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  • 2851.
    Ahnlund, Josefin
    et al.
    KTH, School of Engineering Sciences (SCI).
    Magnusson, Caroline
    KTH, School of Engineering Sciences (SCI).
    Sannolihetsbaserad modellering av flygplansdata -med fokus på ankomsttid.2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Probabilistic modelling of flight data - with

    focus on arrival time

    Flightradar24 is a company that provides services for displaying

    aircraft position and other aircraft information for flights in real

    time. The information originates from data continously transmitted

    by aircrafts, which contains parameters such as position,

    height, direction and velocity. The purpose of the project is to investigate

    how such historical data can be used to predict airplain

    arrival time. In order to do so, a probability model is developed

    based on the historical data.

  • 2852.
    Ahnlén, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    Automatic Detection of Low Passability Terrain Features in the Scandinavian Mountains2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    During recent years, much focus have been put on replacing time consuming manual mappingand classification tasks with automatic methods, having minimal human interaction. Now it ispossible to quickly classify land cover and terrain features covering large areas to a digital formatand with a high accuracy. This can be achieved using nothing but remote sensing techniques,which provide a far more sustainable process and product. Still, some terrain features do not havean established methodology for high quality automatic mapping.The Scandinavian Mountains contain several terrain features with low passability, such asmires, shrub and stony ground. It would be of interest to anyone passing the land to avoid theseareas. However, they are not sufficiently mapped in current map products.The aim of this thesis was to find a methodology to classify and map these terrain featuresin the Scandinavian Mountains with high accuracy and minimal human interaction, using remotesensing techniques. The study area chosen for the analysis is a large valley and mountain sidesouth-east of the small town Abisko in northern Sweden, which contain clearly visible samplesof the targeted terrain features. The methodology was based on training a Fuzzy Logic classifierusing labeled training samples and descriptors derived from ortophotos, LiDAR data and currentmap products, chosen to separate the classes from each other by their characteristics. Firstly,a set of candidate descriptors were chosen, from which the final descriptors were obtained byimplementing a Fisher score filter. Secondly a Fuzzy Inference System was constructed usinglabeled training data from the descriptors, created by the user. Finally the entire study area wasclassified pixel-by-pixel by using the trained classifier and a majority filter was used to cluster theoutputs. The result was validated by visual inspection, comparison to the current map productsand by constructing Confusion Matrices, both for the training data and validation samples as wellas for the clustered- and non-clustered results.The results showed that

  • 2853.
    Ahnlén, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Satellite Positioning.
    MAP DESIGN: A development of background map visualisation in Digpro dpPower application2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    What is good map design and how should information best be visualised for a human reader? This is a general question relevant for all types of design and especially for digital maps and various Geographic Information Systems (GIS), due to the rapid development of our digital world. This general question is answered in this thesis by presenting a number of principles and tips for design of maps and specifically interactive digital visualisation systems, such as a GIS.

    Furthermore, this knowledge is applied to the application dpPower, by Digpro, which present the tools to help customers manage, visualise, design and perform calculations on their electrical networks. The visualisation and design of the network was analysed together with the usage of two common background maps, GSD-Fastighetskartan by Lantmäteriet and Primärkartan by the municipalities, whose default appearances are defined by Digpro. The aim was to answer whether there is a more suitable design of the background maps and network to better complement the usage of dpPower and if so, what is the better design?

    When designing interactive systems that will later have various end-users, a user-centred design is important. Therefore, the initial step was to collect user inputs and feedback on the current design via customer interviews. This gave a set of user criteria for good map design of dpPower specifically.

    A study of existing relevant literature and previous work was also performed where several general key principles for good design could be identified.

    Finally, a comparison between the dpPower design and other existing map products, such as e.g. Google Maps and Eniro, was made where key similarities and dissimilarities were identified and discussed.

    These user criteria and design principles could be combined, both to present an answer to the general question “What is good design?” and to present a suggestion of new map appearance in dpPower. Key considerations in the new design suggestions were e.g. to have a toned down background map with all features in the same hue family. However, for GSD-Fastighetskartan the important convention of land classes, blue = water, green = vegetation \& yellow = open land, should be kept. Colour combinations and contrast is the most important design element and since a design cannot be optimally adapted for all types of colour vision deficiencies, the suggestion is to separate the designs to specifically target user groups of different colour vision abilities. Important map information such as e.g. detailed road data should be kept while unnecessary features such as contour lines and polygon borderlines should be hidden. Text positions should also be considered.

    The results were evaluated both via a survey, distributed to users of dpPower, GIT-students and users with no previous experience of GIT or dpPower, and a seminar with employees at Digpro.

    The conclusions drawn from the evaluation was that the presented design suggestions and principles are good, but adjustments should be made. E.g. a use of yellow for low voltage cables, as suggested for Red-Green impaired, is perhaps not the best solution. The results present a good foundation for design of dpPower but more adjustments should be made based on the evaluation and then another evaluation can be performed. It would give an even better result.

  • 2854. Ahnström, Ulrika
    et al.
    Falk, Johan
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Wikström, Maria
    Detection and direction-finding of spread spectrum signals using correlation and narrowband interference rejection2003In: Nordic Matlab Conference 2003, 2003Conference paper (Refereed)
    Abstract [en]

    An algorithm for correlation-based detection of direct sequence spread spectrum signals with direction finding, including direction-filtering and narrow-band interference rejection, is implemented and evaluated in MATLAB. An analog noise-free signal is generated and sampled by a test-bed system. Numerical simulations are run based on data corrupted by mutually uncorrelated white Gaussian noise sequences, and also with recorded noise from two spatially separated HF radio receivers. The simulations and measurements show promising results for detection and direction-finding of covert wideband signals in low SNR and in presence of narrowband interferers. Direction filtering is shown to improve the results.

  • 2855.
    Aho, Aziz Sebastian
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    Ikzir, Nawar
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    Krockskydd av chassimonterade komponenter2017Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
  • 2856.
    Aho, Daniel
    et al.
    KTH, School of Engineering Sciences (SCI).
    Ellingsen, Ask
    KTH, School of Engineering Sciences (SCI).
    Gravitational Waves from Slow Motion Binary Systems2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this thesis we study gravitational waves in the domain of linearised general relativity. Wepresent the fundamental ideas and theory of general relativity, then, using the traditionalmeans of quadrupole approximation, we derive an expression for the power radiated as gravitationalwaves in a binary system. We limit ourselves to binary systems in the Newtonianlimit, and can therefore use Kepler’s laws in our calculations. We then use the derived expressionto explicitly predict the power radiated by the Sun-planet systems in our solar systemspecifically, regarding each system as a binary consisting of the planet and the Sun. Finally,we calculate the resulting orbital decay and find an expression for the time it would take forthe bodies to come into contact if gravitational radiation were the only means by which thesystem lost energy. As expected, the power radiated by gravitational waves is found to bevery small for systems in the Newtonian limit, and the corresponding time until impact isfound to be on the order of many times the age of the Universe.

