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  • 1.
    Abedan Kondori, Farid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Yousefi, Shahrouz
    Ostovar, Ahmad
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Liu, Li
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    A Direct Method for 3D Hand Pose Recovery2014In: 22nd International Conference on Pattern Recognition, 2014, p. 345-350Conference paper (Refereed)
    Abstract [en]

    This paper presents a novel approach for performing intuitive 3D gesture-based interaction using depth data acquired by Kinect. Unlike current depth-based systems that focus only on classical gesture recognition problem, we also consider 3D gesture pose estimation for creating immersive gestural interaction. In this paper, we formulate gesture-based interaction system as a combination of two separate problems, gesture recognition and gesture pose estimation. We focus on the second problem and propose a direct method for recovering hand motion parameters. Based on the range images, a new version of optical flow constraint equation is derived, which can be utilized to directly estimate 3D hand motion without any need of imposing other constraints. Our experiments illustrate that the proposed approach performs properly in real-time with high accuracy. As a proof of concept, we demonstrate the system performance in 3D object manipulation. This application is intended to explore the system capabilities in real-time biomedical applications. Eventually, system usability test is conducted to evaluate the learnability, user experience and interaction quality in 3D interaction in comparison to 2D touch-screen interaction.

  • 2.
    Algers, Björn
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stereo Camera Calibration Accuracy in Real-time Car Angles Estimation for Vision Driver Assistance and Autonomous Driving2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The automotive safety company Veoneer are producers of high end driver visual assistance systems, but the knowledge about the absolute accuracy of their dynamic calibration algorithms that estimate the vehicle’s orientation is limited.

    In this thesis, a novel measurement system is proposed to be used in gathering reference data of a vehicle’s orientation as it is in motion, more specifically the pitch and roll angle of the vehicle. Focus has been to estimate how the uncertainty of the measurement system is affected by errors introduced during its construction, and to evaluate its potential in being a viable tool in gathering reference data for algorithm performance evaluation.

    The system consisted of three laser distance sensors mounted on the body of the vehicle, and a range of data acquisition sequences with different perturbations were performed by driving along a stretch of road in Linköping with weights loaded in the vehicle. The reference data were compared to camera system data where the bias of the calculated angles were estimated, along with the dynamic behaviour of the camera system algorithms. The experimental results showed that the accuracy of the system exceeded 0.1 degrees for both pitch and roll, but no conclusions about the bias of the algorithms could be drawn as there were systematic errors present in the measurements.

  • 3.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Rezaie, Ali
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Mehta, Amardeep
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Razroev, Stanislav
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Sjöstedt-de Luna, Sara
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Seleznjev, Oleg
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    How will your workload look like in 6 years?: Analyzing Wikimedia's workload2014In: Proceedings of the 2014 IEEE International Conference on Cloud Engineering (IC2E 2014) / [ed] Lisa O’Conner, IEEE Computer Society, 2014, p. 349-354Conference paper (Refereed)
    Abstract [en]

    Accurate understanding of workloads is key to efficient cloud resource management as well as to the design of large-scale applications. We analyze and model the workload of Wikipedia, one of the world's largest web sites. With descriptive statistics, time-series analysis, and polynomial splines, we study the trend and seasonality of the workload, its evolution over the years, and also investigate patterns in page popularity. Our results indicate that the workload is highly predictable with a strong seasonality. Our short term prediction algorithm is able to predict the workload with a Mean Absolute Percentage Error of around 2%.

  • 4.
    Alstergren, Manne
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Development of a spectral and goniophotometric imagingmeasurement system for optical characterization of materials2014Independent thesis Advanced level (degree of Master (Two Years)), 300 HE creditsStudent thesis
    Abstract [en]

    In this thesis, a novel color measurement system has been developed and its performance evaluated.It is a modular spectral imaging goniophotometer that measures angle resolved spectralreflectance and transmittance of materials, e.g. textiles, papers, coated materials and flexibleelectronics. It is a highly flexible system that can, unlike most commercial systems, capturereflectance images of both high spectral and spatial resolution over a wide range of measurementgeometries.

    It is important that the system can produce geometrically correct images of the samples, as well ascapture spectral information with high accuracy, i.e. the system needs to be both geometricallyand photometrically calibrated. A line-scan spectral camera and a high accuracy translationstage provide 2D-scans of the sample, where imaged area, sample position and measurementgeometry is controlled by a high precision robotic arm. Assessment of spectral and spatialresolution, characterization of the light source and spectral accuracy of the camera are someof the evaluations carried out. Spectral accuracy, and thus color measurement accuracy, isevaluated with the color difference formula CIE ∆Eab. During these evaluations the system isable to measure colors at ∆Eab < 14 and ∆Eab < 30 for a matte and glossy sample respectively,both of which are standard color calibration samples. These results show large color differencesthat are most likely caused by the low signal-to-noise ratio for short wavelengths due to thelight source. Finally, the system’s angle resolved measurement capability is demonstrated bymeasurements of goniochromatic samples whose color shifts with the viewing angle. The changein color is successfully captured for viewing angles in the range of 0 to 45 degrees from the surfacenormal.

  • 5.
    Andersson, Sebastian
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Centralised Distribution Grid Energy Storage Systems: Placement and Utilisation for Grid Expansion Deferment2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Following an ongoing change towards an increasingly renewable power generation system Swedish grid operators are facing several challenges in coming years. As authorities plan for the decommissioning of nuclear power an increased reliance on de-centralised energy sources such as photo-voltaic distributed generation (PVDG) is expected. A technology observed in some cases to accompany local power quality issues severe enough to impose grid expansion measures from distribution system operators (DSOs). Considering a combination of an indicative utilisation inefficiency of classical grid expansion measures and a recent year maturing of various energy storage technologies, this report sets out to evaluate the possibility of utilising centralised energy storage systems (ESSs) for deferment of classical grid expansion measures.

    For the purpose of identifying the most prominent problem scenarios of modern production- and consumption behaviours as well as the possible solutions offered by centralised ESSs, a literature review of journal articles and technical reports was conducted in combination with a case-study of an existing urban grid operated by Umeå Energi Elnät AB (UEEN). The work regarding ESSs is directed with specific focus towards evaluating which ESS services can potentially facilitate grid expansion deferment and what ESS placement is advisable for efficient utilisation. Assessing possible grid safety implications, potential for peak load shaving and the presently most suitable energy storage technology was also within the scope of the study.

    The literature review reveals PVDG induced feeder line over-voltage and transformer overload the most likely and previously observed implications imposing grid expansion measures. The former more prominent in elongated, typically rural, grids and the latter in more densely populated urban grids. For deferment of over-voltage related grid expansion measures a centralised ESS can be utilised for voltage support provided placement is made close to the affected grid section, presumably far out the affected feeder line. This result is coherent throughout the reviewed literature and is supported by the results of the case-study. Distribution transformer overload and its imposed grid expansion measures can be deferred through load re-allocation and peak load shaving, two services proven achievable by centralised ESSs and the capacity for which increases if ESS placement is made closer the distribution transformer.

    Provided present regulatory and standards are adhered to upon installation, significant negative impact of centralised ESSs on distribution grid safety can be avoided. Most energy storage technologies, including battery based energy storage technologies indicated from the literature review providing the most suitable characteristics for use in centralised distribution grid ESSs, utilise well established systems for grid connection hence no presently unsolvable grid safety implications are identified. Technical reports of real applications of centralised ESSs reinforce this argument as successful implementation without ESS caused grid safety implications have been achieved in the Swedish distribution grid in the past.

  • 6.
    Aspholm, Mattias
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Utredning av frekvensomriktaresinverkan på sin närmiljö2015Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Fokus läggs mer och mer på hur olinjära laster påverkar spänningsgodheten pånätet. Ledorden är att ”du skall icke sabotera din grannes spänningskvalitet!”.Detta gillar nätbolagen och allmänheten men i vissa delar av nätet är det inte lika nödvändigt att hålla så hårt på elkvaliteten. Industrier har ofta anläggningar som är avskilda öar från det elektriska fastlandet. Därför gjordes mätningar på befintlig anläggning med stor del frekvensomriktardrift för att kunna jämföra med simuleringar från dimensioneringsprogram och slutligen utifrån resultatet dra slutsatser om hur man ska utveckla tankesättet vid dimensionering av frekvensomriktare för att göra den mer kostnadseffektiv.

