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  • 122651.
    Ramírez, Jaime A.
    et al.
    Universidad Técnica Federico Santa María.
    Rojas, Cristian R.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Jarur, Juan C.
    Universidad Técnica Federico Santa María.
    Rojas, Ricardo A.
    Universidad Técnica Federico Santa María.
    Aportes a la Teoría y la Implementación del Método LSCR2010In: RIAI - Revista Iberoamericana de Automatica e Informatica Industrial, ISSN 1697-7912, Vol. 7, no 3, p. 83-94Article in journal (Refereed)
    Abstract [en]

    The LSCR method (Leave-out-Sign-dominant-Correlation-Regions) provides confidence regions for the parameters of a system by evaluating a set of correlation functions calculated for the available data. To do the approximation for the whole region, the procedure must be repeated for each value of the parameter vector. The main attributes of LSCR are its validity for a finite set of data and the scarce assumptions on the noise. However, the procedure needs much computational effort, which limits its application to very simple cases. In this work some theoretical aspects of the LSCR method are improved and some implementation alternatives are suggested. It is also compared, in terms of computational effort, with Bootstrap, another way to obtain confidence regions.

  • 122652.
    Ramírez, Javier
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Hultberg, M.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Wahlund, B.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Martínez, Joaquín
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Transport Parameters and Physical Properties of Gold Ore Tailings1998In: IACChE'98: Proceedings of the 18th Inter-American Congress of Chemical Engineering, Mayagüez, Puerto Rico: University of Puerto Rico at Mayagüez (UPRM) , 1998Conference paper (Refereed)
  • 122653.
    Ramírez, Javier
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Martínez, Joaquín
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Determinación de Propiedades Físicas y Parámetros de Transporte a Colas Auríferas de mina El Limón2006In: Nexo, ISSN 1818-6742, Vol. 19, no 1, p. 57-63Article in journal (Refereed)
  • 122654.
    Ramírez Jiménez, Guillermo
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Electric sustainability analysis for concrete 3D printing machine2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Nowadays, manufacturing technologies become more and more aware of efficiency and sustainability. One of them is the so called 3D printing. While 3D printing is often linked to plastic, the truth is there are many other materials that are being tested which could have several improvements over plastics.One of these options is stone or concrete, which is more suitable the architecture and artistic fields. However, due to its nature, this new technology involves the use of new techniques when compared to the more commonly used 3D printers. This implies that it could interesting to know how much energy efficient these techniques are and how can they be improved in future revisions.This thesis is an attempt to disclose and analyze the different devices that make up one of these printers and with this information, build a model that accurately describes its behavior.For this purpose, the power is measured at many points and later it is analyzed and fitted to a predefined function. After the fitting has been done, an error is calculated to show how accurate the model is when compared to the original data.It was found that many of these devices produce power spikes due to its nonlinear behavior. This behavior is usually related to switching, and can avoided with different devices.Finally, some advice is given focused on future research and revisions, which could be helpful for safety, efficiency and quality.

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  • 122655.
    Ramírez Villegas, Ricardo
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    Sustainable Renovation and Operation of Family Houses for Improved Climate Efficiency: A Case Study2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the developed world, the existing stock of houses will provide shelter to the majority of population in the upcoming years. Houses are physical objects that consume material and energy and need to be maintained, repaired and restructured from time to time. In order to fulfill the requirements of the Kyoto protocol and be comfortable for their inhabitants, the existing stock needs to be renovated.

    Strong disagreement between different parts of the scientific community and overlapping and contradictory concepts make the definition of sustainable renovation confusing. In this Thesis, therefore, an approach of renovation and operation for higher energy efficiency and lower climate impact has been the main focus.

    Based on a systems analysis approach, the aim of this work is to develop a manual to stimulate house owners to become role models in sustainable renovation and operation of family houses, the Thesis providing recommendations to reducing the energy consumption of their houses by evaluating cost and benefits of possible actions and choosing the most energy and cost effective approach of a series of alternatives. With the results of this analysis, a sustainable renovation and operation staircase is proposed.

    The work found that it is possible develop a staircase manual for sustainable renovation and operation of family houses that follows a logical step-by-step approach and could result in considerable life cycle reductions in both costs and climate impact. The work also suggests that it is possible for academic experts to develop material in a simpler form and language to reach the public in a more understandable form.

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  • 122656.
    Ramírez-Chavarría, Roberto G.
    et al.
    Universidad Nacional Autónoma de México.
    Müller, Matias I.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control).
    Mattila, Robert
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control).
    Quintana-Carapia, Gustavo
    Vrije Universiteit Brussel.
    Sánchez-Pérez, Celia
    Universidad Nacional Autónoma de México.
    A framework for high-resolution frequency response measurement and parameter estimation in microscale impedance applications2019In: Measurement, ISSN 0263-2241, Vol. 148, article id 106913Article in journal (Refereed)
    Abstract [en]

    Electrical impedance spectroscopy (EIS) is a tool for characterizing the electrical behavior of matter. Nevertheless, most of the work is focused on purely experimental results, leading aside alternative measurement and estimation techniques. In this paper, we introduce a framework for spectral measurements and parameter estimation applied to EIS. There are two methods in the proposal running independently: frequency response function based non-parametric estimation, and parametric recursive estimation. The former provides consistent estimates even in the presence of noise and works with batches of data. Whilst the latter gives consistent parametric estimates under the right model structure. The proposed platform is designed around a reconfigurable device, which comprises minimal hardware design and digital signal processing. We test the system with a multisine signal by measuring calibration circuits and colloidal samples at microscale. Results show that this method outperforms the state-of-the-art techniques for impedance measurement applications, exhibiting low uncertainty and physical interpretation.

  • 122657.
    Ramírez-Chavarría, Roberto G.
    et al.
    Universidad Nacional Autónoma de México.
    Quintana-Carapia, Gustavo
    Vrije Universiteit Brussel.
    Müller, Matias I.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control).
    Mattila, Robert
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control).
    Matatagui, Daniel
    Universidad Nacional Autónoma de México.
    Sánchez-Pérez, Celia
    Universidad Nacional Autónoma de México.
    Bioimpedance Parameter Estimation using Fast Spectral Measurements and Regularizaton2018In: IFAC-PapersOnLine, IFAC Papers Online, 2018, Vol. 51, no 15, p. 521-526Conference paper (Refereed)
    Abstract [en]

    This work proposes an alternative framework for parametric bioimpedance estimation as a powerful tool to characterize biological media. We model the bioimpedance as an electrical network of parallel RC circuits, and transform the frequency-domain estimation problem into a time constant domain estimation problem by means of the distribution of relaxation times (DRT) method. The Fredholm integral equation of the first kind is employed to pose the problem in a regularized least squares (RLS) form. We validate the proposed methodology by numerical simulations for a synthetic biological electrical circuit, by using a multisine signal in the frequency range of 1kHz to 853kHz and considering an error in variables (EIV) problem. Results show that the proposed method outperforms the state-of-the-art techniques for spectral bioimpedance analysis. We also illustrates its potentiality in terms of accurate spectral measurements and precise data interpretation, for further usage in biological applications.

  • 122658. Ran, L.
    et al.
    Hou, J.
    Cao, S.
    Li, Z.
    Zhang, Y.
    Wu, Y.
    Zhang, B.
    Zhai, P.
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Defect Engineering of Photocatalysts for Solar Energy Conversion2020In: Solar RRL, E-ISSN 2367-198X, Vol. 4, no 4, article id 1900487Article in journal (Refereed)
    Abstract [en]

    Solar energy conversion is one of the most versatile approaches for sustainable energy demands. The fundamental limitations for photocatalysis remain light absorption, charge separation, and photocatalytic (PC) performance of the catalysts. For the past few decades, defect engineering has been proven to be a promising solution for converting solar energy to chemical energy. In this regard, the recent progress of defect engineering toward solar energy conversion is summarized. Beginning with defects classification, the definition of various defects, synthesized strategies, and characterization techniques of controllable material defects are presented. The role of defect engineering on solar energy conversion is developed, extending light absorption, promoting charge separation, and facilitating stable PC reaction. The achievement of the defective photocatalysts is discussed toward versatile applications such as solar water splitting, CO2 reduction, nitrogen fixation, molecular activation, pollutants degradation, and solar cells. Finally, this Review, with regards to defect engineering, ends with the future opportunities and challenges for this exciting and emerging area for solar energy conversion.