  • 2857.
    Aho, Isa
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    Halef, Madeleine
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    Flödeskartläggning avbilflödenpå Södertälje Hamn2013Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
  • 2858.
    Aho, Isa
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    Halef, Madeleine Halef
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    Flödeskartläggning avbilflödenpå Södertälje Hamn(Car-flow mapping at the Port of Södertälje)2013Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
  • 2859.
    Aho, Isa
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    Karlsson, Daniel
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    Säkra förband - kvalitetssäkring av differentialförbandet2011Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
  • 2860.
    Aho, Yousef
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematical Statistics.
    Persson, Johannes
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematical Statistics.
    Factors Affecting the Conversion Rate in the Flight Comparison Industry: A Logistic Regression Approach2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Using logistic regression, we aim to construct a model to examine the factors that are most influential in affecting user behavior on the flight comparison site flygresor.se. The factors examined were number of adults, number of children, number of stops on the inbound trip, number of stops on the outbound trip, number of days between the search date and the departure date and number of search results displayed for the user. The data sample, collected during a one-week period, was taken from Flygresor and consisted of trips to or from Sweden, made within Europe, excluding Nordic countries, and made more than six days before departure. To find the variables which best explain the user behavior, variable selection methods were used along with hypothesis testing. Also, multicollinearity analysis and residual analysis were performed to evaluate the final model. The result showed that the factor number of children had no significant impact on the conversion rate, while the remaining factors had a high impact. The final model has a high predictive ability on the user's propensity to select a certain flight.

  • 2861. Ahola-Tuomi, M.
    et al.
    Punkkinen, Marko Patrick John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Laukkanen, P.
    Kuzmin, M.
    Lang, J.
    Schulte, K.
    Pietzsch, A.
    Perala, R. E.
    Rasanen, N.
    Vayrynen, I. J.
    Properties of self-assembled Bi nanolines on InAs(100) studied by core-level and valence-band photoemission, and first-principles calculations2011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 83, no 24, p. 245401-Article in journal (Refereed)
    Abstract [en]

    We have studied self-assembled bismuth (Bi) nanolines on the Bi-terminated InAs(100) surface by core-level and valence-band photoelectron spectroscopy, and ab initio first-principles calculations. A structural model for this intriguing surface is suggested based on the comparison of the measured and calculated core-level shifts. Also, the atomic origins for the core-level shifts are proposed based on the calculations. A clear peak related to this surface was observed in the valence band 0.34 eV below the Fermi level, which can be used as a "fingerprint" of a well-ordered Bi/InAs(100) nanoline surface.

  • 2862.
    Ahrenstedt, Irina
    KTH, School of Architecture and the Built Environment (ABE), Architecture, Lightning Design.
    Travelling Stockholm from underneath: A journey of light2015Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    The report Stockholm city’s regional biking plan presents information of a continuously rising numbers ofcyclists in central Stockholm. However, the central parts of Stockholm have not now, or in the near future,the capacity or structure to provide a functional as well as safe traffic situation, especially for cyclists. Theincreasing demand from traffic of the commuter street network in central Stockholm make the 6 km longunderground maintenance tunnel along the newly build Citybanan commuter train tracks a possible andinteresting alternative for safe, fast and easy bicycle travelling underneath Stockholm. The tunnel stretchesfrom Fatbursparken to Tomteboda, with exits/entrances along the route in central parts of Stockholm[Fig 1.]There are several examples in the world where former car, train and maintenance tunnels are used as bikingtunnels. The longest existing example is the Croix Rousse tunnel in Lyon, France (2013). A 1,3 km longtunnel with separate lanes for cyclists, pedestrians and commuter busses, which also functions as anevacuation tunnel to the parallel car tunnel. Another example is the Lugaritz-Morland bicycle tunnel in thecity of San Sebastian, Spain (2009), which is a former railway tunnel (850 metres) that connects twoneighbourhoods in the city.The specific conditions a tunnel have with no daylight and limited access, give the lighting designer theimportant task to shape the space using light.Light is the factor that makes us see the world, our visual ability is depending on the light. Light has theability to reveal and transform the character of a space and influence how the observer experiences thesituation, both physically (by vision) and psychologically (emotional experiences as comfort and feeling ofsafety). Therefore a good visual condition in public space, traffic as well as enclosed spaces like tunnels, arevery important and a basic need for humans in the city.The aim with this thesis was to develop a lighting strategy and proposal for the maintenance tunnel ofCitybanan in Stockholm, based on literature and case studies research, a full-scale light observation by areference group in a tunnel context as well as research by questionnaires. The primary purpose of the fullscalelight study was to confirm literature research hypotheses about the importance of light distributionand experienced spatial atmosphere in relation to psychological effects, as well as the importance of lightgiving information. Findings confirm and shows that light distribution have a great impact on how theobservers experience the space visually, as well as emotionally. Findings also show that light can influencepeople’s behaviour to intuitively slow down or be alert. Further this thesis results show that giving a spaceit’s own identity by collaboration between light, colour and architectural elements have a great impact onthe psychological experiences of a space regarding safety, comfort and social interaction, crucial factors in atunnel environment for cyclists.The thesis results in a concept presented in the Proposal chapter, based on design principles and a lightingstrategy where a combination of light typologies is used to create a human centred and comfortableenvironment. Light is used as guiding element and for spatial understanding to create comfort and supportsocial interaction. In addition the concept includes a theme used as inspiration in the lighting strategy tocreate a connection on a human scale between the cyclist and the space. The theme is based on a commonpreference of the reference group, as well as my personal, for the ideal dream biking environment;In the nature. Experiencing for example the variation of light filtered through the leaves, the sunset and theabsence of traffic.The aim with the proposal is to transform the tunnel to an attractive bicycle route for daily cyclists inStockholm, as well as being an interesting tourist attraction.- A large underground landmark and art piece stretching under the city of Stockholm.

  • 2863.
    Ahrenstedt, Lage
    University of Cape Town.
    Drug Eluting Hydrogels: Design, Synthesis and Evaluation2012Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Hydrogels have successfully proved themselves useful for drug delivery applications and several delivery routes have been developed over the years. The particular interest in this work was to design, synthesise and evaluate in situ forming drug eluting hydrogels, which have the potential to ameliorate the healing of cardiovascular diseases.

    With this aim the anti-inflammatory and immunosuppressant drugs rapamycin (Ra) and dexamethasone (Dex) were made water soluble by conjugation with polyethylene glycol (PEG). Ra was attached pendant from the terminal of PEGs while Dex was incorporated into dendritic structures grown from PEGs. These conjugates were further crosslinked into hydrogels by either conjugate or thiol-ene addition. The gel degradation was tuned to take between 5 and 27 days by using gel building block combinations that induced either 2 or 4 hydrolytically labile bonds per crosslink or by varying the number of crosslinking sites of the building blocks. The use of thiol-ene addition prolonged the degradation time nearly seven folded compared to conjugate addition as a more stable crosslink was formed.

    Two different formulations for gelling via conjugate addition were used (acrylate-thiol or vinyl sulphone-thiol) to deliver Ra, which was carried by either a 4- or 2-armed PEG. The elution kinetic for the respective gel formulation was of zero order during 15 and 19 days of gel degradation. In addition, Ra was PEGylated via esters, with a distance of either one or two carbons to a nearby thio-ether functionality. The difference in ester conjugation resulted in a slight but significant change in drug-PEG conjugate stability, which was mirrored by the increased time to reach the half amount of total drug elution; from 9.3 to 10.2 days and from 5.1 to 9.7 days for the two gel formulations, respectively. Dexamethasone was incorporated via an ester into dendrons of first and second generation pending from 2- and 4-armed PEGs at loadings of 2, 4 or 6 Dex molecules per carrier molecule. The resulting elution kinetic was of zero order during degradation periods of 5-27 days. Released Dex still possessed biological activity as determined by an in vitro cell assay.

