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  • Salamat, Rana
    KTH, School of Electrical Engineering and Computer Science (EECS), Media Technology and Interaction Design, MID.
    RichComment: Designing an Interactive Commenting System for Visual Content in Fashion Social Networks2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this study, a new design of commenting system for visual contents is investigated. The aim is to explore the elements which enrich the user interaction and enhance the user experience while commenting, specifically on fashion social networks. This study explores how an improved commenting system may motivate fashion social networks’ users to express their idea about fashion products.  A speculative design approach is used as a means for investigation. A design process consisting of semi structured interviews, thematic analysis, paper prototype, online prototype and user testing is followed to design a human-centered commenting system. 

    The results suggest that providing richer tools for commenting could improve the user interaction. The most promising elements to use in fashion social media commenting system are color and pattern palettes, tagging comment and comment categorization. These elements enable fashion customers to express their ideas easier and obtain a holistic overview around other peoples’ comments.

    Apart from fashion brands’ social networks, the approach may also be more effective in fashion brand websites. People would like to have a strong impact on fashion brands. Therefore, commenting somewhere that is tightly connected to fashion brands are preferred rather than having the conversation just among themselves in social media.

  • Smirnov, Serguei
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Anoshkin, Ilya V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Lioubtchenko, Dmitri
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Oberhammer, Joachim
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Millimeter Wave Phase Shifter Based on Optically Controlled Carbon Nanotube Layers2018Conference paper (Refereed)
    Abstract [en]

    Surfaces with tunable impedance are usually lossy at high frequencies, which limits the design of millimeter wave and Terahertz devices. This work experimentally demonstrates a phase shifter based on single-walled carbon nanotubes and dielectric rod waveguides in the 220–330 GHz frequency range. Thin carbon nanotube layers are used as a tunable impedance surface with the dielectric properties optically controlled by laser illumination.

  • Lyubchenko, Dmitri
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Smirnov, Serguei
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Anoshkin, Ilya V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Oberhammer, Joachim
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Millimeter Wave Beam Steering Based on Optically Controlled Carbon Nanotube Layers2018Conference paper (Refereed)
    Abstract [en]

    In this paper, the dielectric constant changing of thin carbon nanotube layers under light illumination was used for phase shifter development in dielectric rod waveguides. This designed phase shifter was introduced to the dielectric rod waveguide dual-antenna array. The measurements of the beam steering at 90 GHz of the dielectric rod antenna array, covered with carbon nanotubes, were carried out.

  • Urban, Frauke
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Sustainability and Industrial Dynamics.
    Comparing the Technology Trajectories of Solar PV and Solar Water Heaters in China: Using a Patent Lens2018In: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 10, no 4166Article in journal (Refereed)
  • Malenova, Gabriela
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Numerical Analysis, NA.
    Uncertainty quantification for high frequency waves2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    We consider high frequency waves satisfying the scalar wave equation with highly oscillatory initial data represented by a short wavelength ε. The speed of propagation of the medium as well as the phase and amplitude of the initial data is assumed to be uncertain, described by a finite number of independent random variables with known probability distributions. We introduce quantities of interest (QoIs) as spatial and/or temporal averages of the squared modulus of the wave solution, or its derivatives. The main focus of this work is on fast computation of the statistics of those QoIs in the form of moments like the average and variance. They are difficult to obtain numerically by standard methods, as the cost grows rapidly with ε−1 and the dimension of the stochastic space. We therefore propose a fast approximation method consisting of three techniques: the Gaussian beam method to approximate the wave solution, the numerical steepest descent method to compute the QoIs and the sparse stochastic collocation to evaluate the statistics.

    The Gaussian beam method is introduced to avoid the considerable cost of approximating the wave solution by direct methods. A Gaussian beam is an asymptotic solution to the wave equation localized around rays, bicharacteristics of the wave equation. This setup allows us to replace the PDE by a set of ODEs that can be solved independently of ε.

    The computation of QoIs includes evaluations of highly oscillatory integrals. The idea of the numerical steepest descent method is to change the integration path in the complex plane such that the integrand is non-oscillatory along it. Standard quadrature methods can be then utilized. We construct such paths for our case and show error estimates for the integral approximation by the Gauss-Laguerre and Gauss-Hermite quadrature.

    Finally, the evaluation of statistical moments of the QoI may suffer from the curse of dimensionality.  The sparse grid collocation method introduces a framework where certain large group of points can be neglected while only slightly reducing the convergence rate. The regularity of the QoIs in terms of the input random parameters and the wavelength is important for the method to be efficient.  In particular, the size of the derivatives should be bounded independently of ε. We show that the QoIs indeed have this property, despite the highly oscillatory character of the waves.

  • Ottenhall, Anna
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Antimicrobial materials from cellulose using environmentally friendly techniques2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The transition to a more biobased society introduces both new opportunities and new challenges as we replace nonrenewable materials with renewable alternatives. One important challenge will be to control microbial growth on materials, both to protect the materials from biological degradation and to prevent the spread of infections and toxins that can cause illness.