  • 122659. Ran, L.
    et al.
    Li, Z.
    Ran, B.
    Cao, J.
    Zhao, Y.
    Shao, T.
    Song, Y.
    Leung, M. K. H.
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Hou, J.
    Engineering Single-Atom Active Sites on Covalent Organic Frameworks for Boosting CO2Photoreduction2022In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 144, no 37, p. 17097-17109Article in journal (Refereed)
    Abstract [en]

    Solar carbon dioxide (CO2) conversion is an emerging solution to meet the challenges of sustainable energy systems and environmental/climate concerns. However, the construction of isolated active sites not only influences catalytic activity but also limits the understanding of the structure-catalyst relationship of CO2 reduction. Herein, we develop a universal synthetic protocol to fabricate different single-atom metal sites (e.g., Fe, Co, Ni, Zn, Cu, Mn, and Ru) anchored on the triazine-based covalent organic framework (SAS/Tr-COF) backbone with the bridging structure of metal-nitrogen-chlorine for high-performance catalytic CO2 reduction. Remarkably, the as-synthesized Fe SAS/Tr-COF as a representative catalyst achieved an impressive CO generation rate as high as 980.3 μmol g-1 h-1 and a selectivity of 96.4%, over approximately 26 times higher than that of the pristine Tr-COF under visible light irradiation. From X-ray absorption fine structure analysis and density functional theory calculations, the superior photocatalytic performance is attributed to the synergic effect of atomically dispersed metal sites and Tr-COF host, decreasing the reaction energy barriers for the formation of *COOH intermediates and promoting CO2 adsorption and activation as well as CO desorption. This work not only affords rational design of state-of-the-art catalysts at the molecular level but also provides in-depth insights for efficient CO2 conversion. 

  • 122660. Ran, L.
    et al.
    Qiu, S.
    Zhai, P.
    Li, Z.
    Gao, J.
    Zhang, X.
    Zhang, B.
    Wang, C.
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Center of Artificial Photosynthesis for Solar Fuels, School of Science, Westlake University, Hangzhou 310024, P. R. China.
    Hou, J.
    Conformal Macroporous Inverse Opal Oxynitride-Based Photoanode for Robust Photoelectrochemical Water Splitting2021In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 143, no 19, p. 7402-7413Article in journal (Refereed)
    Abstract [en]

    Direct photoelectrochemical (PEC) water splitting is of prime importance in sustainable energy conversion systems; however, it is a big challenge to simultaneously control light harvesting and charge transport for the improvement of PEC performance. Herein, we report a three-dimensional ordered macroporous (3DOM) CsTaWO6-xNx inverse opal array as a promising candidate for the first time. To address the critical challenge, an ultrathin carbon-nitride-based layer-intercalated 3DOM CsTaWO6-xNx architecture as a conformal heterojunction photoanode was assembled. This state-of-the-art conformal heterojunction photoanode with carrier-separation efficiency up to 88% achieves a high current density of 4.59 mA cm-2 at 1.6 V versus a reversible hydrogen electrode (vs RHE) under simulated AM 1.5G illumination, which is approximately 3.4 and 17 times larger than that of pristine CsTaWO6-xNx inverse opals and powers photoelectrodes in alkaline media, corresponding to an incident photon-to-current efficiency of 32% at 400 nm and outstanding stability for PEC water splitting. Density functional theory calculations propose that the intimate interface of a conformal photoanode optimizes the charge separation and transfer, thus enhancing the intrinsic water oxidation performance. This work enables us to elucidate the pivotal importance of 3DOM architectures and conformal heterostructures and the promising contributions to excellent PEC water-splitting applications. 

  • 122661.
    Ran, Ylva
    et al.
    Department of Energy and Technology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Cederberg, Christel
    Division of Physical Resource Theory, Department of Space, Earth and Environment, Chalmers University of Technology, Göteborg, Sweden.
    Jonell, Malin
    Global Economic Dynamics and the Biosphere, Royal Swedish Academy of Science, Stockholm, Sweden; Stockholm Resilience Centre, Stockholm University, Stockholm, Sweden.
    Bergman, Kristina
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    De Boer, Imke J.M.
    Animal Production Systems Group, Wageningen University & Research, Wageningen, Netherlands.
    Einarsson, Rasmus
    Department of Energy and Technology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Karlsson, Johan
    Department of Energy and Technology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Potter, Hanna Karlsson
    Department of Energy and Technology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Martin, Michael
    IVL Swedish Environmental Research Institute, Stockholm, Sweden.
    Metson, Geneviève S.
    Department of Geography and Environment, Social Sciences Centre, University of Western Ontario, London, ON, Canada; Ecological and Environmental Modeling Division, Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.
    Nemecek, Thomas
    Agroscope, Life Cycle Assessment Research Group, Zurich, Switzerland.
    Nicholas, Kimberly A.
    Lund University Centre for Sustainability Studies, Lund, Sweden.
    Strand, Åsa
    IVL Swedish Environmental Research Institute, Stockholm, Sweden.
    Tidåker, Pernilla
    Department of Energy and Technology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Van der Werf, Hayo
    French National Research Institute for Agriculture, Food and Environment, l'Institut Agro Rennes-Angers, Rennes, France.
    Vanham, Davy
    Ispra, Italy.
    Van Zanten, Hannah H.E.
    Farming Systems Ecology Group, Wageningen Universityand Research, Wageningen, Netherlands; Department of Global Development, College of Agriculture and Life Sciences, and Cornell Atkinson Center for Sustainability, Cornell University, Ithaca, NY, USA.
    Verones, Francesca
    Industrial Ecology Programme, Department of Energy and Process Engineering, Norwegian University of Science and Technology, Trondheim, Norway.
    Röös, Elin
    Department of Energy and Technology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Environmental assessment of diets: overview and guidance on indicator choice2024In: The Lancet Planetary Health, E-ISSN 2542-5196, Vol. 8, no 3, p. e172-e187Article, review/survey (Refereed)
    Abstract [en]

    Comprehensive but interpretable assessment of the environmental performance of diets involves choosing a set of appropriate indicators. Current knowledge and data gaps on the origin of dietary foodstuffs restrict use of indicators relying on site-specific information. This Personal View summarises commonly used indicators for assessing the environmental performance of diets, briefly outlines their benefits and drawbacks, and provides recommendations on indicator choices for actors across multiple fields involved in activities that include the environmental assessment of diets. We then provide recommendations on indicator choices for actors across multiple fields involved in activities that use environmental assessments, such as health and nutrition experts, policy makers, decision makers, and private-sector and public-sector sustainability officers. We recommend that environmental assessment of diets should include indicators for at least the five following areas: climate change, biosphere integrity, blue water consumption, novel entities, and impacts on natural resources (especially wild fish stocks), to capture important environmental trade-offs. If more indicators can be handled in the assessment, indicators to capture impacts related to land use quantity and quality and green water consumption should be used. For ambitious assessments, indicators related to biogeochemical flows, stratospheric ozone depletion, and energy use can be added.

