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  • 124001.
    Zackrisson, Mats
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Product orientation of environmental work - barriers & incentives2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Abstract

    The research behind this licentiate is spread out over a decade of intensive development of environmental work in industry. A 1998 survey of Swedish companies with newly installed environmental management systems (EMS) concluded that such systems need more product-orientation. Data collected by companies as part of the process of creating their EMS between 1996-2001 offered further evidence that it is environmentally justified to seek improvements in the materials selection, use and disposal phases of products, i.e., to make the environmental improvement work more product-orientated. In a EU-funded project carried out between 2004-2006 it was demonstrated that developing an environmental product declaration could be a cost-effective product-oriented environmental action even for smaller companies.

    This licentiate thesis relates to methods for companies to orientate their environmental work on their products. In particular, it examines experience and provides insights on the possibilities for companies, including small ones, to use life cycle assessment in product development in order to design products with an environmental performance well above legal compliance.

    It is difficult to give general recommendations to companies about their environmental work because each company has its own unique business idea, customers, work culture, stakeholders etc. Nevertheless, the main findings of the licentiate thesis can be summed up in the following recommendations for, say, a small company in Europe without much previous experience of environmental work:

    §  Focus your environmental work on your products because you will accomplish more environmentally and the chance of profiting economically will motivate your personnel;

    §  Consider doing a life cycle assessment, LCA, on a strategically chosen product in order to learn more about your products and how to improve their environmental performance;

    §  Do not expect to find a general market demand for green products; start a dialogue with your best customers in order to create the demand;

    §  Engage an LCA specialist to do the LCA and work together with your personnel to interpret the results and generate improvement ideas;

    §  If your customers demand that you install an environmental management system, ask them if they would not prefer to receive an environmental product declaration on the particular product they are interested in, and a chance to discuss how its environmental performance can be improved.

  • 124002.
    Zackrisson, Mats
    et al.
    RISE IVF AB, SE-10044 Stockholm, Sweden..
    Jönsson, Christina
    RISE IVF AB, SE-10044 Stockholm, Sweden..
    Johannisson, Wilhelm
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Fransson, Kristin
    Engelsons Postorder AB, SE-31139 Falkenberg, Sweden..
    Posner, Stefan
    Stefan Posner AB, SE-43955 Asa, Sweden..
    Zenkert, Dan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Prospective Life Cycle Assessment of a Structural Battery2019In: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 11, no 20, article id 5679Article in journal (Refereed)
    Abstract [en]

    With increasing interest in reducing fossil fuel emissions, more and more development is focused on electric mobility. For electric vehicles, the main challenge is the mass of the batteries, which significantly increase the mass of the vehicles and limits their range. One possible concept to solve this is incorporating structural batteries; a structural material that both stores electrical energy and carries mechanical load. The concept envisions constructing the body of an electric vehicle with this material and thus reducing the need for further energy storage. This research is investigating a future structural battery that is incorporated in the roof of an electric vehicle. The structural battery is replacing the original steel roof of the vehicle, and part of the original traction battery. The environmental implications of this structural battery roof are investigated with a life cycle assessment, which shows that a structural battery roof can avoid climate impacts in substantive quantities. The main emissions for the structural battery stem from its production and efforts should be focused there to further improve the environmental benefits of the structural battery. Toxicity is investigated with a novel chemical risk assessment from a life cycle perspective, which shows that two chemicals should be targeted for substitution.

  • 124003.
    Zackrisson, Mats
    et al.
    Swerea IVF AB, Sweden.
    Kurdve, Martin
    Mälardalens högskola, Innovation och produktrealisering.
    Shahbazi, Sasha
    Mälardalens högskola, Innovation och produktrealisering.
    Wiktorsson, Magnus
    Mälardalens högskola, Innovation och produktrealisering.
    Winroth, M.
    Chalmers University of Technology, Sweden.
    Landström, A.
    Chalmers University of Technology, Sweden.
    Almström, P.
    Chalmers University of Technology, Sweden.
    Andersson, C.
    Lund University, Sweden.
    Windmark, C.
    Lund University, Sweden.
    Öberg, A.E.
    Volvo Construction Equipment AB, Sweden.
    Myrelid, A.
    GKN Aerospace Engine Systems AB, Sweden.
    Sustainability Performance Indicators at Shop Floor Level in Large Manufacturing Companies2017In: The 24th CIRP Conference on Life Cycle Engineering, Elsevier, 2017, Vol. 61, p. 457-462Conference paper (Refereed)
    Abstract [en]

    This article investigates sustainability in the performance measurement systems of Swedish manufacturing companies. It builds on a previous study that documents relatively few direct environmental indicators at shop floor level, which raises questions about possible indirect links between existing indicators and the environment that could be used to improve the environmental aspect of company's sustainability ambitions. A method for identifying and categorizing indirect links to sustainability issues was defined and used. The results suggest that at shop floor level 90% of the indicators have at least an indirect relation to one or more of the sustainability dimensions economy, environment and social, of which 26% are at least indirectly related to the environmental dimension. Despite the many indirect connections, participating companies perceive a need to improve sustainability indicators and some ideas are suggested. 

  • 124004. Zackrisson, Mats
    et al.
    Rocha, Cristina
    Christiansen, Kim
    Jarnehammar, Anna
    Stepwise environmental product declarations: ten SME case studies2008In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 16, no 17, p. 1872-1886Article in journal (Refereed)
    Abstract [en]

    The lack of reliable communication tools is anticipated to become an important barrier to design and sell products with improved environmental performance. In this paper, environmental product declarations. EPDs, and in particular a Stepwise EPD approach is investigated as a means to overcome the communication barrier. The experiences of ten European SMEs who have tried to use Stepwise EPDs for market communication and as a basis for eco-design are described and discussed. The experiences suggest that Stepwise EPDs based oil life cycle assessment can be a cost-efficient tool to improve the environmental performance of products. For normal marketing activities the Stepwise EPDs were disappointing. Using the underlying LCA as a platform for in-depth communication with selected parties in the supply chain showed more promise.

  • 124005.
    Zackrisson, Samuel
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.).
    Coefficients and zeros of mixed characteristicpolynomials2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The mixed characteristic polynomial (MCP) was introduced in the papersof Marcus, Spielman and Srivastava from 2013 on Ramanujan graphs and the Kadison-Singerconjecture. Several known results and open problems can be formulated in termsof MCPs. The proofs of Marcus, Spielman and Srivastava involve bounding theroots of certain MCPs. Gurvits’ generalization of van der Waerden’s permanentconjecture bounds the constant term of MCPs using the capacity of an underlyingpolynomial.This thesis surveys selected results for MCPs. A counterexample to theHolens-Ðoković conjecture, due to Wanless, is discussed in the context of MCPs.It is used to show how a sequence of MCP coefficients is not monotoneand how the roots of associated Laguerre polynomials do not always majorizethose of other MCPs. Finally, we prove an analogue of the root bound in theproof of the Kadison-Singer conjecture. It applies to product polynomials ofdoubly stochastic matrices through classical results in graph theory due toGodsil, Mohar, Heilmann and Lieb.

  • 124006.
    Zackrisson, Samuel
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Numerical Analysis, NA.
    Suspensions with small, spherical particles2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Feasibly computable analytic solutions for systems of many particles in fluid dynamics and electrostatics are few and far-between. Simulations and numerical approximations are essential to studying these systems. This is commonly done without directly calculating the interacting field between particles. In this report a method utilizing the spectral accuracy of the Fourier transform is studied to calculate particle velocities via the surrounding fluid velocity field. The method is applied to a periodic cube of a suspension of small, spherical particles sedimenting in a fluid affected by gravity, in an attempt to mimic the behaviour of a similar infinite system. Results for a few particles qualitatively relate the shape of the solution to the choice of interpolation between particles to grid and quantitatively maps some convergence properties of a certain class of interpolating functions, cardinal B-splines. The properties of the method on the periodic system are also examined and compared to a similar study of the infinite system for many, ~1000, particles.