  • 7.
    Behring, Sven
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Kontaktpressningssystem: En studie av elsäkerhet2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    This work covers a broad analysis of the risks that could impact the achievement of electrical safety of electrical installations. The work includes both electrical equipment such as the installation of electrical equipment.The report illustrates the main technical characteristics of electrical connections greater than 10 mm2 and provides an introduction to the crimping systems for copper and aluminum conductors. In addition to that analyzes the factors that are important to assure the quality of an electrical connection throughout the value stream in terms of both materials such informations. Furthermore analyzed deeper the need for skills development of technicians and other staff.The different parts of this work are analyzed and presented, in theory to studies carried out both at Elpress AB and partly with the help of other scientific reports dealing with similar subjects. In addition, presents a survey that will help understanding the current perception of the electrical connections and cable crimping systems among end users. Various risks are analyzed in an FMEA analysis with respect to the different stages in the value stream.The project has shown that there is a need for changes in the regulations that deals with, among other things, permission for electrical staff.

  • 8.
    Bostedt, Nicklas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    NGN - Nästa Generations Nätverk (Krav och Målbild) för Piteå kommun2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    My work has been to develop a basis for Piteå Municipality's future investment on a newer and more modern IT-infrastructure. The report describes primarily the areas surrounding network segmentation, a new flexible WAN solution and a central policy engine with IEEE 802.1x. Through these implementations achieved a dynamic role-based access, a tool that all big organizations should have to tackle the challenges that have arisen over the last few years with BYOD (Bring Your Own Device).

    In order to achieve a more dynamic and segmented network, I have separated from layer 2 using MCE and L3VPN transport to various municipal sites, while I logically divided the network into different zones. Network optimization is today largely based on moving the intelligence from hardware to software, a so-called SDN (Software Defined Network). I have therefore chosen in this report to place great emphasis on describing the features of HP IMC, where new opportunities for control, management and logging of the network are presented and how they can optimize the operation of an organization.

    This work is a continuation of NGN – Nästa Generations Nätverk (Nätverks- och Riskanalys) för Piteå Kommun by Johan Carls.

  • 9.
    Bränberg, Agneta
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Holmgren, Ulf
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Kursdesign med utgångspunkt i utveckling av kreativitet, kritiskt förhållningssätt och initiativförmåga2011In: 3e Utvecklingskonferensen för Sveriges ingenjörsutbildningar. 30 november-1 december 2011, 2011, p. 112-116Conference paper (Other academic)
    Abstract [sv]

    Kursen Analog elektronik 15hp är den första renodlade ämneskurs som studenterna på högskoleingenjörsprogrammet i Elektronik och datorteknik möter och den ges under senare delen av höstterminen i första årskursen. Kursen är central på programmet dels ämnesmässigt men framförallt genom önskemålet att etablera ingenjörsmässiga arbetsformer och ett ingenjörsmässigt förhållningssätt i kommande kurser på programmet. Tre aspekter bildar bas för kursens målbeskrivning

     -Kunskapsbasen definierad av klassisk analogiteknik och elementära elektroniska system

    -Färdighetsmålen med fokus på konstruktion, experiment, simulering och analys

    -Formerande av en attityd till lärande där kreativitet, lagarbete och kritiskt förhållningssätt står i centrum

    I presentationen diskuteras hur arbetsmetodik, kursinnehåll och examination kan utformas i syfte att stödja samtliga tre måldimensioner och hur motivation, personligt ansvarstagande och professionellt förhållningssätt kan utvecklas genom en medveten utformning av läraktiviteter.

  • 10.
    Burman, Sebastian
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Energiuppföljning på två flerbostadshus i centrala Skellefteå.2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    One third of Sweden's energy use is used by residential and commercial buildings, of which nearly 60 % go to heating. Opportunities are great for using energy more efficiently and there is a great potential to save energy by improving the construction of the building. The EU places higher demands on energy use and means that monitoring of energy use is becoming increasingly important. From 2021, all new production of buildings in EU Member States will be "close to zero energy houses". The definition of "near zero energy house" has not yet been established in Sweden, but in a throw-out of BBR is the requirement to tighten by 40 % discussed. Efforts to get more energy-efficient buildings are under way and are being carried out in close collaboration with BBR.

     

    This degree project has been carried out on behalf of Skebo, where the goal is to establish the real specific energy use in operation for two properties in Skellefteå, Ringduvan and Odenskrapan. Compare and analyze deviations from projected specific energy use. Ringduvan was ready for occupation in spring 2014 and Odenskrapan in early 2016.Both buildings have electricity and district heating from Skellefteå Kraft. Ringduvan is projected by NCC and Oden of Lindbergs Energi & VVS AB.

     

    Sveby ("Standardize and Verify Energy Performance in Buildings") is a development program run by actors in the construction and real estate industry. Svebys aim is to develop an industry standard that increases the accuracy of the project between projected and real energy use. With increased knowledge of user-related use, a standardized approach, energy monitoring and enhanced cooperation between actors, the goal is to reduce the deviations. Operators in the industry may choose to enter into a Sveby agreement, which includes a common method of procurement, design and verification.

     

    The projected specific energy use for Ringduvan is 76 kWh/m2,year and the real is 101 kWh/m2,year. Odenskrapan projected is 53 kWh/m2,year and the real is 93 kWh/ m2,year. That is, the specific energy use exceeds the estimated energy consumption by 33 % for Ringduvan and 75 % for Odenskrapan. This means that much more district heating and real estate is needed than expected.

     

    In general, potential causes of higher energy use have been identified. But nothing has been confirmed and more work is required against the buildings in order to compare and identify the exact reasons.

  • 11.
    Bylund, Kristoffer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Elnätsautomation i distibutionsnätet: Feldetektering och fjärrstyrning som metoder att förbättre leveranssäkerheten i elnätet2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Att öka leveranskvaliteten i sina elnät är något som varje nätbolag strävar mot. En metod att göra detta kan vara att utrusta nätstationer i mellanspänningsnätet med feldetektering och fjärrstyrning för snabbare felsökning och sektionering vid fel. I denna studie har dessa möjligheter utretts och även de potentiella vinsterna i kortare avbrottstider mätt i indikatorn SAIDI. Studien har resulterat i ett förslag för fortsatt investering i feldetektering och fjärrstyrning i Umeå Energis elnät. Den metod som använts är att beräkna SAIDI för det värsta felscenariot för varje matande linje som tittats på, både med och utan elnätsautomation. Det förslag som tagits fram har utgått ifrån de enskilda matningarna förutsättningar vad gäller kundantal, antal nätstationer och nättopologi och har sedan jämförts med två standardalternativ, med detektering i samtliga nätstationer samt detektering i mitten av linjen. Resultatet visar att det förslag som lämnats till Umeå Energi har potential att sänka det summerade SAIDI-värdet vid värsta felscenario från 37 minuter till 10 minuter i de matningar som undersökts. Detta till en kostnad av mindre än två miljoner kronor, eller en kostnad per potentiellt minskad SAIDI-minut på ca. 70 000 kr. Studien har tittat på 16 matande linjer med totalt ca. 17 000 kunder. 

  • 12.
    Carls, Johan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    NGN – Nästa Generations Nätverk (Nätverks- och Riskanalys) för Piteå Kommun2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    My mission has been to technical documentation and identify Piteå Municipality's existing network infrastructure. Everything has been summarized in several different areas: Network Services, Network-related services, Technology, Management/Control and Security. A risk analysis has been developed where I have identified a total of 28 risks and deficiencies in the municipality's existing network infrastructure. 4 risks and deficiencies under Design, 9 risks and deficiencies under Security, 5 risks and deficiencies under Network related services, 2 risks and deficiencies under Network Services, 2 risks and deficiencies under Management/Control and 5 risks and deficiencies under Technology. All risks and deficiencies have been categorized in order of low, medium and high risks and deficiencies of varying action time (0-24 + months). This final report has been the basis for then developing a new future-proof network infrastructure using a Requirements and Vision for the Municipality of Piteå.

  • 13.
    Carlsson, Viktor
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Measuring routines of ice accretion for Wind Turbine applications: The correlation of production losses and detection of ice2010Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Wind power will play a major role in the future energy system in Sweden. Most of the major wind parks are planned to be built in sites where the cold climate and atmospheric icing can cause serious problems. This underlines the importance of addressing these issues. The major cause of these problems is in-cloud icing of the rotor blades due to super cooled liquid droplets of clouds. The droplets freeze upon impact with the rotor blade and form hard rime ice. This rime ice causes disruption in the aerodynamics that leads to production losses, extra loads on the rotor blades and when the ice is shed it poses a safety risk to people in the near environment. This master thesis focuses on how to measure the accretion of ice and the correlation between measured ice and production losses of two wind parks in northern Sweden.

