Change search
Refine search result
1234567 1 - 50 of 3157
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the 'Create feeds' function.
  • 1.
    Abbas, Asad
    Karlstad University, Faculty of Technology and Science.
    Flow sheeting software as a tool when teaching Chemical Engineering2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of this thesis is to design different chemical processes by using flow sheeting software and to show the usefulness of flow sheeting software as an educational tool. The industries studied are hydrogen, sulfur, nitric acid and ethylene glycol production and a model of drying technique is also included. Firstly, there is an introduction of chemcad as a tool when teaching chemical processes and explanation of each industry which is selected to design. Various production methods for each product are explained and the advantages of the method which is selected to design the chemical flow sheet are discussed. There is also an introduction of the industrial uses of these products formed in Pakistan. The models are designed by using different reactors, heat exchangers, pumps, mixers, boilers and distillation column. The models are designed based upon data taken from literature. The temperature and pressure values are in good agreement with data mentioned in literature. The material balance shown by Chemcad is quite different from data mentioned in literature. Some changes in thermodynamic properties of components in Chemcad software might lead to better agreement between the Chemcad models and literature data. It is not possible to use catalyst in Chemcad to increase the rate of reaction. One possibility is to introduce new components. It is good to use equilibrium reactor when it is required to convert the given component into respective products provided that either conversion of the equilibrium constant are known. It is difficult to study the hidden critical assumptions built in the model when using Gibb’s reactor, as a result there is a deviation in behavior from the system described in the literature. Gibb’s reactor is useful when neither conversion ratio nor equilibrium constant is known.

  • 2.
    Abbas, Azhar
    Karlstad University, Faculty of Technology and Science.
    GPIB- kommunikation och PID reglering med LabVIEW2009Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [sv]

    LabVIEW ger en snabb och enkel tillgång till att styra instrument och en mycket stor databas med drivrutiner för DAQ-kort och olika datorgränssnitt (GPIB, serie, osv.).

    Många instrument och datorer kan anslutas till GPIB-bussen.  Detta kan ge en praktisk modell för utveckling av instrumentets styrprogram i LabVIEW med hjälp av GPIB-gränssnittet.

    Ett program i LabVIEW 8.2 med hjälp av GPIB-bussen kan kopplas till t.ex. multimetern (HP-34401A) för att mäta och visa multimeters noggrannhet. Men på grund av fel i drivrutiner för GPIB-gränssnittet kunde jag inte köra programmet med GPIB-bussen.

    Genom att använda LabVIEW 8.2 med hjälp av DAQ-kort kan en PID-regleringsalgoritm simuleras. PID konstrueras med virtuella instrument som innehåller alla nödvändiga komponenter och utrustning som krävs för att reglera någon linjär eller olinjär process exempelvis att nivåreglera två tankar i serie. Här stöter vi på alla de grundläggande regulatorer och får möjlighet att bygga PID med LabVIEW på ett enkelt sätt. Det finns två metoder för att bygga PID. Den första är med matematiska funktioner och den andra är med ’’Simulations functions control’’. Arbetet visar att bägge metoderna fungerar bra för att lösa uppgiften jämfört med färdiga PID-controls på LabVIEW.

  • 3.
    Abdulhadi, Sami
    Karlstad University, Faculty of Technology and Science.
    ARM i inbyggt system: med prototyp2009Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Embedded systems has become more and more common in today's society. The embedded systems are included in almost everything today, from various vehicles to children's toys.

    Today's technology means that yesterday's solutions can be realised on a fraction of the area. More and more become surface mounted with smaller and more complex circuits. This is not always an advantage for the developers when assembling and soldering prototype circuit boards become a more difficult and/or an expensive process.

    The goal is to create an embedded system with an ARM-processor. The system will consist of USB-OTG, ethernet, various memory like FRAM and microSD and a display with touchscreen for user interface. The project includes everything from choice of components to test and verification with program code.

    The time was too short to include all the parts that was planned. The result of the project was a prototype card and two small program sequences, one that blinks the two light diodes on the card and one that writes a picture on the display.

    This embedded system is intended for evaluating ARM-processors by Mikrododakt AB.

  • 4.
    Abrahamsson, Adam
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    de Bourgh, Simon
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Hållbarhetscertifieringssystem i anläggningsbranschen: En studie om upphandlingskrav kopplat till hållbarhetscertifieringar i offentliga upphandlingar2014Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Sustainability rating schemes has come to be used extensively since it´s arrival to Sweden during the 21th century. Today, the number of sustainability certifications increases for projects in the construction industry while only a few projects has been certified in the civil engineering industry. The reasons of the interesting development has been studied by investigating how the construction industry clients in the public sector should be able to claim use of sustainability rating schemes without infracting the Swedish public procurement act.

    The study has been conducted by literature- and interview research. Interviews were conducted with various stakeholders in the industry. The purpose was to obtain an unambiguous opinion of how clients should require use of sustainability rating schemes in public procurements. The study also discussed how stakeholders monitor and evaluate their work. The literature research analyzes previous work in the topic and evaluates procurements which contains requirements of sustainability rating schemes.

    The overall conclusions from this study is:

    • The industry demands a standardized framework about how to phrase requirements. Public clients should procure likewise, regardless of their location in Sweden.

    • More pilot projects must be implemented to find out how to achieve maximum benefit with sustainability rating schemes.

    • The industry wants more clear and measurable requirements.

    • Not to be contrary to the Swedish public procurement act, clients can phrase functional requirements based on the manual of the sustainability rating scheme they wish to use.

    • The clients should not worry about appeals, since appealed procurements because of sustainability requirements is rare. It is important to have clearly phrased requirements where the choice of sustainability rating scheme, specified criteria and level is clarified.

    • By the new EU-directives comes an update of the Swedish procurement act, which will enforce in 2016 with the intention of making it easier to set requirements for sustainability rating schemes.

  • 5.
    Abrahamsson, Erika
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Gröna tak - potentialen för dagvattenreglering i Karlstad: Simuleringar i Mike Urban2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As urban areas become more populated and denser, stormwater management becomes an important matter. Since natural areas are becoming exploited and green areas in cities are removed the stormwater flow increases due to the conversion of impermeable surfaces into hard surface areas. The increase in stormwater flow can cause flooding if the pipeline system is insufficient.

    Change in climate caused by anthropogenic emissions will expose our communities to difficult challenges. Urban flooding from sewers is one of them, and may become more frequent in parts of the world where precipitation is predicted to increase in the future. In order to develop our cities in a sustainable manner and create resilience, the urban drainage system has to be a part of this development. Many of the techniques related to sustainable urban drainage systems, like storage reservoirs and open channels, require access to land space. However, about 40-50 % of the impermeable surfaces in cities consist of roof. Consequently, an interesting alternative to decrease stormwater flow is green roof due to its ability to reduce and attenuate the flow.

    The aim of this thesis is to demonstrate the benefits of green roof’s stormwater management through simulations in Mike Urban. The simulations are made over two neighborhoods in Karlstad with future climate changes. The simulations indicated that green roof in these neighborhoods show good potential to lower the risk of flooding and the numbers of flooded wells by a 10- and 2-year rain is decreased by 42 and 58 %.