     

  • 124007. Zaconte, V.
    et al.
    Fuglesang, Christer
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Schardt, D.
    et al.,
    ALTEA: flight model calibration at GSI2006In: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 37, no 9, p. 1704-1709Article in journal (Refereed)
    Abstract [en]

    The ALTEA project, an international and multi-disciplinary collaboration scheduled to fly in the International Space Station (ISS) after July 2006, is aimed at studying particle radiation in space environment and its effects on astronauts, in particular the anomalous perception of 'light flashes'. In this paper, we present experimental results obtained by testing the Flight Model of the ALTEA particle detector in two measurement sessions performed at the heavy ion accelerator of GSI laboratory in Darmstadt, Germany. Instrument response was compared with Monte-carlo simulations to study its linearity and calculate amplification.

  • 124008.
    Zade, Sagar
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Experimental studies of large particles in Newtonian and non-Newtonian fluids2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In everyday human life, laminar flow is arguably an exception whereas turbulent flow is the norm. Yet, the former has been much better understood, naturally since laminar flow renders itself to treatment in a relatively easier fashion compared to turbulence with its chaotic dynamics across multiple scales in space and time. A parallel analogy in terms of sophistication of dynamics can be drawn between single phase and multiphase flows; the latter being the norm yet poorly understood due to numerous complexities arising on account of the huge parameter space involved. It is also remarkable that numerical studies are more prevalent in this field and there is a dearth of experimental results, which are important for both validation purposes and as a beacon to navigate research in practically relevant directions. This work has emerged to address the above issues. The attention has been largely directed towards understanding the flow of spherical particles in a square duct at moderately high concentrations using Particle Image Velocimetry (PIV) with refractive-index-matched (RIM) hydrogel particles. Fluids with Newtonian, viscoelastic and elastoviscoplastic rheology have been investigated due to their presence in natural and industrially relevant flows. Experiments and Direct Numerical Simulations (DNS) with spherical particles in a round pipe with turbulent flow of a Newtonian fluid are also conducted to extend and generalise the observations made in the square duct.

    With the ability to optically interrogate the bulk of the flow at high particle concentrations (20\% in this work), many interesting measurements are made possible, focussing on the turbulent regime. For the Newtonian fluid, the pressure drop or, equivalently, the energy required to pump the fluid-particle mixture is a complex function of particle size and concentration in the duct. This phenomenon arises due to the particle concentration distribution, with a local maxima at the core and the walls, and its resulting effect on the dominant stresses in the system i.e.\ the Reynolds shear stress and particle-induced stress. Particles also migrate in a similar fashion in a turbulent flow of viscoelastic suspending fluid but, with a larger tendency to accumulate in the core compared to its Newtonian counterpart at the same Reynolds number leading to a faster rise in total stress with concentration. Finally, for the \textit{thick} elastoviscoplastic fluid, the single-phase flow is laminar but it exhibits turbulence-like fluctuations when particles are added, which are distributed in exotic configurations depending on the interplay between the viscoelastic forces and the ensuing secondary flows as well as inertial forces. On the other hand, a quantitative comparison between simulations and experiments for particles transported along the floor of the duct under turbulent conditions has helped in reinforcing confidence in both approaches.

    We believe that these results will establish more confidence in the experimental usage of hydrogel particles for studying the flow of moderately dense suspensions. A natural extension would be the investigation of flow geometries more complex than a pipe or a square duct. Our results at higher Reynolds numbers is expected to motivate numerical simulations which are capable of investigating the detailed causes behind these observations, which are still unclear as of now. The information provided about the overall drag and the associated particle concentration and stress distribution will be helpful in painting a unified picture of turbulent suspension dynamics for a comprehensive range of flow rates and particle sizes. Future studies, either experimental or numerical, bearing similarities or deviations from our observations would also be constructive, for e.g.\ in assessing the sensitivity of the system to parameters that may be overlooked in the present study.

  • 124009.
    Zade, Sagar
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH Mech, Linne Flow Ctr, SE-10044 Stockholm, Sweden.;KTH Mech, SeRC Swedish E Sci Res Ctr, SE-10044 Stockholm, Sweden..
    Costa, Pedro
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH Mech, Linne Flow Ctr, SE-10044 Stockholm, Sweden.;KTH Mech, SeRC Swedish E Sci Res Ctr, SE-10044 Stockholm, Sweden..
    Fornari, Walter
    KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH Mech, Linne Flow Ctr, SE-10044 Stockholm, Sweden.;KTH Mech, SeRC Swedish E Sci Res Ctr, SE-10044 Stockholm, Sweden..
    Lundell, Fredrik
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH Mech, Linne Flow Ctr, SE-10044 Stockholm, Sweden.;KTH Mech, SeRC Swedish E Sci Res Ctr, SE-10044 Stockholm, Sweden..
    Brandt, Luca
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Mechanics, Stability, Transition and Control. KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics. KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Mechanics of Industrial Processes. KTH Mech, Linne Flow Ctr, SE-10044 Stockholm, Sweden.;KTH Mech, SeRC Swedish E Sci Res Ctr, SE-10044 Stockholm, Sweden..
    Experimental investigation of turbulent suspensions of spherical particles in a squareduct2018In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 857, p. 748-783Article in journal (Refereed)
    Abstract [en]

    We report experimental observations of turbulent flow with spherical particles in a square duct. Three particle sizes, namely 2H/d(p) = 40, 16 and 9 (2H being the duct full height and d(p) being the particle diameter), are investigated. The particles are nearly neutrally buoyant with a density ratio of 1.0035 and 1.01 with respect to the suspending fluid. Refractive index matched-particle image velocimetry (RIM-PIV) is used for fluid velocity measurement even at the highest particle volume fraction (20 %) and particle tracking velocimetry (PTV) for the particle velocity statistics for the flows seeded with particles of the two largest sizes, whereas only pressure measurements are reported for the smallest particles. Settling effects are seen at the lowest bulk Reynolds number R-e2H approximate to 10 000, whereas, at the highest R-e2H approximate to 27 000, particles are in almost full suspension. The friction factor of the suspensions is found to be significantly larger than that of single-phase duct flow at the lower R-e2H investigated; however, the difference decreases when increasing the flow rate and the total drag approaches the values of the single-phase flow at the higher Reynolds number considered, R-e2H = 27 000. The pressure drop is found to decrease with the particle diameter for volume fractions lower than (sic) = 10% for nearly all R-e2H investigated. However, at the highest volume fraction (sic) = 20 %, we report a peculiar non-monotonic behaviour: the pressure drop first decreases and then increases with increasing particle size. The decrease of the turbulent drag with particle size at the lowest volume fractions is related to an attenuation of the turbulence. The drag increase for the two largest particle sizes at (sic) = 20 %, however, occurs despite this large reduction of the turbulent stresses, and it is therefore due to significant particle-induced stresses. At the lowest Reynolds number, the particles reside mostly in the bottom half of the duct, where the mean velocity significantly decreases; the flow is similar to that in a moving porous bed near the bottom wall and to turbulent duct flow with low particle concentration near the top wall.

  • 124010.
    Zade, Sagar
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Fornari, Walter
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Lundell, Fredrik
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Brandt, Luca
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Buoyant finite-size particles in turbulent duct flow2019In: Physical Review Fluids, E-ISSN 2469-990X, no 4, article id 024303Article in journal (Refereed)
    Abstract [en]

    Particle image velocimetry and particle tracking velocimetry have been employed to investigate the dynamics of finite-size spherical particles, slightly heavier than the carrier fluid, in a horizontal turbulent square duct flow. Interface resolved direct numerical simulations (DNSs) have also been performed with the immersed boundary method at the same experimental conditions, bulk Reynolds number Re2H=5600, duct height to particle-size ratio 2H/dp=14.5, particle volume fraction Φ=1%, and particle to fluid density ratio ρp/ρf=1.0035. Good agreement has been observed between experiments and simulations in terms of the overall pressure drop, concentration distribution, and turbulent statistics of the two phases. Additional experimental results considering two particle sizes 2H/dp=14.5 and 9 and multiple Φ=1%, 2%, 3%, 4%, and 5% are reported at the same Re2H. The pressure drop monotonically increases with the volume fraction, almost linearly and nearly independently of the particle size for the above parameters. However, despite the similar pressure drop, the microscopic picture in terms of fluid velocity statistics differs significantly with the particle size. This one-to-one comparison between simulations and experiments extends the validity of interface resolved DNS in complex turbulent multiphase flows and highlights the ability of experiments to investigate such flows in considerable detail, even in regions where the local volume fraction is relatively high.