     

    The results show a good correlation between the ice accretion on a stationary sensor and the production loss from a wind turbine. In most icing events the icing of the sensor and large production losses from the wind turbine correlated clearly. Attempts to quantify the production losses at a certain ice rate measured with the stationary sensors was done, however no clear results was produced. The reason for this is that the wind turbines often stop completely during an icing event and that the time series analyzed was too short to be able to quantify the losses at certain wind speed and ice rates.

     

    Recommendations on the type of sensor which should be used was to be produced, however the conclusion was that no single sensor has acted satisfactory and could be recommended to measure ice accretion for wind turbine applications. Due to this, at least two sensors are recommended to increase the redundancy in the measurement system. Modeling ice accretion with standard parameters measured has been done and the results show that the time of icing could be determined quite well when the sensors was ice free, however when the sensors and especially the humidity sensors was iced the time of icing was overestimated.

     

    The main conclusion drawn is that there is a clear relationship between the icing of a stationary sensor and the rotor blade. There is still no which fulfills all demands of measuring ice accretion for wind turbine applications, further it is possible with simple models to roughly determine when icing occurs with standard measurements.

  • 14.
    Darvish, Ali Mohammed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Super-resolution facial images from single input images based on discrete wavelet transform2014In: 22nd International Conference on Pattern Recognition, 2014, p. 843-848Conference paper (Refereed)
    Abstract [en]

    In this work, we are presenting a technique that allows for accurate estimation of frequencies in higher dimensions than the original image content. This technique uses asymmetrical Principal Component Analysis together with Discrete Wavelet Transform (aPCA-DWT). For example, high quality content can be generated from low quality cameras since the necessary frequencies can be estimated through reliable methods. Within our research, we build models for interpreting facial images where super-resolution versions of human faces can be created. We have worked on several different experiments, extracting the frequency content in order to create models with aPCA-DWT. The results are presented along with experiments of deblurring and zooming beyond the original image resolution. For example, when an image is enlarged 16 times in decoding, the proposed technique outperforms interpolation with more than 7 dB on average.

  • 15.
    Ekspong, Joakim
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Boulanger, Nicolas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gracia-Espino, Eduardo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Surface activation of graphene nanoribbons for oxygen reduction reaction by nitrogen doping and defect engineering: An ab initio study2018In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 137, p. 349-357Article in journal (Refereed)
    Abstract [en]

    Introducing heteroatoms and creating structural defects on graphene is a common and rather successful strategy to transform its inert basal plane into an efficient metal-free electrocatalyst for oxygen reduction reaction (ORR). However, the intricate atomic configuration of defective graphenes difficult their optimization as ORR electrocatalysts, where not only a large density of active sites is desirable, but also excellent electrical conductivity is required. Therefore, we used density functional theory to investigate the current-voltage characteristics and the catalytic active sites towards ORR of nitrogen-doped and defective graphene by using 8 zig-zag graphene nanoribbons as model systems. Detailed ORR catalytic activity maps are created for ten different systems showing the distribution of catalytic hot spots generated by each defect. Subsequently, the use of both current-voltage characteristics and catalytic activity maps allow to exclude inefficient systems that exhibit either low electrical conductivity or have adsorption energies far from optimal. Our study highlights the importance of considering not only the interaction energy of reaction intermediates to design electrocatalysts, but also the electrical conductivity of such configurations. We believe that this work is important for future experimental studies by providing insights on the use of graphene as a catalyst towards the ORR reaction. 

  • 16.
    Elvelind, Sofia
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Mönsterigenkänning och trendanalys i elnät: Prognostisering av elkvalitet samt effektuttag inom industrin2019Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Interest in power quality has increased as electrical equipment, such as inverters, nowadays emits more disturbances. Electrical equipment has also become less tolerant to disturbances, while industries have become less tolerant to disturbances in the production. Traditionally, fault diagnosis and handling have been performed when the fault has already arisen and has been based on historical data. Through its application PQ4Cast, Metrum have introduced pattern recognition to forecast power quality parameters and active power, and thereby contribute to proactive maintenance. The application creates a forecast for the coming week based on data for the last few weeks. Under development is also a function for trend analysis of, among other things, power consumption and voltage level.

    The objective with the implementation of PQ4Cast is to achieve higher availability and minimize costs for maintenance and unplanned interruptions. A second objective is to increase the control over variations in power consumption. The aim of this thesis is to determine which deviations are important for Sandvik, develop methods for evaluating the application’s functionality and provide a basis for how forecasts from the application should be managed. The aim is also to determine the usefulness of the trend analysis function.

    For Sandvik, the greatest benefit is seen in gaining control over future values for active power, reactive power and variations in the RMS value of the voltage. Of these, variations in active and reactive power should be most suitable for PQ4Cast to identify. For examination of the conformity between prognosis and actual outcome, the use of correlation coefficient, determination coefficient and significance level of five percent is recommended. Use of MAPE, Mean Absolute Percentage Error, is also recommended to quantify the forecast error. In the event of good conformity, the forecasts for active power from PQ4Cast are recommended for weekly forecasts to the electricity trading company, Statkraft, in combination with temperature forecasts and forecasts of production following week.

    The trend analysis function shows MAPE at a few percent for the active effect. Further investigations of the function are recommended and in case of good conformity, the prognosis is recommended as the basis for forecasts given to Statkraft and as the basis for new power agreements with Vattenfall in combination with production forecast. For analysis of the trend for the voltage's RMS value, the deviation from the forecasted value is only a few tenths of a percentage. Here further studies are recommended and then specifically at area in the grid where installation of solar power is planned.

    The application PQ4Cast and the trend analysis function are expected to lead to economic benefits, such as reduced costs for purchase of electricity, reduced electricity grid charges and significant savings if disturbances that may lead to interruptions can be detected and prevented. Disturbances of short duration, such as voltage dips, are however hard to detect with the current setup of the application.

  • 17.
    Granberg, Niklas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Elkvalitetsutredning vid ett kartong- och massabruk2016Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report contains an investigation on the quality of the distributed electricity to Metsä Board Mill in Husum. Because the Mill has gone through large changes in the process, the end product is nowadays cardboard instead of paper and an investigation is needed. These changes have lead to a different consumption of electricity, both of the amount and the way it is consumed. There’s no summarizing image of how the electricity quality looked like before therefore a full investigation of the whole factory is needed. That includes an investigation of the pulp mill that hasn’t gone through any changes. The report investigates disturbances such as THD, voltage dips, flicker and transients with extra focus on THD. The result of the measurements is compared to agreement that’s been signed with Vattenfall but also to regulations and standards that exist.

    After the schedule of the main distribution of electricity for the factory has been studied, a plan is set for how the work should be done. Measurements is going to be taken at the incoming lines that are distributed by Vattenfall, but also at lower voltage transformers in the factory to be able to see where sources of disturbances might be.  

    The result shows that the quality of the electricity overall is good, the only thing is that the 7th harmonic on the incoming lines sometimes is higher that the acceptable limits. Further the investigation shows that the factory itself isn’t the source of these distortions. The distortion comes from a VAr (reaktiv effect) capacitor bank that is installed at Vattenfalls transformer station in Gideåbacka. The capacitor bank creates resonance with the connected load and that leads to amplification of certain harmonics.

  • 18.
    Hellborg, Jonatan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Analys av industrinät med spänning 7,8 kV2019Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The Bofors industrial power grid in Karlskoga is aged and currently operating with a non-standardized voltage level. This analysis has been done in collaboration with “Karlskoga energi och miljö AB” with the purpose of determining what needs to be replaced, added or removed in order to facilitate an increase in voltage from today’s level (7.8 kV) to the same level as the rest of the distribution grid (10 kV). In addition to this also produce the framework for a plan on how this voltage increase is to be accomplished, as well a determining how much the losses can be reduced and how much of an economic impact this has.

    The results of the analysis are that all of the 39 distribution transformers currently in use must be replaced in order to not have these break down. The cables in use, however, will be fine due to them being constructed for 12 kV. The framework produced determines that the best course of action is for the company to build a new grid on top of the old one, with a voltage of 10 kV and allow existing customers to connect to this grid during a set time period.

    In regards of the losses in the grid, a potentially large saving can be made.  Approximately 415 708 SEK per year, calculated with an energy price of 0.85 SEK per kWh, of which the no-load losses of the transformers is the majority. The calculated cable losses were almost non-existing.

    All this proves the benefits of performing this voltage increase, and the construction required. Initially there is quite a large investment needed from the company, but the benefits are large enough that It would be irresponsible to not go through with the voltage increase. By doing this the company gets a better grid, not just better dimensioned but also a much more reliable grid with shorter delivery times on for example transformers.

    This analysis has not gone into depth regarding the two hydropower plants connected to the grid.