  • 6.
    Adeva Rodil, Teresa
    Karlstad University, Division for Engineering Sciences, Physics and Mathematics.
    Edge effect on abrasive wear mechanisms and wear resistance in WC-6wt.% Co hardmetals2006Independent thesis Advanced level (degree of Magister), 20 points / 30 hpStudent thesis
    Abstract [en]

    Wear of hardmetals is a complicated topic because the wear resistance and the wear mechanisms are influenced by microstructural factors. Although edge wear resistance has a vital importance, most of the researches made in laboratories are related to flat wear resistance using coarse abrasive paper. This situation produces problems with the prediction of abrasive wear behaviour and with the estimation of the lifetime of cutting edges of different kinds of tooling.

    Several studies have been done in order to clarify edge wear behaviour. It has been published correlations of the edge toughness to the load and to the bulk fracture toughness. In those publications coarse abrasive or Vickers indenter were used.

    In the present research, edge shaped specimens of WC-6wt%Co grades were investigated. In order to compare the obtained results for flat sliding and edge wear behaviour two test arrangements, pin on flat disc and edge on flat disc were employed. The specimens were tested using 120, 320, 800 and 2400 mesh SiC abrasive paper and the worn surfaces were investigated using SEM instrument to evaluate wear mechanisms. The edge wear was observed was discussed in relation to wear mechanisms investigated and correlated to the flat wear behaviour.

    The obtained results showed limited applicability of the results obtained with the pin on the flat disc test arrangement for prediction of the edge wear resistance, especially in the case when size of the abrasive particles is close to the WC grain size. However, both edge and flat wear results were similar in; 1) large WC grain sized hard metals wore more than fine grain sized against coarse abrasive paper whereas the reverse occurred against fine abrasives, and 2) wear mechanisms were mainly ploughing (or grooving) for fine grain sized hardmetals in all cases, whereas wear mechanisms changed from ploughing to binder removal and carbide pull-out going from coarse to fine abrasive paper.

  • 7.
    Adolfsson, Karin
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT.
    Albinsson, Stina
    Karlstad University, Faculty of Economic Sciences, Communication and IT.
    Friår - av vilken anledning?: Kopplingar mellan anledningar till friår och livsformerna2007Independent thesis Basic level (degree of Bachelor), 10 points / 15 hpStudent thesis
    Abstract [sv]

    Undersökningens syfte är att se vilka anledningar individen har till att välja friår och hur det kopplas samman med livsformerna de lever. Syftet har också varit att se individens upplevelse av friåret och vad de använt friåret till. Undersökningen bygger på kvalitativa intervjuer med sex friårslediga. Intervjuerna har handlat om individens upplevelse av friåret och tiden före det.

    Friår är en arbetsmarknadspolitisk åtgärd med målsättning att ge arbetstagare en längre ledighet från sitt arbete. Arbetslösa får samtidigt en chans att komma in på arbetsmarknaden. Friåret innebär att vara ledig från sitt arbete i tre till tolv månader för att kunna göra något annat utanför arbetsplatsen. För att kunna undersöka av vilka anledningar individen har friår och hur det kopplas med de olika sociala strukturer som villkorar människors vardag. Vi har studerat om livsformsanalysen kan användas till att beskriva, förklara och förstå skillnaderna i människors vardag. Livsformerna är sociala strukturer som villkorar människors vardag. De olika livsformsbegreppen som vi har använt oss av är arbetarlivsformen – husmorslivsformen, karriärenslivsform – representationshustrunslivsform och självständighetens livsform – medhjälperskans livsform. Det är dock vanligt att leva en blandning mellan två eller flera livsformer, det kallas en blandform.

    Vi har kommit fram till att livsformerna till viss del kan kopplas samman med hur intervjupersonerna lever under sitt friår och av vilken anledning de har friår. Det visar sig i att de som använder friåret till att starta ett företag lever till stor del självständighetens livsform. Att använda friåret till utbildning kan kopplas samman med karriärens livsformer. Vidare kan vi se att karriärenslivsform kan kopplas samman med att pressen på arbetet är stor och då är rekreation under friåret vanligt. Många kvinnor lever blandformer och det gör att de har svårt att kombinera de olika arbets- och kärleksformerna. De använder friåret till att ta hand om sin familj och sig själva.

  • 8.
    Adolfsson, Rasmus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Utformning av en infästningsstandard: En utveckling av kvalitetsarbetet hos Nordmarkens Fasader AB2015Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    As the construction industry today is increasing the demands on its actors and procedures to ensurethe quality of the final product, the work on quality assurance has increased in a greater degree.Quality assurance involves a systematic approach that often follow a specific quality system orquality mark. That this is conducted is often demonstrated by a certain certification.Nordmarkens Fasader in Töcksfors is a manufacturer and installator of windows, doors, walls androofs in aluminum and glass. To ensure the quality of their products, they work for the P-markingsystem that later allows them to P-label their products. The P-mark is the Science Partners ownquality mark and proves, among other things, that the product complies with statutory or regulatoryrequirements but also in most cases higher standards demanded by the market.In their work, Nordmarkens Fasader follows a quality manual, which in its turn is modeled after therules for P-marking. This is the official summarized description of the P-marking and contains orrefers to all the documents and document types included in the quality system of NordmarkensFasader.For the products of Nordmarkens Fasader to be developed a further step in working towards a goodquality and function, they want to establish drawings that deal with attaching elements in the wall, inthe quality manual. All this to get better track of what happens to the product after manufacture.Something that makes this even more important is that they do not always handle assembly of theirproducts. A standard of attachments in this case would result in that they can influence whathappens after manufacture. To achieve this it was necessary for a standard of attachments ofelements to be designed and then also integrated in the quality manual.Because there are many wall types to choose from, the most common and most abundant of thesewas elected. It all resulted in a number of standard drawings showing where some of the products ofNordmarkens Fasader should be attached in the selected wall. For this to be put into use in everydaylife it also had to be integrated into the quality manual. In addition to these standard drawings, themanual were changed while new documents also were created in this. All to achieve the best resultswith the quality work at Nordmarkens Fasader.This work will serve as a basis for future work on attachment drawings, in the quality manual, asthere is interest in bringing in multi-wall types in this.

  • 9.
    Adolfsson, Robin
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Jönsson, Caroline
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Är SundaHus materialklassning kompatibel med Miljöbyggnads, BREEAMs och LEEDs materialkrav?: En studie om SundaHus miljöklassningar.2015Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    We live in a society where there is a shortage of housing and the demand for new and sustainable buildings is growing. The houses that are being built today are focused on being energy efficient to save resources. Something that is forgotten is the choice of materials to house constructions. Materials can affect nature and people from the cradle to the grave by for example material hazardous components. The certification systems Miljöbyggnad, BREEAM and LEED have been checked and their material criteria have been defined. Through a selection of construction materials taken from SundaHus a review has been made of these materials towards the certification systems´ criteria on materials to see if they are compatible. The minority of the criteria were reviewed to separate materials and could be verified in SundaHus. Almost all materials passed the criteria that could be used of Miljöbyggnad and BREEAM regardless of classification in SundaHus. None of the LEED criteria were compatible with SundaHus for separate materials. The fact that the worse classifications in SundaHus could pass the criteria that were reviewed indicates that the requirements in environmental certification systems are too low. Higher and more demands should be made on individual materials and the hazardous substances in them.