  • 124011.
    Zade, Sagar
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Lundell, Fredrik
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Brandt, Luca
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Turbulence modulation by finite-size spherical particles in Newtonian and viscoelastic fluids2019In: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533, Vol. 112, p. 116-129Article in journal (Refereed)
    Abstract [en]

    We experimentally investigate the influence of finite-size spherical particles in turbulent flows of a Newtonian and a drag reducing viscoelastic fluid at varying particle volume fractions and fixed Reynolds number. Experiments are performed in a square duct at a Reynolds number Re2H of nearly 1.1 × 104, Weissenberg number Wi for single phase flow is between 1 and 2 and results in a drag-reduction of 43% compared to a Newtonian flow (at the same Re2H). Particles are almost neutrally-buoyant hydrogel spheres having a density ratio of 1.0035 ± 0.0003 and a duct height 2H to particle diameter dp ratio of around 10. We measure flow statistics for four different volume fractions ϕ namely 5, 10, 15 and 20% by using refractive-index-matched Particle Image Velocimetry (PIV). For both Newtonian Fluid (NF) and Visceolastic Fluid (VEF), the drag monotonically increases with ϕ. For NF, the magnitude of drag increase due to particle addition can be reasonably estimated using a concentration dependent effective viscosity for volume fractions below 10%. The drag increase is, however, underestimated at higher ϕ. For VEF, the absolute value of drag is lower than NF but, its rate of increase with ϕ is higher. Similar to particles in a NF, particles in VEF tend to migrate towards the center of the duct and form a layer of high concentration at the wall. Interestingly, relatively higher migration towards the center and lower migration towards the walls is observed for VEF. The primary Reynolds shear stress reduces with increasing ϕ throughout the duct height for both types of fluid.

  • 124012.
    Zade, Sagar
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics.
    Shamu, Tafadzwa John
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Lundell, Fredrik
    KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics.
    Brandt, Luca
    KTH, Superseded Departments (pre-2005), Mechanics.
    Finite-size spherical particles in a square duct flow of an elastoviscoplastic fluid: an experimental studyManuscript (preprint) (Other academic)
    Abstract [en]

    The present experimental study addresses the flow of a Yield Stress Fluid (YSF) with some elasticity (Carbopol gel) in a square duct. The behaviour of two fluids with lower and higher yield stress is investigated in terms of the friction factor and flow velocities at multiple Reynolds numbers $Re^* \in$ (1, 200) and, hence, Bingham numbers $Bi \in$ (0.01, 0.35). Taking advantage of the symmetry planes in a square duct, we reconstruct the entire 3-component velocity field from 2-dimensional Particle Image Velocimetry (PIV). A secondary flow consisting of eight vortices is observed to recirculate the fluid from the core towards the wall-center and from the corners back to the core. The extent and intensity of these vortices grows with increasing $Re^*$ or, alternately, as the plug-size decreases. The second objective of this study is to explore the change in flow in the presence of particles. To this end, almost neutrally-buoyant finite-size spherical particles with duct height, $2H$, to particle diameter, $d_p$, ratio of 12 are used at two volume fractions $\phi$ = 5 and 10\%. Particle Tracking Velocimetry (PTV) is used to measure the velocity of these refractive-index-matched spheres in the clear Carbopol gel, and PIV to extract the fluid velocity. Additionally, simple shadowgraphy is also used for qualitatively visualising the development of the particle distribution along the streamwise direction. The particle distribution pattern changes from being concentrated at the four corners, at low flow rates, to being focussed along a diffused ring between the center and the corners, at high flow rates. The presence of particles induces streamwise and wall-normal velocity fluctuations in the fluid phase; however, the primary Reynolds shear stress is still very small compared to turbulent flows. The size of the plug in the particle-laden cases appears to be smaller than the corresponding single phase cases. Similar to Newtonian fluids, the friction factor increases due to the presence of particles, almost independently of the suspending fluid matrix. Interestingly, predictions based on an increased effective suspension viscosity agrees quite well with the experimental friction factor for the concentrations used in this study.

  • 124013. Zadeh, Iman Esmaeil
    et al.
    Elshaari, Ali W.
    KTH, School of Electrical Engineering (EES). Delft Univ Technol, Netherlands.
    Jöns, Klaus D.
    KTH, School of Electrical Engineering (EES). Delft Univ Technol, Netherlands.
    Fognini, Andreas
    Dalacu, Dan
    Poole, Philip J.
    Reimer, Michael E.
    Zwiller, Val
    KTH, School of Electrical Engineering (EES). Delft Univ Technol, Netherlands.
    Deterministic Integration of Single Photon Sources in Silicon Based Photonic Circuits2016In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 16, no 4, p. 2289-2294Article in journal (Refereed)
    Abstract [en]

    A major step toward fully integrated quantum optics is the deterministic incorporation of high quality single photon sources in on-chip optical circuits. We show a novel hybrid approach in which preselected III-V single quantum dots in nanowires are transferred and integrated in silicon based photonic circuits. The quantum emitters maintain their high optical quality after integration as verified by measuring a low multiphoton probability of 0.07 +/- 0.07 and emission line width as narrow as 3.45 +/- 0.48 GHz. Our approach allows for optimum alignment of the quantum dot light emission to the fundamental waveguide mode resulting in very high coupling efficiencies. We estimate a coupling efficiency of 24.3 +/- 1.7% from the studied single-photon source to the photonic channel and further show by finite-difference time-domain simulations that for an optimized choice of material and design the efficiency can exceed 90%.

  • 124014. Zadeh, Iman Esmaeil
    et al.
    Los, Johannes W. N.
    Gourgues, Ronan B. M.
    Steinmetz, Violette
    Bulgarini, Gabriele
    Dobrovolskiy, Sergiy M.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Nano Photonics. Single Quantum BV, Netherlands.
    Dorenbos, Sander N.
    Single-photon detectors combining high efficiency, high detection rates, and ultra-high timing resolution2017In: APL PHOTONICS, ISSN 2378-0967, Vol. 2, no 11, article id 111301Article in journal (Refereed)
    Abstract [en]

    Single-photon detection with high efficiency, high time resolution, low dark counts, and high photon detection rates is crucial for a wide range of optical measurements. Although efficient detectors have been reported before, combining all performance parameters in a single device remains a challenge. Here, we show a broadband NbTiN superconducting nanowire detector with an efficiency exceeding 92%, over 150 MHz photon detection rate, and a dark count rate below 130 Hz operated in a Gifford-McMahon cryostat. Furthermore, with careful optimization of the detector design and readout electronics, we reach an ultra-low system timing jitter of 14.80 ps (13.95 ps decoupled) while maintaining high detection efficiencies (>75%).

  • 124015.
    Zadeh, Navid Shariat
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Lindberg, Lars
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    El-Khoury, Jad
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Sivard, Gunilla
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Service Oriented Integration of Distributed Heterogeneous IT Systems in Production Engineering Using Information Standards and Linked Data2017In: Modelling and Simulation in Engineering, ISSN 1687-5591, E-ISSN 1687-5605, article id 9814179Article in journal (Refereed)
    Abstract [en]

    While design of production systems based on digital models brings benefits, the communication of models comes with challenges since models typically reside in a heterogeneous IT environment using different syntax and semantics. Coping with heterogeneity requires a smart integration strategy. One main paradigm to integrate data and IT systems is to deploy information standards. In particular, ISO 10303 STEP has been endorsed as a suitable standard to exchange a wide variety of product manufacturing data. One the other hand, service-oriented tool integration solutions are progressively adopted for the integration of data and IT-tools, especially with the emergence of Open Services for Lifecycle Collaboration whose focus is on the linking of data from heterogeneous software tools. In practice, there should be a combination of these approaches to facilitate the integration process. Hence, the aim of this paper is to investigate the applications of the approaches and the principles behind them and try to find criteria for where to use which approach. In addition, we explore the synergy between them and consequently suggest an approach based on combination of them. In addition, a systematic approach is suggested to identify required level of integrations and their corresponding approaches exemplified in a typical IT system architecture in Production Engineering.