    In this thesis, both existing and new types of cellulose-based materials were treated with environmentally friendly alternatives to usual biocides to prevent microbial growth and remove bacteria from water. Two types of antimicrobial systems were studied, and the antimicrobial effects were evaluated for bacteria and fungi using both model organisms and wild-type cultures.

    The first antimicrobial approach employed was a nonleaching and contact-active layer-by-layer adsorption of polyelectrolytes to provide the cellulose fibers with a cationic surface charge, which attracts and captures bacteria onto the fiber surface. The study showed that paper filters with pores much larger than bacteria could remove more than 99.9 % of E. coli from water when used in filtration mode. The polyelectrolyte-modified materials showed a good antibacterial effect but did not prevent fungal growth.

    The second approach was to utilize biobased compounds with antimicrobial properties, which were applied to cellulose fiber foam materials. Chitosan and extractives from birch bark were selected as biobased options for antimicrobial agents. Two types of cellulose fiber foam materials were developed and evaluated for their antimicrobial properties.

    This thesis shows the importance of understanding both the application and the targeted microorganism when selecting an environmentally friendly antimicrobial system for treating biobased materials. It highlights that a good understanding of both material science and microbiology is important when designing new antimicrobial materials.

  • Pevere, Federico
    KTH, School of Engineering Sciences (SCI), Applied Physics, Photonics.
    Optical Properties of Single Silicon Quantum Dots2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    For over 60 years silicon (Si) has dominated the semiconductor microelectronics industry mainly due to its abundance and good electrical and material properties. The advanced processing technology of Si has made it the workhorse for photovoltaics industry as well. However, this material has also a big drawback: it is an indirect-bandgap semiconductor in its bulk form, hence an inefficient light emitter. This has hindered the silicon photonics revolution envisioned in 1980s, where photons were thought to replace electrons inside computer chips.

    In parallel with the exponential scaling of Si transistor's size over the years, the discovery of quantum phenomena at the nanoscale raised new hopes for this semiconductor. In the 1990s bright luminescence from nanostructured porous Si was demonstrated claiming the quantum confinement effect as origin of the emission. Since then, an intense research activity has been focused on Si quantum dots (Si-QDs) due to their potential use as abundant and non-toxic light emitters. More precisely, they could be used as fluorescent biolabels in biomedicine, as light-emitting phosphors in e.g. TV screens or as down-converters in luminescent solar concentrators. Nevertheless, in order to realize such applications, it is necessary not only to improve the fabrication of Si-QDs but also to gain a better understanding of their photo-physics. Among different types of optical measurements, those performed at the single-dot level are free of sample inhomogeneities, hence more accurate for a correct physical description.

    This doctoral thesis presents a study of the optical properties of single Si-QDs of different type: encapsulated in an oxide matrix, capped with ligands or covered by a thin passivation layer. The homogeneous photoluminescence (PL) linewidth is found to strongly depend on the type of embedding matrix, being narrower for less rigid ones. A record resolution-limited linewidth of ~200 μeV is measured at low temperatures whereas room-temperature values can even compete with direct-bandgap QDs like CdSe. Such narrow PL lines exhibit intensity saturation at high excitation fluxes without any indication of emission from multiexciton states, suggesting the presence of fast non-radiative Auger recombination. Characteristic Auger-related lifetimes extracted from power-dependent decays show a variation from dot-to-dot and confirm the low biexciton quantum efficiency.

    For the first time, the absorption curve of single Si-QDs is probed by means of photoluminescence excitation in the range 2.0-3.5 eV. A step-like structure is found which depends on the nanocrystal shape considered and agrees well with simulations of the exciton level structure. Rod-like Si-QDs can exhibit ~50 times higher absorption than spherical-like ones due to local field effects and enhanced optical transitions. In contrast with previous studies, evidence of a direct-bandgap red-shift for small Si-QDs is missing at the single dot level, in agreement with atomistic calculations.

    Low-temperature PL decay measurements reveal no triplet-like emission lines, but two ~μs decay constants appearing at low temperatures. They suggest presence of a temperature-dependent fast blinking process based on trapping/detrapping of carriers in the oxide matrix, leading to delayed emission. The proposed model allows to extract characteristic trapping/de-trapping rates for Si-QDs featuring mono-exponential blinking statistics. From PL saturation curves, ligand-passivated Si-QDs do not exhibit such detrimental phenomenon, in agreement with the proposed model.

    Last, Si-QDs demonstrate to be very hard against ~10 keV X-ray radiation, in contrast with CdSe-QDs whose PL quenching is correlated with a change in the blinking parameters. This property could be exploited for example in space applications, where radiation-hard materials are required.

    To conclude, the results achieved in this thesis will help to understand and engineer the properties of Si-QDs whose application potential has increased after several years of research both at the ensemble and at the single-dot level.

