristics of the proposed radiator are measured in concave and convex bent shapes at various radii to analyze its flexibility. Performance of the antenna remains almost unaffected in the bent situation. Measurements demonstrate good coherence with simulations. The compactness and good performance of the design both in bent and unbent conditions proves it to be the better contender for future multiband conformal wireless applications.

  • 3097.
    Akhtar, Malik Usman
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Variable speed drive as an alternative solution for a micro-hydro power plant2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This diploma work is mainly focused on developing the control strategy for avariable speed drive as an alternative solution to a micro-hydro power plant. The detailed mathematical model for a micro-hydro system including a Kaplan turbine, mechanical shaft and electrical machines is presented and validated through simulations. A control strategy for an autonomous operation of a doubly-fed induction machine-based drive is developed for a wide range of speed. The drive can operate at a unity power factor.The possible applications of the analyzed system are also presented. As a positive side of the system, it is found that the direct interaction between the power electronic converters and the utility grid can be avoided by exploiting the proposed topology, which might lead to a better quality of the produced power in terms of harmonics. This could also lead to removal or reduction of the size of the harmonic filters that are being used in conventional doubly-fed induction generator installations. As regards to the drawbacks of the system, a comparison of converter and generator ratings between the analyzed solution and the conventional solution was performed. While the converters rating remain the same, there is one more electrical machine and the doubly-fed generator rating is slightly increased. Losses are also slightly larger due to the presence of the second machine.

  • 3098. Akhtar, Nadeem
    et al.
    Markendahl, Jan
    Univ Surrey.
    Moessner, Klaus
    Analysis of Complexity and Transaction Costs For Cooperating Networks2007In: 2007 IEEE 18TH INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOLS 1-9, 2007, p. 4270-4274Conference paper (Refereed)
    Abstract [en]

    In this paper we investigate the impact that introduction of new Ambient Networks (AN) functionality will have on usage of system resources and on connection delay. The signalling load for multiple attachment and negotiation procedures is assessed by modelling signalling sequences for a WLAN system enabled with AN technology. The load is computed for varying numbers of users and for users with different levels of “willingness to evaluate and negotiate offers”. The results show that the most important parameter is the number of attachment attempts per time unit, which is an indicator of user activity level. In the investigated scenarios, the relative load of signalling is 0.1 – 1.0 % of the transferred user data. The delay depends on the current load situation of the network.

  • 3099.
    Akhtar, Nadeem
    et al.
    University of Surrey, UK.
    Markendahl, Jan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Queseth, Olav
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Analysis of Signaling Load and Negotiation Complexity using Network Composition2007Conference paper (Refereed)
    Abstract [en]

    In future mobile communications networks using Ambient Networks (AN) technology, users will be able to connect to a multitude of networks operated by different business entities. The technology enablers are advertising of access and service offers, multi-radio access, network selection and roaming support, negotiation of terms and conditions for attachment to networks. In this paper, we investigate the additional load on users and network resources for establishment and management of multiple network connections and business relations. The administrative load is analyzed using commercial uses cases and scenarios with a number of available networks, service providers and payment and ID providers. The signaling load for multiple attachment and negotiation procedures is estimated by modeling signaling sequences for a WLAN system enabled with AN technology. The signaling load is computed for varying numbers of users and for users with varying "willingness to evaluate and negotiate offers". The results show that the most important parameters are the number of attachment attempts per time unit. In the investigated scenarios, the relative load of business related signaling is 0.1 -1.0 % of the transferred user data. Although a large of number of different networks may be used, the number of business agreements and network connections that need to be handled simultaneously will be quite low.

  • 3100.
    Akhtar, Shahid
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Shaikh, Md. Robiul Haque
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Micro Porosity Development in Directionally Solidified A356 Castings Doped with Anodized Plates and Sintered Aluminium2011In: European Congress and Exhibition on Advanced Materials and Processes (EUROMAT) 2011, Symposium C52: Processing and characterizing techniques, 2011Conference paper (Refereed)
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