  • 124016.
    Zaeid, Jabar
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Lind, Andreas
    KTH, School of Information and Communication Technology (ICT).
    Utveckling av ny teknik för hjärtpulsdetektion2017Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this thesis we suggest a technique for detecting pulses by signal processing of a raw ECG signal registered from 4 electrodes located on the left upper arm. The signal processing is performed in Matlab and consists of normalization, lowpass filtering, highpass filtering, derivation, squaring and a moving average window to reduce interference. The technology is capable of extracting periods between heartbeats after an implemented detection algorithm. The thesis also includes reflections on the types of interferences that may affect an electrical development equipment and also methods of how major parts of the interference can be reduced by different shields. Before the technique is applied in a final product, further tests may need to be performed during the monitoring of a person's pulse. Finally, we believe that our development of pulse detection is the beginning of a new technology that in the future can save lives.

  • 124017. Zafar, B.
    et al.
    Ben Slimane, Slimane
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Communication Systems, CoS (closed 2012-01-01).
    Javed, Muhammad Umar
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Communication Systems, CoS (closed 2012-01-01).
    Network product coding2010In: 2010 7th IEEE Consumer Communications and Networking Conference, CCNC 2010, IEEE , 2010, p. -266Conference paper (Refereed)
    Abstract [en]

    Network coding is a useful tool to increase the multicast capacity of networks. The traditional approach to network coding involving XOR operation has several limitations such as low robustness and can support only two users/packets at a time,per relay, in the mixing process to achieve optimal error performance. We propose the employment of product coding at the relay station instead of xor and investigate such a system where we use the relay to generate product codes by combining packets from different users. Our scheme uses relays to transmit only the redundancy of the product code instead of the whole product code. We seek to employ product coding can be able to support more than two users/packets per relay per slot, while maintaining a good error performance. Our scheme can accomodate as many users per relay as the costituent block code allows, thus reducing the number of relays required in the network.Product codes also offer increased robustness and flexibility as well as several other advantages, such as proper structure for burst error correction without extra interleaving. We compare the performance of such a scheme to the conventional xor scheme and see that our scheme not only reduces the number of relays required but gives improved error performance as well as. Another encouraging result is that our scheme starts to significantly outperform the conventional one by introducing a gain at the relay.

  • 124018.
    Zafar, Bilal
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Network Coding Employing Product Coding at Relay Stations2009Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Network coding is a useful tool to increase the multicast capacity of networks. The traditional approach to network coding involving XOR operation has several limitations such as low robustness and can support only two users/packets at a time,per relay, in the mixing process to achieve optimal error performance. We propose the employment of product coding at the relay station instead of xor and investigate such a system where we use the relay to generate product codes by combining packets from different users.Our scheme uses relays to transmit only the redundancy of the product code instead of the whole product code.We seek to employ product coding can be able to support more than two users/packets per relay per slot,while maintaining a good error performance. Our scheme can accomodate as many users per relay as the costituent block code allows, thus reducing the number of relays required in the network. Product codes also offer increased robustness and flexibility as well as several other advantages, such as proper structure for burst error correction without extra interleaving. We compare the performance of such a scheme to the conventional xor scheme and see that our scheme not only reduces the number of relays required but gives improved error performance as well as. Another encouraging result is that our scheme starts to significantly outperform the conventional one by introducing a gain at the relay.

  • 124019.
    Zafarzadeh, Masoud
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Sustainable production development.
    Baalsrud Hauge, Jannicke
    KTH, School of Industrial Engineering and Management (ITM), Sustainable production development.
    Wiktorsson, Magnus
    KTH, School of Industrial Engineering and Management (ITM), Sustainable production development.
    Real-time data gathering in production logistics: A research review on applications and technologies affecting environmental and social sustainability2019Conference paper (Refereed)
    Abstract [en]

    This paper aims to identify the challenges and issues concerning environmental or social sustainability in Production Logistics that are affected by implementing real-time data collection concepts, technologies and applications. A systematic literature review has been conducted to shed a light on sustainability aspect of real-time technologies and applications. According to the findings, few researches directly investigated how real-time data collection affect the environmental and social aspects of sustainability. Besides, the indirect effects are discussed in order to find a better picture about the relation between these technologies and sustainability.

  • 124020.
    Zafarzadeh, Masoud
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Sustainable production development.
    Baalsrud Hauge, Jannicke
    KTH, School of Industrial Engineering and Management (ITM), Sustainable production development.
    Wiktorsson, Magnus
    Hedman, Ida
    Bahtijarevic, Jasmin
    Real-Time Data Sharing in Production Logistics: Exploring Use Cases by an Industrial Study2019In: Advances in Production Management Systems. Towards Smart Production Management Systems: IFIP WG 5.7 International Conference, APMS 2019, Austin, TX, USA, September 1–5, 2019, Proceedings, Part II / [ed] F. Ameri et al. (Eds.):, New York: Springer, 2019, Vol. 567, p. 285-293Conference paper (Refereed)
    Abstract [en]

    Production logistics systems consist often of a number of low value-added activities combined with a high degree of manual work. Therefore, increasing effectivity and responsiveness has always been a target for production logistics systems. Sharing data in real-time may have a considerable potential to increase effectivity and responsiveness. The first step to realise real-time data sharing is to have a clear understanding of current state of PL systems and their requirements. This work is performed an ‘as-is’ situation analysis of an industrial case aiming at identifying which areas and applications would benefit most from real-time data sharing. The findings take a step closer to have a better understanding of CPS and Industry 4.0.

  • 124021.
    Zafeiropoluos, Andreas
    KTH, School of Electrical Engineering (EES).
    An MMC-based topology with Dual-Active-Bridge power channels for load balancing in 50 Hz-railway applications2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this thesis report is to investigate challenges related to railway electrification. Inac-railway systems, trains are most often single-phase loads, which can create significantunbalances in the grid, when fed directly from two adjacent phases. To enhance power quality atthe railway feeding point, one alternative is to design the system such as the power is fed to thecatenary through Static Frequency Converters (SFCs), which can be a costly solution. Anotheroption is to use Static Compensators (STATCOMs) in shunt connections, handling only theunbalanced amount of power, in order to symmetrize the railway load as seen from the grid side.Modular multilevel converters (MMCs) are the state of the art solutions for medium- and highvoltage/power converter applications, such as load balancing and reactive-power compensation.This project will focus on analyzing Modular Multilevel Converter (MMC) topologies to be usedas load balancers in railway systems. However, the specific requirements of this application reveala potential weakness of MMCs. That is the asymmetrical character of the load may require muchhigher device rating in an MMC compared to a conventional converter, due to the symmetrizingcomponents to rebalance the capacitor voltages in the submodules.This project analyzes a reduced MMC-based topology with only two branches in order to meet therailway load-balancing characteristics. This chain-link compensator uses dc-dc converters tofacilitate power channels in order to restore the power imbalance, without overrating thesemiconductors in the main current path.

  • 124022.
    Zafirakis, Zacharias
    KTH, School of Electrical Engineering (EES).
    Development of a Testing Assembly for Powertrain Speed Sensors2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Knowledge about the speed and the direction of the di˙erent shafts in the gearbox and the engine of trucks is becoming more and more important, especially as the industry moves towards autonomous vehicles. The most common way to measure these parame-ters today is by using inductive or Hall sensors. Testing and benchmarking these sensors has a large significance for heavy truck manufacturers such as Scania.In order to test these components, a rig assembly was constructed. In this project a LabVIEW program was developed for controlling the rig and gathering the required data. The aim of the rig was to try and simulate the behaviour of the components that are commonly measured in the gearbox or the engine, as well as use it for testing and benchmarking new rotational speed sensors. In order to achieve this, di˙erent processes were studied that cover certain working conditions in a Scania truck. The rig’s ability to follow these processes was then studied. In addition, a test case for inductive and Hall sensors was also presented.It is shown that the implemented solution for testing the sensors can be used for benchmarking di˙erent sensors and can be a useful tool for future sensor development at Scania. However, the rig with its current hardware was unable to closely replicate processes that are of interest. There are a lot of improvements that have to be made in order to properly simulate the behaviour of the powertrain components that are of interest for speed sensor applications.