  • 19.
    Hjelmqvist, Gudmund
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    En jämförande analys mellanElbyggnadsrationalisering och Allmän Material ochArbetsbeskrivning2018Independent thesis Basic level (university diploma), 180 HE creditsStudent thesis
    Abstract [en]

    This thesis has been aimed at responding to major issues regarding the dierencesbetween the two systems Electricity Rationalization (EBR) and General Materials andWork Description (AMA). The background to this survey is the prevailing and forth-coming major investment needs in Sweden's electricity grid and nearby infrastructure.The dierences between the two systems are both essential while they both canproduce an equivalent nal result. As will be shown in the thesis work are:•EBR is specic for construction and maintenance of electrical infrastructure ac-cording to standardizations that the Swedish electricity industry has achieved.•AMA a reference work that, in its entirety and complete edition, can dene allbuilt-in environments, regardless of the basis of specic technical solutions orworking methods.•Structures and construction technology dier mainly because EBR provides com-plete design solutions and standardized working methods.•There is nothing compulsory in EBR or AMA, which means that maintenanceneeds with regard to quality aspects need to be dierent.•The pros and cons of each system depends largely on what you want to achieveand whether you are a client or a performer.• It is easier to integrate new technologies when working through AMA.• You can achieve similar results, regardless of whether you are purchasing via EBRor AMA.The report writer sees a value in performing more future deepenings;1. Compare EBR with how to work in other countries.2. Evaluate how the use of cost catalogs and time studies at both clients and execu-tives aects market, eciency and competition.3. Evaluate what any prots CoClass would provide to the electrical industry inplanning, execution and management.4. How does the state of the economy aect the procurement system.

  • 20.
    Holmberg, Marc
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Life Time BoM: BoM-effektivisering ur ett Lean-perspektiv.2019Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Beskrivning och analys av ett effektiviseringsprojekt på Sanminas fabrik i Örnsköldsvik. Projektet ska effektivisera BoM-hanteringsprocessen primärt genom tre förändringar. 1: Införa en BoM istället för flera. 2: Datorstöd istället för manuell hante-ring. 3: En konform hantering för alla projekt. Analysen av projektet grundas påLean-principer. Centrala begrepp som Lean och BoM beskrivs. En kvalitativ studiegenomförs med en fokusgrupp bestående av komponentingenjörer. Resultatet fråndenna ligger till grund för analysen. Ny metodik tolkas som effektivare än gammalmetodik på alla tre relevanta punkter. Ny metodik löser dock inte alla de bristersom finns i den gamla processen. Detta då de verktyg avsedda för interna processerinte har större inverkan på externa problem. Förändringarna tolkas som ett steg moten mer Lean BoM-hanteringsprocess. Fullständig analys kommer kunna genomförasnär ny metodik är implementerad. Diskussion kring tolkning av data och osäkerhet i analys av densamma. Detta då datan är kvalitativ.

  • 21.
    Hörnfeldt, Robert
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Fjärrvärme som möjlighet till reservdrift av elproduktion2014Independent thesis Basic level (university diploma), 180 HE creditsStudent thesis
    Abstract [sv]

    Rapporten är en utvärdering av möjligheten att generera elektrisk energi från fjärrvärme med Seebeck-effekten och görs på uppdrag av Skellefteå Kraft. Kursen är examensarbete för högskoleingenjörsexamen i Elkraftteknik, 5EL210 vid institutionen tillämpad fysik och elektronik på Umeå Universitet under vårterminen 2014.En termoelektrisk generator fungerar enligt Seebeck-effekten och genererar en elektrisk spänning som är linjär mot temperaturskillnaden mellan sina två metallytor. För att få en temperaturskillnad så krävs ett kylmedium vilket skapar ett värmeflöde från den varma energikällan till kylmediumet. Utan kylmediumet så kommer temperaturerna gå mot samma värde. Ett kylmedium kan till exempel vara snö, markgrunden eller vattenradiatorer. Eftersom en termoelektrisk generator är väldigt ineffektiv så lämpar det sig inte att använda markgrunden eller snö som kylmedium för att endast generera upp till 4% el av den tillförda värmeenergin och resten går till förluster. Av denna anledning valdes radiatorerna i villan som kylmedium för detta examensarbete.En teoretisk experimentuppställning gjordes med 16 stycken termoelektriska generatorer. Resultatet visade att värmeöverföringen genom de termoelektriska generatorerna begränsades till ca. 250W värmeenergi. Med relativt låga temperaturer så är effektiviteten endast 2% vilket genererar ca. 5W elektrisk energi.Slutsatsen är att med denna experimentuppställning så genereras inte tillräckligt med energi för att driva en cirkulationspump. Effektiviteten av de termoelektriska generatorerna är för dålig och de leder värme dåligt på grund av dess höga termiska resistans.

  • 22.
    Ivarsson, Jörgen
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Direktuppspelande video från Umeå kommuns webbplats: En undersökning om Umeå kommuns förutsättningar att sända direktuppspelande video över Internet från en mobil studio2005Independent thesis Basic level (professional degree), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [sv]

    Användningen av strömmande media ökar explosionsartat och är nära knu- tet till utbyggnaden av bredband. Intresset för direktuppspelande video bland kommuner, stat och landsting har ökat på senare år. I dag sänder bl.a. Region Skåne, Uddevalla-, Sigtuna- och Bollnäs kommun direktupp- spelande video från sina kommunfullmäktige.Den här rapporten handlar om Umeå kommuns förutsättningar att sända direktuppspelande video från sin webbplats. Min uppgift blev att undersöka vilka krav kan ställas på en myndighet som sänder video både när det gäller teknik och tillgänglighet.En fördjupning om multicasting görs, då det är en teknik för att drastiskt minska behovet av bandbredd för direktsänd video. Dessutom tas en mobil utrustning fram för att spela in och sända direktuppspelande video över Internet.Avslutningsvis görs en testsändning från den mobila studion. 

  • 23.
    Johansson Sävenberg, David
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Fiberoptisk nätplanering2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report describes how you can build a fiberoptical broadband network in and for the community of Ersliden outside the city of Umeå. The system design is planned after a detailed description of the network requirements.

    The report is in two parts. The first part brings up the planning of the fiberoptic network. The second describes the wireless access point.

    This study brings up what kind of fiberoptics the network should have, and how nodes and channelization are planned. It also provides examples of hardware that matches the network’s needs.

  • 24.
    Jonsson, Ulf G.
    et al.
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Andersson, Britt M.
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Lindahl, Olof A.
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    A FEM-Based Method Using Harmonic Overtones to Determine the Effective Elastic, Dielectric, and Piezoelectric Parameters of Freely Vibrating Thick Piezoelectric Disks2013In: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, ISSN 0885-3010, E-ISSN 1525-8955, Vol. 60, no 1, p. 243-255Article in journal (Refereed)
    Abstract [en]

    To gain an understanding of the electroelasticproperties of tactile piezoelectric sensors used in the characterizationof soft tissue, the frequency-dependent electric impedanceresponse of thick piezoelectric disks has been calculatedusing finite element modeling. To fit the calculated to the measuredresponse, a new method was developed using harmonicovertones for tuning of the calculated effective elastic, piezoelectric,and dielectric parameters. To validate the results, theimpedance responses of 10 piezoelectric disks with diameterto-thickness ratios of 20, 6, and 2 have been measured from10 kHz to 5 MHz. A two-dimensional, general purpose finiteelement partial differential equation solver with adaptive meshingcapability run in the frequency-stepped mode, was used.The equations and boundary conditions used by the solver arepresented. Calculated and measured impedance responses arepresented, and resonance frequencies have been compared indetail. The comparison shows excellent agreement, with averagerelative differences in frequency of 0.27%, 0.19%, and0.54% for the samples with diameter-to-thickness ratios of 20,6, and 2, respectively. The method of tuning the effective elastic,piezoelectric, and dielectric parameters is an importantstep toward a finite element model that describes the propertiesof tactile sensors in detail.

  • 25.
    Kaddori, Bashar
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Kabelförläggning i mark2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The thesis work was carried out at the consulting company WSP Group- Stockholm, with the purpose of identifying and finding installation methods that facilitate the placement of cables today and in the future. The thesis focuses only on regional and local grids but with elements of main grids in major cities. This degree project is based on information gathering from standards EBR KJ41: 15 cabling max 145 kV, SS-EN 424 14 37 and Stockholm City Technical Manual and the differences between them. As a supplement to the standards, different manuals were used by different companies and also past thesis work.

    Answers to main question and subquery are based on interviews with various actors in the industry such as grid owners, consultants, and entrepreneurs.