  • 122662. Rana, A.
    et al.
    Wurthwein, F.
    Keahey, K.
    Freeman, T.
    Vaniachine, A.
    Malon, D.
    May, E.
    Martin, S.
    Gardner, R.
    Sotomayor, B.
    Holzman, B.
    Pordes, R.
    Skow, D.
    Wenaus, T.
    Popescu, R.
    Shank, J.
    Laure, Erwin
    Bird, I.
    Schulz, M.
    Litmaath, M.
    Campana, S.
    Smith, D.
    Blummenfield, B.
    De, K.
    Vranciar, M.
    Weicher, J.
    Smith, P.
    Wang, S.
    An edge services framework (esf) for egee, lcg, AND osg2006Conference paper (Refereed)
    Abstract [en]

    We report on first experiences with building and operating an Edge Services Framework (ESF) based on Xen virtual machines instantiated via the Workspace Service available in Globus Toolkit, and developed as a joint project between EGEE, LCG, and OSG. Many computing facilities are architected with their compute and storage clusters behind firewalls. Edge Services are instantiated on a small set of gateways to provide access to these clusters via standard grid interfaces. Experience on EGEE, LCG, and OSG has shown that at least two issues are of critical importance when designing an infrastructure in support of Edge Services. The first concerns Edge Service configuration. It is impractical to assume that each virtual organization (VO) using a facility will employ the same Edge Service configuration, or that different configurations will coexist easily. Even within a VO, it should be possible to run different versions of the same Edge Service simultaneously. The second issue concerns resource usage: since Edge Services may become a bottleneck to a site, it is essential that an ESF be able to effectively arbitrate resource usage (e.g., memory, CPU, and networking) among different VOs. By providing virtualization on the level of instruction set architecture, virtual machines allow configuration of independent software stacks for each VM executing on a resource. Modern implementations of this abstraction are extremely efficient and have outstanding fine-grained enforcement capabilities. To securely deploy virtual machines, we use the Workspace Service from the Globus Toolkit, which allows a VO administrator to dynamically launch appropriately-configured system images. In addition, we are developing a library of such images, reflecting the needs of presently participating communities ATLAS, CMS, and CDF. We will report on first experiences building and operating this Edge Services Framework.

  • 122663.
    Rana, Balwan
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Numerical Simulations of Wave Propagation between a Left-Handed Material and a Right-Handed Material2021Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The discovery of metamaterials has led to major advances in different fields of physics including optics, microwave engineering and acoustics. Specific to theoretical electromagnetism, the introduction of metamaterials have led to the development of negative-index materials (NIMs) with simultaneous negative permittivity and negative permeability with backward-wave propagation. In recent studies, exact analytical solutions for wave propagation from a step/graded-index interface between a right-handed material (RHM) and a left-handed material (LHM) have been obtained. This study attempts to provide numerical validation of the analytical solutions obtained by Dalarsson et al. by using the simulation tool CST. An square-SRR/strip-wire unit element was designed, with real part of relative permittivity equal to -1.96 and real part of relative permeability equal to -1.01. Such unit elements were orderly structured to produce a NIM structure. Furthermore, a positive-index material (PIM) structure was produced by reversing the sign of the material properties of the NIM. Both the results for the step- and graded-index interfaces have shown to possess backward-wave propagation for a normal incidence angle. The graded-index interface profiles have a more smooth and continuous wave propagation between the materials, which counteracts the effects of discontinuous material transitions present in step-index interface profiles. However, because the results of the present study were considerably affected by unwanted field effects, the analytical solutions are only qualitatively validated, and not validated in terms of their numerical accuracy. 

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  • 122664.
    Rana, Balwan
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    Dalarsson, Mariana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering.
    Absorption Cross-section Analysis For Human Tissue With Embedded Gold Nanoparticles2023In: 17th International Congress on Artificial Materials for Novel Wave Phenomena, Metamaterials 2023, Institute of Electrical and Electronics Engineers Inc. , 2023, p. 285-287Conference paper (Refereed)
    Abstract [en]

    We present a parametric analysis of the absorption cross-section of small ellipsoidal composite structures (particles) with gold nanoparticles (GNP) embedded in lossy human tissue. The optimal permittivity of the ellipsoidal particle that maximizes the absorption at any given frequency, derived in our previous work with the surrounding tissue as a saline water, is used. We present new results for realistic tissue material parameters and for different GNP-host media and surrounding media. Present results are useful to assess the feasibility of the proposed radiotherapeutic hyperthermia-based methods to treat cancer, based on electrophoretic heating of gold nanoparticle suspensions using microwave radiation, as well as to improve the general understanding of plasmonic resonances in lossy media.

  • 122665.
    Rana, Balwan
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Dalarsson, Mariana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering.
    TEM-wave propagation over a graded periodic RHM-LHM composite in a coaxial waveguide2022In: 2022 International Symposium On Antennas And Propagation (ISAP), Institute of Electrical and Electronics Engineers (IEEE) , 2022, p. 557-558Conference paper (Refereed)
    Abstract [en]

    In this paper, we perform analytical and numerical studies of TEM-wave propagation in a coaxial waveguide filled with a graded periodic RHM-LHM composite, for which the real parts of the effective permittivity and permeability vary along the propagation direction (chosen to be the z-direction) according to an arbitrary periodic function. We obtain an excellent agreement between analytical and numerical results in the important special case of abrupt transitions between the two materials.

  • 122666.
    Rana, Balwan
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Dalarsson, Mariana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    TEM-wave propagation over an impedance-matched periodic RHM to LHM transition in a coaxial waveguide2023In: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 13, no 4, p. 1118-1130Article in journal (Refereed)
    Abstract [en]

    We study TEM-wave propagation inside a hollow coaxial waveguide filled with a periodic composite of lossy impedance-matched right-handed (RHM) and left-handed (LHM) media. The z-direction, chosen as the direction perpendicular to the boundaries between the two media, is where the transitions and TEM-wave propagation take place. The relative permittivity epsilon(omega, z) and permeability mu(omega, z) of the periodic RHM-LHM composite vary according to an arbitrary periodic function f(z) along the z-direction. In particular, we consider two specific periodic permittivity and permeability profiles: one with abrupt RHM-LHM transitions and one with linear RHM-LHM transitions. The expected properties of impedance-matched periodic RHM-LHM structures are confirmed by the derived precise analytical solutions to Maxwell's equations, which also include solutions for the wave behavior and field components. Furthermore, a numerical study of the wave propagation over the impedance-matched graded RHM-LHM composites is performed using the COMSOL Multiphysics software. The resulting numerical simulations and analytical results were virtually identical. The present method can model smooth, realistic material transitions and includes the abrupt transition as a limiting case.

  • 122667.
    Rana, Balwan
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Svendsen, Brage B.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Dalarsson, Mariana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    TEM-wave propagation in a coaxial waveguide with impedance-matched RHM to LHM transition2022In: Optics Express, E-ISSN 1094-4087, Vol. 30, no 18, p. 32610-32620Article in journal (Refereed)
    Abstract [en]

    In this paper, we study TEM-wave propagation inside a hollow coaxial waveguide filled with an inhomogeneous metamaterial composite, with a graded transition between a right-handed material (RHM) and an impedance-matched left-handed material (LHM). The graded transition and the TEM-wave propagation occur in the direction perpendicular to the boundary between the two media, which has been chosen to be the z-direction. The relative permittivity epsilon(omega, z) and permeability mu(omega, z) of the RHM-LHM composite vary according to hyperbolic tangent functions along the z-direction. The exact analytical solutions to Maxwell's equations are derived, and the solutions for the field components and wave behavior confirm the expected properties of impedance-matched RHM-LHM structures. Furthermore, a numerical study of the wave propagation over an impedance-matched graded RHM-LHM interface, using the COMSOL Multiphysics software, is performed. An excellent agreement between the analytical results and numerical simulations is obtained, with a relative error of less than 0.1%. The present method has the ability to model smooth realistic material transitions, and includes the abrupt transition as a limiting case. Finally, the RHM-LHM interface width is included as a parameter in the analytical and numerical solutions, allowing for an additional degree of freedom in the design of practical devices using RHM-LHM composites. Published by Optica Publishing Group under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

  • 122668.
    Rana, Balwan
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Svendsen, Brage B.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Dalarsson, Mariana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    TEM-wave propagation in a parallel plate waveguide with impedance-matched RHM to LHM transition2022In: 2022 16th International Congress on Artificial Materials for Novel Wave Phenomena, Metamaterials 2022, Institute of Electrical and Electronics Engineers (IEEE) , 2022, p. 356-358Conference paper (Refereed)
    Abstract [en]

    We study TEM-wave propagation in a parallel plate waveguide with a graded transition between a lossy right-handed material (RHM) and an impedance-matched lossy left-handed material (LHM). The transition between the two media is graded along the direction perpendicular to the boundary between the two materials, and the permittivity and permeability vary according to hyperbolic tangent functions. We obtain exact analytical solutions to Maxwell's equations for lossy media, and the solutions for the field components confirm the expected properties of RHM-LHM structures. Finally, we perform a numerical study of the wave propagation over an impedance-matched graded RHM-LHM interface, using COMSOL, and obtain an excellent agreement between the numerical simulations and analytical results.