  • 124023.
    Zafoschnig, Lisa Anna
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    SnOx electron selective layers for perovskite/silicon tandem solar cells using atomic layer deposition2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this work the application of ALD deposited SnOx films as electron transport layers in perovskite solar cells is analysed. Processes to fabricate homogeneous, transparent and conductive tin oxide films were developed on an Oxford Instruments FlexAL tool using a TDMASn precursor and H2O as oxidiser. Two process regimes were investigated; an ALD regime, where the precursor gases are fully separated by long purging steps and a pulsed-CVD regime, where short purge times allow for continuous reactions. Both process regimes were analysed at deposition temperatures from 100 – 250°C and showed a decrease in growth rate with an increase in refractive index for higher temperatures. In terms, of optical properties highly transparent films in the visible range (> 80%) were obtained for all analysed processes. The samples with the lowest absorption were SnOx films deposited at low temperatures in the pulsed-CVD regime. Films with low absorption also exhibited improved conductivity in the range of 200 – 500 Ωcm, which decreased further when the samples were heated. All investigated films were amorphous with a tin rich atomic composition of SnOx. The processes were performed to be compatible with n-i-p and inverted perovskite single junction solar cells as well as tandem devices on textured silicon bottom cells, due to conformal coating at low deposition temperatures and no need for thermal annealing steps.

    For the application on cell level, perovskite single junction solar cells in a n-i-p architecture were fabricated with a ~15 nm SnOx film as electron transport layer. To improve electron extraction properties different organic interlayers and mesoporous TiO2 were investigated below the perovskite absorber. It was seen that the use of PCBM on top of SnOx improved the solar cell performance of devices with a co-evaporated MAPbI3 absorber. Solar cells with efficiencies close to 6% were fabricated which exhibited a moderately high Voc of ~990 mV but low Jsc of < 10 mA/cm². For devices with wet-chemically deposited perovskite absorber materials, the fullerene solutions did not form a closed film due to wettability issues on SnOx and the risk of washing away by the spin-coated perovskite solution. SEM-images confirmed that no closed interlayers were formed in the wet-chemical devices which could be the cause of poor reproducibility for devices with a planar structure and SnOx as electron contact. The best performing device was achieved with SnOx and mesoporous TiO2 deposited by spin-coating and a MAPbI3 absorber. It showed a mean PCE from forward and reverse scans of 12.8% with a Voc > 990 mV and a Jsc close to 20 mA/cm². Compared to the TiO2 reference cells the devices using SnOx showed lower efficiencies but improved reproducibility and reduced hysteresis in the mesoporous structure. The produced cells serve as an initial proof of concept for the use of SnOx by ALD in the analysed solar cell structure. 

    To analyse the potential for commercialisation of perovskite based photovoltaic technologies a techno-economic analysis was performed. Taking into account up-scaled manufacturing processes for perovskite modules, manufacturing costs of 21.0 $/m² were calculated. This cost is below the calculated allowed extra costs for the top cell of a tandem device with 30 % efficiency, estimated at 30 – 80 $/m². Projections of the LCOE showed that perovskite single junction cells with a PCE of 15% and a lifetime of 25 years could achieve an LCOE of 5.2 c/kWh. For two-terminal tandem devices with a similar lifetime and an efficiency of 27% an LCOE of 6.6 c/kWh could potentially be achieved, making both technologies competitive with conventional energy technologies in Germany. An overview of literature on life cycle assessments showed that despite the use of lead based absorber materials, perovskite technologies have a minor environmental impact and are considered more sustainable than other photovoltaic technologies.

  • 124024.
    Zafra, Sebastian Ortega
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Acreo Swedish ICT AB, Sweden.
    Pang, Xiaodan
    Jacobsen, Gunnar
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Sergeyev, Sergey
    Phase noise tolerance study in coherent optical circular QAM transmissions with Viterbi-Viterbi carrier phase estimation2014In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 22, no 25, p. 30579-30585Article in journal (Refereed)
    Abstract [en]

    We present a performance evaluation of a non-conventional approach to implement phase noise tolerant optical systems with multilevel modulation formats. The performance of normalized Viterbi-Viterbi carrier phase estimation (V-V CPE) is investigated in detail for circular m-level quadrature amplitude modulation (C-mQAM) signals. The intrinsic property of C-mQAM constellation points with a uniform phase separation allows a straightforward employment of V-V CPE without the need to adapt constellation. Compared with conventional feed-forward CPE for square QAM signals, the simulated results show an enhanced tolerance of linewidth symbol duration product (Delta vT(s)) at a low sensitivity penalty by using feed-forward CPE structure with C-mQAM. This scheme can be easily upgraded to higher order modulations without inducing considerable complexity.

  • 124025.
    Zagal, Juan Cristobal
    et al.
    KTH, Superseded Departments, Numerical Analysis and Computer Science, NADA.
    Björkman, Eva
    Lindeberg, Tony
    KTH, Superseded Departments, Numerical Analysis and Computer Science, NADA.
    Roland, P.
    Signficance determination for the scale-space primal sketch by comparison of statistics of scale-space blob volumes computed from PET signals vs. residual noise2000In: : HBM'00 published in Neuroimage, volume 11, number 5, 2000, 2000, Vol. 11, p. 493-493Conference paper (Refereed)
    Abstract [en]

    A dominant approach to brain mapping is to define functional regions in the brain by analyzing brain activation images obtained by PET or fMRI. In [1], it has been shown that the scale-space primal sketch provides a useful tool for such analysis. Some attractive properties of this method are that it only makes few assumptions about the data and the process for extracting activations is fully automatic.

    In the present version of the scale-space primal sketch, however, there is no method for determining p-values. The purpose here is to present a new methodology for addressing this question, by introducing a descriptor referred to as the -curve, which serves as a first step towards determining the probability of false positives, i.e. alpha.

  • 124026.
    Zagorodni, Andrei
    KTH, Superseded Departments, Materials Science and Engineering.
    Evaluation of results obtained by analysis of fractions2004In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 512, no 2, p. 251-256Article in journal (Refereed)
    Abstract [en]

    The paper discusses treatment of experimental data obtained from the monitoring of continuous processes by a series of batch analyses (i.e. by analysis of fractions sequentially collected during the process). Common errors that are committed when graphically representing and fitting such data are shown. An approach for identification of such errors in published data is presented. One error results from the incorrect positioning of the analysis results along the X-axis when plotting data. In the case of equal fractions, this results in a systematic error along the X-axis. For non-equal fractions, the error in the coefficients of the fitting equation can be both systematic and random. A correct representation does not introduce any error if the actual function is linear in the region of the fraction collection. This plotting method is also a satisfactory procedure for low curvature functions. Another error originates because of the incorrect application of the least squares method. The reason lies in the fact that the analysis of each fraction does not represent an instant value of the measured parameter, but rather the averaged value over some period of time or over some volume. The actual error depends on the curvature of the fitting function. Furthermore, a reader encounters difficulties when evaluating published scientific information because many authors do not explain the methods by which their data were plotted and fit. The presented approach to the evaluation of graphical data makes it possible to identify the described errors.

  • 124027. Zagorodni, Andrei
    Ion Exchange Materials: Properties and Applications2007Book (Other academic)
    Abstract [en]

    Ion Exchange Materials: Properties and Applications fills a "two-dimensional" gap in books currently available on the subject. Firstly, there is a lack of modern comprehensive publications on the chemistry of ion exchange materials and on the relationships between their properties and practical applications. Secondly, there are few books on ion exchange chemistry that are targeted to industrial R&D specialists and research students who (i) do not work with ion exchange on a daily basis, (ii) need to develop competence in this area, and (iii) find it difficult to start studying the subject from primary scientific publications. The book bridges these gaps by describing classical and modern theoretical concepts, as well as practical approaches for using ion exchange materials. Ion exchange materials combine properties of homogeneous and heterogeneous materials. Besides being an interesting subject for investigation, they are essential in a wide variety of industrial technologies: in the chemical and biochemical industries, pharmacy, medicine, microelectronics, the nuclear industry, food production, waste treatment, and many other areas. Ion exchange is a powerful tool in chemical analysis and scientific research. The main focus in this book is on ion exchange polymers: ion exchange resins, chelating resins, imprinted (templated), and other functional polymers. It provides an in-depth study of ion exchange materials, suitable for postgraduate students and R&D industrial specialists in chemistry, chemical and biochemical technology. * Comprehensively covers the subject. * Provides links between theoretical concepts, material properties, practical applications, and technical solutions. * Easy to understand - requires only ground knowledge of university-level chemistry and can be read without an in-depth knowledge of mathematics. * Supported with an interactive web-site. © 2007 Elsevier Ltd All rights reserved.