     The interviews revealed that pipes are used primarily not to protect cables, but to pass through a road. Pipes Installation lead to deterioration of heat dissipation in cables, which means that the temperature of the cable rises and, in the worst case, shortens the life of cable. Walking up the cable wiring area is not possible because it is crowded in the ground and requires a lot of space.

    Bentonite filling is not a good method because there is no data on what can happen with the bentonite after 5 years or 20 years. It would be difficult to access the cables and repair them because the bentonite must be flushed out. If the bentonite is stiff, it can be difficult to access the cable. It turned out that excavation is the only method used in metropolitan areas because other methods can cause damage to existing wires lying in the ground. The most common cable damages are digging in cables, it is very easy to access the ground cables at the installation work.

    In order to expand the network in the future, cables with larger wires can be placed to cover future needs. In areas where you know that the network does not need to be strengthened, pipes can be placed to facilitate maintenance work in the future.

    The city needs to be clear about where the future constructions will be and develop a plan and stick to it. The city must also be responsible for its land and not let anyone else take care of the network.

    Management owners need to be better at co-ordinating and acting quickly to come up with details on where to co-ordinate to avoid bottleneck and disturbing landowners several times.

    It seems that tunnels will be a way to go in the future. Tunnels is an expensive infrastructure and if several actors choose to collaborate, the costs of tunnel construction can be divided between different actors. OPI channelization is also another type of solution and it is very good if several players can also collaborate

  • 26.
    Karlsson, Johannes
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wireless video sensor network and its applications in digital zoo2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Most computing and communicating devices have been personal computers that were connected to Internet through a fixed network connection. It is believed that future communication devices will not be of this type. Instead the intelligence and communication capability will move into various objects that surround us. This is often referred to as the "Internet of Things" or "Wireless Embedded Internet". This thesis deals with video processing and communication in these types of systems.

    One application scenario that is dealt with in this thesis is real-time video transmission over wireless ad-hoc networks. Here a set of devices automatically form a network and start to communicate without the need for any previous infrastructure. These devices act as both hosts and routers and can build up large networks where they forward information for each other. We have identified two major problems when sending real-time video over wireless ad-hoc networks. One is the reactive design used by most ad-hoc routing protocols. When nodes move some links that are used in the communication path between the sender and the receiver may disappear. The reactive routing protocols wait until some links on the path breaks and then start to search for a new path. This will lead to long interruptions in packet delivery and does not work well for real-time video transmission. Instead we propose an approach where we identify when a route is about to break and start to search for new routes before this happen. This is called a proactive approach. Another problem is that video codecs are very sensitive for packet losses and at the same time the wireless ad-hoc network is very error prone. The most common way to handle lost packets in video codecs is to periodically insert frames that are not predictively coded. This method periodically corrects errors regardless there has been an error or not. The method we propose is to insert frames that are not predictively coded directly after a packet has been lost, and only if a packet has been lost.

    Another area that is dealt with in this thesis is video sensor networks. These are small devices that have communication and computational capacity, they are equipped with an image sensor so that they can capture video. Since these devices in general have very limited resources in terms of energy, computation, communication and memory they demand a lot of the video compression algorithms used. In standard video compression algorithms the complexity is high for the encoder while the decoder has low complexity and is just passively controlled by the encoder. We propose video compression algorithms for wireless video sensor networks where complexity is reduced in the encoder by moving some of the image analysis to the decoder side. We have implemented our approach on actual low-power sensor nodes to test our developed algorithms.

    Finally we have built a "Digital Zoo" that is a complete system including a large scale outdoor video sensor network. The goal is to use the collected data from the video sensor network to create new experiences for physical visitors in the zoo, or "cyber" visitors from home. Here several topics that relate to practical deployments of sensor networks are addressed.

  • 27.
    Karlsson, Johannes
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Israelsson, Mikael
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Real-time video over wireless ad-hoc networks2004In: Proceedings, Symposium on Image Analysis, 2004, p. 106-109Conference paper (Refereed)
  • 28.
    Karlsson, Johannes
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wark, Tim
    CSIRO.
    Valencia, Philip
    CSIRO ICT Centre, Brisbane, Australia .
    Ung, Michael
    CSIRO ICT Centre, Brisbane, Australia .
    Corke, Peter
    CSIRO ICT Centre, Brisbane, Australia .
    Demonstration of Image Compression in a Low-Bandwidth Wireless Camera Network2007In: Processing in Sensor Networks (IPSN 2007), New York: ACM , 2007, p. 557-558Conference paper (Refereed)
  • 29.
    Kouma, Jean-Paul
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Söderström, Ulrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wyner-Ziv Video Coding using Hadamard Transform and Deep Learning2016In: International Journal of Advanced Computer Sciences and Applications, ISSN 2158-107X, E-ISSN 2156-5570, Vol. 7, no 7, p. 582-589Article in journal (Refereed)
    Abstract [en]

    Predictive schemes are current standards of video coding. Unfortunately they do not apply well for lightweight devices such as mobile phones. The high encoding complexity is the bottleneck of the Quality of Experience (QoE) of a video conversation between mobile phones. A considerable amount of research has been conducted towards tackling that bottleneck. Most of the schemes use the so-called Wyner-Ziv Video Coding Paradigm, with results still not comparable to those of predictive coding. This paper shows a novel approach for Wyner-Ziv video compression. It is based on the Reinforcement Learning and Hadamard Transform. Our Scheme shows very promising results.

  • 30.
    Krantz, Sebastian
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Underlag till energieffektiviserande åtgärder i nätstationer2014Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Umeå Energi are working towards a goal, that in the year of 2018, they will be completely climate neutral. As a part of this, one target is to reduce their grid losses by 4 % of the 2012 level, which corresponds to an overall reduction of the grid losses of just over 1.7 GWh. In many residential areas, the distribution grid is designed and rated for electric heating as the heating in the houses. As many of the houses later has been converted to other types of heating, their electricity use has decreased and the total power output from many of the secondary substations has decreased significantly. Because of this, many of these stations today are well oversized, which in turn means that the energy losses in these stations are unnecessarily high.

    In this degree project, 25 secondary substations have been studied, all located in residential areas in and around central Umeå. All of the stations have an installed capacity of 1600 kVA, evenly distributed over two transformers, with 800 kVA each. For each station the annual energy losses has been calculated, and based on economy and environmental factors, various actions has been presented and recommended. The actions are either direct, which means they only require that transformers are turned off during all or part of the year, or long-term, which means they require investments.

    The recommended direct actions for these 25 stations, will lead to a potential energy loss reduction of 188 MWh per year, which corresponds to 70 000 SEK or 118 tons of carbon dioxide emission. This represents approximately 11 % of the total target in energy loss reduction and can be done immediately, with no need for investments. For long-term actions a possible 424 MWh can be reduced, which would represent about 25 % of the target, although that would require an investment of 5.12 million SEK.

  • 31.
    Kröger, Niklas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Prototyputveckling av absolutläges- sensor2015Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report describes the development of a prototype for an "Absolute Orientation Sensor" (AOS). The work is performed on behalf of Electrum Automation AB, who with the help of the prototype will evaluate whether a sharp product can be produced by using inexpensive sensors that are primarily intended for consumer use. AOS will be used to measure absolute orientation, i.e. inclination and direction relative to the earth's gravity and magnetic field, and deliver the information over a CAN bus 100 times / sec. It should meet the necessary safety requirements, ISO 13849-1 PL d, to be applicable in tough and safety-critical environments, such as forestry machines. Because of this the AOS will use a double set of sensors from different manufacturers. During the development phase the system has been built on a breadboard, using an evaluation board for each circuit, and the source code for the various sensor circuits have been developed. The code is written in CooCox CoIDE with the C programming language, and libraries such as the CAN library has been provided by Electrum. Finally, a circuit board is designed in Altium Designer. The board is designed with EMC in mind and has two channels with a sensor, microprocessor and CAN transceiver each to avoid "Common Cause failure" (CCF). Due to long delivery times, it was decided not to order the PCB as there were no room for this within the project timeframe. The work therefore results in an early prototype using source code that is adapted for easy implementation in any system and a circuit board that is ready to order.