  • 122669.
    Rana, Balwan
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Svendsen, Brage B.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Dalarsson, Mariana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    TE-Wave Propagation over an Impedance-Matched RHM to LHM Transition in a Hollow Waveguide2022In: Progress In Electromagnetics Research M, ISSN 1937-8726, Vol. 110, p. 1-10Article in journal (Refereed)
    Abstract [en]

    We study TE-wave propagation in a hollow waveguide with a graded transition from a lossy right-handed material (RHM) filling the left-hand half of the waveguide to the impedance-matched lossy left-handed material (LHM) filling the right-hand half of the waveguide. The transition between the two media is graded along the direction perpendicular to the boundary between the two materials (chosen to be the z-direction), and the permittivity epsilon(omega, z) and permeability mu(omega, z) are chosen to vary according to hyperbolic tangent functions along the z-direction. We obtain exact analytical solutions to Maxwell's equations for lossy media, and the solutions for the field components confirm the expected properties of RHM-LHM structures. Thereafter, a numerical study of the wave propagation over an impedance-matched graded RHM-LHM interface is performed, using COMSOL software. The numerical study shows an excellent agreement between the numerical simulations and analytical results. Compared to other solution methods, the present approach has the advantage of being able to model more realistic smooth transitions between different materials. However, in the limiting case, it includes correct results for abrupt transitions as well. In the present approach we also introduce interface width as an additional degree of freedom that can be used in the design of practical RHM-LHM interfaces.

  • 122670.
    Rana, Chinar
    et al.
    Indian Inst Technol Ropar, Dept Math, Rupnagar 140001, Punjab, India.;ULB, Nonlinear Phys Chem Unit, B-1050 Brussels, Belgium..
    Pramanik, Satyajit
    Indian Inst Technol Ropar, Dept Math, Rupnagar 140001, Punjab, India.;Stockholm Univ, SE-10691 Stockholm, Sweden.;Nordita SU.
    Martin, Michel
    PSL Paris Sci & Lettres Univ, PMMH, ESPCI Paris, Sorbonne Univ,Univ Paris Diderot,CNRS, Campus Jussieu, F-75252 Paris 05, France..
    De Wit, A.
    ULB, Nonlinear Phys Chem Unit, B-1050 Brussels, Belgium..
    Mishra, Manoranjan
    Indian Inst Technol Ropar, Dept Math, Rupnagar 140001, Punjab, India.;Indian Inst Technol Ropar, Dept Chem Engn, Rupnagar 140001, Punjab, India..
    Influence of Langmuir adsorption and viscous fingering on transport of finite size samples in porous media2019In: Physical Review Fluids, E-ISSN 2469-990X, Vol. 4, no 10, article id 104001Article in journal (Refereed)
    Abstract [en]

    We examine the transport in a homogeneous porous medium of a finite slice of a solute which adsorbs on the porous matrix following a Langmuir adsorption isotherm and can influence the dynamic viscosity of the solution. In the absence of any viscosity variation, the Langmuir adsorption induces the formation of a shock layer wave at the frontal interface and of a rarefaction wave at the rear interface of the sample. For a finite width sample, these waves interact after a given time that varies nonlinearly with the adsorption properties to give a triangle-like concentration profile in which the mixing efficiency of the solute is larger in comparison to the linear or no-adsorption cases. In the presence of a viscosity contrast such that a less viscous carrier fluid displaces the more viscous finite slice, viscous fingers are formed at the rear rarefaction interface. The fingers propagate through the finite sample to preempt the shock layer at the viscously stable front. In the reverse case, i.e., when the shock layer front features viscous fingering, the fingers are unable to intrude through the rarefaction zone and the qualitative properties of the expanding rear wave are preserved. A nonmonotonic dependence with respect to the Langmuir adsorption parameter b is observed in the onset time of interaction between the nonlinear waves and viscous fingering. The coupled effect of viscous fingering at the rear interface and of Langmuir adsorption provides a powerful mechanism to enhance the mixing efficiency of the adsorbed solute.

  • 122671.
    Rana, Pravin Kumar
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Taking Television Viewing To A New DimensionManuscript (preprint) (Other (popular science, discussion, etc.))
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  • 122672.
    Rana, Pravin Kumar
    et al.
    KTH, School of Electrical Engineering (EES), Sound and Image Processing.
    Dash, Mihir Kumar
    Routray, A.
    Pandey, Prem Chand
    Prediction of Sea Ice Edge in the Antarctic Using GVF Snake Model2011In: Journal of the Geological Society of India, ISSN 0016-7622, E-ISSN 0974-6889, Vol. 78, no 2, p. 99-108Article in journal (Refereed)
    Abstract [en]

    Antarctic sea ice cover plays an important role in shaping the earth's climate, primarily by insulating the ocean from the atmosphere and increasing the surface albedo. The convective processes accompanied with the sea ice formation result bottom water formation. The cold and dense bottom water moves towards the equator along the ocean basins and takes part in the global thermohaline circulation. Sea ice edge is a potential indicator of climate change. Additionally, fishing and commercial shipping activities as well as military submarine operations in the polar seas need reliable ice edge information. However, as the sea ice edge is unstable in time, the temporal validity of the estimated ice edge is often shorter than the time required to transfer the information to the operational user. Hence, an accurate sea ice edge prediction as well as determination is crucial for fine-scale geophysical modeling and for near-real-time operations. In this study, active contour modelling (known as Snake model) and non-rigid motion estimation techniques have been used for predicting the sea ice edge (SIE) in the Antarctic. For this purpose the SIE has been detected from sea ice concentration derived using special sensor microwave imager (SSM/I) observations. The 15% sea ice concentration pixels are being taken as the edge pixel between ice and water. The external force, gradient vector flow (GVF), of SIE for total the Antarctic region is parameterised for daily as well as weekly data set. The SIE is predicted at certain points using a statistical technique. These predicted points have been used to constitute a SIE using artificial intelligence technique, the gradient vector flow (GVF). The predicted edge has been validated with that of SSM/I. It is found that all the major curvatures have been captured by the predicated edge and it is in good agreement with that of the SSM/I observation.

  • 122673.
    Rana, Pravin Kumar
    et al.
    KTH, School of Electrical Engineering (EES), Sound and Image Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Flierl, Markus
    KTH, School of Electrical Engineering (EES), Sound and Image Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Depth consistency testing for improved view interpolation2010In: , 2010, p. 384-389Conference paper (Refereed)
    Abstract [en]

    Multiview video will play a pivotal role in the next generation visual communication media services like three-dimensional (3D) television and free-viewpoint television. These advanced media services provide natural 3D impressions and enable viewers to move freely in a dynamic real world scene by changing the viewpoint. High quality virtual view interpolation is required to support free viewpoint viewing. Usually, depth maps of different viewpoints are used to reconstruct a novel view. As these depth maps are usually estimated individually by stereo-matching algorithms, they have very weak spatial consistency. The inconsistency of depth maps affects the quality of view interpolation. In this paper, we propose a method for depth consistency testing to improve view interpolation. The method addresses the problem by warping more than two depth maps from multiple reference viewpoints to the virtual viewpoint. We test the consistency among warped depth values and improve the depth value information of the virtual view. With that, we enhance the quality of the interpolated virtual view.

  • 122674.
    Rana, Pravin Kumar
    et al.
    KTH, School of Electrical Engineering (EES), Sound and Image Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Flierl, Markus
    KTH, School of Electrical Engineering (EES), Sound and Image Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Depth Pixel Clustering for Consistency Testing of Multiview Depth2012In: European Signal Processing Conference, 2012, p. 1119-1123Conference paper (Refereed)
    Abstract [en]

    This paper proposes a clustering algorithm of depth pixels for consistency testing of multiview depth imagery. The testing addresses the inconsistencies among estimated depth maps of real world scenes by validating depth pixel connection evidence based on a hard connection threshold. With the proposed algorithm, we test the consistency among depth values generated from multiple depth observations using cluster adaptive connection thresholds. The connection threshold is based on statistical properties of depth pixels in a cluster or sub-cluster. This approach can improve the depth information of real world scenes at a given viewpoint. This allows us to enhance the quality of synthesized virtual views when compared to depth maps obtained by using fixed thresholding. Depth-image-based virtual view synthesis is widely used for upcoming multimedia services like three-dimensional television and free-viewpoint television.