  • 124028.
    Zagorodni, Andrei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Ion Exchange Materials: Properties and Applications2007Book (Refereed)
    Abstract [en]

    Ion Exchange Materials: Properties and Applications fills a "two-dimensional" gap in books currently available on the subject. Firstly, there is a lack of modern comprehensive publications on the chemistry of ion exchange materials and on the relationships between their properties and practical applications. Secondly, there are few books on ion exchange chemistry that are targeted to industrial R&D specialists and research students who (i) do not work with ion exchange on a daily basis, (ii) need to develop competence in this area, and (iii) find it difficult to start studying the subject from primary scientific publications. The book bridges these gaps by describing classical and modern theoretical concepts, as well as practical approaches for using ion exchange materials. Ion exchange materials combine properties of homogeneous and heterogeneous materials. Besides being an interesting subject for investigation, they are essential in a wide variety of industrial technologies: in the chemical and biochemical industries, pharmacy, medicine, microelectronics, the nuclear industry, food production, waste treatment, and many other areas. Ion exchange is a powerful tool in chemical analysis and scientific research. The main focus in this book is on ion exchange polymers: ion exchange resins, chelating resins, imprinted (templated), and other functional polymers. It provides an in-depth study of ion exchange materials, suitable for postgraduate students and R&D industrial specialists in chemistry, chemical and biochemical technology. * Comprehensively covers the subject. * Provides links between theoretical concepts, material properties, practical applications, and technical solutions. * Easy to understand - requires only ground knowledge of university-level chemistry and can be read without an in-depth knowledge of mathematics. * Supported with an interactive web-site.

  • 124029. Zagorodni, Andrei A.
    et al.
    Salazar-Alvarez, German
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Bar-shaped nanoparticles of iron(II) hydroxide2008In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 10, no 2, p. 377-381Article in journal (Refereed)
    Abstract [en]

    Formation of elongated nanoparticles was observed when FE3O4 was precipitated from solutions containing excess of Fe2+. The average diameter of the particles was 23 nm; the length to diameter ratio was up to 14. This shape was an unexpected phenomenon because bar- or needle-like nanoparticles have been earlier reported only for Fe(III)-based materials. Chemical analysis revealed Fe(OH)(2) nature of the obtained particles. In addition, this conclusion was verified with a new simple method for quantitative evaluation of the particle morphology. Application of this method to the mixed Fe(OH)(2/)Fe3O4 samples allowed to distinguish between the two different compounds and to attribute different morphologies to Fe(OH)(2) or Fe3O4. Results indicate that bars are frequent shapes of nano-sized iron oxides/hydroxides.

  • 124030. Zagorodskikh, S.
    et al.
    Vapa, M.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Univ Oulu, Finland.
    Vahtras, Olav
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Zhaunerchyk, V.
    Mucke, M.
    Eland, J. H. D.
    Squibb, R. J.
    Linusson, P.
    Jankala, K.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Feifel, R.
    An experimental and theoretical study of core-valence double ionisation of acetaldehyde (ethanal)2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 4, p. 2535-2547Article in journal (Refereed)
    Abstract [en]

    Core-valence double ionisation spectra of acetaldehyde (ethanal) are presented at photon energies above the carbon and oxygen 1s ionisation edges, measured by a versatile multi-electron coincidence spectroscopy technique. We use this molecule as a testbed for analyzing core-valence spectra by means of quantum chemical calculations of transition energies. These theoretical approaches range from two simple models, one based on orbital energies corrected by core valence interaction and one based on the equivalent core approximation, to a systematic series of quantum chemical electronic structure methods of increasing sophistication. The two simple models are found to provide a fast orbital interpretation of the spectra, in particular in the low energy parts, while the coverage of the full spectrum is best fulfilled by correlated models. CASPT2 is the most sophisticated model applied, but considering precision as well as computational costs, the single and double excitation configuration interaction model seems to provide the best option to analyze core-valence double hole spectra.

  • 124031.
    Zahedi, Sara
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Numerical Analysis, NA.
    A Space-Time Cut Finite Element Method with Quadrature in Time2017In: Geometrically Unfitted Finite Element Methods and Applications: Proceedings of the UCL Workshop 2016, Cham: Springer, 2017, p. 281-306Chapter in book (Refereed)
  • 124032.
    Zahedi, Sara
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis, NA.
    Numerical Methods for Fluid Interface Problems2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis concerns numerical techniques for two phase flowsimulations; the two phases are immiscible and incompressible fluids. Strategies for accurate simulations are suggested. In particular, accurate approximations of the weakly discontinuousvelocity field, the discontinuous pressure, and the surface tension force and a new model for simulations of contact line dynamics are proposed.

    In two phase flow problems discontinuities arise in the pressure and the gradient of the velocity field due to surface tension forces and differences in the fluids' viscosity. In this thesis, a new finite element method which allows for discontinuities along an interface that can be arbitrarily located with respect to the mesh is presented. Using standard linear finite elements, the method is for an elliptic PDE proven to have optimal convergence order and a system matrix with condition number bounded independently of the position of the interface.The new finite element method is extended to the incompressible Stokes equations for two fluid systemsand enables accurate approximations of the weakly discontinuous velocity field and the discontinuous pressure.

    An alternative way to handle discontinuities is regularization. In this thesis, consistent regularizations of Dirac delta functions with support on interfaces are proposed. These regularized delta functions make it easy to approximate surface tension forces in level set methods.

    A new model for simulating contact line dynamics is also proposed. Capillary dominated flows are considered and it is assumed that contact line movement is driven by the deviation of the contact angle from its static value. This idea is used together with the conservative level set method. The need for fluid slip at the boundary is eliminated by providing a diffusive mechanism for contact line movement. Numerical experiments in two space dimensions show that the method is able to qualitatively correctly capture contact line dynamics.

  • 124033.
    Zahedi, Sara
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis, NA.
    Numerical Modeling of Fluid Interface Phenomena2009Licentiate thesis, comprehensive summary (Other academic)
  • 124034.
    Zahedi, Sara
    et al.
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis, NA.
    Gustavsson, Katarina
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis, NA.
    Kreiss, Gunilla
    Division of Scientific Computing, Department of Information Technology, Uppsala University.
    A Conservative Level Set Method for Contact Line Dynamics2009In: Journal of Computational Physics, ISSN 0021-9991, E-ISSN 1090-2716, Vol. 228, no 17, p. 6361-6375Article in journal (Refereed)
    Abstract [en]

    A new model for simulating contact line dynamics is proposed. We apply the idea of driving contact-line movement by enforcing the equilibrium contact angle at the boundary, to the conservative level set method for incompressible two-phase flow [E. Olsson, G. Kreiss, A conservative level set method for two phase flow, J. Comput. Phys. 210 (2005) 225-246]. A modified reinitialization procedure provides a diffusive mechanism for contact-line movement, and results in a smooth transition of the interface near the contact line without explicit reconstruction of the interface. We are able to capture contact-line movement without loosing the conservation. Numerical simulations of capillary dominated flows in two space dimensions demonstrate that the model is able to capture contact line dynamics qualitatively correct.

  • 124035.
    Zahedi, Sara
    et al.
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis, NA (closed 2012-06-30).
    Knonbichler, Martin
    Uppsala Univ, Uppsala, Sweden .
    Kreiss, Gunilla
    Uppsala University.
    Spurious currents in finite element based level set methods for two-phase flow2012In: International Journal for Numerical Methods in Fluids, ISSN 0271-2091, E-ISSN 1097-0363, Vol. 69, no 9, p. 1433-1456Article in journal (Refereed)
    Abstract [en]

    A study of spurious currents in continuous finite element based simulations of the incompressible Navier-Stokes equations for two-phase flows is presented on the basis of computations on a circular drop in equilibrium. The conservative and the standard level set methods are used. It is shown that a sharp surface tension force, expressed as a line integral along the interface, can give rise to large spurious currents and oscillations in the pressure that do not decrease with mesh refinement. If instead a regularized surface tension representation is used, exact force balance at the interface is possible, both for a fully coupled discretization approach and for a fractional step projection method. However, the numerical curvature calculation introduces errors that cause spurious currents. Different ways to extend the curvature from the interface to the whole domain are discussed and investigated. The impact of using different finite element spaces and stabilization methods is also considered.