    The novelties in this thesis are: (A) slow release of rapamycin obtained by covalent incorporation into hydrogels, (B) the use of unique PEG-based dendrimers to incorporate dexamethasone into a hydrogel and (C) zero order sustained release of dexamethasone at physiological pH.

  • 2864.
    Ahrenstedt, Lage
    KTH, School of Biotechnology (BIO).
    Surface modification of cellulose materials: from wood pulps to artificial blood vessels2007Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis describes the improvement of two radically different cellulose materials, paper and artificial blood vessels, constructed from two diverse cellulose sources, wood pulp and Acetobacter xylinum. The improvement of both materials was possible due to the natural affinity of the hemicellulose xyloglucan for cellulose.

    Chemical and mechanical pulps were treated with xyloglucan in the wet-end prior to hand sheet formation or by spray application of dry hand sheets, loading a comparable amount of xyloglucan. The tensile strength increases for the wet-end treatment and spray application were 28% and 71% respectively for bleached soft wood, compared to untreated sheets (20.7 Nm/g). The corresponding strength increases for hand sheets made of thermo-mechanical pulp were 6% and 13% respectively compared to untreated sheets (42.4 Nm/g). The tendency for chemical pulp to be superior to mechanical pulp with respect to strength increase was valid even for tear strength and Scott-Bond. These results suggest, in agreement with other studies, that adhesion of xyloglucan to wood fibres is dependent on their degree of surface lignification.

    Also, a method was developed to increase the blood compatibility of artificial blood vessels constructed of bacterial cellulose. Xyloglucan was covalently linked to the endothelial cell adhesion motif (Arg-Gly-Asp). To obtain this, new solid-phase coupling chemistry was developed. Xyloglucan oligosaccharides (XGO) were transformed into XGO-succinamic acid via the corresponding XGO--NH2 derivative prior to coupling with the N-terminus of the solid-phase synthesised Gly-Arg-Gly-Asp-Ser peptide. The resin-bound glyco-peptide was then cleaved and enzymatically re-incorporated into high molecular weight xyloglucan. The glyco-peptide was further adsorbed onto bacterial cellulose scaffolds, increasing the adhesion and proliferation of endothelial cells and therefore blood compatibility.

  • 2865.
    Ahrenstedt, Lage
    et al.
    KTH, School of Biotechnology (BIO). KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Olksanen, Antti
    VTT Technical Research Centre of Finland.
    Salmien, Kristian
    VTT Technical Research Centre of Finland.
    Brumer, Harry
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Paper dry strength improvement by xyloglucan addition: Wet-end application, spray coating and synergism with borate2008In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 62, no 1, p. 8-14Article in journal (Refereed)
    Abstract [en]

    The polysaccharide xyloglucan as a wet-end additive improves paper properties. In the present study, paper strength improvement was analysed for dry handsheets made from chemical, mechanical and recycled pulps coated with xyloglucan in a spray application. Results are compared with sheets made from the same pulps treated with xyloglucan in the wet-end. Kraft pulp handsheets of bleached hardwood and softwood showed significant improvements of tensile, tear and Z-strength by xyloglucan spray treatment versus wet-end application, whereas handsheets of de-inked and thermomechanical pulp were improved only slightly. In both wet-end and spray applications, the effect of xyloglucan addition was intimately related to the presence of non-cellulosic components on the fibre surface. Further strength improvements were obtained for chemical pulps by addition of borax to the spray solution, which were likely to be due to the formation of borate-mediated xyloglucan cross-links. Spray coating of xyloglucan, with or without borax, thus represents a potential new application of this polysaccharide to increase paper dry strength.

  • 2866.
    Ahrnstein, Lina
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Dahlberg, Johanna
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    En jämförelse av RDF och avfall som förbränningsbränsle2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In the EU the amount of waste increased by 14 percent during the years 2000 to 2010. EU’s target to reduce waste generation runs parallel with the aim of increasing the efficiency and profitability aligned with energy recovery. In Sweden the energy recovery through incineration is increasing steadily, and 46 percent of the municipal solid waste (MSW) is treated by combustion. This report aims to examine the profitability of processing MSW into Refuse Derived Fuel (RDF) from an economic-, energy- and environmental perspective. In order to obtain a comparison with incineration of MSW the starting point of the feasibility study is one ton of combustible MSW incinerated directly in a stocker grate type incinerator, compared to the same ton of MSW processed to RDF and incinerated in a fluidized bed.The proportion of MSW processed to RDF varies between 23-85 percent, which leads to an average of 540 kg, 54 percent, processed RDF from a ton of MSW. One ton of RDF has a calorific value between 18.5-23 MJ/kg. The calorific value of combustible MSW is calculated to 10.38 MJ/kg. The two different boilers for combustion of the fuels have the same power of 28 MW. The comparison shows the total energy recovery, of heat and electricity, for the combustible MSW in the stocker grate to 2.51 MWh, and for the 540 kg RDF incinerated in a fluidized bed to be 2,56 MWh. As long as the proportion of RDF processed from a ton of MSW is greater than 51 percent, the energy recovery is higher for the RDF.A cost-benefit analysis, calculated from the combustion of 70 000 tons of MSW, and 54 percent of the amount processed to RDF, shows a higher net present value for RDF, 1042 million. However, the net present value of the combusted MSW was also positive, 1024 million, which indicates that both investments are profitable. The payback method showed the same result, with a payback time of 3.17 years for RDF-combustion and 4.24 years for combustion of MSW.Emissions of carbon dioxide and nitrogen oxide are both higher when incineration of 540 kg RDF takes place in a fluidized bed, than of a ton of MSW in a stocker grate incinerator. Emission of carbon dioxide is 17,7 percent higher and for nitrogen oxide 23 percent higher.

  • 2867.
    Ahrsjö, Carl
    KTH, School of Computer Science and Communication (CSC).
    Real-time event based visualization of multivariate abstract datasets: Implementing and evaluating a dashboard visualization prototype2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As datasets in general grow in size and complexity over time while the human cognitive ability to interpret said datasets essentially stays the same, it becomes important to enable intuitive visualization methods for analysis. Based on previous research in the field of information visualization and visual analytics, a dashboard visualization prototype handling real-time event based traffic was implemented and evaluated. The real-time data is collected by a script and sent to a self-implemented web server that opens up a websocket connection with the dashboard client where the data is then visualized. Said data consisted of transactions and related metadata of an ecommerce retail site applied to a real customer scenario.

    The dashboard was developed using an agile method, continuously involving the thesis supervisor in the design and functionality process. The final design also depended on the results of an interview with a representative from one of the two target groups. The two target groups consisted of 5 novice and 5 expert users to the field of information visualization and visual analytics. The intuitiveness of the dashboard visualization prototype was evaluated by conducting two user studies, one for each target group, where the test subjects were asked to interact with the dashboard visualization, answer some questions and lastly solving a predefined set of tasks. The time spent solving said tasks, the amount of serious misinterpretations and the number of wrong answers was recorded and evaluated.

    The results from the user study showed that the use of colors, icons, level on animation, the choice of visualization method and level of interaction were the most important aspects for carrying out an efficient analytical process according to the test subjects. The test subjects desired to zoom in on each component, to filter the contents of the dashboard and to get additional information about the components on-demand. The most important result produced from developing the dashboard was how to handle the scalability of the application. It is highly important that the websocket connection remain stable when scaling out to handle more concurrent HTTP requests. The research also conclude that the dashboard should handle visualization methods that are intuitive for all users, that the real-time data needs to be put into relation to historical data if one wishes to carry out a valid analytical process and that real-time data can be used to discover trends and patterns in an early-as-possible stage. Lastly, the research provides a set of guidelines for scalability, modularity, intuitiveness and relations between datasets. 