  • 10.
    Aeyadi, Amin
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Formation of protective lubricious oxide layers on the surface of nitrogen alloyed steels in self-mated sliding2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 11.
    Ahl, Daniel
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Analysis of how different mesh functions influence the result in CFD-simulation of a marine propeller:  2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 12.
    Ahlgren, Bengt
    et al.
    RISE SICS.
    Hurtig, Per
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Abrahamsson, Henrik
    RISE SICS.
    Grinnemo, Karl-Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Are MIRCC and Rate-based Congestion Control in ICN READY for Variable Link Capacity?2017In: The 13th Swedish National Computer Networking Workshop (SNCNW 2017), Halmstad University, May 29.30., 2017Conference paper (Other academic)
    Abstract [en]

    Information-centric networking (ICN) has been introduced as a potential future networking architecture. ICN promises an architecture that makes information independent from lo- cation, application, storage, and transportation. Still, it is not without challenges. Notably, there are several outstanding issues regarding congestion control: Since ICN is more or less oblivious to the location of information, it opens up for a single application flow to have several sources, something which blurs the notion of transport flows, and makes it very difficult to employ traditional end-to-end congestion control schemes in these networks. Instead, ICN networks often make use of hop-by-hop congestion control schemes. How- ever, these schemes are also tainted with problems, e.g., several of the proposed ICN congestion controls assume fixed link capacities that are known beforehand. Since this seldom is the case, this paper evaluates the consequences in terms of latency, throughput, and link usage, variable link capacities have on a hop-by-hop congestion control scheme, such as the one employed by the Multipath-aware ICN Rate-based Congestion Control (MIRCC). The evaluation was carried out in the OMNeT++ simulator, and demonstrates how seemingly small variations in link capacity significantly deterio- rate both latency and throughput, and often result in inefficient network link usage. 

  • 13.
    Ahlgren, Joakim
    et al.
    Karlstad University, Faculty of Technology and Science.
    Lidström, Joakim
    Karlstad University, Faculty of Technology and Science.
    Gastromax Duo: Ett kompakt rivjärn för den moderna hemmakocken2010Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    ”Gastromax Duo” is a degree project for the Innovation and Design Engineering program at Karlstad University. Joakim Ahlgren and Joakim Lidström have independently carried out the project during Spring Term 2010. The degree project extends 22,5 ECTS credits.

    The assigners for this project are Peter Ottosson and Jonas Eriksson at Sveico AB in Gnosjö, Sweden. Peter Johansson is the project supervisor at Sveico AB and Monica Jacobsson is the academic supervisor at Karlstad University. The examiner at Karlstad University is Lennart Wihk, who has also supported the project team during the design process.

    Sveico AB is located in Gnosjö, Sweden and manufactures kitchen utensils and other kitchen accessories. In the Sveico AB product portfolio resides the Gastromax series of kitchen tools for the ”home chef”. The lack of a foldable grater within the Gastromax series was noticed by the Sveico AB management, which brought about this project.

    The largest part of this project was a very thorough pre-study phase, where the project team mapped out the needs and wishes of the users, along with research about the market of the product. The pre-study consists of interviews with consumers, professional users and representatives of commerce, along with user studies.

    During the product development process, a number of idea generation methods has been used, both internally in the project team and externally with uninitiated individuals. During the subsequent concept generation phase, emphasis was put on the development of physical models, used to evaluate ideas and solutions.

    Out of the 19 concepts that were developed during the concept generation phase, six was chosen through a set of systematic evaluation routines. These six concepts were presented to the assigners that in turn chose two of the concepts for the project team to develop further. These two concepts was then combined and transformed into the final product proposal.

    The final, detailed solution is surrounded with secrecy, but three key concepts in the final foldable grater can be officially stated:

    • A long grating surface
    • Adjustable work angle
    • Two grating surfaces: one fine and one coarse

    The final result of the project is a product description of the grater, with a proposal of a general design, a mechanical solution of the adjustability aspect and a suggestion of materials for the different product components.

  • 14.
    Ahlquist, Ulrika
    Karlstad University, Division for Information Technology.
    Trådlöst elektriskt lås2007Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Syftet med examensarbetet är att göra en trådlös version av det elektriska lås som tillverkas av Electec System AB.

    För att göra ett trådlöst elektriskt lås måste ett batteri monteras i låset. Batteriet måste hållas uppladdat hela tiden för att kunna driva motorn och ge strömförsörjning till elektroniken i låset. Alla signaler mellan låset och styrenheten ska dessutom överföras trådlöst istället för med kabel. Signalerna måste kodas innan sändning så att ingen obehörig kan läsa signalen och sedan öppna dörren.

    Det svåraste i ett trådlöst elektriskt lås är att överföra effekt från dörrkarmen till låset eftersom utrymmet är begränsat och avståndet mellan låsblecket i karmen och låset i dörren kan uppgå till 10 mm. För att överföra effekt från dörrkarmen till låset konstruerades en transformator. Förlusterna i transformatorn ökar kraftigt då luftgapet ökas.

    Det visar sig att motor och övriga kretsar kan drivas med ett avstånd mellan kärnorna på upp till 7 mm. Luftgapet kan sannolikt ökas när andra transformatorkärnor används. Dessa fanns dock inte tillgängliga under examensarbetets gång på grund av lång leveranstid. I jämförelse med överföring av effekt är problemet att koda och överföra signaler mellan styrenheten och låset enklare och kan lösas med hjälp av färdiga kretsar.

  • 15.
    ahmad, waqas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Development of algorithm for li-ion batteries in electric vehicles, taking into account SOC, charge control, cell balancing and SOF.2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 16.
    Ahmed, Faisal Mahmood
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Estimated Droop Control for Parallel Connected Voltage Source Inverters: Stability Enhancement2013Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Renewable Energy Sources (RES) are considered as the replacement of conventionalenergy sources. These RES can use wind energy, solar light, bio waste and can alsobe in the form of small hydro power units. These RES has very poor power qualityand contains voltage uctuations and variable frequency. These factors make RES astability risk for the main utility grid. As a solution, currently inverters with dierentdesign techniques are being used as an interface between RES and main utility grid. Thecurrent study proposed a new technique "estimated droop control" for inverter design.The conventional droop control technique which was already used in inverter design, hasdiculty in synchronizing parallel connected inverters with dierent droop gains and lineimpedances. The proposed "estimated droop control" does not use any predened droopvalues for inverters and all inverters are responsible for the estimation of their own droopvalues with respect to their output power. Therefore, inverters are not bound to usesame and static droop values which are considered as a vital communication link. Theproposed design methodology has made inverters independent from this only virtual linkof communication due to which the reliability of a system has increased. The proposeddesign technique has given very good results in a simulation run. When the Simulinkmodel was run in parallel connected inverter with dierent line impedances, it was asuccess as both inverters started operating with same droop values as they were sharingan equal load. The most important test was with dierent line impedances because inconventional droop control it is dicult for inverters to keep their synchronism withdierent line impedances and an unequal load sharing make inverters to deviate fromtheir nominal values and to generate dierent tracking signals for each set. This problemhas been successfully solved with estimated droop control as in this method each inverterset its droop gains according to its output power, which helps an inverter to operate atnominal values with dierent droop gains and line impedance.