  • 122675.
    Rana, Pravin Kumar
    et al.
    KTH, School of Electrical Engineering (EES), Sound and Image Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Flierl, Markus
    KTH, School of Electrical Engineering (EES), Sound and Image Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    View Interpolation with structured depth from multiview video2011Conference paper (Refereed)
    Abstract [en]

    In this paper, we propose a method for interpolating multiview imagery which uses structured depth maps and multiview video plus inter-view connection information to represent a three-dimensional (3D) scene. The structured depth map consists of an inter-view consistent principal depth map and auxiliary depth information. The structured depth maps address the inconsistencies among estimated depth maps which may degrade the quality of rendered virtual views. Generated from multiple depth observations, the structuring of the depth maps is based on tested and adaptively chosen inter-view connections. Further, the use of connection information on the multiview video minimizes distortion due to varying illumination in the interpolated virtual views. Our approach improves the quality of rendered virtual views by up to 4 dB when compared to the reference MPEG view synthesis software for emerging multimedia services like 3D television and free-viewpoint television. Our approach obtains first the structured depth maps and the corresponding connection information. Second, it exploits the inter-view connection information when interpolating virtual views.

  • 122676.
    Rana, Pravin Kumar
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Ma, Zhanyu
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Taghia, Jalil
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Flierl, Markus
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Multiview Depth Map Enhancement by Variational Bayes Inference Estimation of Dirichlet Mixture Models2013In: 2013 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), IEEE , 2013, p. 1528-1532Conference paper (Refereed)
    Abstract [en]

    High quality view synthesis is a prerequisite for future free-viewpointtelevision. It will enable viewers to move freely in a dynamicreal world scene. Depth image based rendering algorithms willplay a pivotal role when synthesizing an arbitrary number of novelviews by using a subset of captured views and corresponding depthmaps only. Usually, each depth map is estimated individually bystereo-matching algorithms and, hence, shows lack of inter-viewconsistency. This inconsistency affects the quality of view synthesis negatively. This paper enhances the inter-view consistency ofmultiview depth imagery. First, our approach classifies the colorinformation in the multiview color imagery by modeling color witha mixture of Dirichlet distributions where the model parameters areestimated in a Bayesian framework with variational inference. Second, using the resulting color clusters, we classify the correspondingdepth values in the multiview depth imagery. Each clustered depthimage is subject to further sub-clustering. Finally, the resultingmean of each sub-cluster is used to enhance the depth imagery atmultiple viewpoints. Experiments show that our approach improvesthe average quality of virtual views by up to 0.8 dB when comparedto views synthesized by using conventionally estimated depth maps.

  • 122677.
    Rana, Pravin Kumar
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Taghia, Jalil
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Flier, Markus
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Statistical methods for inter-view depth enhancement2014In: 2014 3DTV-Conference: The True Vision - Capture, Transmission and Display of 3D Video (3DTV-CON), IEEE , 2014, p. 6874755-Conference paper (Refereed)
    Abstract [en]

    This paper briefly presents and evaluates recent advances in statistical methods for improving inter-view inconsistency in multiview depth imagery. View synthesis is vital in free-viewpoint television in order to allow viewers to move freely in a dynamic scene. Here, depth image-based rendering plays a pivotal role by synthesizing an arbitrary number of novel views by using a subset of captured views and corresponding depth maps only. Usually, each depth map is estimated individually at different viewpoints by stereo matching and, hence, shows lack of inter-view consistency. This lack of consistency affects the quality of view synthesis negatively. This paper discusses two different approaches to enhance the inter-view depth consistency. The first one uses generative models based on multiview color and depth classification to assign a probabilistic weight to each depth pixel. The weighted depth pixels are utilized to enhance depth maps. The second one performs inter-view consistency testing in depth difference space to enhance the depth maps at multiple viewpoints. We comparatively evaluate these two methods and discuss their pros and cons for future work.

  • 122678.
    Rana, Pravin Kumar
    et al.
    KTH, School of Electrical Engineering (EES), Sound and Image Processing.
    Taghia, Jalil
    KTH, School of Electrical Engineering (EES), Sound and Image Processing.
    Flierl, Markus
    KTH, School of Electrical Engineering (EES), Sound and Image Processing.
    A Variational Bayesian Inference Framework for Multiview Depth Image Enhancement2012In: Proceedings - 2012 IEEE International Symposium on Multimedia, ISM 2012, IEEE , 2012, p. 183-190Conference paper (Refereed)
    Abstract [en]

    In this paper, a general model-based framework for multiview depth image enhancement is proposed. Depth imagery plays a pivotal role in emerging free-viewpoint television. This technology requires high quality virtual view synthesis to enable viewers to move freely in a dynamic real world scene. Depth imagery of different viewpoints is used to synthesize an arbitrary number of novel views. Usually, the depth imagery is estimated individually by stereo-matching algorithms and, hence, shows lack of inter-view consistency. This inconsistency affects the quality of view synthesis negatively. This paper enhances the inter-view consistency of multiview depth imagery by using a variational Bayesian inference framework. First, our approach classifies the color information in the multiview color imagery. Second, using the resulting color clusters, we classify the corresponding depth values in the multiview depth imagery. Each clustered depth image is subject to further subclustering. Finally, the resulting mean of the sub-clusters is used to enhance the depth imagery at multiple viewpoints. Experiments show that our approach improves the quality of virtual views by up to 0.25 dB.

  • 122679.
    Rana, Pravin Kumar
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Taghia, Jalil
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Ma, Zhanyu
    Flierl, Markus
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Probabilistic Multiview Depth Image Enhancement Using Variational Inference2015In: IEEE Journal on Selected Topics in Signal Processing, ISSN 1932-4553, E-ISSN 1941-0484, Vol. 9, no 3, p. 435-448Article in journal (Refereed)
    Abstract [en]

    An inference-based multiview depth image enhancement algorithm is introduced and investigated in this paper. Multiview depth imagery plays a pivotal role in free-viewpoint television. This technology requires high-quality virtual view synthesis to enable viewers to move freely in a dynamic real world scene. Depth imagery of different viewpoints is used to synthesize an arbitrary number of novel views. Usually, the depth imagery is estimated individually by stereo-matching algorithms and, hence, shows inter-view inconsistency. This inconsistency affects the quality of view synthesis negatively. This paper enhances the multiview depth imagery at multiple viewpoints by probabilistic weighting of each depth pixel. First, our approach classifies the color pixels in the multiview color imagery. Second, using the resulting color clusters, we classify the corresponding depth values in the multiview depth imagery. Each clustered depth image is subject to further subclustering. Clustering based on generative models is used for assigning probabilistic weights to each depth pixel. Finally, these probabilistic weights are used to enhance the depth imagery at multiple viewpoints. Experiments show that our approach consistently improves the quality of virtual views by 0.2 dB to 1.6 dB, depending on the quality of the input multiview depth imagery.