  • 2868.
    Ahrsjö, Carl
    et al.
    KTH, School of Computer Science and Communication (CSC).
    Roshult, Tommy
    KTH, School of Computer Science and Communication (CSC).
    Vad påverkar medieteknikstudenternas kursval?2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    With many different elective courses to choose between, a lot of students  experience anxiety over deciding which courses to study next semester. The  choice of a specific course can have a big impact on the students future studies  and/or employment. Therefore the anxiety is justified. At the same time the  number of students applying for a course often vary from year to year. This  creates issues for the responsible teachers because of the ever-changing  resource requirements.

    There are several different theories on decision making, addressing the  different time related states as well as the different habitual styles. With  help of theories on these styles and time states, which were investigated with  two surveys and a focus group, and statistical data mining from a database  consisting of former course decision data we have studied how the students  reason when it comes to selecting courses and which aspects that influence their  choice. This gave us a better insight and understanding of the students’ situation and what the varying of applicants to different courses may depend  on.

    The results of this study show that the students at media technology often  have issues choosing between the elective courses. Many students experience that  the available information on the corresponding course homepages is brief and  therefore they call for a clarification of the course information. Because of  this, the majority of the students in the lower grades often rely on the advice  that the students in the higher grades provide. The database analysis shows that  the grades in the mathematics courses have an effect on which track (and its  corresponding elective courses) a student will choose.

  • 2869.
    Ahrén, Jesper
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Bühlman, Carl
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Lean Production: Redogörelse av Lean och jämförelse med Scanias produktionssystem2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Abstract

    The aim of this report was to cover and explain the basis of Lean production, how it’s implemented in the industry and to compare how lean in theory and practice is interlaced. Lean production is a further spinoff from TPS (Toyota production system), to make a company more resource effective. Developed by Toyota as a result of studies on how to approach and process flaws.

    To get a good hold of lean we chose to look specifically at lean in the vehicle industry. To better understand the industry today and how lean is used we interviewed an employed at Scania. The theoretical part of our work was done by studies of literature, KTH databases search and homepages. Scania has developed their own lean philosophy SPS (Scania Production System) which is a result of a cooperation with Toyota.

    There are several different strategies a company can take to identify and improve imperfections/weaknesses. Lean aims for eliminating waste but also how to use resources in the most efficient way, giving more concrete improvement-­‐suggestions while TPS is more about priorities throughout the company. The Toyota Production system is based out of 14 principles while Lean Production has its base build on five principles but there are also more interpretations.

    During the work we have found that a key factor for a successful Lean implementation is to get the entire organization to see and to believe in the concept, but one must also pretty quickly be able to demonstrate results and improvements. In order to achieve this goal, a clear presentation of results and good leaders is important key factors. In order not to fall back into old habits we have found that a standardized approach which creates opportunities for employees to constantly improve their situation is a must.

    For Scania, the Lean implementation resulted in increased quality and productivity, better attendance, lower energy consumption and better profitability than its competitors. It has created a good organization for the society, customers and its employees, which has been necessary for Scania's survival.

  • 2870. Ahrén, M.
    et al.
    Selegård, L.
    Söderlind, F.
    Linares, M.
    Kauczor, J.
    Norman, Patrick
    Käll, P. -O
    Uvdal, K.
    A simple polyol-free synthesis route to Gd 2O 3 nanoparticles for MRI applications: An experimental and theoretical study2012In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 14, no 8, article id 1006Article in journal (Refereed)
    Abstract [en]

    Chelated gadolinium ions, e.g., Gd-DTPA, are today used clinically as contrast agents for magnetic resonance imaging (MRI). An attractive alternative contrast agent is composed of gadolinium oxide nanoparticles as they have shown to provide enhanced contrast and, in principle, more straightforward molecular capping possibilities. In this study, we report a new, simple, and polyol-free way of synthesizing 4-5-nm-sized Gd 2O 3 nanoparticles at room temperature, with high stability and water solubility. The nanoparticles induce high-proton relaxivity compared to Gd-DTPA showing r 1 and r 2 values almost as high as those for free Gd 3+ ions in water. The Gd 2O 3 nanoparticles are capped with acetate and carbonate groups, as shown with infrared spectroscopy, near-edge X-ray absorption spectroscopy, X-ray photoelectron spectroscopy and combined thermogravimetric and mass spectroscopy analysis. Interpretation of infrared spectroscopy data is corroborated by extensive quantum chemical calculations. This nanomaterial is easily prepared and has promising properties to function as a core in a future contrast agent for MRI. © 2012 Springer Science+Business Media B.V.

  • 2871.
    Ahsan, Ayesha
    KTH, School of Computer Science and Communication (CSC).
    Consumer ratings-reviews and its impact on consumer purchasing behavior2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Storytelling is one of the most creative, powerful and effective tools of modern marketing strategies and communication. Due to the expansion of social media, storytelling has become a popular marketing and sales tool that may affect consumer behavior. This research has been conducted from a storytelling perspective with the purpose of finding the correlation between consumer reviews and consumer purchasing behavior. This study focuses on consumer stories which are reflected in terms of product reviews and ratings. Where the correlation between these reviews and ratings and their effects on overall product sales are investigated. The study answers the question, “If reviews & rating have a correlation with consumer purchasing behavior in digital marketing, and if so then how this correlation could be defined?”

    The data collection and tests have been conducted in a practical environment. The German online stores have been used as the main mode of data collection. Depending on the nature of the data, the quantitative analysis approach has been adopted. By conducting real-time sales data tests, this study fills the gap in previous consumer research studies. The in-depth analysis of results show the correlation between consumer reviews and product sales. The results have revealed that consumer reviews may influence overall product sales and help a consumer in purchasing decision.

  • 2872.
    Ahsan, Mohammed Sabbir
    KTH, School of Information and Communication Technology (ICT).
    Experimental Setup of High Harmonic Generation Based Angle Resolved Photoemission Spectroscopy (HHG-ARPES) And Test Measurement on Tungsten (W) [110] Surface2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 2873.
    Ahsan, Tahmina
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Urban and Regional Studies.
    Passive Design Features for Energy-Efficient Residential Buildings in Tropical Climates: The context of Dhaka, Bangladesh2009Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This study aimed at identifying passive design features through extensive literature study that can be incorporated in residential buildings to make them energy efficient. The study also aimed at identifying changes in the design process that can affect energy efficiency in residential buildings. It has analyzed the design features of typical residential buildings representative of upper middle income households in Dhaka through a case study conducted in Dhaka. It also analyzed the present electric energy use for cooling and lighting typical residential buildings of upper middle income households in Dhaka and the possible energy savings by adopting certain energy efficient features in the case study building. It also distinguishes the different roles of developers, architects, interior designers, land owners (clients) and residents that can act as a barrier in achieving energy efficiency in residential buildings. The findings from this study indicate that doubling the thickness of external walls on east and west, use of hollow clay tiles instead of weathering course for roofs and use of appropriate horizontal overhang ratios for all four orientations can reduce the cooling load of the case study building by 64% and hence reduce the total energy use of the building by 26%. Finally it can be concluded that the process of designing energy efficient residential buildings is not a ‘one-man’s show’. Architects, developers, interior designers and clients are the other actors who can bring a change in the design practice.