  • 17.
    Ahmed, Naeem
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Cooperative Spectrum Sensing for Cognitive Radio Networks2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The great developments in the field of wireless communications that has been accelerated by the commercial need for better services has led to the application of wireless systems in many fields of life. The effect of wireless technology is much widened, like for safety applications, home automation, smart grid control, medical wearable, embedded wireless devices, entertainment systems etc.

    Direct and indirect surveillance of spectrum treatment has acknowledged the sequential and spatial accessibility of spectrum inside allocated frequency bands. This implies that spectrum deficiency is becoming a main problem. Therefore, spectrum deficiency problem arises here in terms of that most of the licensed primary users are not using their spectrum due to any reason of either geographical variation or temporal basis, and lot of allotted spectrum is unused and under-utilized. Moreover, along with spectrum deficiency problem, other issues are also linked like interference caused by secondary unlicensed users to primary licensed users while sharing the work load among each others, and problem of vacating the spectrum band in less fewer time frames after primary users detection.

    Cognitive networks assure to tackle these spectrum deficiency and other associated problems by accommodating secondary (unlicensed) users, in the spectrum region which is under-utilized. Spectrum Sensing is the prime motivation for cognitive radio and ensures that secondary (unlicensed) users do not propose unbearable levels of interference to primary (licensed) users.

    Cooperative Spectrum Sensing methodologies are still an open window of research. This work is related to cope up the problem of spectrum deficiency and associated problems, by developing an approach for establishment of grouping/clustering between secondary users in a cooperative spectral environment. This approach ensures that members within a group are highly correlated. As a result, the workload on each sensing node within a group is reduced. The effectiveness of this approach depends upon the accuracy of fused decision related to the presence or absence of primary (licensed) user at a particular band (50MHZ to 100MHZ). This approach also depends on the factor that time taken in sensing the primary (licensed) users should be less enough so that decision in vacating the band by the Cognitive Radio secondary users could be taken in fewer time frames. This latter metric is known to be ‘agility’, which eventually comes with the outcome of minimum interference to primary users via their early recognition.

  • 18.
    Ahmed, Umair
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Racing Driver Model in Dymola Vehicle Dynamics Library (VDL): Steering Controller Design2012Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Racing drivers always want to traverse path at vehicle’s maximum performance limits while keeping the vehicle at its ideal trajectory. The main objective of this report is to elaborate strategy for the path following problem in which driver has to follow the predefined 2D roads. New steering controller design for closed loop racing driver model in Dymola vehicle dynamics library is developed. The methodology proposed by Sharp et al. [2] is followed with the optimal velocity profile that tries to mimic the actions of the real drivers in real time scenarios. Vehicle handling limits i.e. longitudinal and lateral limits are defined before simulation. While travelling in the neighbourhood of optimal velocity on the straight road as well as during the curves, the performance of the steering controller is tested by conducting the test on J turn, Clothoid, Extended chicane and the closing curve path and also tested during the different environment effects e.g. when there is a side wind affecting the vehicle. Performance of existing and new steering controllers discussed and compared in result chapter. It is ensured that the drawbacks in the existing steering controller are eliminated by using the proposed methodology in new implemented steering controller.

    Key Words: Driver Model, Steering Controller, Path following, Velocity profile

  • 19.
    Ahrnens, Alexander
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Lägesställare med I/P-omvandlare som alternativ2016Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    This report covers a project instigated by Lennart Proper, Aspervall Instrument AB. The report deals with the development of Aspervalls pneumatic actuator, ASPEdonet and it is a part of the course degree project of Bachelor of Science in Mechanical Engineering, MSGC17. The course covers 22.5 ECTS credits and it was accomplished during the spring term of 2016 at the faculty of health, natureand engineering, Karlstad University. Aspervall is a company located in Säffle that specialize in precision engineering, contract manufacturing and development of own products like ASPEdonet. ASPEdonet is a pneumatic actuator constructed of a pneumatic double-acting cylinder and a positioner. The pneumatic cylinder is used to convert air pressure into mechanical work through the moment of a piston with piston rod in a cylinder tube. The positioner is used to regulate the pressure to different sides of the piston with the use of a control signal. The thesis objective was to further develop the pneumatic positioner by converting it to electropneumatic, which means that the previous pneumatic control signal was replaced with a electronic analog control signal. This was accomplished through installing proportional technology into the positioner in the form of an I/P-transducer. I/P-transducer is also preferred to as E/P-transudcer or proportionalvalve, is a pressure regulator that is used to regulate air pressure proportional to an electronic signal. The problem definition of the project was how the positioner could be complemented with a I/P-transducer without compromising the basic function or the design of the positioner. The project followed the different stages of the product development process, pre-study, product specification, idea generation, concept selection and structure with detail design. The project resulted in a documentation that can serve as basis for product manufacturing and further development. The solution that was generated has the same basic construction and design as the previous model. Norgren VP12 was selected as I/P-transducer since it is compact enough to be integrated in the positioner. Standard components from Norgren and Nelco served as fittings and cable gland. A new more compact valve was designed as a part of the construction, the valve is manufactured from a single unit.

  • 20.
    Aidantausta, Elin
    Karlstad University, Faculty of Social and Life Sciences, Department of Geography and Tourism.
    3D-byggnadsmodeller utifrån takkonstruktioner: Lagring, hantering och bearbetning2013Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A growing number of cities and municipalities in Sweden begin to work with city models in 3D. For the most part the models are used for visualizations of ongoing planning processes, but also for the analysis of noise, shadow studies and environmental disaster simulations.

    Gothenburg continues to develop the use of 3D maps in municipal operations and is demanding a way to create building elements (walls), which generates in 3D buildings, from roof constructions that are mapped from the primary map. A method has been investigated in the present study. The results are then presented as a 3D model of buildings, along with a terrain map that will facilitate the localization of the area. The created 3D buildings are then compared with roof-data from the primary map to see how well they harmonize with each other. Then also the handling and storage of three-dimensional data with the information model CityGML is investigated. A specification of the requirements and characteristics that the customer, the City Planning in Gothenburg, looks are essential for building modeling in 3D has also been established.

    The final result shows of 4% increase in the plane of 3D buildings compared to primary map. The increase would be slightly greater if the comparison is made on the volume instead. The results also revealed that the increase in plan is something that has occurred during the creation of the roof constructions, which was something that I couldn’t have affected during the work. The results also show that the CityGML is an appropriate information model for storage and handling of 3D. Gothenburg still have insufficient knowledge of CityGML, which is also one of the reasons why the information model hasn’t been implemented in the municipality work with 3D models.