  • 32. Lam, Norris
    et al.
    Nathanson, Marcus
    Lundgren, Niclas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Rehnström, Robin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Lyon, Steve W.
    A Cost-Effective Laser Scanning Method for Mapping Stream Channel Geometry and Roughness2015In: Journal of the American Water Resources Association, ISSN 1093-474X, E-ISSN 1752-1688, Vol. 51, no 5, p. 1211-1220Article in journal (Refereed)
    Abstract [en]

    This brief pilot study implements a camera-based laser scanning system that potentially offers a viable, cost-effective alternative to traditional terrestrial laser scanning (TLS) and LiDAR equipment. We adapted a low-cost laser ranging system (SICK LSM111) to acquire area scans of the channel and bed for a temporarily diverted stream. The 5mx2m study area was scanned at a 4mm point spacing which resulted in a point cloud density of 5,600 points/m(2). A local maxima search algorithm was applied to the point cloud and a grain size distribution of the stream bed was extracted. The 84th and 90th percentiles of this distribution, which are commonly used to characterize channel roughness, were 90mm and 109mm, respectively. Our example shows the system can resolve both large-scale geometry (e.g., bed slope and channel width) and small-scale roughness elements (e.g., grain sizes between about 30 and 255mm) in an exposed stream channel thereby providing a resolution adequate for the estimation of ecohydraulic roughness parameters such as Manning's n. While more work is necessary to refine our specific field-deployable system's design, these initial results are promising in particular for those working on a limited or fixed budget. This opens up a realm of laser scanning applications and monitoring strategies for water resources that may not have been possible previously due to cost limitations associated with traditional TLS systems.

  • 33.
    Lanz, Thomas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sandström, Andreas
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Tvistevägen 47, PO Box 7970, SE-90719 Umeå, Sweden.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Tvistevägen 47, PO Box 7970, SE-90719 Umeå, Sweden.
    Chabrecek, Peter
    Sefar AG.
    Sonderegger, Uriel
    Sefar AG.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Tvistevägen 47, PO Box 7970, SE-90719 Umeå, Sweden.
    A light–emission textile device: conformal spray-sintering of a woven fabric electrode2016In: Flexible and Printed Electronics, ISSN 2058-8585, Vol. 1, no 2, article id 025004Article in journal (Refereed)
    Abstract [en]

    We report on the realization of an ultra-flexible, light-weight and large-area emissive textile device. The anode and active material of a light-emitting electrochemical cell (LEC) were deposited by conformal spray-coating of a transparent fabric-based electrode, comprising a weave of fine Ag-coated Cu wires and poly(ethylene naphthalene) monofilament fibers embedded in a polyurethane matrix. The yellow-emitting textile featured low turn-on voltage (5 V), high maximum brightness (>4000 cd m−2), good efficiency (3.4 cd A−1), and reasonable lifetime (180 h at >100 cd m−2). Uniform emission to the eye was attained from thin and highly flexible textiles featuring a large emission area of 42 cm2, without resorting to planarization of the partially wavy-shaped (valley-to-peak height = 2.7 μm) fabric electrode. The key enabling factors for the functional emissive textile are the characteristic in situ electrochemical doping of LEC devices, the 'dry' spray-sintering deposition of the active material, and the attractive mechanical, electronic and optical properties of the fabric-based electrode.

  • 34.
    Larsen, Christian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Forchheimer, Robert
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tu, Deyu
    Design, fabrication and application of organic power converters: Driving light-emitting electrochemical cells from the AC mains2017In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 45, p. 57-64Article in journal (Refereed)
    Abstract [en]

    The design, fabrication and operation of a range of functional power converter circuits, based on diode configured organic field-effect transistors as the rectifying unit and capable of transforming a high AC input voltage to a selectable DC voltage, are presented. The converter functionality is demonstrated by selecting and tuning its constituents so that it can effectively drive a low-voltage organic electronic device, a light-emitting electrochemical cell (LEC), when connected to high-voltage AC mains. It is established that the preferred converter circuit for this task comprises an organic full-wave rectifier and a regulation resistor but is void of a smoothing capacitor, and that such a circuit connected to the AC mains (230 V, 50 Hz) successfully can drive an LEC to bright luminance (360 cd m(-2)) and high efficiency (6.4 cd A(-1)).

  • 35.
    Lindahl, Rikard
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Förlängt nyttjande av elbussbatterier2019Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    As the consequences for the environment of using internal combustion engines are becoming increasingly apparent, the need for alternatives for the transport of people and goods increases. Electric vehicles are sold to a greater extent than ever before. But the batteries in electric vehicles are also a burden on the environment when they are produced. If the batteries were to be used further after they could no longer be used in cars, the relative environmental impact of the production would be reduced and it would be easier to compensate for the impact already made by each battery.

    To achieve this, the characteristics of the batteries need to be investigated. The degradation needs to be determined to calculate how much energy they can cycle during their life. How this energy can be used efficiently and in a meaningful way in a modern grid is also important. What then happens at the end of battery life? Recycling is an important step in the process to minimize climate change instead of leaving the batteries in landfill.

    The results show that the amount of cycles a battery can handle down to a certain capacity level depends heavily on operating temperature, discharge depth, C-ratio and battery type. Hybricons batteries of LTO-type is estimated to sustain for 11 459 cycles at 10 % depth of discharge och 2 490 cycles at 50 % depth of discharge. Applications in this report, where battery storage is expected to be used efficiently, is short-circuit amplification and limitation of voltage hikes at customers with high impedance in rural networks as well as UPSs to telecommunications. Costs for these applications is estimated to cost between circa 170 USD/kWh och 760 USD/kWh depending on construction type and second hand price of the batteries. The value of a battery is estimated in this report is the amount of energy it can store during its life, which varies depending on the factors mentioned earlier and necessitates analysis of each case.

    The conclusion is that there are conditions that make it possible to efficiently and with economical gain use batteries in the grid, especially as the trend shows that the equipment is constantly getting cheaper and the technology is getting better. Although more analysis is required, foremost on the aging of the batteries second life.

  • 36.
    Lindmark, Isak
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Mediacentral för skogsmaskiner: Ny konstruktion för Komatsu Forest AB2017Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Komatsu Forrest AB have a demand for a media solution where the user can select between different input sources as well as output channels. The input sources are Radio, Bluetooth, AUX, two microphones and PC. The system shall also be able to mix sound from an ANC unit (Active Noise Control). Due to the demands from the company, the system must be able to be digitally controlled. The goal is to present a concept that offers the solution for these demands.To specify the needs from the user a dialog with employees with more knowledge about the user’s use have resulted in a table. From this a technical design has been created and resulted in a technical design requirement. With the design structure as a base, simulations have been done. After the structure has been verified by simulations a prototype with the basic functions have been designed and programmed and verified to clarify the function.Simulations and measurements have shown that the design works as desired. The result shows that the unit can meet the requirements set by the company in a user-friendly manner. The project has resulted in different solutions and these evaluated for pros and cons compared to the chosen solution.

  • 37.
    Lindmark, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Databasverktyg för rapporter till TV-programbolag2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Detta projekt är genomfört på AllTele Sverige AB och är beställt av CTO Mikael Peterson. Månatligen genomför AllTele en rapportering till de Tv-programbolag av vilka de köper Tvkanaler. Rapporteringen är en redovisning av sålda och aktiva Tv-kanaler hos AllTeles slutkunder och ligger till grund för det AllTele debiteras av Tv-programbolagen. Denna rapportering är ett tidskrävande arbete där data samlas från olika delsystem och sammanställs manuellt med stor risk för mänskliga fel.

    Syftet med projektet är att analysera den nuvarande processen att samla nödvändig data från de olika delsystemen och att hitta en ny optimal lösning för AllTeles behov. Detta realiseras sedan som ett automatiserat verktyg i form av en modul i ett kostnadskontrollssystem som heter Atis.

    I rapporten beskrivs den gamla processen och hur den effektiviserats genom att integrera data från tre till två delsystem. Denna integration tillåter konstruktion av ett automatiserat verktyg då all data finns tillgänglig i databaser.

    Rapporten presenterar med förklarande bilder och instruktioner hur kommunikationen mellan webbsidan och databasen möjliggörs och används för att skapa den rapportmallshantering som är kravspecificerad för verktyget. Utöver detta sker även en diskussion i rapporten kring metoder att sammanföra data från olika system och hur det implementerats i verktyget.