  • 122680.
    Rana, Sunil
    et al.
    University of Bristol.
    Mouro, João
    University of Bristol.
    Bleiker, Simon J.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Micro and Nanosystems.
    Reynolds, Jamie D.
    University of Southampton.
    Chong, Harold M. H.
    University of Southampton.
    Niklaus, Frank
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Micro and Nanosystems.
    Pamunuwa, Dinesh
    University of Bristol.
    Nanoelectromechanical relay without pull-in instability for high-temperature non-volatile memory2020In: Nature Communications, E-ISSN 2041-1723, Vol. 11, no 1, article id 1181Article in journal (Refereed)
    Abstract [en]

    Emerging applications such as the Internet-of-Things and more-electric aircraft require electronics with integrated data storage that can operate in extreme temperatures with high energy efficiency. As transistor leakage current increases with temperature, nanoelectromechanical relays have emerged as a promising alternative. However, a reliable and scalable non-volatile relay that retains its state when powered off has not been demonstrated. Part of the challenge is electromechanical pull-in instability, causing the beam to snap in after traversing a section of the airgap. Here we demonstrate an electrostatically actuated nanoelectromechanical relay that eliminates electromechanical pull-in instability without restricting the dynamic range of motion. It has several advantages over conventional electrostatic relays, including low actuation voltages without extreme reduction in critical dimensions and near constant actuation airgap while the device moves, for improved electrostatic control. With this nanoelectromechanical relay we demonstrate the first high-temperature non-volatile relay operation, with over 40 non-volatile cycles at 200 °C.

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  • 122681. Ranade, Abhiram
    et al.
    Johnsson, Lennart
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    The Communication Efficiency of Meshes, Boolean Cubes, and Cube Connected Cycles for Wafer Scale Integration1987Conference paper (Refereed)
    Abstract [en]

     In this paper we analyze the emulation of two-dimensional meshes, butterfly networks, and spanning trees on meshes, Boolean cubes, and Cube Connected Cycles (CCC) networks. We consider three timing models for signal propagation dong a wire: constant delay, capacitive delay, and resistive delay. We ais0 present novel layouts for hypercubes and CCCs that offer better performance for some problems, while essentially maintainingthe performance for other problems. The mesh interconnection performs better on all emulations for all delay models,if the communication throughput determines the performance. With resistive delay model, meshes also offer the best latency for all emulations. The hypercube and CCC layouts yield lower latency for emulating butterlly networks and spanning trees for the constant delay and capacitive delay models.

  • 122682. Ranade, Abhiram R.
    et al.
    Bhatt, Sandeep N.
    Johnsson, Lennart
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    The Fluent Abstract Machine1987In: Advanced Research in VLSI, MIT Press, 1987, p. 71-93Chapter in book (Refereed)
    Abstract [en]

    The fluent abstract machine supports a very powerful programming model. In addition to arbitrary access patterns, the instruction repertoire of the fluent machine also includes the multiprefix operation and high-level set operations. The fluent machine consists of over one hundred thousand processors interconnected by a butterfly network. The efficiency of the fluent machine derives from a very simple router, which effectively eliminates the possibility of congestion. The routing hardware is extremely simple inexpensive, and probably efficient.

  • 122683.
    Ranara, Jeff
    KTH, School of Architecture and the Built Environment (ABE), Architecture.
    Building Community with Bamboo: ”Six volcanoes” multifunctional public space in Los Baños, Laguna, Philippines2021Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Inspired by regional Austronesian vernacular architecture, volcanic forms in the northern island of Luzon in the Philippines, and the natural geometry of the Fibonacci spiral, “Six volcanoes” is a multifunctional public space in the municipality of Los Baños, Laguna, Philippines, located a stone’s throw southeast of the University of the Philippines, Los Baños campus, in the peri-urban community of Barangay (village) Tuntungin Putho.   The 3500 sqm. site rises one meter from the original street level to a 14 m. high 1100 sqm. main space. A slightly lower 6 m. high 150 sqm. auxiliary space is southwest of the main space.  Bamboo poles, which could be grown and harvested on an adjacent mini-mountain, “Pulong Malake”, serve as building material, with steel connector joinery where appropriate.  Laid-stone foundations and the thatched-roof cogon grass material are sourced from a local quarry and local fields.  Possible uses of the spaces include a wifi-lounge, learning and workshop activities, sporting events, festivities and concerts, church services, meetings and conferences.  Open to all in the area, from impoverished squatters to residents of adjacent gated communities and walled homes, “Six volcanoes” would facilitate social networking and cohesion, combating informal social segregation and bridging socio-economic class divides.

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  • 122684.
    Ranara, Jeff
    KTH, School of Architecture and the Built Environment (ABE), Architecture.
    Publikum Nynäshamn: Social-ecological Architecture in Public Municipal Space2019Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Publikum Nynäshamn docks directly to the west façade of the existing 9 story municipal building with seven floors of open activity space. These surround a full-height atrium across which a two-floor living plant green wall provides the monumental living presence of nature and its ecosystem services in an office environment.  Plants also grace the other side of this two story wall, providing a living backdrop for the heart of the building - the raised three floor high assembly hall. A lunchroom with balconies above the assembly hall provides city views and a roof garden for municipal staff. The two floor high lobby beneath the assembly hall provides a new internal city street between Banana Square and Floravägen – a former back alleyway.  A ground-level colonnade walkway with benches surrounds the new and old buildings, inviting citizens into the building spaces. Public space and circulation is further enhanced with a new passageway opening up the former dead-end southwest corner of Banana Square where the old municipal building met Folkets hus (People’s House). A generous stair complex in this new sunny southern square provides spontaneous seating and meeting spaces as well as additional outdoor access to the two floor café, art gallery, and the largest green roof – one of three accessible green roofs that enhance social and ecological values.  Pedestrian movement can continue through this new passageway directly down to Svandammen (swan pond), and in the opposite direction, directly up to Banana square from the commuter rail station.   The café and two-floor meeting room spaces provide evening and weekend public social spaces for the city residents, complementing existing bars and restaurants in the adjoining Folkets Hus.   Reduced use of energy is encouraged with progressively rising central spaces allowing for the possibility of natural stack ventilation, thermal mass energy storage in concrete (HD/F) slabs, and generous natural daylight through the glazed curtain wall climate shell surrounding the building.  Abstracted winged structures crown the top of the building and grace the building entrances, inspired by the sightings of sea eagles reported in this coastal area, and provides both a signum for the building (instead of a more traditional municipal building tower) and extended surface for rainwater collection that can be used for watering indoor green plant walls and the roof garden vegetation.  The deeper soil of the intensive green roofs not only provides more uptake and retention of rainwater (and thus reduced peak flow rates favorable for stormwater management) but also allows planting of larger, woody plants and bushes, and even small trees, which in turn, among other social and ecological benefits, add natural habitat to a predominantly impervious-surfaced downtown urban area.

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  • 122685.
    Ranasinghe, C.
    et al.
    KTH.
    Noor, Hina
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Jayasuriya, Jeevan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    A simplified method for determining gas turbine performance parameters based upon available catalogue data2014In: Proceedings of the ASME Turbo Expo, 2014Conference paper (Refereed)
    Abstract [en]

    Overall theoretical performance analysis of gas turbines can be conducted by applying design parameters into several thermodynamic theories and equations. However, limited availability of the design parameters will not provide sufficient room for a detailed analysis. Ga s turbine manufacturers publish only a limited amount of design/performance data, while important parameters remained hidden and the available information is not sufficiently enough for obtaining a complete gas turbine performance dataset. Five main parameters commonly provided by a gas turbine manufacturer's catalogues; pressure ratio of the compressor, exhaust mass flow rate, exhaust temperature of flue gas, overall efficiency, and electrical output. A theoretical model developed based on Mathcad software as documented in literature is used to reveal other hidden gas turbine parameters. A similar theoretical model using another solver was developed to obtain a complete dataset by using the available catalogue data with additional assumptions, which correspond to the commercial state of the art. The engineering equation solver (EES) software has been used as a platform to rebuild the theoretical model. As the main development, a graphical user interphase (GUI) has been introduced to the new program with the aim to make it more user friendly. Furthermore on top of obtaining the hidden thermodynamic parameters for the gas turbine, performing flue gas analysis and an exergy analysis has now become possible through this program. The developed EES program is expected to be run in the learning laboratory at the Division of Heat and Power Technology, Department of Energy Technology, Royal Institute of Technology (KTH), Stockholm and finally it is going to be incorporated into CompEdu Learning Platform of the same division.