  • 21. Aiki, T.
    et al.
    Muntean, Adrian
    Eindhoven Univ Technol, Dept Math & Comp Sci.
    A free-boundary problem for concrete carbonation: Front nucleation and rigorous justification of the root t-law of propagation2013In: Interfaces and free boundaries (Print), ISSN 1463-9963, E-ISSN 1463-9971, Vol. 15, no 2, 167-180 p.Article in journal (Refereed)
  • 22.
    Aiki, Toyohiko
    et al.
    Gifu University, Japan.
    Anthonissen, Martijn
    Eindhoven University Technology, Netherlands.
    Muntean, Adrian
    Eindhoven University Technology, Netherlands.
    On a one-dimensional shape-memory alloy model in its fast-temperature- activation limit2012In: Discrete and Continuous Dynamical Systems. Series S, ISSN 1937-1632, E-ISSN 1937-1179, Vol. 5, no 1, 15-28 p.Article in journal (Refereed)
  • 23. Aiki, Toyohiko
    et al.
    Muntean, Adrian
    Eindhoven University of Technology.
    Large-time behavior of a two-scale semilinear reaction-diffusion system for concrete sulfatation2014In: Mathematical methods in the applied sciences, ISSN 0170-4214, E-ISSN 1099-1476, Vol. 38, no 7, 1451-1464 p.Article in journal (Refereed)
  • 24.
    Aimal, Pir
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Mohsin, Main
    Analyzing Voltage control and reactive power support from full power converter wind turbine2011Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
  • 25.
    Al Motasem, Ahmed
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics. Assiut University, Egypt.
    Bergström, Jens
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Gåård, Anders
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Holleboom, Thijs
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Tool microstructure impact on the wear behavior of ferrite iron during nanoscratching: An atomic level simulation2017In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 370-371, 39-45 p.Article in journal (Refereed)
    Abstract [en]

    In the present work, molecular dynamics simulations were used to investigate the impact of the tool microstructure on the wear behavior of ferrite workpiece during nanoscratching. The tool microstructure was modified by varying the carbide (cementite) contents. The simulation results show that dislocations are the primary mechanism for plastic deformation of the workpiece material. It is found that total dislocation length varies significantly depending on the carbide content in the tool. Furthermore, other tribological phenomena were also observed to depend on the carbide contents. For example, the average value of frictional forces decreased while the normal force increases with increasing carbide contents, and hence the friction coefficient was decreased. Additionally, the shape and size of lateral and frontal pileups are lowered. The structural analysis of the pileup region reveals the loss of long range order and start of amorphisation. The temperature distribution of the pileup regions showed an increase of the pileup temperature when carbide is added into tool. The wear volume is considerably reduced when the carbide content increases. The average scratch hardness was found to decrease and the result was analyzed with the theoretical Taylor hardening model.

  • 26.
    Alay, Özgü
    et al.
    Simula Research Laboratory, Norway.
    Lutu, Andra
    Simula Research Laboratory, Norway.
    García, Rafael
    IMDEA Networks Institute, Spain.
    Peón Quirós, Miguel
    IMDEA Networks Institute, Spain.
    Mancuso, Vincenzo
    IMDEA Networks Institute, Spain.
    Hirsch, Thomas
    Celerway AS, Norway.
    Dély, Tobias
    Celerway AS, Norway.
    Werme, Jonas
    Celerway AS, Norway.
    Evensen, Kristian
    Celerway AS, Norway.
    Hansen, Audun
    Celerway AS, Norway.
    Alfredsson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Karlsson, Jonas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Safari Khatouni, Ali
    Politecnico di Torino.
    Mellia, Marco
    Politecnico di Torino.
    Ajmone Marsan, Marco
    Politecnico di Torino.
    Monno, Roberto
    Nextworks, Italy.
    Lønsethagen, Håkon
    Telenor R&D, Norway.
    MONROE, a distributed platform to measure and assess mobile broadband networks2016In: Proceedings of the Tenth ACM International Workshop on Wireless Network Testbeds, Experimental Evaluation, and Characterization, New York, NY, USA: ACM Digital Library, 2016Conference paper (Refereed)
    Abstract [en]

    This demo presents the MONROE distributed platform and how it can be used to implement measurement and assessment experiments with operational mobile broadband networks (MBBs). MONROE provides registered experimenters with open access to hundreds of nodes, distributed over several European countries and equipped with multiple MBB connections, and a backend system that collects the measurement results. Experiments are scheduled through a user-friendly web client, with no need to directly access the nodes. The platform further embeds tools for real-time traffic flow analysis and a powerful visualization tool.

  • 27.
    Alay, Özgü
    et al.
    Simula Research Laboratory, Norway.
    Lutu, Andra
    Simula Research Laboratory, Norway.
    Rafael, García
    IMDEA Networks Institute, Spain.
    Peón Quirós, Miguel
    IMDEA Networks Institute, Spain.
    Mancuso, Vincenzo
    IMDEA Networks Institute, Spain.
    Hirsch, Thomas
    Celerway AS, Norway.
    Tobias, Dély
    Celerway AS, Norway.
    Werme, Jonas
    Celerway AS, Norway.
    Evensen, Kristian
    Celerway AS, Norway.
    Fosselie Hansen, Audun
    Celerway AS, Norway.
    Alfredsson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Karlsson, Jonas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Safari Khatouni, Ali
    Politecnico di Torino, Italy.
    Mellia, Marco
    Politecnico di Torino, Italy.
    Ajmone Marsan, Marco
    Politecnico di Torino & IMDEA Networks, Italy.
    Monno, Roberto
    Nextworks, Italy.
    Lønsethagen, Håkon
    Telenor R&D, Norway.
    Measuring and Assessing Mobile Broadband Networks with MONROE2016In: 2016 IEEE International Symposium on a World of Wireless, Mobile, and Multimedia Networks (WoWMoM), Red Hook: IEEE conference proceedings, 2016Conference paper (Refereed)
    Abstract [en]

    Mobile broadband (MBB) networks underpin numerous vital operations of the society and are arguably becoming the most important piece of the communications infrastructure. In this demo paper, our goal is to showcase the potential of a novel multi-homed MBB platform for measuring, monitoring and assessing the performance of MBB services in an objective manner. Our platform, MONROE, is composed of hundreds of nodes scattered over four European countries and a backend system that collects the measurement results. Through a user-friendly web client, the experimenters can schedule and deploy their experiments. The platform further embeds traffic analysis tools for real-time traffic flow analysis and a powerful visualization tool.

  • 28.
    Aldaron, Mattias
    Karlstad University, Division for Engineering Sciences, Physics and Mathematics.
    Anaerob rening vid StoraEnso Skoghalls Bruk2009Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    An analysis of a specific application of anaerobic wastewater treatment at a pulp and board mill, Stora Enso Skoghall, was carried out. A literature study was done and effluent wastewater from CTMP pulp production was analyzed. The analysis consisted of a broad constituent analysis and an anaerobic treatment trial. Results from these test where used to calculate the treatment effectiveness and resulting energy potential at the mill.