     

     

     

     

    Keywords: Energy- efficient; passive design features; residential building; tropical climate

     

     

     

  • 2874.
    Ahsan, Tahmina
    et al.
    KTH.
    Svane, Örjan
    KTH, School of Architecture and the Built Environment (ABE).
    Energy Efficient Design Features for Residential Buildings in Tropical Climates: The Context of Dhaka, Bangladesh2010In: SUSTAINABLE ARCHITECTURE AND URBAN DEVELOPMENT (SAUD 2010), VOL IV / [ed] Lehmann, S AlWaer, H AlQawasmi, J, CSAAR PRESS-CENTER STUDY ARCHITECTURE ARAB REGION , 2010, p. 183-202Conference paper (Refereed)
    Abstract [en]

    This study aimed at identifying passive design features through literature study that can be incorporated in residential buildings of Dhaka to make them energy efficient. The study also aimed at identifying changes in the design process that can affect energy efficiency in residential buildings. It has analyzed the present electric energy use for cooling and lighting typical residential buildings of upper middle income households in Dhaka through a case study conducted in Dhaka. It has also calculated the possible energy savings by adopting certain energy efficient features in the case study building. The findings from this study indicate that doubling the thickness of external walls on east and west of the building, use of hollow clay tiles instead of weathering course for roofs and use of appropriate horizontal overhang ratios for all four orientations can reduce the cooling load of the case study building by 64% and thus reduce the total energy use of the building by 26%. Finally, it can be concluded that the process of designing energy efficient residential buildings is not a 'one-man's show'. Architects, developers, interior designers and clients are the other actors who can bring a change in the design practice.

  • 2875.
    Ahsant, Mehran
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    On-demand Restricted Delegation: A Framework for Dynamic, Context-Aware, Least-Privilege Delegation in Grids2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In grids, delegation is a key facility that can be used to authenticate and authorize requests on behalf of disconnected users. In current grid systems,delegation is either performed dynamically, in an unrestricted manner, or by a secure but static method. Unfortunately, the former compromises security and the latter cannot satisfy the requirements of dynamic grid application execution. Therefore, development of a delegation framework that enables a restricted and flexible delegation mechanism becomes increasingly urgent as grids are adopted by new communities and grow in size. The main barriers in development of such a mechanism are the requirements for dynamic execution of grid applications, which make it difficult to anticipate required access rights for completing tasks in advance.

    Another significant architectural requirement in grids is federated security and trust. A considerable barrier to achieving this is cross-organizational authentication and identification. Organizations participating in Virtual Organizations (VOs) may use different security infrastructures that implement different protocols for authentication and identification; thus, there exists a need to provide an architectural mechanism for lightweight, rapid and interoperable translation of security credentials from an original format to a format understandable by recipients.

    This thesis contributes the development of a delegation framework that utilizes a mechanism for determining and acquiring only required rights and credentials for completing a task, when they are needed. This is what we call an on-demand delegation framework that realizes a bottom-up delegation model and provides a just-in-time acquisition of rights for restricted and dynamic delegation.

    In this thesis, we further contribute the development of a credential mapping mechanism using off-the-shelf standards and technologies. This mechanism provides support for an on-the-fly exchange of different types of security credentials used by the security mechanisms of existing grids.

  • 2876.
    Ahsant, Mehran
    et al.
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Basney, Jim
    Workflows in Dynamic and Restricted Delegation2009In: 2009 INTERNATIONAL CONFERENCE ON AVAILABILITY, RELIABILITY, AND SECURITY (ARES), New York: IEEE , 2009, p. 17-24Conference paper (Refereed)
    Abstract [en]

    Delegation is a key facility in dynamic, distributed and collaborative environments like e rids and enables an effective use of a wide range of dynamic applications. Traditional delegation frameworks approach a top-down model of delegation for delegating rights from a superior to a subordinate in advance before a delegate starts off a delegated task. However, a top-down model of delegation cannot meet all the requirements of dynamic execution of distributed applications, as in such environments. required access rights for completing a task cannot easily be anticipated in advance. Delegating fewer rights than required for completing a task may cause the task execution to fail while delegating more rights than needed may threaten abuse by malicious parties. It is therefore reasonable and more robust to utilize a mechanism that allows determining and acquiring only required rights and credentials for completing a task, when they are needed. This is what we call an on-demand delegation framework, which realizes a bottom-up delegation model and provides a just-in-time acquisition of rights for a restricted and dynamic delegation. In this paper we elaborate the concept of bottom-up delegation and describe how an on-demand delegation framework can leverage workflows to meet the requirements of the least privileges principle. We also discuss the vital need for dynamic and adaptive scientific workflows to support an on-demand delegation framework. We present three different models or bottom-up delegation, which cover a wide range or usage scenarios in Grids and dynamic collaborative environments. Using a standard RBAC authorization model and a graph-based workflow model (DAG), we define and analyze a formal model of our proposed bottom-up delegation approach.

  • 2877.
    Ahsant, Mehran
    et al.
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Basney, Jim
    Johnsson, Lennart
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Dynamic, Context-Aware, Least-Privilege Grid Delegation2007In: 8th IEEE/ACM International Conference on Grid Computing, New York: IEEE , 2007, p. 209-216Conference paper (Refereed)
    Abstract [en]

    Performing delegation in large scale, dynamic and distributed environments with large numbers of shared resources is more challenging than inside local administrative domains. In dynamic environments like Grids, on one hand, delegating a restricted set of rights reduces exposure to attack but also limits the flexibility and dynamism of the application; on the other hand, delegating all rights provides maximum flexibility but increases exposure. This issue has not yet been adequately addressed by current Grid security mechanisms and is becoming a very challenging and crucial issue for future Grid development. Therefore, providing an effective delegation mechanism which meets the requirements of the least privilege principle is becoming an essential need. Furthermore, we are witnessing a phenomenal increase in the automation of organizational tasks and decision making, as well as the computerization of information related services, requiring automated delegation mechanisms. In order to meet these requirements we introduce an Active Delegation Framework which extends our previous work on on-demand delegation, making it context-aware. The framework provides a just-in-time, restricted and dynamic delegation mechanism for Grids. In this paper we describe the development of this framework and its implementation and integration with the Globus Toolkit.

  • 2878.
    Ahsant, Mehran
    et al.
    KTH, Superseded Departments, Numerical Analysis and Computer Science, NADA.
    Mulmo, Olle
    KTH, Superseded Departments, Numerical Analysis and Computer Science, NADA.
    Basney, Jim
    University of Illinois.
    Grid Delegation Protocol2004In: Workshop on Grid Security Practice and Experience, 2004, p. 81-91Conference paper (Refereed)
    Abstract [en]

    We propose a delegation protocol based on the WS-Trust specification, which is applicablefor a wide range of Grid applications. The protocol is independent of underlying securitymechanisms and is therefore applicable to all security mechanisms of common use in Gridenvironments, such as X.509 proxy certificates, Kerberos based delegation, and SAML assertions.We emphasize that this is work in progress. In this paper, we document our thoughtsand current strategy, and we solicit comments and feedback on our approach.