  • Rosvall, Kathrin
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Mohammadat, Tage
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics.
    Ungureanu, George
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics.
    Öberg, Johnny
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics, Electronic and embedded systems.
    Sander, Ingo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics.
    Exploring Power and Throughput for Dataflow Applications on Predictable NoC Multiprocessors2018Conference paper (Refereed)
    Abstract [en]

    System level optimization for multiple mixed-criticality applications on shared networked multiprocessor platforms is extremely challenging. Substantial complexity arises from the interdependence between the multiple subproblems of mapping, scheduling and platform configuration under the consideration of several, potentially orthogonal, performance metrics and constraints. Instead of using heuristic algorithms and problem decomposition, novel unified design space exploration (DSE) approaches based on Constraint Programming (CP) have in the recent years shown promising results. The work in this paper takes advantage of the modularity of CP models, in order to support heterogeneous multiprocessor Network-on-Chip (NoC) with Temporally Disjoint Networks (TDNs) aware message injection. The DSE supports a range of design criteria, in particular the optimization and satisfaction of power and throughput. In addition, the DSE now provides a valid configuration for the TDNs that guarantees the performance required to fulfil the design goals. The experiments show the capability of the approach to find low-power and high-throughput designs, and validate a resulting design on a physical TDN-based NoC implementation.

  • Sibani, Riccardo
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Applied design of distributed ledgers for real estate and land registration2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The recent emergence of a distributed technology named blockchain, clearly created a new point of view in the data storing and data distribution fields. If on one hand blockchain is mainly known for Bitcoin (an auto-regulated decentralized digital currency), on the other hand it has the potential to set up an auto regulated economy.In this thesis, the blockchain technology will be analyzed and described starting from P2P architecture and its origin in 2009 Satoshi Nakamoto’s whitepaper, and leading to the most up to date blockchains. The advantages and disadvantages of such architecture will be pointed out keeping in mind the security, speed and cost of such infrastructure.While Real Estate companies have often anticipated the technological innovations, land registries, instead, derive and keep a working manner which is extremely old and out of date: made of unclear procedures and wet signatures. The market needs and legislation will be researched mainly referring to other works and integrated with a technical point of view with particular focus on the decentralization of such systems.After analyzing the flow, problems and flaws of the current system, a new proposal will be researched, in particular trying to minimize the dead time in between the different steps of the mortgage, increase transparency, as well as reducing dependence on the central authorities, leading to more convenient interactions among the properties’ stakeholders. An attractive low capitalization decentralized financial product will also be proposed and implemented able to lower the interest rate and create a profitable investment with low risk, low interest and durable in time.Secure and ad-hoc algorithms will be presented and, in a later section, analyzed in combination with different blockchain technologies. Scalability and performance will also be evaluated, taking into account all the current technology limitations and the near future opportunities.

  • Li, Hengsha
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Real-time Cloudlet PaaS for GreenIoT: Design of a scalable server PaaS and a GreenIoT application2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Cloudlet is a recent topic that has attained much interest in network system research. It can be characterized as a PaaS (Platform as a Service) layer that allows mobile clients to execute their code in the cloud. Cloudlet can be seen as a layer at the edge of the communication network.In this thesis, we present a cloudlet architecture design which includes cloudlet code as a part of client application itself. We first provide an overview of related work and describe existing challenges which need to be addressed. Next, we present an overview design for a cloudlet-based implementation. Finally, we present the cloudlet architecture including a prototype of both client application and cloudlet server. For the prototype of a CO2 data visualization application, we focus on how to format the functions in client side, how to schedule cloudlet PaaS in the server, and how to make the server scalable. Finally, we conclude with a performance evaluation.Cloudlet technology is likely to be widely applied in IoT projects, such as data visualization of air quality and water quality, for fan control and traffic steering, or other use cases. Compared to the traditional centralized cloud architecture, cloudlet has high responsiveness, flexibility and scalability.

  • Nassir, Cesar
    KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, perception and learning, RPL.
    Domain-Independent Moving Object Depth Estimation using Monocular Camera2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Today automotive companies across the world strive to create vehicles with fully autonomous capabilities. There are many benefits of developing autonomous vehicles, such as reduced traffic congestion, increased safety and reduced pollution, etc. To be able to achieve that goal there are many challenges ahead, one of them is visual perception.

    Being able to estimate depth from a 2D image has been shown to be a key component for 3D recognition, reconstruction and segmentation. Being able to estimate depth in an image from a monocular camera is an ill-posed problem since there is ambiguity between the mapping from colour intensity and depth value. Depth estimation from stereo images has come far compared to monocular depth estimation and was initially what depth estimation relied on. However, being able to exploit monocular cues is necessary for scenarios when stereo depth estimation is not possible.

    We have presented a novel CNN network, BiNet which is inspired by ENet, to tackle depth estimation of moving objects using only a monocular camera in real-time. It performs better than ENet in the Cityscapes dataset while adding only a small overhead to the complexity.