  • 38.
    Magnusson, Johan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Användande av lokala nollpunktsreaktorer: Hantering av kapacitiva jordfelsströmmar i kabelnät2017Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The rural power grid has traditionally mostly consisted of overhead power lines. In recent years the trend has been to replace the overhead lines with cables instead. The reason is that overhead lines are relatively vulnerable, strong winds and storms can cause trees and branches to fall over the power lines and cause a phase to ground fault. This will then trip the ground fault relays and disconnect the faulty power line. A cable grid is not vulnerable in the same way, and could be considered a solution to make the power grid more reliable. A cable grid does come whit other types of problems instead. It generates about 50 times more phase to ground capacitance compared with the same length of overhead lines. When a phase to ground fault occurs the capacitance in the healthy phases will generate a current to ground and then through the fault. On average a cable grid generates about 2 A per kilometer. Large cable grids can therefore cause very large capacitive currents to flow through the fault.  To counter this, a reactor is placed between the neutral point of the transformer and ground. When a phase to ground fault occurs, the reactor will generate an inductive current which is in the opposite phase compared to the capacitive current. This current will flow through the faulty line and cancel out the capacitive current. In a perfectly tuned power grid the only component left in the fault is a smaller resistive current. Large cable grids will require a large reactor to generate the large inductive current, which might need to flow over a great distance in the grid to reach the fault location. To reduce the inductive current from the central reactor, it is possible to install smaller local reactors in the grid. These will then in the event of a phase to ground fault generate a part of the inductive current, which will reduce the currents from the central reactor. This report will look at the factors related to grounding systems and how these factors affect the ground fault currents. The purpose of the report is to give recommendations to Umeå Energi on where in their grid they should install additional local reactors and also which factors they should consider when doing future expansions and rebuilds of their power grid.  

  • 39.
    Manchester, Ian
    et al.
    Computer Scinece and Artificial Intelligence Lab, Massachusetts Institute of Technology, Cambridge MA, 02139, USA .
    Mettin, Uwe
    Umeå University, Faculty of Science and Technology, Applied Physics and Electronics.
    Iida, Fumiya
    Institute of Robotics and Intelligent Systems, ETH Zürich, CH-8092 Zürich, Switzerland.
    Tedrake, Russ
    Computer Science and Artificial Intelligence Lab, Massachusetts Institute of Technology, Cambridge MA, 02139, USA.
    Stable dynamic walking over rough terrain: Theory and experiment2009In: 14th International Symposium on Robotics Research: Lucerne, Switzerland, Springer-Verlag , 2009, p. 1-16Conference paper (Refereed)
    Abstract [en]

    We propose a constructive control design for stabilization of non-periodic trajectories of underactuated mechanical systems. An important example of such a system is an underactuated ``dynamic walking'' biped robot walking over rough terrain. The proposed technique is to compute a transverse linearization about the desired motion: a linear impulsive system which locally represents dynamics about a target trajectory. This system is then exponentially stabilized using a modified receding-horizon control design. The proposed method is experimentally verified using a compass-gait walker: a two-degree-of-freedom biped with hip actuation but pointed stilt-like feet. The technique is, however, very general and can be applied to higher degree-of-freedom robots over arbitrary terrain and other impulsive mechanical systems.

  • 40.
    Mettin, Uwe
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Principles for planning and analyzing motions of underactuated mechanical systems and redundant manipulators2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Motion planning and control synthesis are challenging problems for underactuated mechanical systems due to the presence of passive (non-actuated) degrees of freedom. For those systems that are additionally not feedback linearizable and with unstable internal dynamics there are no generic methods for planning trajectories and their feedback stabilization. For fully actuated mechanical systems, on the other hand, there are standard tools that provide a tractable solution. Still, the problem of generating efficient and optimal trajectories is nontrivial due to actuator limitations and motion-dependent velocity and acceleration constraints that are typically present. It is especially challenging for manipulators with kinematic redundancy.

    A generic approach for solving the above-mentioned problems is described in this work. We explicitly use the geometry of the state space of the mechanical system so that a synchronization of the generalized coordinates can be found in terms of geometric relations along the target motion with respect to a path coordinate. Hence, the time evolution of the state variables that corresponds to the target motion is determined by the system dynamics constrained to these geometrical relations, known as virtual holonomic constraints. Following such a reduction for underactuated mechanical systems, we arrive at integrable second-order dynamics associated with the passive degrees of freedom. Solutions of this reduced dynamics, together with the geometric relations, can be interpreted as a motion generator for the full system. For fully actuated mechanical systems the virtually constrained dynamics provides a tractable way of shaping admissible trajectories.

    Once a feasible target motion is found and the corresponding virtual holonomic constraints are known, we can describe dynamics transversal to the orbit in the state space and analytically compute a transverse linearization. This results in a linear time-varying control system that allows us to use linear control theory for achieving orbital stabilization of the nonlinear mechanical system as well as to conduct system analysis in the vicinity of the motion. The approach is applicable to continuous-time and impulsive mechanical systems irrespective of the degree of underactuation. The main contributions of this thesis are analysis of human movement regarding a nominal behavior for repetitive tasks, gait synthesis and stabilization for dynamic walking robots, and description of a numerical procedure for generating and stabilizing efficient trajectories for kinematically redundant manipulators.

  • 41.
    Mettin, Uwe
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    La Hera, Pedro X.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid B.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton S.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Parallel elastic actuators as a control tool for preplanned trajectories of underactuated mechanical systems2009In: The international journal of robotics research, ISSN 0278-3649, E-ISSN 1741-3176, Vol. 29, no 9, p. 1186-1198Article in journal (Refereed)
    Abstract [en]

    A lack of sufficient actuation power as well as the presence of passive degrees of freedom are often serious constraints for feasible motions of a robot. Installing passive elastic mechanisms in parallel with the original actuators is one of a few alternatives that allows for large modifications of the range of external forces or torques that can be applied to the mechanical system. If some motions are planned that require a nominal control input above the actuator limitations, then we can search for auxiliary spring-like mechanisms complementing the control scheme in order to overcome the constraints. The intuitive idea of parallel elastic actuation is that spring-like elements generate most of the nominal torque required along a desired trajectory, so the control efforts of the original actuators can be mainly spent in stabilizing the motion. Such attractive arguments are, however, challenging for robots with non-feedback linearizable non-minimum phase dynamics that have one or several passive degrees of freedom. We suggest an approach to resolve the apparent difficulties and illustrate the method with an example of an underactuated planar double pendulum. The results are tested both in simulations and through experimental studies.

  • 42.
    Mettin, Uwe
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    La Hera, Pedro X.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Ortiz Morales, Daniel
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Westerberg, Simon
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Trajectory planning and time-independent motion control for a kinematically redundant hydraulic manipulator2009In: Advanced Robotics, 2009. ICAR 2009. International Conference on, IEEE conference proceedings, 2009, p. 1-6Conference paper (Refereed)
    Abstract [en]

    In this paper we consider the problem of motion planning and control of a kinematically redundant manipulator, which is used on forestry machines for logging. Once a desired path is specified in the 3D world frame, a trajectory can be planned and executed such that all joints are synchronized and constrained to the Cartesian path. We introduce an optimization procedure that takes advantage of the kinematic redundancy so that time-efficient joint and velocity profiles along the path can be obtained. Differential constraints imposed by the manipulator dynamics are accounted for by employing a phase-plane technique for admissible path timings. In hydraulic manipulators, such as considered here, the velocity constraints of the individual joints are particularly restrictive. We suggest a time-independent control scheme for the planned trajectory which is built upon the standard reference tracking controllers. Experimental tests underline the benefits and efficiency of the model-based trajectory planning and show success of the proposed control strategy.

  • 43.
    Mettin, Uwe
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Bätz, Georg
    Institute of Automatic Control Engineering, Technical University of Munich.
    Wollherr, Dirk
    Institute of Automatic Control Engineering, Technical University of Munich.
    Ball dribbling with an underactuated continuous-time control phase2010In: 2010 IEEE International Conference on Robotics and Automation (ICRA), 2010, p. 4669-4674Conference paper (Refereed)
    Abstract [en]

    Ball dribbling is a central element of basketball. One main challenge for realizing basketball robots is to stabilize periodic motions of the ball. This task is nontrivial due to the hybrid (discrete-continuous) nature of the corresponding dynamics. The ball can be only controlled during ball-manipulator contact and moves freely otherwise. We propose a manipulator equipped with a spring that gets compressed when the ball bounces against it. Hence, we can have continuous-time control over this underactuated Ball-Spring-Manipulator system until the spring releases its accumulated energy back to the ball. This paper illustrates the motion-planning procedure for a ball-dribbling cycle with such an underactutated continuous-time control phase. An orbital stabilizing controller is designed based on a transverse linearization along a desired periodic motion. Numerical simulations show the performance of the control system in preparation to experimental studies.