  • 2879.
    Ahsant, Mehran
    et al.
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Mulmo, Olle
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Johnsson, Lennart
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Basney, Jim
    Lee, Adam J.
    Toward An On-demand Restricted Delegation Mechanism for Grids2006In: 2006 7TH IEEE/ACM INTERNATIONAL CONFERENCE ON GRID COMPUTING, New York: IEEE , 2006, p. 152-159Conference paper (Refereed)
    Abstract [en]

    Grids are intended to enable cross-organizationalinteractions which makes Grid security a challenging and nontrivialissue. In Grids, delegation is a key facility that canbe used to authenticate and authorize requests on behalf ofdisconnected users. In current Grid systems there is a tradeoffbetween flexibility and security in the context of delegation.Applications must choose between limited or full delegation: onone hand, delegating a restricted set of rights reduces exposure toattack but also limits the flexibility/dynamism of the application;on the other hand, delegating all rights provides maximumflexibility but increases exposure. In this paper, we propose anon-demand restricted delegation mechanism, aimed at addressingthe shortcomings of current delegation mechanisms by providingrestricted delegation in a flexible fashion as needed for Grid applications.This mechanism provides an ontology-based solutionfor tackling one the most challenging issues in security systems,which is the principle of least privileges. It utilizes a callbackmechanism, which allows on-demand provisioning of delegatedcredentials in addition to observing, screening, and auditingdelegated rights at runtime. This mechanism provides supportfor generating delegation credentials with a very limited andwell-defined range of capabilities or policies, where a delegatoris able to grant a delegatee a set of restricted and limited rights,implicitly or explicitly.

  • 2880.
    Ahsant, Mehran
    et al.
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Mulmo, Olle
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Nefedova, V.
    Ananthakrishnan, R.
    Liming, L.
    Madduri, R.
    Pearlman, L.
    Siebenlist, F.
    Streamlining Grid Operations: Definition and Deployment of a Portal-based User Registration Service2006In: Journal of Grid Computing, ISSN 1572-9814, Vol. 4, no 2, p. 135-144Article in journal (Refereed)
    Abstract [en]

    Manual management of public key credentials can be a significant and often off-putting obstacle to Grid use, particularly for casual users. We describe the Portal-based User Registration Service (PURSE), a set of tools for automating user registration, credential creation, and credential management tasks. PURSE provides the system developer with a set of customizable components, suitable for integration with portals, that can be used to address the full lifecycle of Grid credential management. We describe the PURSE design and its use in portals for two systems, the Earth System Grid data access system and the Swegrid computational Grid. In both cases, the user is entirely freed from the need to create or manage public key credentials, thus simplifying the Grid experience and reducing opportunities for error. We argue that this capturing of common use cases in a reusable ‘solution’ can be a model for how Grid ease-of-use can be addressed in other domains as well.

  • 2881.
    Ahsant, Mehran
    et al.
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Surridge, Mike
    Leonard, Thomas
    Krishna, Ananth
    Mulmo, Olle
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Dynamic Trust Federation in Grids2006In: Trust Management, Proceedings / [ed] Stolen, K; Winsborough, WH; Martinelli, F; Massacci, F, 2006, Vol. 3986, p. 3-18Conference paper (Refereed)
    Abstract [en]

    Grids are becoming economically viable and productive tools. They provide a way of utilizing a vast array of linked resources such as computing systems, databases and services online within Virtual Organizations (VO). However, today's Grid architectures are not capable of supporting dynamic, agile federation across multiple administrative domains and the main barrier, which hinders dynamic federation over short time scales is security. Federating security and trust is one of the most significant architectural issues in Grids. Existing relevant standards and specifications can be used to federate security services, but do not directly address the dynamic extension of business trust relationships into the digital domain. In this paper we describe an experiment which highlights those challenging architectural issues and forms the basis of an approach that combines a dynamic trust federation and a dynamic authorization mechanism for addressing dynamic security trust federation in Grids. The experiment made with the prototype described in this paper is used in the NextGRID(1) project to define the requirements of next generation Grid architectures adapted to business application needs.

  • 2882.
    Ahsant, Mehran
    et al.
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Talavera González, Esteban
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Basney, Jim
    Security Credential Mapping in Grids2009In: 2009 INTERNATIONAL CONFERENCE ON AVAILABILITY, RELIABILITY, AND SECURITY (ARES), New York: IEEE , 2009, p. 481-486Conference paper (Refereed)
    Abstract [en]

    Federating security and trust is one of the most significant architectural requirements in grids. In this regard, one challenging issue is the cross-organizational authentication and identification. Organizations participated in Virtual Organizations (VOs) may use different security infrastructures that implement different authentication and identification protocols. Thus, arises an architectural need to provide a mechanism for a lightweight, rapid and interoperable translation of security credentials from an original format to a format understandable by recipients. In this paper, we describe the development and the implementation of an architecture for credential mapping in grids using off-the-shelf technologies and standard specifications. Our open-source implementation of this architecture provides support for an on-the-fly exchange for different types of security credentials used by diverse grid security infrastructures'.

  • 2883.
    Ahsin, Tafzeel ur Rehman
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Cooperative Communications: Link Reliability and Power Efficiency2012Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Demand for high data rates is increasing rapidly for the future wireless generations, due to the requirement ofubiquitous coverage for wireless broadband services. More base stations are needed to deliver these services, in order tocope with the increased capacity demand and inherent unreliable nature of wireless medium. However, this would directly correspond to high infrastructure costand energy consumption in cellular networks. Nowadays, high power consumption in the network is becoming a matter of concern for the operators,both from environmental and economic point of view.

    Cooperative communications, which is regarded as a virtual multi-input-multi-output (MIMO) channel, can be very efficient in combating fading multi-path channels and improve coverage with low complexity and cost. With its distributed structure, cooperativecommunications can also contribute to the energy efficiency of wireless systems and green radio communications of the future. Using networkcoding at the top of cooperative communication, utilizes the network resources more efficiently.

    Here we look at the case of large scale use of low cost relays as a way of making the links reliable, that directly corresponds to reductionin transmission power at the nodes. A lot of research work has focused on highlighting the gains achieved by using network codingin cooperative transmissions. However, there are certain areas that are not fully explored yet. For instance, the kind of detectionscheme used at the receiver and its impact on the link performance has not been addressed.The thesis looks at the performancecomparison of different detection schemes and also proposes how to group users at the relay to ensure mutual benefit for the cooperating users.Using constellation selection at the nodes, the augmented space formed at the receiver is exploited for making the links more reliable. Thenetwork and the channel coding schemes are represented as a single product code, that allows us to exploit the redundancy present in theseschemes efficiently and powerful coding schemes can also be designed to improve the link performance.

    Heterogeneous network deployments and adaptive power management has been used in order to reduce the overall energy consumption in acellular network. However, the distributed structure of nodes deployed in the network, is not exploited in this regard. Here we have highlightedthe significance of cooperative relaying schemes in reducing the overall energy consumption in a cellular network.  The role of differenttransmission and adaptive resource allocation strategies in downlink scenarios have been investigated in this regard.It has been observed that the adaptive relaying schemes can significantly reduce the total energy consumption as compared to the conventionalrelaying schemes. Moreover, network coding in these adaptive relaying schemes, helps in minimizing the energy consumption further.The balance between the number of base stations and the relays that minimizes the energy consumption, for each relaying scheme is also investigated.