  • 124036.
    Zahedi, Sara
    et al.
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis, NA.
    Kreiss, Gunilla
    An unfitted Nitsche method for the incompressible two fluid Stokes systemManuscript (preprint) (Other academic)
    Abstract [en]

    An easy-to-use finite element method for two fluid Stokes flow, with accurate treatment of jumps in pressure and in velocity gradients at the fluid-fluid interface, is presented. The method allows for an interface not aligned with the grid, and is based on continuous linear finite elements. The jumps at the interface are enforced by a variant of Nitsche's method. Numerical experiments demonstrate optimal convergence order.

  • 124037.
    Zahedi, Sara
    et al.
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis, NA.
    Kreiss, Gunilla
    Gustavsson, Katarina
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis, NA.
    An Interface Capturing Method for Two-Phase Flow with Moving Contact Lines2008In: Proccedings of the 1st European Conference on Microfluidics 2008, SOCIETE HYDROTECHNIQUE DE FRANCE , 2008Conference paper (Refereed)
  • 124038.
    Zahedi, Sara
    et al.
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis, NA.
    Tornberg, Anna-Karin
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis, NA.
    Delta Function Approximations in Level Set Methods by Distance Function Extension2010In: Journal of Computational Physics, ISSN 0021-9991, E-ISSN 1090-2716, Vol. 229, no 6, p. 2199-2219Article in journal (Refereed)
    Abstract [en]

     In [A.-K. Tornberg, B. Engquist, Numerical approximations of singular source terms in differential equations, J. Comput. Phys. 200 (2004) 462-488], it was shown for simple examples that the then most common way to regularize delta functions in connection to level set methods produces inconsistent approximations with errors that are not reduced with grid refinement. Since then, several clever approximations have been derived to overcome this problem. However, the great appeal of the old method was its simplicity. In this paper it is shown that the old method - a one-dimensional delta function approximation extended to higher dimensions by a distance function - can be made accurate with a different class of one-dimensional delta function approximations. The prize to pay is a wider support of the resulting delta function approximations.

  • 124039.
    Zahedi, Sara
    et al.
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis, NA.
    Wadbro, Eddie
    Kreiss, Gunilla
    Berggren, Martin
    A uniformly well-conditioned, unfitted Nitsche method for interface problems: PartIIn: SIAM Journal on Numerical Analysis, ISSN 0036-1429, E-ISSN 1095-7170Article in journal (Other academic)
    Abstract [en]

    A finite element method for elliptic partial differential equations that allows for discontinuities along an interface not aligned with the mesh is presented.The solution on each side of the interface is separately expanded in standard continuous, piecewise-linear functions, and a variant of Nitsche's method enforces the jump conditions at the interface.In this method, the solutions on each side of the interface are extended to the entire domain, which results in a fixed number of unknowns independent of the location of the interface. A stabilization procedure is included to ensure well-defined extensions. Numerical experiments are presented showing optimal convergence order in the energy and $L^2$ norms, and also for pointwise errors. The presented results also show that the condition number of the system matrix is independent of the position of the interface relative to the grid.

  • 124040. Zahedinejad, M.
    et al.
    Awad, A. A.
    Dürrenfeld, P.
    Houshang, A.
    Yin, Y.
    Muduli, P. K.
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. University of Gothenburg, Sweden.
    Current Modulation of Nanoconstriction Spin-Hall Nano-Oscillators2017In: IEEE Magnetics Letters, ISSN 1949-307X, E-ISSN 1949-3088, Vol. 8, article id 7858729Article in journal (Refereed)
    Abstract [en]

    A single nanoconstriction spin-Hall nano-oscillator (NC-SHNO) in out-of-plane fields is presented as a nonlinear amplitude and frequency modulator operated by radio-frequency (RF) current modulation. The current modulation was carried out in different NC-SHNO nonlinearity regimes corresponding to negative, zero, and positive values of df/dI in order to investigate the device response to an 80 MHz modulating current. Our study shows that current modulation of SHNOs can be quantitatively predicted by a nonlinear frequency and amplitude modulation (NFAM) model using the values of df/dI and d2f/dI2 extracted from the free-running frequency f versus current I profile. The NFAM model reproduces the asymmetric sideband amplitude as well as the red and blue shift of the frequency in excellent agreement with the experimental results. The ability to predict the modulation process is a necessary benchmark in designing SHNO modulators for future integrated microwave circuits.

  • 124041.
    Zahedinejad, M.
    et al.
    Univ Gothenburg, Dept Phys, S-41296 Gothenburg, Sweden..
    Mazraati, Hamid
    KTH, School of Engineering Sciences (SCI), Applied Physics. NanOsc AB, S-16440 Kista, Sweden.
    Fulara, H.
    Univ Gothenburg, Dept Phys, S-41296 Gothenburg, Sweden..
    Yue, J.
    Univ Gothenburg, Dept Phys, S-41296 Gothenburg, Sweden..
    Jiang, Sheng
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Awad, A. A.
    Univ Gothenburg, Dept Phys, S-41296 Gothenburg, Sweden..
    Åkerman, Johan
    KTH, School of Engineering Sciences (SCI), Applied Physics. Univ Gothenburg, Dept Phys, S-41296 Gothenburg, Sweden.;NanOsc AB, S-16440 Kista, Sweden.
    CMOS compatible W/CoFeB/MgO spin Hall nano-oscillators with wide frequency tunability2018In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 112, no 13, article id 132404Article in journal (Refereed)
    Abstract [en]

    We demonstrate low-operational-current W/Co20Fe60B20/MgO spin Hall nano-oscillators (SHNOs) on highly resistive silicon (HiR-Si) substrates. Thanks to a record high spin Hall angle of the beta-phase W (theta(SH) = -0.53), a very low threshold current density of 3.3 x 10(7) A/cm(2) can be achieved. Together with their very wide frequency tunability (7-28GHz), promoted by a moderate perpendicular magnetic anisotropy, HiR-Si/W/CoFeB based SHNOs are potential candidates for wide-band microwave signal generation. Their CMOS compatibility offers a promising route towards the integration of spintronic microwave devices with other on-chip semiconductor microwave components.

  • 124042.
    Zaheer, Muhammad
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Kinematic orbit determination of low Earth orbiting satellites, using satellite-to-satellite tracking data and comparison of results with different propagators2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The GPS data from Challenging Mini-satellite Payload (CHAMP) is used for its orbit determination for the epoch day of January 1st 2002.  The orbit of CHAMP is computed from the GPS data and ionospheric effects are removed by frequency combination.

    Further, the orbits of CHAMP for the same epoch day are computed using the satellite tool kit (STK) employing simplified general perturbations (SGP4) and a high precision orbit propagator (HPOP). Results from both techniques (GPS computed orbit and STK computed orbit) are compared.

    Furthermore, orbits computed using GPS data are also compared with jet propulsion laboratory’s published CHAMP spacecraft orbit and we have found that root mean square difference in ECEF position X component is below 0.01km other than some spikes at poles. The standard deviation of the difference in ECEF position X coordinate is 11.7m.

    The accuracy of our computed satellite positions (using GPS data) is about 12 metres for other than polar areas. However there are some occasional spikes, especially at poles, having maximum errors (about 0.055 km).

  • 124043.
    Zaheer, Muhammad
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Kinematic orbit determination of low Earth orbiting satellites, using satellite-to-satellite tracking data and comparison of results with different propagators2014Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    GPS data from Challenging Mini-satellite Payload (CHAMP) is used for its orbit determination for the epoch day of January 1st 2002.  The orbit of CHAMP is computed from the GPS data and ionospheric effects are removed by frequency combination.

    Further, the orbits of CHAMP for the same epoch day are computed using the satellite tool kit (STK) employing simplified general perturbations (SGP4) and a high precision orbit propagator (HPOP).