  • 122686.
    Ranasinghe, Chamila
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. Polytechnic University, Turin.
    DEVELOPMENT OF A PROGRAM TO DETERMINE HIDDEN PERFORMANCE PARAMETERS OF A GASTURBINE2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Gas turbines overall theoretical performance analysis can be performed by using several thermodynamic theories and equations with the help of design parameters. However, limited availability of the design parameters will complicate the analysis. The turbines manufactures published a limited amount of data, while important parameters remain hidden and this available information is not enough for overall gas turbine cycle analysis. A theoretical model based on Mathcad software is already available in literature to reveal such hidden gas turbine parameters nevertheless requires improvements in various facets.Five main parameters commonly published by the gas turbine manufactures in the catalogue are exhaust temperature of flue gas, exhaust mass flow rate, overall efficiency, electrical output and compression ratio of the compressor. Theoretical model was developed to obtain all the hidden thermodynamic parameters by using available catalogue data with realistic assumptions. The engineering equation solver (EES) program has been used as a platform to rebuild the theoretical model and the graphical user interface of the new programme. After obtaining the hidden thermodynamic parameters, an exergy analysis has been carried out for the gas turbine. The developed EES programme is expected to be used in the learning laboratory at the Department of Energy Technology, The Royal Institute of Technology (KTH), Stockholm, incorporated into CompEdu learning platform.

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    Ranasinghe Chamila EGI-2013-104MSC EKV972
  • 122687.
    RANAWEERA, CHAMINDA
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Electric Power System of an Emergency Energy Module2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Abstract

    This thesis study is on designing and analysing the “Electric Power System of an Emergency Energy Module”. KTH is running a project to create a mobile system for power supply in refugee camps and during the recovery of natural disasters. This is an independent power system comprising solar, wind and biomass based power generations and control. The design and analysis of electric power system is mainly focused on increasing the renewable energy efficiency of the system while saving excess power on the battery bank and controlling the battery discharging.

     

    The analysis of the designed electric power system is done with using actual site data of solar irradiation and wind for one week period. Further, it has been developed a program based on MS Excel for analysing the module performances at any site in the world.

     

    Keywords: Emergency Energy Module; Integration of wind and solar PV

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  • 122688.
    Ranaweera, Chathurika
    et al.
    Univ Melbourne, Melbourne, Vic, Australia..
    Monti, Paolo
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Skubic, Björn
    Ericsson Res, Stockholm, Sweden..
    Furdek, Marija
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    Ericsson Res, Stockholm, Sweden..
    Nirmalathas, Ampalavanapillai
    Univ Melbourne, Melbourne, Vic, Australia..
    Lim, Christina
    Univ Melbourne, Melbourne, Vic, Australia..
    Wong, Elaine
    Univ Melbourne, Melbourne, Vic, Australia..
    Optical X-haul Options for 5G Fixed Wireless Access: Which One to Choose?2018In: IEEE INFOCOM 2018 - IEEE CONFERENCE ON COMPUTER COMMUNICATIONS WORKSHOPS (INFOCOM WKSHPS), IEEE , 2018Conference paper (Refereed)
    Abstract [en]

    5G is anticipated to be a significant leap in the evolution of mobile communication. Being designed to facilitate 10 to 100 times more capacity than 4G, 5G is considered to be the most cost-efficient solution to provide Fixed Wireless Access (FWA)to households on a large scale where providing last mile access using wired solution might not be economically viable. With a range of promises to deliver user experience improvements, facilitating cost-efficient data transportation between FWA users and network core still remains an unsolved issue, given the enormous volume of data that will be traversing the superior 5G network. This work addresses this compelling problem by formulating a joint-optimization framework to plan and analyze the optimal deployment of diverse optical x-haul strategies that can be used in 5G-based FWA networks. The work provides a cornerstone for deployment strategies that will be imperative to realize future-proof FWA network.

  • 122689.
    Ranaweera, Sandushan
    et al.
    Univ Moratuwa, Dept ENTC, Moratuwa 10400, Sri Lanka..
    Weeraddana, Chathuranga
    Univ Oulu, Fac ITEE, Oulu 90014, Finland..
    Dharmawansa, Prathapasinghe
    Univ Moratuwa, Dept ENTC, Moratuwa 10400, Sri Lanka..
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Network and Systems Engineering.
    On the Convergence of Inexact Gradient Descent With Controlled Synchronization Steps2023In: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 30, p. 703-707Article in journal (Refereed)
    Abstract [en]

    We develop a gradient-like algorithm to minimize a sum of peer objective functions based on coordination through a peer interconnection network. The coordination admits two stages: the first is to constitute a gradient, possibly with errors, for updating locally replicated decision variables at each peer and the second is used for error-free averaging for synchronizing local replicas. Unlike many related algorithms, the errors permitted in our algorithm can cover a wide range of inexactnesses, as long as they are bounded. Moreover, we do not impose any gradient boundedness conditions for the objective functions. Furthermore, the second stage is not conducted in a periodic manner, like many related algorithms. Instead, a locally verifiable criterion is devised to dynamically trigger the peer-to-peer coordination at the second stage, so that expensive communication overhead for error-free averaging can significantly be reduced. Finally, the convergence of the algorithm is established under mild conditions.

  • 122690.
    Ranby, Erik
    KTH, School of Computer Science and Communication (CSC).
    A comparison of clustering techniques for short social text messages2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The amount of social text messages authored each day is huge and the information contained within is potentially very valuable. Software that can cluster and thereby help analyze these messages would consequently be helpful. This thesis explores several ways of clustering social text messages. Two algorithms and several setups with these algorithms have been tested and evaluated with the same data as input. Based on these evaluations, a comparison has been conducted in order to answer the question which algorithm setup is best suited for the task. The two clustering algorithms that have been the main subjects for the comparison are K-means and agglomerative hierarchical. All setups were run with 3-grams as well as with only single words as features.

    The evaluation measures used were intra-cluster distance, inter-cluster distance and silhouette value. Intra-cluster distance is the distance between data points in the same cluster while inter-cluster is the distance between the clusters. Silhouette value is another more general evaluation measure that is often used to estimate the quality of a clustering.

    The results showed that if running time is a high priority, using K-means without 3-grams is preferred. On the other hand, if the quality of the clusters is important and performance is less so, introducing 3-grams together with any of the two algorithms will suit your needs better.

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  • 122691.
    Ranby, Erik
    et al.
    KTH, School of Computer Science and Communication (CSC).
    Rönnholm, Niklas
    KTH, School of Computer Science and Communication (CSC).
    Slumpgeneratorer: Implementation och test av pseudoslumptalsgeneratorer2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis looks into pseudo random number generators and how statistical tests can determine under what circumstances one should choose one of these. This is done by implementing two widely used pseudo random number generators and six common statistical tests. This provides a basis on how to decide which pseudo random number generator is more suitable in a given situation. All implementation of generators and tests are done using MATLAB. The results showed a few differences between the pseudo random number generators. The conclusions that could me made from the results was that when there is need only for shorter sequences the linear congruency algorithm is more preferable. Only when longer or continuous sequences are required the algorithm Mersenne Twister should be used.

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  • 122692.
    Ranco, Annarita
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Design and synthesis of a software-based transceiver PHY controller2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Companies developing integrated circuits are expected to enhance their products’ performance at every new release, while reducing size and power consumption. The demand for more elaborate and diverse functionality, together with a reduced time-to-market, irremediably raises costs and increases the probability of bugs. Even high-performance ASICs are not immune: the complexity of the design flow implies significant non-recurring engineering and production costs. Similar challenges affect the FPGA design flow, where the allocation of programmable logic requires considerable engineering effort. Moreover, due to the limited visibility of internal operations, isolating and back-tracing malfunctions are open challenges. Ericsson AB is exploring novel approaches to deal with this complex ecosystem.This thesis investigates the feasibility and the benefits of a flexible design approach, by developing and characterizing a Proof-of-Concept (PoC) transceiver handler for highspeed link applications. The flexibility lies in the software-based controller, exploited to handle the reset and dynamic reconfiguration of a transceiver physical layer (PHY). The objective of the software implementation is to simplify error detection and on-the-fly modification compared to a traditional HW-based controller. The firmware, running on a Nios II soft-core processor, drives the control signals while monitoring the transceiver’s status. Unexpected synchronization losses are handled by a dedicated Interrupt Service Routine.The correct HW/SW interaction has been tested through simulation, whereas the software profiling proves that the timing requirements are met (only 167µs are spent on the reset sequence). Finally, the PoC has been benchmarked against an analogous system with a traditional HW-based controller, to evaluate the drawbacks of the introduction of a soft-core processor (in terms of logic utilization and power consumption).Despite the promising engineering effort reduction, further research is required to scale up the system and move from the PoC stage towards product release.