  • 2884.
    Ahsin, Tafzeel ur Rehman
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Link Reliability in Cooperative Relaying Using Network Coding2010Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Demand for high data rates is increasing rapidly for future wireless systems.This trend is due to the increase in the number of mobile subscribers that need bandwidth hungry multimedia applications anywhere, anytime. Fourth generation cellular systems like IMT-advanced are being developed to meet these requirements. The unreliable nature of the wireless medium is one of the main hinderance in providing high data rates. Cooperative communication in cellular networks is emerging as a new paradigm to deal with the channel impairments. User cooperation via fixed relays in cellular systems form multiple access relay channels (MARCs) and provide an effective and cost efficient solution to achieve spatial diversity gains. Network resources can be utilized efficiently by using network coding at cooperating nodes.

    A lot of research work has focused on highlighting the gains achieved by using network coding in MARCs. However, there are certain areas that are not fully explored yet. For instance, the kind of the detection scheme used at the base station receiver and its impact on the link performance has not been addressed. In most cases, the outage probability has been used as a performance measure of MARCs. However, it is well known that the outage probability gives information about the signal availability, but it does not give the complete picture about the reliability of the link and the achieved quality of service.

    This thesis work looks at the link performance, in terms of symbol error probability, of multiple access relay channels that employ network coding at the relay node. Different types of detection schemes are considered and their performance is compared under different link conditions. Analytical expressions for the average symbol error probability of the cooperating users are derived. Focusing on the uplink of cellular systems, certain rules are devised on how to group users at relay node to ensure mutual benefit for the cooperating users. As a way of improving the link performance of multiple access relay channels and their robustness, the thesis considers constellation selection for the different branches. This method takes advantage of the redundancy between the transmitted symbols created by network coding and the augmented signal space obtained at the base station receiver. The obtained results show that, with a proper selection of the constellation sets, the link performance of MARCs can be improved. The thesis further looks at the interaction between the channel coding schemes of the cooperating users and network coding. It is shown that joint channel-network coding in MARCs can be seen as a product code. This new representation provides considerable flexibility in selecting efficient decoding algorithms at the base station receiver and gives the possibility to use more powerful network coding schemes for MARCs.

  • 2885.
    Ahsin, Tafzeel Ur Rehman
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Ben Slimane, Slimane
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Constellation Selection in Network Coded Distributive Antenna System2009In: GLOBECOM 2009 - 2009 IEEE Global Telecommunications Conference / [ed] Ulema M, IEEE , 2009, p. 342-346Conference paper (Refereed)
    Abstract [en]

    Relays can improve wireless links by providing an extra path to the direct path which together form a virtual multiple antenna system. Network Coded-Distributive Antenna System (NC-DAS) and Plain-Distributive Antenna System (P-DAS) are examples of realizations of such scenario. Although the asymptotic diversity gain for both the schemes is comparable, the network coded scheme can further take advantage of the redundancy and the extra dimension provided by the relay link. This extra signal dimension can be very useful when multilevel modulation is employed as it gives the possibility for a better spread of the modulation signal points within the augmented signal space. This article presents a simple and effective Constellation Selection (CS) scheme for all the three links within the NC-DAS system. This selection procedure improves the bit error probability in both AWGN and Rayleigh fading channels. Two different detections schemes are considered in the paper. Joint detection where the both users are decoded simultaneously and detection with successive cancelation where the strongest user is detected first followed by cancelation and maximum ratio combining. Analytical expressions for the error probability supported by simulation results are presented. The obtained results show that constellation selection provides good performance gain as compared to the case of same constellation.

  • 2886.
    Ahsin, Tafzeel Ur Rehman
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Ben Slimane, Slimane
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Energy Efficiency using Cooperative Relaying2011In: 2011 IEEE 22nd International Symposium On Personal Indoor And Mobile Radio Communications (PIMRC), New York: IEEE , 2011, p. 1698-1702Conference paper (Refereed)
    Abstract [en]

    The rising demand for the high data rates in the future cellular systems, is directly linked with the power consumption at the transmitting nodes. Due to the various economical and environmental factors, it is becoming difficult to maintain the current rate of power consumption per unit of data, for the upcoming generations of the cellular systems. This has shifted the focus of many researchers towards the energy efficiency aspect of the cellular systems and power consumption has become an important design parameter in the recent works. In this article, we propose the use of cooperative communications using low cost fixed relays, in order to reduce the energy consumption at the transmitting nodes for a given quality of service requirement. It has been investigated that, how different factors, such as cell radius, relay position, number of relays and target data rate effects the area energy consumption for the different relaying schemes. It has been shown that, the cooperative relaying schemes along with adaptive resource allocation provides minimum energy consumption along with the better coverage as compared to the non adaptive cooperative relaying schemes.

  • 2887.
    Ahsin, Tafzeel ur Rehman
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Ben Slimane, Slimane
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Network coding based on product codes in cooperative relaying2010In: IEEE Wireless Communications and Networking Conference 2010, WCNC 2010, 2010Conference paper (Refereed)
    Abstract [en]

    Employing network coding at the relay in cooperative relay system can improve the system throughput. However, XOR based network coding does not provide a strong error correction capability that can be used at the base station (receiver) in decoding the information of the cooperating users. Instead a block code can be used to combine the received user packets at the relay station where only the extra redundancy of the block code are forwarded by the relay station. With this structure a better error correction capability is embedded to the network coding scheme providing a better help to the receiver when decoding the user information. Combining this network coding structure with the individual block codes of the users, an overall product code can be obtained which gives the possibility of generating more powerful overall codes and increases the correction capability of the decoding process at the receiver. The obtained results show that the proposed scheme outperforms the conventional XOR based network coding scheme and gives the possibility of combining more users in the cooperation process.

  • 2888.
    Ahsin, Tafzeel ur Rehman
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Slimane, Ben
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Detection strategies in cooperative relaying with network coding2010In: IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC, 2010, p. 12-17Conference paper (Refereed)
    Abstract [en]

    Network coding in cooperative relaying can improve the performance of both users and provide improved efficiency as compared to the conventional relaying. This paper considers different detection schemes for cooperative relaying with network coding. Analytical upper bounds on the bit error probability are derived and used to assess the performance of the different schemes. The obtained results show that simple and low complexity detectors can provide good performance, quite close to that of joint detection.

  • 2889.
    Ahsin, Tafzeel Ur Rehman
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Slimane, Ben
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Energy efficient resource allocation and deployment strategies for wireless networks2012In: 2012 5th International Conference on New Technologies, Mobility and Security - Proceedings of NTMS 2012 Conference and Workshops, IEEE , 2012, p. 6208715-Conference paper (Refereed)
    Abstract [en]

    Future wireless systems are being designed for extremely high data rates and are directly contributing to the global energy consumption. This trend is undesirable not only due to the environmental concerns, but to cost as well since energy costs are becoming a significant part of the operating expenditures for the telecom operators. Recently, energy efficient wireless systems have become a new research paradigm. Cooperative communication has shown good potential in improving coverage, providing robust radio links, reducing infrastructure cost, and has the possibility to reduce the total system energy consumption. This paper looks at possible deployment strategies for wireless networks that can reduce the energy consumption. We look at the tradeoff between the number of relay nodes and the number of base stations and their implications on the total energy consumption of wireless networks. The obtained results show that adaptive resource allocation between the base station and the relay node is an efficient way of reducing the energy consumption of the system. Furthermore, this reduction in energy consumption increases with increasing the system target spectral efficiency.