    Furthermore, orbits computed using GPS data are also compared with jet propulsion laboratory’s published CHAMP spacecraft orbit and we have found that root mean square difference in ECEF position X component is below 0.01km other than some spikes at poles. The standard deviation of the difference in ECEF position X coordinate (JPL results – GPS computed results) is 11.7m. Since JPL computed orbits are considered as true orbits of CHAMP with accuracy of centimeter level (https://gipsy-oasis.jpl.nasa.gov/). Therefore this difference can also be referred as observed error in GPS computed orbits. Considering above discussion, we can expect that accuracy of our computed satellite positions (using GPS data) is about 12 metres for other than poles area. However there are some occasional spikes, especially at poles, having maximum errors (about 0.055 km).

  • 124044.
    Zahharova, Taimi
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    Gustafsson, Veronica
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    Energieffektivitet i hemmet – En litteraturstudie: En byggnad och allt som hör till2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 124045. Zahid, W.
    et al.
    Johnson, Jonas
    KTH, School of Technology and Health (STH), Medical Engineering.
    Westholm, C.
    Eek, C.
    Skulstad, R.
    Fosse, E.
    Winter, Reider
    Edvardsen, T.
    Mitral annular excursion in patients with suspected non-ST-elevation acute coronary syndrome can identify coronary occlusion and predict mortality2012In: European Heart Journal, ISSN 0195-668X, E-ISSN 1522-9645, Vol. 33, p. 912-912Article in journal (Other academic)
  • 124046. Zahid, Wasim
    et al.
    Johnson, Jonas
    KTH, School of Technology and Health (STH), Medical Engineering.
    Westholm, Carl
    Eek, Christian H.
    Haugaa, Kristina H.
    Smedsrud, Marit Kristine
    Skulstad, Helge
    Fosse, Erik
    Winter, Reidar
    KTH, School of Technology and Health (STH), Medical Engineering.
    Edvardsen, Thor
    Mitral Annular Displacement by Doppler Tissue Imaging May Identify Coronary Occlusion and Predict Mortality in Patients with Non-ST-Elevation Myocardial Infarction2013In: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 26, no 8, p. 875-884Article in journal (Refereed)
    Abstract [en]

    Background: Mitral annular displacement (MAD) is a simple marker of left ventricular (LV) systolic function. The aim of this study was to test the hypothesis that MAD can distinguish patients with non-ST-segment elevation myocardial infarctions (NSTEMIs) from those with significant coronary artery disease without infarctions, identify coronary occlusion, and predict mortality in patients with NSTEMIs. MAD was compared with established indices of LV function. Methods: In this retrospective study, 167 patients with confirmed NSTEMIs were included at two Scandinavian centers. Forty patients with significant coronary artery disease but without myocardial infarctions were included as controls. Doppler tissue imaging was performed at the mitral level of the left ventricle in the three apical planes, and velocities were integrated over time to acquire MAD. LV ejection fraction, global longitudinal strain (GLS), and wall motion score index were assessed according to guidelines. Results: MAD and GLS could accurately distinguish patients with NSTEMIs from controls. During 48.6 +/- 12.1 months of follow-up, 22 of 167 died(13%). MAD, LV ejection fraction, and GLS were reduced and wall motion score index was increased among those who died compared with those who survived (P<.001, P<.001, P<.001, and P=.02, respectively). Multivariate Cox proportional-hazards analyses revealed that MAD was an independent predictor of death (hazard ratio, 1.36; 95% confidence interval, 1.07-1.73; P=.01). MAD and GLS were reduced and wall motion score index was increased in patients with coronary artery occlusion compared with those without occlusion (P=.006, P=.001, and P=.02), while LV ejection fraction did not differ (P=.20). Conclusions: MAD accurately identified patients with NSTEMIs, predicted mortality, and identified coronary occlusion in patients with NSTEMIs.

  • 124047. Zahnd, G.
    et al.
    Larsson, Matilda
    KTH, School of Technology and Health (STH), Medical Engineering.
    Gao, H.
    Serusclat, A.
    Vray, D.
    D'Hooge, J.
    A novel method to generete synthetic ultrasound data of the carotid artery based on in vivo observation as a tool to validate algorithm accuracy2012In: 2012 IEEE International Ultrasonics Symposium (IUS), 2012, p. 1674-1677Conference paper (Refereed)
    Abstract [en]

    Ultrasound imaging represents a well designed modality to estimate the motion of biological tissues in vivo, from which relevant clinical information can be assessed. However, the lack of ground truth constitutes a challenging issue when it comes to evaluate the accuracy of computerized methods. Indeed, quantification of the reliability of experimental results often involves manual or visual human operations, which may introduce subjectivity and variability. Nonetheless, numerical simulation of the imaged tissues allow a comparison with a known reference. For this purpose, we propose in this work a realistic kinematic multi-layer model of the common carotid artery. A set of 10 models was generated by randomly positioning scatterers, on which intensity, specular reflection, and bi-dimensional motion over the duration of one cardiac cycle were applied. Two computerized methods, namely a block-matching method and a segmentation method, were also applied on our model using identical parameter settings as those used for in vivo clinical data, in the objective to assess their accuracy. The tracking errors were 42 ± 40 μm and 12 ± 10 μm in the longitudinal and radial directions, respectively. The segmentation errors were 28±18 μm for the lumen diameter, and 15±10 μm for the intima-media thickness. We conclude from these results that our model can constitute a reliable method to quantify the accuracy of computerized algorithms.

  • 124048.
    Zahr, Meia
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Separation of Tryptic Digested IgG with HPLC2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The antibody immunoglobulin G (IgG) can be tryptically digested into smaller peptides. This study attempted to develop a separation method for those peptides using RP-HPLC with a C18 column at room temperature. Optimizing separation of trypsin cleaved cytochrome C was used as a guideline before analyzing IgG. The optimized analysis of Cytochrome C was performed at wavelength 280nm (UV) and methanol was used as an organic solvent in mobile phase (B). A fast gradient to 100% mobile phase B with low flow rate gave favorable results for cytochrome C. A slow gradient to 100% mobile phase B was suited for IgG separation. The optimized gradient elution of cytochrome C and IgG was performed at 0.3 and 0.8 ml/min, respectively.

  • 124049.
    Zahra, Anum
    et al.
    Univ Engn & Technol, Dept Telecommun Engn, ACTSENA Res Grp, Taxila 47050, Punjab, Pakistan..
    Shahid, Humayun
    Univ Engn & Technol, Dept Telecommun Engn, ACTSENA Res Grp, Taxila 47050, Punjab, Pakistan..
    Riaz, Muhammad Ali
    Univ Engn & Technol, Dept Telecommun Engn, ACTSENA Res Grp, Taxila 47050, Punjab, Pakistan..
    Amin, Yasar
    KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK. Univ Engn & Technol, Dept Telecommun Engn, ACTSENA Res Grp, Taxila 47050, Punjab, Pakistan..
    Tenhunen, Hannu
    KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK. Univ Turku, Dept Informat Technol, TUCS, FIN-20520 Turku, Finland..
    A chipless RFID tag for smart temporal applications2018In: International Journal of RF and Microwave Computer-Aided Engineering, ISSN 1096-4290, E-ISSN 1099-047X, Vol. 28, no 8, article id e21405Article in journal (Refereed)
    Abstract [en]

    A compact, robust, chipless radio frequency identification (RFID) tag is proposed. Resonant elements patterned in a concentric fashion encode data in the spectral domain employing frequency shift encoding. The proposed tag encodes 28.25 data bits over a miniscule physical footprint of 25 x 25 mm(2). The formulated scheme is demonstrated to be viable for encoding of temporal variables. The electromagnetic performance of the presented design is investigated for different laminates: Rogers RT/duroid (R) 5880 and Taconic TLX-0. Multiple tag prototypes employing a variety of substrates are realized and evaluated for in-laboratory performance. The proposed design is compared with existing work reported in literature. Code density of 4.52 bits/cm(2) has been successfully achieved. The tag design operates from 3.07 to 10.6 GHz and is readily realizable on flexible laminates. Smart retail, intelligent packaging, adaptive ticketing, and similar time-related applications can be materialized using the proposed tag.

  • 124050.
    Zahrai, Sima
    KTH, Superseded Departments, Mechanics.
    On the fluid mechanics of twin-wire formers1997Doctoral thesis, comprehensive summary (Other scientific)
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