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  • 122693.
    Rand, Antoan
    KTH, School of Biotechnology (BIO).
    Enzyme development for degradation of organic pollutants2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 122694.
    Rand, Henrik
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management.
    Green Buildings Lärdomar från den internationella marknaden Strategisk vägledning för ett svenskt fastighetsbolag 20082015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The environmental awareness among tenants, as well as with other stakeholders in the real estate industry, has increased significantly in recent years. More and more companies and interest groups think more and more about what they can do to reduce the negative effects on the environment and not least what business opportunities there are to find.

    On the international real estate market Green Buildings have become a familiar concept, but what is meant by Green Buildings and what are the reasons for the low performance of the Swedish real estate market?

    The thesis aims to study the more developed international market and with the knowledge from there define the concept of Green Buildings. The thesis also discusses the factors and above all which stakeholders drive the market for Green Buildings on the international market. The work is also aimed at from the more developed markets learn lessons from various stakeholders, and especially from a property owner perspective, in order to guide one of Sweden’s largest commercial real estate company AP Real Estate how to be an industry leader in Sweden. The study was conducted in 2008 with concluding reflections made during 2014.

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  • 122695.
    Randelius, Mats
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Influence of microstructure on fatigue and ductility properties of tool steels2008Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Fatigue and ductility properties in various tool steels, produced by powder metallurgy, spray forming or conventionally ingot casting, have been analysed experimentally and successfully compared to developed models. The models are able to predict the fatigue limit and cause for fatigue fracture, and strain- and stress-development until fracture during the ductile fracture process respectively. Total fracture in a tool steel component, both in fatigue and ductility testing, is caused by a propagating crack initiated by particles, i.e. carbides or non-metallic inclusions. The models are based on experimentally observed size distributions.

    The axial fatigue strength at two million cycles was determined for various tool steels. The fracture surface of each test bar broken was examined in SEM to determine the cause for fatigue failure, i.e. a single carbide or inclusion particle or a cluster of carbides, and the size of the particle. The particles act as stress concentrators where a crack is easily initiated when the material is subjected to alternating stresses. The developed models calculate the probability that at least one particle will be present in the material which is larger than the threshold level for crack initiation at a certain stress range.

    The ductility testing was performed on various tool steels by four-point bending under static load. The load and displacement until total fracture were recorded and the maximum strain and stress acting in the material were calculated. The fracture surface of each broken test bar was examined in SEM, though the crack initiating area appears different compared to a fatigue failure. Ductile fracture is caused by a crack emanating from voids nucleated around many particles in a joint process and then linked together. By finite element modelling of void initiation and propagation in 2D of an experimentally observed carbide microstructure for each tool steel, successful comparisons with experiments were performed. Carbides were modelled as cracked when larger than a certain size, based on fracture surface observations, and the matrix cracked above a pre-defined plastic deformation level. The stresses and strains at total failure were in good agreement between model and experiments when evaluated.

    The use of these developed models could be a powerful tool for optimisation of fatigue and ductility properties for tool steels. With good fatigue and ductility properties normal failures appearing during operation of a tool steel product could be minimised. By theoretical tests in the developed models of various carbide microstructures the optimum mechanical properties could be achieved with a minimum of experiments performed.

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  • 122696.
    Randelius, Mats
    et al.
    Swerea KIMAB, Sweden.
    Krantz, Therese
    Swerea KIMAB, Sweden.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology. Swerea KIMAB, Sweden.
    Experimental Testing and Computer Simulations of Ductile Fracture in Tool Steels2012In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 83, no 1, p. 91-99Article in journal (Refereed)
    Abstract [en]

    Ductility was determined in experimental four-point bending tests of smooth specimens of tool steel. The tool steels had different contents of carbides and carbide sizes and with a hardness of approximately 60HRc. Two of the materials tested were produced powder metallurgically, one was spray formed and one was conventionally uphill ingot cast. Carbide size distribution analysis was performed on planar polished sections of each material. Correlation between carbide microstructure and ductility performance was obtained. The fracture mechanisms were investigated with fractography. A 3D FE-model was used to simulate the four-point bending tests and thereby analyse the matrix flow curve. Also the strain at failure was analysed for each material when simulations were performed based on experimental data. SEM-images of the materials carbide microstructure were used to create 2D FE-models. The models simulated crack initiation and propagation by removing elements in the steel matrix as the plastic strain reached a critical level. With three variants, simulations of crack initiation and propagation at carbides were investigated. That was carbides with no cohesion to matrix, carbides fixed to the matrix and carbides with internal cracks. Comparison of strains at failure for the 2D and the 3D FE-models showed good correlation.

  • 122697.
    Randelius, Mats
    et al.
    Corrosion and Metals Research Institute (KIMAB), Stockholm.
    Melander, Arne
    Corrosion and Metals Research Institute (KIMAB), Stockholm.
    How carbides and inclusions influence fatigue strength in tool steels2006In: 7th International Tooling Conference, 2006Conference paper (Other academic)
  • 122698.
    Randelius, Mats
    et al.
    Swerea Kimab, Sweden.
    Sandström, Rolf
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology. Swerea Kimab, Sweden.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology. Swerea Kimab, Sweden.
    Fatigue Strength of Conventionally Cast Tool Steels and its Dependence of Carbide Microstructure2012In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 83, no 1, p. 83-90Article in journal (Refereed)
    Abstract [en]

    The axial fatigue strength at two million cycles was experimentally determined for two conventionally cast tool steels and successfully compared with results from a fatigue limit model. Specimens were tested both in the rolling and transverse direction and showed large differences in fatigue properties due to the segregated carbide microstructure. Rolling direction specimens experienced higher fatigue strength than the transverse direction specimens. This is due to smaller carbides present in the load affected cross section of the rolling direction fatigue test bars compared to the cross section of the transverse direction fatigue test bars. Fractographic analysis of failed specimens showed that large carbides had caused fatigue failure, which was also predicted by the model. Measured size distributions of carbides and inclusions were used as input data in the model. The probability that at least one particle will be present in the material volume having a size larger than the threshold value for crack propagation was calculated.

  • 122699.
    Randleff, Veronica
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Native app vs Web app: Multi-criteria decision-making for optimised mobile solution2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In today’s digital and mobile world it is more important than ever that companies offer a mobile solution for their costumers. Deciding which mobile solution to implement can be difficult. The purpose of this study is therefore to make this decision easier. Two mobile solutions, web apps and native apps, were compared in order to identify the most important factors that differentiate the two. By assigning the two mobile solutions one score each for every factor, we created a multi-criteria decision-making model. The model was then evaluated, improved and implemented as a decision-making tool. The second evaluation showed that the majority of the respondents agreed with the decision-making tool, suggesting that it could be applied as a recommendation for companies choosing between developing a native app and a web app.

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  • 122700.
    Randleff, Veronica
    et al.
    KTH, School of Computer Science and Communication (CSC).
    Schwermer, Patrik
    KTH, School of Computer Science and Communication (CSC).
    A comparative study of regularised SVD and item-based kNN for movie recommender systems2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis compares the performance of two algorithms for rating predictions in movie recommender systems. The two algorithms examined, regularised singular value decomposition (RegSVD) and item-based k-Nearest Neighbour (item-based kNN), are compared on 9 different datasets. These datasets consists of constellations of 1,000-100,000 users and 100-10,000 movies. The problem statement is to find which algorithm performs the best on each dataset with respect to both accuracy and speed. These results are then  compared in order to identify general tendencies. The experiments are performed using the implementations of the algorithms in the LibRec library, where accuracy is measured using root-mean-square error (RMSE). Finally, the results show that item-based kNN outperforms RegSVD with respect to accuracy when evaluated on smaller datasets. However, RegSVD is a better alternative for larger datasets with respect to both accuracy and execution time.

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