  • 2890.
    Ahteensuu, Marko
    KTH.
    Kai Horsthemke: Animals and African Ethics: Palgrave Macmillan, 2015. xi + 187pp. £60.00. isbn 978-0-230-57686-52016In: Theoria, ISSN 0040-5825, E-ISSN 1755-2567, Vol. 82, no 3, p. 288-294Article, book review (Other academic)
  • 2891. Ahtiainen, Heini
    et al.
    Artell, Janne
    Czajkowski, Mikolaj
    Hasler, Berit
    Hasselström, Linus
    Enveco Environmental Economics Consultancy, Sweden.
    Huhtala, Anni
    Meyerhoff, Jürgen
    Smart, James C.R.
    Söderqvist, Tore
    Alemu, Muhammed H.
    Angeli, Daija
    Dahlbo, Kim
    Fleming-Lehtinen, Vivi
    Hyytiäinen, Kari
    Karloseva, Aljona
    Khaleeva, Julia
    Maar, Marie
    Martinsen, Louise
    Nommann, Tea
    Pakalniete, Kristine
    Oskolokaite, Ieva
    Semeniene, Daiva
    Benefits of meeting nutrient reduction targets for the Baltic Sea: a contingent valuation study in the nine coastal states2014In: Journal of Environmental Economics and Policy, ISSN 2160-6544, E-ISSN 2160-6552, Vol. 3, no 3, p. 278-305Article in journal (Refereed)
  • 2892. Ahtiainen, Heini
    et al.
    Artell, Janne
    Czajkowski, Mikolaj
    Hasler, Berit
    Hasselström, Linus
    Enveco Environmental Economics Consultancy, Ltd., Sweden.
    Hyytiäinen, Kari
    Meyerhoff, Jürgen
    Smart, James C.R.
    Söderqvist, Tore
    Zimmer, Katrin
    Khaleeva, Julia
    Rastrigina, Olga
    Tuhkanen, Heidi
    Public preferences regarding use and condition of the Baltic Sea: An international comparison informing marine policy2013In: Marine Policy, ISSN 0308-597X, E-ISSN 1872-9460, no 42, p. 20-30Article in journal (Refereed)
  • 2893. Ahtiainen, Heini
    et al.
    Artell, Janne
    Elmgren, Ragnar
    Hasselström, Linus
    Enveco.
    Håkansson, Cecilia
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms).
    Baltic Sea nutrient reductions: What should we aim for?2014In: Journal of Environmental Management, ISSN 0301-4797, E-ISSN 1095-8630, Vol. 145, p. 9-23Article in journal (Refereed)
    Abstract [en]

    Nutrient load reductions are needed to improve the state of the Baltic Sea, but it is still under debate how they should be implemented. In this paper, we use data from an environmental valuation study conducted in all nine Baltic Sea states to investigate public preferences of relevance to three of the involved decision-dimensions: First, the roles of nitrogen versus phosphorus reductions causing different eutrophication effects; second, the role of time – the lag between actions to reduce nutrient loads and perceived improvements; and third; the spatial dimension and the roles of actions targeting the coastal and open sea environment and different sub-basins. Our findings indicate that respondents view and value the Baltic Sea environment as a whole, and are not focussed only on their local sea area, or a particular aspect of water quality. We argue that public preferences concerning these three perspectives should be one of the factors guiding marine policy. This requires considering the entire range of eutrophication effects, in coastal and open sea areas, and including long-term and short-term measures.

  • 2894.
    Ahuja, Dipali
    et al.
    Univ Limerick, Synth & Solid State Pharmaceut Ctr, Bernal Inst, Dept Chem Sci, Castletroy, Co Limerick, Ireland..
    Svärd, Michael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Transport Phenomena. Univ Limerick, Synth & Solid State Pharmaceut Ctr, Bernal Inst, Dept Chem Sci, Castletroy, Co Limerick, Ireland..
    Rasmuson, Åke C.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Transport Phenomena. Univ Limerick, Synth & Solid State Pharmaceut Ctr, Bernal Inst, Dept Chem Sci, Castletroy, Co Limerick, Ireland..
    Investigation of solid-liquid phase diagrams of the sulfamethazine-salicylic acid co-crystal2019In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 21, no 18, p. 2863-2874Article in journal (Refereed)
    Abstract [en]

    The influence of temperature and solvent on the solid-liquid phase diagram of the 1 : 1 sulfamethazinesalicylic acid co-crystal has been investigated. Ternary phase diagrams of this co-crystal system have been constructed in three solvents: methanol, acetonitrile and a 7 : 3 (v/v) dimethylsulfoxide-methanol mixture, at three temperatures. The system exhibits congruent dissolution in acetonitrile and the co-crystal solubility has been determined by a gravimetric technique. The Gibbs energy of co-crystal formation from the respective solid components has been estimated from solubility data, together with the corresponding enthalpic and entropic component terms. The Gibbs energy of formation ranges from -5.7 to -7.7 kJ mol -1, with the stability increasing with temperature. In methanol and the DMSO-methanol mixture, the co-crystal dissolves incongruently. It is shown that the solubility ratio of the pure components cannot be used to predict with confidence whether the co-crystal will dissolve congruently or incongruently. The size of the region where the co-crystal is the only stable solid phase is inversely related to the pure component solubility ratio of salicylic acid and sulfamethazine.

  • 2895. Ahuja, R.
    et al.
    Arwin, H.
    da Silva, A. F.
    Persson, Clas
    Osorio-Guillen, J. M.
    de Almeida, J. S.
    Araujo, C. M.
    Veje, E.
    Veissid, N.
    An, C. Y.
    Pepe, I.
    Johansson, Börje
    Electronic and optical properties of lead iodide2002In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 92, no 12, p. 7219-7224Article in journal (Refereed)
    Abstract [en]

    The electronic properties and the optical absorption of lead iodide (PbI2) have been investigated experimentally by means of optical absorption and spectroscopic ellipsometry, and theoretically by a full-potential linear muffin-tin-orbital method. PbI2 has been recognized as a very promising detector material with a large technological applicability. Its band-gap energy as a function of temperature has also been measured by optical absorption. The temperature dependence has been fitted by two different relations, and a discussion of these fittings is given.

  • 2896. Ahuja, R.
    et al.
    Dubrovinsky, L.
    Dubrovinskaia, N.
    Guillen, J. M. O.
    Mattesini, M.
    Johansson, Börje
    KTH, Superseded Departments, Materials Science and Engineering.
    Le Bihan, T.
    Titanium metal at high pressure: Synchrotron experiments and ab initio calculations2004In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 69, no 18Article in journal (Refereed)
  • 2897. Ahuja, R.
    et al.
    Eriksson, O.
    Johansson, Börje
    KTH, Superseded Departments, Materials Science and Engineering.
    Electronic and optical properties of BaTiO3 and SrTiO32001In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 90, no 4, p. 1854-1859Article in journal (Refereed)
  • 2898. Ahuja, R.
    et al.
    Eriksson, O.
    Johansson, Börje
    Theoretical high-pressure studies of Cs metal2001In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 6301, no 1Article in journal (Refereed)
  • 2899. Ahuja, R.
    et al.
    Eriksson, O.
    Johansson, Börje
    Theoretical study of the high-pressure orthorhombic TlI-type phase in NaBr and NaI2001In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 6309, no 9Article in journal (Refereed)
  • 2900. Ahuja, R.
    et al.
    Eriksson, O.
    Wills, J. M.
    Johansson, Börje
    Electronic structure of Ti3SiC22000In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 76, no 16, p. 2226-2228Article in journal (Refereed)
55565758596061 2851 - 2900 of 124286
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