  • 44.
    Mettin, Uwe
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid B.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Sampei, Mitsuji
    Tokyo Institute of Technology, Department of Mechanical and Control Engineering.
    Optimal ball pitching with an underactuated model of a human arm2010Conference paper (Refereed)
    Abstract [en]

    A new approach for solving an optimal motion planning problem for a simplified 2-degrees-of-freedom model of a human arm is proposed. The motion of interest resembles ball pitching. The model of a planar two-link robot is used with actuation only at the shoulder joint and a passive spring at the elbow joint representing the stiffness of the arm. The goal is formulated as finding a trajectory and the associated torque of the active joint that maximizes the velocity of the end effector in horizontal direction at the moment of crossing a vertical ball-release line. The basic idea is to search for an optimal motion parametrized by the horizontal displacement of the end-effector from the start point to the release point. The suggested procedure leads to analytical expressions for the coefficients of a nonlinear differential equation that governs the geometric relation between the links along an optimal motion. The motion planning task is reformulated to a finite-dimensional search for the corresponding initial conditions.

  • 45.
    Mettin, Uwe
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Westerberg, Simon
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    La Hera, Pedro X.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Analysis of human-operated motions and trajectory replanning for kinematically redundant manipulators2009In: 2009 IEEE/RSJ International Conference on Intelligent Robots and Systems: St.Louis, USA, 2009, p. 795-800Conference paper (Refereed)
    Abstract [en]

    We consider trajectory planning for kinematically redundant manipulators used on forestry machines. The analysis of recorded data from human operation reveals that the driver does not use the full potential of the machine due to the complexity of the manipulation task. We suggest an optimization procedure that takes advantage of the kinematic redundancy so that time-efficient joint and velocity profiles along the path can be obtained. Differential constraints imposed by the manipulator dynamics are accounted for by employing a phase-plane technique for admissible path timings. Velocity constraints of the individual joints are particularly restrictive in hydraulic manipulators. Our study aims for semi-autonomous schemes that can provide assistance to the operator for executing global motions.

  • 46.
    Mirzaali, Mehdi
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Förlustbesparingsåtgärder för nätstationer (LV) och fördelningsstationer (HV) och dess påverkan på nätets tillförlitlighet.2016Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
  • 47.
    Nitze, Florian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mazurkiewicz, Marta
    Malolepszy, Artur
    Mikolajczuk, Anna
    Kedzierzawski, Piotr
    Tai, Cheuk-Wai
    Hu, Guangzhi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Kurzydlowski, Krzysztof Jan
    Stobinski, Leszek
    Borodzinski, Andrzej
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Synthesis of palladium nanoparticles decorated helical carbon nanofiber as highly active anodic catalyst for direct formic acid fuel cells2012In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 63, p. 323-328Article in journal (Refereed)
    Abstract [en]

    We present a single metal approach to produce highly active catalyst materials based on Pd-decorated helical carbon nanofibers. Helical carbon fibers are synthesized by a chemical vapor deposition process on a C-60 supported Pd catalyst and the obtained fibers are functionalized by H2O2 followed by a decoration with Pd nanoparticles. Although transmission electron microscopy images show that the decoration is relatively inhomogeneous the electrocatalytic activity for formic acid oxidation is very high. Cyclic voltammetry measurements (CV) show that the generated current peak value for Pd-decorated helical carbon nanofibers is 300 mA/mg(Pd) for a scan rate of 10 mV/s. This is significantly higher than the corresponding value of a reference sample of multiwalled carbon nanotubes decorated with Pd nanoparticles by the same process. Fuel cell tests for our Pd-decorated helical carbon nanofibers also displayed a high power density, although not as superior to Pd-decorated multiwalled nanotubes as measured by CV. Our results show that helical carbon nanofibers have several good properties, such as a rigid anchoring of catalyst nanoparticles and a suitable structure for creating functionalization defects which make them an interesting candidate for electrochemical applications. (C) 2012 Elsevier Ltd. All rights reserved.

  • 48.
    Norling, Johan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Solcellssystem och dess påverkan på lågspänningsnät i tätort2014Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    With government investment aid and a future proposal on a tax relief for the input of renewable electricity on the grid, predicts a continued large increase in grid-connected photovoltaic systems. The continued drop in price for turnkey photovoltaic systems due to increased competition and mass production provides further reason to expect an increasing interest.The purpose of this report is therefore, based on expected continued increase in grid-connected installations in urban areas, to examine how these affect the voltage in the mains at both single-phase and three-phase connection as well as how load losses are affected by the reversed power flow. The goal is that the result should be able to provide power companies a good foundation for further investigation.The standard which form the basis for the investigation is SS-EN 50160 which target the voltage characteristics of electricity grids for general distribution. Based on the standard, requirements on voltage level and allowable voltage unbalance in the grid is retrieved and furthermore the recommendations from the report MICRO - the connection of micro production to consumption facilities from the Swedish Energy is used.Software used to perform simulations and calculations of grid-connected photovoltaic systems is dp-Power from the company Digpro. Inside the program existing grid and its customers may receive photovoltaic plants connected by single-phase or three-phase, and grid calculations can be performed with a variation of rated power depending on the operational scenario. True meter readings for the year 2013 have been processed to produce a highest and lowest power consumption during an hour.Five operating scenarios have been prepared. Three scenarios deals with 3.5 kW single-phase connection, where the connection is made in the same phase and the same feeder cable, the same phase but different feeder cable and a scenario where every photovoltaic system was appointed a specific phase in an attempt to achieve symmetry and connection takes place in one feeder cable at a time. The two remaining covers three-phase connection where the first scenario concerns a rated power of 3.5 kW, and finally a rated output of 8 kW.The results show early problems when connecting single-phase photovoltaic systems. In the first scenario, an unauthorized voltage level occurs in an access point after only five connected appliances. The remaining single-phase scenarios also demonstrate problems but not to the same extent. Three-phase connection provides a much better result and everyone in the area can connect their PV system. The main conclusion to be drawn is that the single-phase connection of PV systems is not advised. Even if you try to assign a specific phase in an attempt to create symmetry, it may come to cause problems at an early stage. Attempted operational scenarios also demonstrates a number of weak points in the grid where the voltage increase will be more powerful compared to other locations.

  • 49.
    Nyberg, Jakob
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Panda Cloud System Management Stjärna Fyrkant Umeå2015Independent thesis Basic level (degree of Bachelor), 180 HE creditsStudent thesis
    Abstract [en]

    Panda Cloud Systems Management (PCSM) is a cloud-based system for monitoring, inventorying and managing computers, servers and networks. Stjarna Fyrkant started its IT-department in August 2014 where they manage for Stjarna Fyrkants computers and networks but also other companies as IT consultants. They have chosen to use PCSM to manage and to monitor these networks.

     

    The project was started because Stjarna Fyrkant wants a better insight of the system as they have gone through with the basics of it. They have chosen four areas where they wants to know more about and these are monitoring of computers and servers, SNMP for monitoring other equipment, automated processes such as updating programs and Windows automatically and for Mobile Management (MDM) to manage and monitor iPhones.

     

    To make this happen I was given login information to PCSM, two computers and an iPhone to test PCSM and its other functionalities for what Stjarna Fyrkant want to accomplish. For monitors the report will go through about which monitor that exists in the store and in PCSM and later assign these to two groups for monitoring the servers and clients. Then how to monitor other devices via SNMP and how this was applied to the devices that Stjarna Fyrkant has, such as printers. However, this didn’t work for all devices.

     

    For maintenance of computers the report analyzes how to keep important updates for programs like Java and .NET but also for Windows. Additionally it was looked into how to remove unnecessary files found on the computers, such as the temporary files.

     

    For MDM the report looks in to which functionalities that exists and these were later tested for an iPhone. These functions worked surprisingly fast when it took only a few seconds for them to apply. There were plans to create a product sheet for companies of these features, but this was handed to someone else with more knowledge for design such towards companies.

     

  • 50.
    Nyberg, John-Levi
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Lightning Impulse Breakdown Tests: Triggered Spark Gap Analysis2017Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This project was made by student from UmeåUniversity and a request from the universityETH in Zürich, Switzerland. In this research project the electrical strengthof different natural gases and mixtures was investigated, and the aim was to finda gas or gas mixture with a natural origin or strongly attaching gases that couldreplace SF6 (Sulfur Hexafluoride). The gases were tested with breakdown experiments,one of those test was called lightning impulse breakdown test. The mainpart of this project was to investigate triggered spark gaps, which could be used inlightning impulse breakdown test. These spark gaps were made in a previous thesis,but have proved to not be reliable, therefore an investigation was needed. In thelab, a breakdown test setup, made up of a rectifying circuit and a transformer, wasused. In this project voltages up to 140kV were used. The two main parts of theproject were the spark gap unit and circuit analyzing and the spark gap characterization.These two parts contained test to see if the spark gap worked as it shouldor if there were any problems with it. The results from the tests showed that therewere problems with the spark gap, but these problems could be corrected or avoidedthrough controls of the spark gap before use.

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