    The literature study and constituent analysis showed that toxicity of the water to be treated, due to wood extractives and sulphur content, was of concern. Detoxification chemicals targeting these constituents where used in the anaerobic treatment trial. The trial consisted of a two chamber upflow reactor and aerobic post treatment. The result of the trial is that the water of concern has about 50% anaerobically degradable content. A full scale implementation of anaerobic wastewater treatment would result in a methane production of 3,76 to 7,76 GWh/yr. An application of anaerobic wastewater treatment will also result in electricity savings, in aerated pond, and increase the capacity margin on current sludge handling techniques.

  • 29.
    Alfredsson, Lottie
    et al.
    Karlstad University, Faculty of Technology and Science.
    Christenson, Sara
    Karlstad University, Faculty of Technology and Science.
    Supplier Selection & Quality Expectations: Development of a Simple Supplier Evaluation Tool in a Norwegian Ventilation Systems Company2014Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In today’s competitive market, survival and response to customer needs and

    expectations are enabled through high-quality products for low costs – quality

    products provided by suppliers fulfilling today’s quality-requirements for a low

    price. Companies have until recent years selected suppliers only according to a

    pricing structure, leaving other criteria’s, such as quality, behind.

    The purpose of this master thesis is therefore to investigate quality aspects that

    must be considered from a supplier evaluation perspective and design a simple

    evaluation tool for first-time supplier selections. Both new and existing

    suppliers will be tested with the tool according to information given during a

    case study made at Flexit AS, a Norwegian ventilation-systems company

    looking to introduce a structured approach for selecting suppliers.

    Through an extensive literature- and empirical study, where a survey, of which

    evaluation criteria’s to be included in the evaluation tool, was conducted

    together with several both semi-structured and unstructured interviews, a

    foundation for the design of the tool was presented.

    Quality management systems and quality performance measurements, such as

    rejection rate and delivery precision, are considered as fundamental aspects to

    consider when assessing a supplier. Acceptance levels of approval are set

    according to in-house objectives. If any evaluation tool including quality

    should be usable, an in-house quality system must therefore first be

    implemented by the in-house company – a notable improvement

    recommended to the case company.

    The design of the tool given from the thesis provides the evaluator with an

    opportunity to visualize and compare existing suppliers according to five

    criteria’s including cost, together with an additional spreadsheet for evaluation

    of new suppliers put forward as a foundation and an indicator if new suppliers

    are considering quality on a basic level.

  • 30.
    Alfredsson, Patrik
    et al.
    Karlstad University, Faculty of Technology and Science.
    Haeffner, Fredric
    Karlstad University, Faculty of Technology and Science.
    Åtgärdsförslag för erosionsskador i Kölaälv2006Independent thesis Basic level (professional degree), 15 points / 22,5 hpStudent thesis
  • 31.
    Alfredsson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    A Case Study of Recent Mifare Classic Field Deployments From an (In-)Security Perspective2013In: Proceedings of the 21st International Conference on Software, Telecommunications and Computer Networks (SoftCOM 2013), Split, Croatia: FESB, University of Split , 2013Conference paper (Refereed)
    Abstract [en]

    Mifare Classic is a very popular near-field communication technology that provides a shared-key, access-controlled, storage. Although the authentication protocol of Mifare Classic is compromised since half a decade, systems are still being deployed based on this technology, e.g. for access control systems and for public transport ticketing. By using commodity hardware, such as NFC enabled smartphones, by passing the security measures in some cases only require the installation and operation of a smartphone app. To this end, we present case studies of a number of recent Mifare Classic systems deployed during the last year, to serve as an illustration of practical security problems and to raise awareness thereof among NFC technology buyers and system implementors.

  • 32.
    Alfredsson, Stefan
    Karlstad University, Division for Information Technology.
    TCP in Wireless Networks: Challenges, Optimizations and Evaluations2005Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents research on transport layer behavior in wireless networks. As the Internet is expanding its reach to include mobile devices, it has become apparent that some of the original design assumptions for the dominant transport protocol, TCP, are approaching their limits. A key feature of TCP is the congestion control algorithm, constructed with the assumption that packet loss is normally very low, and that packet loss therefore is a sign of network congestion. This holds true for wired networks, but for mobile wireless networks non-congestion related packet loss may appear. The varying signal power inherent with mobility and handover between base-stations are two example causes of such packet loss. This thesis provides an overview of the challenges for TCP in wireless networks together with a compilation of a number of suggested TCP optimizations for these environments. A TCP modification called TCP-L is proposed. It allows an application to increase its performance, in environments where residual bit errors normally give a degraded throughput, by making a reliability tradeoff. The performance of TCP-L is experimentally evaluated with an implementation in the Linux kernel. The transport layer performance in a 4G scenario is also experimentally investigated, focusing on the impact of the link layer design and its parameterization. Further, for emulation-based protocol evaluations, controlled packet loss and bit error generation is shown to be an important aspect.

  • 33.
    Alfredsson, Stefan
    et al.
    Karlstad University, Division for Information Technology.
    Brunstrom, Anna
    Karlstad University, Division for Information Technology.
    Bit Error Tolerant Multimedia Transport2004In: Perspectives on Multimedia: Communication, Media and Information Technology, Chichester: John Wiley & Sons, 2004, 175-191 p.Chapter in book (Other academic)
  • 34.
    Alfredsson, Stefan
    et al.
    Karlstad University, Division for Information Technology.
    Brunstrom, Anna
    Karlstad University, Division for Information Technology.
    TCP-L: Allowing Bit Errors in Wireless TCP2003In: Proceedings of the 12th IST Summit on Mobile and Wireless Communications: Enabling a Pervasive Wireless World / [ed] Atílio Gameiro, Institute for Operations Research and the Management Sciences (INFORMS), 2003, 149-154 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a technique to improve the performance of TCP and the utilization of wireless networks.Wireless links exhibit high rates of bit errors, compared to communication over wireline or fiber. Since TCP cannotseparate packet losses due to bit errors versus congestion,all losses are treated as signs of congestion and congestionavoidance is initiated. This paper explores the possibility of accepting TCP packets with an erroneous checksum, toimprove network performance for those applications that can tolerate bit errors. Since errors may be in the TCP header aswell as the payload, the possibility of recovering the headeris discussed. An algorithm for this recovery is also presented.Experiments with an implementation have been performed,which show that large improvements in throughput can beachieved, depending on link and error characteristics.

  • 35.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Division for Information Technology.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Division for Information Technology.
    Mikael, Sternad
    Signaler och System, Uppsala universitet.
    A 4G Link Level Emulator for Transport Protocol Evaluation2004In: Proceedings of The Second Swedish National Computer Networking Workshop (SNCNW), 2004, 19-23 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a wireless link and networkemulator, based upon the "Wireless IP" 4G system proposalfrom Uppsala University and partners. In wireless fading down-links (base to terminals) link-level frames are scheduled andthe transmission is adapted on a fast time scale. With fastlink adaptation and fast link level retransmission, the fading properties of wireless links can to a large extent be counteractedat the physical and link layers. A purpose of the emulatoris to investigate the resulting interaction with transport layer protocols. The emulator is built on Internet technologies, andis installed as a gateway between communicating hosts. The paper gives an overview of the emulator design, and presentspreliminary experiments with three different TCP variants. The results illustrate the functionality of the emulator by showing theeffect of changing link layer parameters on the different TCP variants.

  • 36.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Mikael, Sternad
    Signaler och System, Uppsala universitet.
    Cross-layer analysis of TCP performance in a 4G system2007In: Proceedings of the 15th International Conference on Software, Telecommunications and Computer Networks, IEEE Computer Society, 2007Conference paper (Refereed)
    Abstract [en]

    This paper presents results from an experimental study of TCP in a wireless 4G evaluation system. Test-bed results on transport layer performance are presented and analyzed in relation to several link layer aspects. The aspects investigated are the impact of channel prediction errors, channel scheduling, delay, and adaptive modulation switch level, on TCP performance. The paper contributes a cross-layer analysis of the interaction between symbol modulation levels, different scheduling strategies, channel prediction errors and the resulting frame retransmissions effect on TCP. The paper also shows that highly persistent ARQ with fast link retransmissions do not interact negatively with the TCP retransmission timer even for short round trip delays.

  • 37.
    Alfredsson, Stefan
    et al.
    Karlstad University, Division for Information Technology. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Division for Information Technology.
    Mikael, Sternad
    Signaler och System, Uppsala universitet.
    Emulation and Validation of a 4G System Proposal2005In: Proceedings of RadioVetenskap och Kommunikation 2005: Volume II, 2005, 357-362 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a wireless link and network emulator,along with experiments and validation against the "Wireless IP" 4G system proposal from Uppsala University and partners. In wireless fading downlinks (base to terminals) link-level frames are scheduled and the transmission is adapted on a fast time scale. With fast link adaptation and fast link level retransmission, the fading properties of wireless links can to a large extent be counteracted at thephysical and link layers. The emulator has been used to experimentally investigate the resulting interaction between the transport layer and the link layer. The paper gives an overview of the emulator design, and presents experimental results with three different TCP variants in combination with various link layer characteristics.

  • 38.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Mikael, Sternad
    Signaler och System, Uppsala universitet.
    Impact of 4G Wireless Link Configurations on VoIP Network Performance2008In: Proceedings of the 2008 IEEE International Symposium on Wireless Communication Systems, IEEE Communications Society, 2008, 708-712 p.Conference paper (Refereed)
    Abstract [en]

    The performance of applications in wireless networks is partly dependent upon the link configuration. Link characteristics varies with frame retransmission persistency, link frame retransmission delay, adaptive modulation strategies, coding, and more. The link configuration and channel conditions can lead to packet loss, delay and delay variations, which impact different applications in different ways. A bulk transfer application may tolerate delays to a large extent, while packet loss is undesirable. On the other hand, real-time interactive applications are sensitive to delay and delay variations, but may tolerate packet loss to a certain extent. This paper contributes a study of the effect of link frame retransmission persistency and delay on packet loss and latency for real-time interactive applications. The results indicate that a reliable retransmission mechanism with fast link retransmissions in the range of 2-8 ms is sufficient to provide an upper delay bound of 50 ms over the wireless link, which is well within the delay budget of voice over IP applications.

  • 39.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Mikael, Sternad
    Signaler och System, Uppsala universitet.
    Transport Protocol Performance over 4G Links: Emulation Methodology and Results2006In: Proceedings of the International Symposium on Wireless Communication Systems (ISWCS), IEEE Computer Society, 2006, 327-332 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a wireless link and network emulator for the "Wireless IP" 4G system proposal from Uppsala University and partners. In wireless fading downlinks (base to terminals) link-level frames are scheduled and the transmission is adapted on a fast time scale. With fast link adaptation and fast link level retransmission, the fading properties of wireless links can to a large extent be counteracted at the physical and link layers. The emulator has been used to experimentally investigate the resulting interaction between the transport layer and the physical/link layer in such a downlink. The paper introduces the Wireless IP system, describes the emulator design and implementation, and presents experimental results with TCP in combination with various physical/link layer parameters. The impact of link layer ARQ persistency, adaptive modulation, prediction errors and simple scheduling are all considered.

  • 40.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Del Giudice, Giacomo
    Politecnico di Bari, Italy.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    De Cicco, Luca
    Ecole superieure d'Electricite, France; Politecnico di Bari, Italy.
    Mascolo, Saverio
    Politecnico di Bari, Italy.
    Impact of TCP Congestion Control on Bufferbloat in Cellular Networks2013In: Proceedings of the 14th IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks (WoWMoM 2013) / [ed] Angelos Lazaris, Balaji Rengarajan, IEEE Press, 2013Conference paper (Refereed)
    Abstract [en]

    The existence of excessively large and too filled network buffers, known as bufferbloat, has recently gained attention as a major performance problem for delay-sensitive applications. One important network scenario where bufferbloat may occur is cellular networks.

    This paper investigates the interaction between TCP congestion control and buffering in cellular networks. Extensive measurements have been performed in commercial 3G, 3.5G and 4G cellular networks, with a mix of long and short TCP flows using the CUBIC, NewReno and Westwood+ congestion control algorithms. The results show that the completion times of short flows increase significantly when concurrent long flow traffic is introduced. This is caused by increased buffer occupancy from the long flows. In addition, for 3G and 3.5G the completion times are shown to depend significantly on the congestion control algorithms used for the background flows, with CUBIC leading to significantly larger completion times.

  • 41.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Del Giudice, Giacomo
    Politecnico di Bari, Italy.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    De Cicco, Luca
    Ecole superieure d'Electricite, France; Politecnico di Bari, Italy.
    Mascolo, Saverio
    Politecnico di Bari, Italy.
    Observations of Bufferbloat in Swedish Cellular Networks2013In: Proceedings of the 9th Swedish National Computer Networking Workshop (SNCNW 2013) / [ed] Bengt Ahlgren, 2013Conference paper (Refereed)
  • 42.
    Alfredsson, Svante
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Konceptutveckling av transportlösning för kaffeutrustning till event2016Independent thesis Basic level (university diploma), 180 HE creditsStudent thesis
    Abstract [en]

    This thesis is done during the spring semester 2016 for the Bachelor of Science in Innovation and Design programme at Karlstad University. The mission of the thesis was provided by the company 3TEMP AB in Arvika.

    In order to serve large quantities of coffee at big events, festivals and fairs a powerful coffee machine is required. Due to its size the machine is difficult handle during transport. This project is about finding a solution that makes the transport of the coffee machine and its related equipment safer and easier to handle during transportation between events.

    The goal of the project was to find a possible solution that makes the transportation of the equipment more efficient and ergonomic. In order to find as many ideas as possible the design process has been used. This includes a research followed by an ideation, concept development and concept evaluation. The project ended with one concept presented in the form of a layout design in CAD together with assembly drawings, sketches and a model.

    In this project interviews and observations has been done together with the people who transport coffee equipment on a daily basis. The results of the observations were later compared with the recommended lifting weight for manual lifting tasks using NOISH lifting equation. In the event business different types of vehicles are used to transport equipment at the event areas. Everything from ATVs and snowmobiles to tractors and caterpillar vehicles are used. In the project there has been a search for a common denominator between those vehicles.

    During the project benchmarking of similar products has also been done to find inspiration for new ideas. To further evaluate the concepts an examination of laws and regulations for transportation of equipment in traffic and off-road has been done.

    The equipment also has to withstand long distance transport by rail, road, sea and air. To meet these requirements interviews were made with the company MariTerm AB who works with educating in cargo securing of goods for worldwide shipment.

  • 43. Ali, A
    et al.
    Hoagg, J. B
    Mossberg, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Bernstein, D. S
    Growing window recursive quadratic optimization with variable regularization2010Conference paper (Refereed)
  • 44.
    Ali, Asad A.
    et al.
    Univ Michigan, Dept Aerosp Engn, Ann Arbor, MI 48109 USA..
    Hoagg, Jesse B.
    Univ Kentucky, Dept Mech Engn, 151 Ralph G Anderson Bldg, Lexington, KY 40507 USA..
    Mossberg, Magnus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Bernstein, Dennis S.
    Univ Michigan, Dept Aerosp Engn, Ann Arbor, MI 48109 USA..
    On the stability and convergence of a sliding-window variable-regularization recursive-least-squares algorithm2016In: International journal of adaptive control and signal processing (Print), ISSN 0890-6327, E-ISSN 1099-1115, Vol. 30, no 5, 715-735 p.Article in journal (Refereed)
    Abstract [en]

    A sliding-window variable-regularization recursive-least-squares algorithm is derived, and its convergence properties, computational complexity, and numerical stability are analyzed. The algorithm operates on a finite data window and allows for time-varying regularization in the weighting and the difference between estimates. Numerical examples are provided to compare the performance of this technique with the least mean squares and affine projection algorithms. Copyright (c) 2015 John Wiley & Sons, Ltd.

  • 45.
    Allard, Marie-Louise
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Bilen, ett tekniskt system: 3-åringars uppfattning kring bilen som ett tekniskt system och dess komponenter2014Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of the survey is to find out what perception children in preschool have about the car as a technical system, how its components interact, and also their perception on various components of the traffic system. Qualitative interviews were conducted with eleven children in the age of three about their experiences on this.

     

    The result shows that most of the children in the study have experience on the components that are most prominent on a car such as steering wheel, wheels and engine. The results are mixed in terms of knowledge of the components' importance and how they interact with each other. The survey also shows that the children who have the greatest knowledge of the components' importance are those who have been with an adult when changing tires, refueling, minor repairs, etc. According to the results, most of the kids know that there must be roads to drive on and they recognize for example traffic lights and Mr. Gårman plate available at pedestrian crossings. However, there is general uncertainty about the significance of them.

  • 46. Alm, Magnus
    et al.
    Fauhlér, Robert
    Nätplanering på Fortum Distribution2012Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
  • 47.
    Almered Olsson, Gunilla
    et al.
    Norges Teknisk-Naturvitenskapelige Universitet, Trondheim, Norge.
    Bladh, GabrielKarlstad University, Division for Social Sciences.Månsson, BengtKarlstad University, Division for Engineering Sciences, Physics and Mathematics.Nyberg, LarsKarlstad University, Division for Environmental Sciences.
    Inte bara träd: hållbart mångbruk av skogslandskapet2004Collection (editor) (Refereed)
    Abstract [sv]

    Skogslandskapen - hur skall vi värdera dem? Ska de betraktas som rekreationsområden och kulturlandskap eller som arena för konflikter och dragkamp om olika resurser? Är skogsregionerna närande eller tärande? Vilka viktiga samband finns mellan skandinaviska och tropiska landskap?Detta är några av de teman som behandlas i denna spänannde bok om de många dimensionerna och resurserna som ryms i skogslandskapen. Boken ger nya och stimulerande aspekter på framtidsmöjligheterna för en hållbar utveckling för boreala skogslandskap. Den tar också upp det nödvändiga mångbruket av skogens resurser liksom den förändrade synen på människans roll i skogen. Och inte minst behandlas den ekologiska paradoxen att störningar behövs för att bevara skogens ekologiska mångfald.Boken är författad av samhällsvetare, miljöteknologer och ekologer inom den tvärvetenskapliga forskargruppen MiljöFocus vid Karlstads universitet.

  • 48.
    Almlöf Ambjörnsson, Heléne
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Mercerization and Enzymatic Pretreatment of Cellulose in Dissolving Pulps2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with the preparation of chemically and/or enzymatically modified cellulose. This modification can be either irreversible or reversible. Irreversible modification is used to prepare cellulose derivatives as end products, whereas reversible modification is used to enhance solubility in the preparation of regenerated cellulose.

    The irreversible modification studied here was the preparation of carboxymethyl cellulose (CMC) using extended mercerization of a spruce dissolving pulp. More specifically the parameters studied were the effect of mercerization at different proportions of cellulose I and II in the dissolving pulp, the concentration of alkali, the temperature and the reaction time. The parameters evaluated were the degree of substitution, the filterability and the amount of gel obtained when the resulting CMC was dissolved in water. Molecular structures of CMC and its gel fractions were analysed by using NIR FT Raman spectroscopy. It was found that the alkali concentration in the mercerization stage had an extensive influence on the subsequent etherification reaction. FT Raman spectra of CMC samples and their gel fractions prepared with low NaOH concentrations (9%) in the mercerization stage indicated an incomplete transformation of cellulose to Na-cellulose before carboxymethylation to CMC. Low average DS values of the CMC, i.e. between 0.42 and 0.50 were obtained. Such CMC dissolved in water resulted in very thick and semi solid gum-like gels, probably due to an uneven distribution of substituents along the cellulose backbone. FT Raman spectra of CMC samples and their gel fractions mercerized at higher alkaline concentration, i.e. 18.25 and 27.5% in the mercerization stage, indicated on the other hand a complete transformation of cellulose to Na-cellulose before carboxymethylation to CMC. Higher average DS values of the CMC, i.e. between 0.88 and 1.05 were therefore obtained. When dissolved in water such CMC caused gel formation especially when prepared from dissolving pulp with a high fraction of cellulose II.

    The reversible modification studied was the dissolution of cellulose in NaOH/ZnO. Here the effect of enzyme pretreatment was investigated by using two mono-component enzymes; namely xylanase and endoglucanase, used in consecutive stages. It was found that although the crystallinity and the specific surface area of the dissolving pulp sustained minimal change during the enzymatic treatment; the solubility of pulp increased in a NaOH/ZnO solution from 29% for untreated pulp up to 81% for enzymatic pretreated pulp.

  • 49.
    Almlöf Ambjörnsson, Heléne
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Enzyme treatment of dissolving pulps as a way to improve the following dissolution of the fibres2012Conference paper (Other academic)
  • 50.
    Almlöf Ambjörnsson, Heléne
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Extended Mercerization Prior to Carboxymethyl Cellulose Preparation2011Conference paper (Other (popular science, discussion, etc.))
1234567 1 - 50 of 3157
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf