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  • 301.
    Abdul Abas, Riad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Hayashi, Miyuki
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Thermal Diffusivity Measurements of some Industrially Important Alloys by a Laser Flash Method2007In: International journal of materials reseach, ISSN 1862-5282, Vol. 98, no 6, p. 535-540Article in journal (Refereed)
    Abstract [en]

    In the present work, thermal diffusivity measurements of three industrially significant alloys, viz. 90Ti.6Al.4V, stainless steel with 25Cr and 6Ni as well as plain carbon steel with 0.7 % carbon have been carried out as a function of temperature. The aim of this work is to study the effect of temperature and microstructure on the thermal diffusivities of these alloys. For the 90Ti.6Al.4V alloy, thermal diffusivity increases with temperature below 1225 K. Above this temperature, the values started decreasing probably due to the dissolution of Ti3Al intermediate phase in the matrix, which would result in an increase in the disorder of the structure. For 25Cr: 6Ni stainless steel, the thermal diffusivity is nearly constant up to about 700 K. Above this, there is an increase in the thermal diffusivities with temperature during the heating cycle, which was reproducible during thermal cycling. On the other hand, the slope of the curve increases above 950 K.

    In the case of the 0.7 % carbon steel, the thermal diffusivity shows a decreasing trend with temperature below the Curie point for the alloy, where the alloy consists of bcc + fcc phases. Above this point, only the fcc phase is prevalent and the thermal diffusivity was found to increase with temperature. Heat transfer is carried out by lattice vibration (phonons) as well as electrons. The contribution of electrons varies depending upon the type of alloy. In this study, the highest electron contribution was found in 0.7 % carbon steel, while the lowest was in stainless steel. The thermal conductivity values of these alloys are in good agreement with the calculated values using the model proposed by Mills.

  • 302.
    Abdul Abas, Riad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jakobsson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Hayashi, Miyuki
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Studies on Graphitisation of Blast Furnace Coke by X-ray Diffraction Analysis and Thermal Diffusivity Measurements2005In: Steel research, ISSN 0177-4832, Vol. 77, no 11, p. 763-769Article in journal (Refereed)
    Abstract [en]

    High temperature XRD and thermal diffusivity experiments were employed to investigate the degree of graphitisation in blast furnace coke. The experiments were conducted between room temperature and 1473 K. X-ray diffraction studies were carried out in order to monitor the degree of graphitisation in the coke samples from the same campaign. In these cases, the degree of graphitisation was followed by the changes in the vertical dimension. The degree of graphitisation was found to be dependent on temperature. On the other hand, the graphitisation at each temperature was instantaneous, even at as low a temperature as 973 K and no dependency on time could be noticed. The thermal diffusivities of the coke samples taken from deeper level of the experimental blast furnace were measured using the laser-flash technique. The results from these measurements showed that thermal diffusivities increased with the degree of graphitisation, which in turn, can be affected by the level in the blast furnace at which the coke sample was taken. The present results indicate that the degree of graphitisation as followed by X-ray diffraction analysis as well as thermal diffusivities can be used to trace the thermal history of coke. DSC measurements show that the heat capacity of the coke increases with temperature towards the heat capacity of graphite, which could be due to the increasing the graphitisation degree of the coke.

  • 303.
    Abdul Abas, Riad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Thermal Diffusivity of Sintered Stainless steel-Alumina Composite2006In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 37, no 4, p. 513-518Article in journal (Refereed)
    Abstract [en]

    Thermal diffusivity measurements were carried out as a function of temperature on sintered AISI 304 stainless steel-alumina composites having various compositions (0.001, 0.01, 0, 1, 1, 2, 3, 5, 7, 8, and 10 wt pct Al2O3). The measurements were carried out between room temperature and 1473 K. The thermal diffusivity and the thermal conductivity were found to increase with temperature in all the composite specimens. The thermal diffusivity was found to decrease with increasing weight fraction of alumina. This tendency can clearly be seen at temperatures above 755 K. The experimental results are in good agreement with the simple rule of mixture, the Eucken equation, and the Ohm’s law model developed by Hayashi et al. at weight fractions of alumina below 5 wt pct. Beyond this composition, the thermal diffusivity/conductivity shows a large discrepancy from the models. This could probably be attributed to the accumulation of alumina particles during cooled pressing and sintering.

  • 304.
    Abdul Al, Fatima
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Urban and Regional Studies.
    Alla barns lekplats: En studie om tillgängligheten på lekplatser2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Sweden is one of the leading countries when it comes to availability in the physical environment. Approximately 7 000 children in Sweden are disabled. Half of these children use a wheelchair. It is every child’s right to play, and it’s thereby interesting to know whether every child is given the opportunity to use a playground. In the county of Helsingborg there are playgrounds appealing to many children, although the question is whether every child is given the chance to play at these playgrounds.

    The aim of this study is to highlight the importance of availability at playgrounds and outline ways to improve the availability. The method used in this thesis is a literature study, focusing on legal framework and literature about availability, usability and playgrounds. The case study provides information about eight playgrounds in Helsingborg. There is also an interview with landscape architect Johanna Elgström.

    Playgrounds where availability has been prioritized are often more available and useable for wheelchair-bound children. Still, the legal framework is in need of a more precise definition of availability and usability to ensure that playgrounds are suitable for children using a wheelchair. The playgrounds that are more available and useable can favor children using a wheelchair and give them the opportunity to socially interact with other children.

  • 305.
    Abdul Amir, Saga
    KTH, School of Engineering Sciences (SCI).
    Hur skapas en filmsuccé: En analys av inhemska filmintäkter i USA2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis seeks to examine, through the method of linear regression, if the profits of a movie can be predicted using information known prior to the release of the movie. The predictive variables were obtained from a dataset containing information available on the website IMDB. The films were split up into two groups and two different models were created: one for films with an experienced director and lead actor and one where experince wasn't taken into consideration. The results showed that while budget is consistently the driving factor for a films success, the involvement of an experienced director make predictions of success much easier.

  • 306.
    Abdul Aziz Hasan Ali, Aamir
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Shahzad, Muhammad Adil
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    A Joint Subcarrier/Power allocation Scheme for OFDMA-based Cellular Networks2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The assignment of this master thesis consists of initiating power, subcarrier allocation in a dynamic FFR based scheme designed for multi-cell OFDMA networks and to enhance the throughput of all center users in bandwidth hungry borrower cells (overloaded cells) which was previously degraded by original FFR3 scheme as a result of partitioning of system bandwidth into center and edge bands respectively. The method uses band borrowing to compensate center user’s throughput loss in a semi and fully overloaded system. The scheme uses dynamic programming method (0/1 knapsack problem) to bargain an edge band on various power levels and tends to check the best combination (power and sub-carrier) which the system can utilize while still maintaining acceptable throughput loss for the users at the edge of the neighboring cell (lender cell).

    The algorithm consists of generating a borrowing request to neighboring cells for utilizing their edge bands by the overloaded borrower cell if their average center user throughput reaches below a minimum threshold value set in the system. The borrowing method uses 0/1 knapsack problem to capture an edge band based on limiting factors of total cost in average throughput losses by neighbors (Ci) and Un (tolerable mean user edge user throughput loss by lending cell). While solving knapsack problem the lender (neighbors) will check Ci and Un before granting the right to use its edge band. The later stage requires reducing subcarrier power level in order to utilize the lenders edge band using "soft borrower" mode. The borrowed sub-carriers will be activated take power from the original center band sub-carriers of the overloaded cell by taking into account the interference between the lender and the borrower. In case of negative (0) reply from the lender cell after the first request, multiple requests are generated at reduce power level at every step to order to acquire more bands. If a neighbor has band borrowing requests from multiple overloaded base stations, the band will be granted to the one which gives minimal loss in terms of throughput to the lender cell.

    The simulation results are analyzed w.r.t reuse-1 and FFR3 scheme of a multi cell regular and irregular scenarios comprising of lightly to heavily overloaded cells with various subcarrier allocation patterns. An overhead and time assessment is also presented between borrower and lender cells. Simulation results show an increase of 60% in center user’s throughput w.r.t original FFR3 scheme with an acceptable loss of 18% at the edges in complex overloaded scenarios while the overall system throughout increases by 35%.

  • 307.
    Abdul Hamid, Kamila
    Linnaeus University, Faculty of Technology, Department of Informatics.
    Gränssnittets betydelse i främjandet av kognitiv bearbetning: En undersökning om praktisk utnyttjande av designprinciper i skapandet av webbgränssnitt2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Många webbgränssnitt idag misslyckas med att möta användarnas behov och blir därför bristfälliga gällande användarvänligheten. Detta leder till att användarna begår stora misstag och anstränger sig vid användningen av webbaserade system. Visuell design och struktur i ett gränssnitt spelar en stor roll i hur användarna förstår sig på och tolkar ett gränssnitt då de avser hur olika beteenden och information kommuniceras till användarna. I denna studie undersöks hur visuell design, struktur och användbarhet i ett gränssnitt underlättar användarnas kognitiva bearbetning av information vid utförande av komplexa uppgifter. Studien har utförts genom ett uppdrag för Ahltorpmedia AB, som skapar lösningar för bl.a. webbplatser, webbaserade system och e-handel. Uppdraget har varit att förbättra en av deras egen utvecklade tjänst Nuhet som är bristfällig gällande områdena ovan.

     

    Först har en heuristisk utvärdering av Nuhets befintliga gränssnitt samt sju intervjuer med tjänstens befintliga- och potentiella användare inom huvudområdena visuell design, struktur och kognitiv bearbetning av information gjorts. Resultaten från intervjuerna och utvärderingen har använts för att bilda en persona varefter fokusområden för prototyparbetet har skapats. Sedan har en prototyp på Nuhets nya utseende och en ny funktionalitet skapats. Designprinciper för användbarhet samt gestaltlagar har nyttjats i skapandet av Nuhets nya gränssnitt.

     

    Utifrån de metoder som har genomförts i detta examensarbete har det framkommit att det beror på flera faktorer gällande hur användarnas kognitiva bearbetning av information underlättas med hjälp av visuell design, struktur och användarvänlighet. Dessa är då en bra struktur, gruppering och organisering av innehåll i ett gränssnitt. Dessutom är det tydliga kontraster, bra färgval och standardisering som underlättar den. 

  • 308.
    Abdul Hayee, Muhammad
    KTH, School of Chemical Science and Engineering (CHE).
    Characterization and utilization of agroforestryresidues as energy source in Brazil2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Brazil is very much rich in agriculture and forestry. The agro industry occupies an area of 28840726 ha. The more important crops are sugarcane (7080920 ha), rice (289030 ha), wheat (1853220 ha), coconut (283205 ha), cassava (1894460 ha), corn (13767400 ha) and grass (140000 ha). These crops generated 597 million tons of residues. Forest plantations in Brazil supplied 102.9 million m3 of industrial roundwood, of which nearly half is for renewable fuelwood and charcoal. Part of this plantation output is destined for the pulp and paper industry:

    The renewable sources are fulfilling 46.4% of the total Brazilian energy demands.

    Energy forestation in Brazil includes mainly Eucalyptus and Bracatingas.

    In this study three biomasses abundant in the Brazil are studied:  i.e. Eucalyptus, Garapeira/Peroba (wood dust) and Sewage Sludge.

    The wood samples (Eucalyptus and Peroba/Garapeira) have higher heating value than the sewage sludge because the wood samples have higher amounts of carbon and hydrogen than the sewage sludge. The sewage sludge has higher ash content and lower amount of volatiles and fixed carbon than the wood samples resulting in a lower heating value.

    The pyrolysis of eucalyptus, garapeira/peroba and sewage sludge has been studied in a thermobalance over a wide range of degradation temperatures. Between 225 °C - 375 °C (for eucalyptus) and 225 °C - 425 °C (for garapeira), the thermal decomposition of the biomass leads to significant weight loss.

    The weight loss for Eucalyptus between 265°C and 350°C is 0.48 % / °C and taking into account a heating rate of 10°C/min, the weight loss is 4.8 % /min. Garapeira has a similar behaviour than eucalyptus. The weight loss for garapeira between 265°C and 365°C is 0.4 % / °C and taking into account a heating rate of 10°C/min, the weight loss is 4 % /min.

    The behaviour of the sewage sludge to the increase of temperature from 25°C to 700 °C in an inert atmosphere do not show such different zones as the behaviour of the woody biomass. Between 150 °C and 235°C the weight loss of the sewage sludge was 0.07 %/°C (0.7 %/min). The highest weight loss takes place between 300 °C and 390 °C (0.15 %/°C or 1.5 %/min). In the third zone, between 500 °C and 600°C, the weight loss was 0.03 %/°C (0.3 %/min).

    The pyrolysis is assumed to be a first order decomposition. The activation energy (E) and the pre exponential factor (A) are calculated for the studied samples.

    The proximate analysis shows differences between the woody biomass and the sewage sludge. The sewage sludge has higher ash content and lower fixed carbon and volatiles. Eucalyptus has lower carbon fixed and higher volatiles than peroba-garapeira.

  • 309.
    Abdul Hussein, Murtada
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    Al-Entabe, Faysal
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    Vattenjet som poleringsmetod2016Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
  • 310.
    Abdul Khaliq, Ali
    et al.
    Örebro University, School of Science and Technology.
    Pecora, Federico
    Örebro University, School of Science and Technology.
    Saffiotti, Alessandro
    Örebro University, School of Science and Technology.
    Point-to-point safe navigation of a mobile robot using stigmergy and RFID technology2016In: 2016 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), Institute of Electrical and Electronics Engineers (IEEE), 2016, p. 1497-1504, article id 7759243Conference paper (Refereed)
    Abstract [en]

    Reliable autonomous navigation is still a challenging problem for robots with simple and inexpensive hardware. A key difficulty is the need to maintain an internal map of the environment and an accurate estimate of the robot’s position in this map. Recently, a stigmergic approach has been proposed in which a navigation map is stored into the environment, on a grid of RFID tags, and robots use it to optimally reach predefined goal points without the need for internal maps. While effective,this approach is limited to a predefined set of goal points. In this paper, we extend this approach to enable robots to travel to any point on the RFID floor, even if it was not previously identified as a goal location, as well as to keep a safe distance from any given critical location. Our approach produces safe, repeatable and quasi-optimal trajectories without the use of internal maps, self localization, or path planning. We report experiments run in a real apartment equipped with an RFID floor, in which a service robot either reaches or avoids a user who wears slippers equipped with an RFID tag reader.

  • 311.
    Abdul Malek, Nurul Aida
    et al.
    Universiti Tun Hussein Onn Malaysia (UTHM), Malaysia / Department of Production, University of Vaasa, Finland.
    Shahzad, Khuram
    Department of Production, University of Vaasa, Finland.
    Takala, Josu
    Department of Production, University of Vaasa, Finland.
    Bojnec, Stefan
    Faculty of Management, University of Primorska, Slovenia.
    Papler, Drago
    Faculty of Management, University of Primorska, Slovenia.
    Liu, Yang
    Department of Production, University of Vaasa, Finland.
    Analyzing Sustainable Competitive Advantage: Strategically Managing Resource Allocations to Achieve Operational Competitiveness2015In: Management and Production Engineering Review, ISSN 2080-8208, E-ISSN 2082-1344, Vol. 6, no 4, p. 70-86Article in journal (Refereed)
    Abstract [en]

    In today’s dynamic business environment, a key challenge for all companies is to make adaptive adjustments to their manufacturing strategy. This study demonstrates the competitive priorities of manufacturing strategy in hydro-power case company to evaluate the level of sustainable competitive advantage and also to further analyze how business strategies are aligned with manufacturing strategies. This research is based on new holistic analytical evaluation of manufacturing strategy index, sense and respond, and sustainable competitive advantage models. These models help to describe, evaluate, and optimize resource allocation to meet the performance requirements in dynamic decision making. Furthermore, these models evaluate operational competitiveness for manufacturing strategies according to the multi-criteria priority. The results show that the adjustments of competitive priorities in manufacturing strategies by implementing the proposed holistic analytical models are helpful in strategically managing business operations. The discussion derives the most critical attributes in business operations while alignment of resource allocation with competitive priorities help to strategically focus those attributes. In conclusion, we argue that resource allocation and manufacturing strategies have become the most important capabilities in a business environment where companies focus to get a sustainable competitive advantage.

  • 312.
    Abdul- Rasool, Mustafa
    KTH, School of Electrical Engineering (EES), Automatic Control.
    THE IMPACT OF ECOROLL ON FUEL CONSUMPTION - USING LOOK AHEAD2011Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    EcoRoll reduces fuel consumption with small development costs, since no additional hardware is required. It is a function that enables a more efficient conversion of potential to kinetic energy, when travelling downhill. This is achieved by opening the powertrain, and let the engine run on idle to reduce engine losses. In this Master’s thesis, two control strategies were developed, where one is based on prevailing conditions and one utilizes Look-Ahead data. Compared to a vehicle with a conventional cruise control, the first strategy gave a fuel reduction of approximately 3.4% and the other 3.7%. This was simulated on the highway between Södertälje and Norrköping in Sweden.

  • 313.
    Abdul Waheed, Malik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Thörnberg, Benny
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Cheng, Xin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Lawal, Najeem
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Imran, Muhammad
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Kjeldsberg, Per Gunnar
    NTNU.
    Generalized Architecture for a Real-time Computation of an Image Component Features on a FPGAManuscript (preprint) (Other academic)
    Abstract [en]

    This paper describes a generalized architecture for real-time component labeling and computation of image component features. Computing real-time image component features is one of the most important paradigms for modern machine vision systems. Embedded machine vision systems demand robust performance, power efficiency as well as minimum area utilization. The presented architecture can easily be extended with additional modules for parallel computation of arbitrary image component features. Hardware modules for component labeling and feature calculation run in parallel. This modularization makes the architecture suitable for design automation. Our architecture is capable of processing 390 video frames per second of size 640x480 pixels. Dynamic power consumption is 24.20mW at 86 frames per second on a Xilinx Spartran6 FPGA.

  • 314.
    Abdula, Sham
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oksman, Dan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Attefallshus som komplementbostadshus: Drömhus eller mardröm?2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Den 2 juli 2014 blev det enligt lag tillåtet för en- och tvåbostadshusägare att uppföra en bygglovsbefriad komplementbyggnad på max 25 kvadratmeter på den egna fastigheten. Rapporten undersöker vilket genomslag lagändringen har haft i Stor-Stockholm, Stor-Göteborg och Stor-Malmö. Undersökningen visar att lagändringen ännu inte har haft något stort genomslag. I rapporten undersöks även en utvald del av marknadsaktörers utbud av attefallshus avsett som komplementbostadshus. 

    Ett attefallshus utformas med miljövänligt hållbara material och inspireras av Vitruvius tre principer för god arkitektur. Huset konstrueras med avsikt att uppfylla kraven som ställs i PBL, PBF, BBR och EKS. Målet med de framtagna bygghandlingarna är att få startbesked från byggnadsnämnden i Växjö. 

  • 315.
    Abdul-Ahad, Amir Stefan
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Cürüklü, Baran
    Mälardalen University, School of Innovation, Design and Engineering.
    Mahmoud, W. A.
    Al-Isra Private University, Amman, Jordan.
    Robust distance-based watermarking for digital image2008In: Proceedings of the 2008 International Conference on Security and Management, SAM 2008, 2008, p. 404-409Conference paper (Refereed)
    Abstract [en]

    In this paper, an algorithm is developed to invisibly watermark a cover object (color image) using watermark object (iconic image). The algorithm is based on the distances among the addresses of values of the cover object. These distances use to make the embedding. The order of manipulating these distances are specified by the values of the watermark data which is dealt with serially. The algorithm serves and achieves self encryption key. Each watermark object has its unique pattern of distances at different possible lengths of distance bits. This enhances the complexity of sequential embedding. The algorithm is tested using direct and single level and double level of Two-Dimensional Discrete Wavelet Transform (2D DWT) embeddings. Two important issues are addressed. Firstly is to achieve a high Peak Signal to Noise Ratio (PSNR). The ratio was found to increase with an increasing of distance bits. Secondly is that the watermarked object retains the same properties of cover object. The algorithm shows resisting and withstanding against the most important attacks. Some of these include the lossy compression, blurring, resize and some types of Noise.

  • 316. Abdul-Ahad, Amir Stefan
    et al.
    Lindén, Maria
    Mälardalen University, School of Innovation, Design and Engineering.
    Larsson, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Mahmoud, Waleed A.
    Robust Distance-Based Watermarking for Digital Video2008In: Proceedings of The Annual SIGRAD Conference, Stockholm, 2008Conference paper (Refereed)
  • 317.
    Abdul-Ahad, Amir Stefan
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Çürüklü, Baran
    Mälardalen University, School of Innovation, Design and Engineering.
    Folke, Mia
    Mälardalen University, School of Innovation, Design and Engineering.
    Lindén, Maria
    Mälardalen University, School of Innovation, Design and Engineering.
    Indirect Wavelet-Based Cardio Arrhythmia Detection Algorithm2008In: Medicinteknikdagarna, Gothenburg, Sweden, 2008, p. 14-15Conference paper (Refereed)
  • 318.
    Abdulahi Mohamed, Abdirahman
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Aksel, Wännström
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Quality Control of Light Emitting Diodes: Using power factor, harmonic distortion and light to power ratios2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This study addresses quality control for Light Emitting Diodes (LED) according to fouraspects, the power factor of LED lamps, their harmonics and total harmonic distortion (THD), the luminosity for total power to radiated power ratio. It focuses on four brands and six different LED lamps, and concludes that IKEA's LED lamps pertain as the quality lamp, with a power factor over 0.9, THD less than 4% and a power to radiated light of over 4%. 

  • 319.
    Abdulameer, Hasanain
    et al.
    Jönköping University, School of Engineering, JTH, Civil Engineering.
    Chamoun, Kristian
    Jönköping University, School of Engineering, JTH, Civil Engineering.
    BIM i små och medelstora anläggningsföretag.2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Purpose: The purpose of this bachelor thesis is to improve the usage of BIM in facility projects.

    Method: The methods used for this bachelor thesis are qualitative interviews and literature studies.

    Findings: Free programs will be available for usage where models can be opened, viewed, examined and studied. The small and medium-sized facility companies will not be forced to use resources to cope with the requirements of Trafikverket.

    Implications: Consequences are that the small and medium-sized civil engineering companies understand and follow the requirements.

    • Using more 3D models to gain more experience and skills in the subject.

    • Attend the Trafikverkets industry days when opportunities arise, the authors believe that it was very instructive.

    • Engage in more BIM projects.

    • Older projects where the drawings are in 2D is converted into 3D.

     

    Limitations: How BIM is used during the management process will not be covered.

    Keywords: Productivity, resource, competence, experience, BIM.

  • 320.
    ABDULAZIZ, ALI ABDULBASIT
    et al.
    KTH, School of Chemical Science and Engineering (CHE).
    GHARIB ALI JALAL, IBRAHIM
    KTH, School of Chemical Science and Engineering (CHE).
    GHATTAS, ANGELIKA
    KTH, School of Chemical Science and Engineering (CHE).
    SWENSSON, BEATRICE
    KTH, School of Chemical Science and Engineering (CHE).
    Utformning av bränslecellssystem för fordon2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    I detta kandidatexamensarbete var målet att optimera ett bränslecellssystem med avseende på ett antal olika parametrar. Bränslecellssystemet var tänkt att användas i fordonet Sleipner V som är konstruerad i samarbete med andra KTH studenter. En annan bränslecell av företaget Horizon användes för att driva fordonet Sleipner i tävlingen Shell-Eco Marathon eftersom den ursprungliga bränslecellen var i dåligt skick. Sleipner utrustat med bränslecellen från Horizon klarade av att köra två varv i Shell-Eco Marathon.

    I denna rapport tas det upp grundläggande teori om bränsleceller, försökuppställning för experimenten och resultat med tillhörande analys. För att åstadkomma målet med detta arbete så skulle olika parametrar undersökas, men detta kunde inte utföras. På grund av diverse problem med bränslecellen så ändrades fokus till att reparera bränslecellen, vid undersökningen av problemen har vissa resultat uppnåtts.

    Vid körning uppstod spänningsfall och det kan ha berott på masstransportbegränsningar. För att åtgärda dessa problem utfördes en torknings- respektive fuktningsprocess som hade olika påverkan på de individuella cellerna. Efter torkningsprocessen fungerade 18 av 22 celler medan 19 celler fungerade efter fuktningsprocessen.  De icke fungerade cellerna som gav låg spänning kan ha varit för blöta eller för torra.

  • 321.
    Abdulbaki, Mohammad
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Mammar Chaouche, Abdelah
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Användning av flygaska i vattenbyggnadsbetong 2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Engineering Concrete is used as a collective term for concrete structures related to the hydropower plants, dams and heavier plants. With great success, concrete has been used for a very long time for these types of structures. These constructions make high demands on the concrete quality and construction design as they are expected to have a lifetime of a hundred years or more.

     

    In casting such concrete is exposed to a temperature which can lead to cracking of the newly cast structure. Because the temperature rise is the primary cause of cracking, you can use various methods to reduce this. An effective way to reduce the temperature rise is to try to keep the cement content in the concrete as low as possible, because at the adiabatic conditions may say that the total temperature rise is directly proportional to the cement content in the concrete. An effective way to reduce the temperature rise is to use out some fly ash instead of cement. Fly ash is a powder mass obtained in the production of electricity and heat in coal-fired plants and cogeneration plants. Fly ash is a puzzolanic material which means that it reacts with calcium hydroxide and water, and can thus partially replace cement clinker.

     

    The purpose of this report is to provide a better understanding of how the fly ash affecting hydraulic concrete. By reading this report you will get at first a basic knowledge of what the concrete, hydraulic concrete and fly ash are. Furthermore, the section that dealt with the cracking of the hydraulic concrete, general knowledge followed out causes and remedies. A comparison has been made between a typical water building structural component, with and without fly ash. What has been compared are how the construction affected with and without fly ash on strength, resistance and the risk of cracking. Furthermore, the temperature dot calculations performed with the program HACON. The purpose of the calculations was to show how the different parameters with and without fly ash affects the risk of cracking of a typical hydraulic structures.

     

    The result of the temperature calculations show that you get a lower temperature development in a monolith cast with the fly ash and the construction cements compared to a monolith molded with construction cement without fly ash. With the reduced temperature development arose lower tensions in the flyashmonolith. In the survey carried out in this report, the results show that there is tension that exceeds the tensile strength of the monolith without fly ash and thereby bursting the structure. The monolith examined with fly ash as crackreducing action occurs tensile stresses which are lower than the tensile strength and thus does not crack structure. The results show that the cracking in a typical hydraulic structures can be reduced with fly ash.

  • 322.
    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.

  • 323.
    Abdulhalim, Mohammed
    et al.
    Halmstad University, School of Business and Engineering (SET).
    Angmyr, Sebastian
    Tillämpning av Partnering vid ombyggnad av bostäder: Vad krävs för ett framgångsrikt partnering projekt?2013Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
  • 324.
    Abdul-Jalbar, Beatriz
    et al.
    Universidad de La Laguna.
    Segerstedt, Anders
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Business Administration and Industrial Engineering.
    Sicilia, Joaquín
    Universidad de La Laguna.
    Nilsson, Andreas
    A new heuristic to solve the one-warehouse N-retailer problem2010In: Computers & Operations Research, ISSN 0305-0548, E-ISSN 1873-765X, Vol. 37, no 2, p. 265-272Article in journal (Refereed)
    Abstract [en]

    We deal with a multi-echelon inventory system in which one warehouse supplies an item to multiple retailers. Customer demand arrives at each retailer at a constant rate. The retailers replenish their inventories from the warehouse that in turn orders from an outside supplier. It is assumed that shortages are not allowed and lead times are negligible. The goal is to determine replenishment policies that minimize the overall cost in the system. We develop a heuristic to compute efficient policies, which also can easily be used in a spreadsheet application. The main idea consists of finding a balance between the replenishment and the inventory holding costs at each installation. This new heuristic we compare with two other approaches proposed in the literature; the computational studies show that in most of the instances generated the new method provides lower costs.

  • 325.
    ABDUL-JALIL, CARLO
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    BEGLARYAN, SARGIS
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    Ultralätt hopfällbar reflektor2017Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Datapath manufactures satellite antenna for telecommunication systems. These antennas have a wide range of application scope and are used in extreme environments, in war zones and hotspots. The antennas are very heavy, difficult to transport so the project group was asked to come up with a new design of light, foldable and easy transportable antenna reflectors. Datapath chose the M-Model for the future development, which was made for the military use. The existing antennas are very heavy and solid which makes it difficult to transport because it takes a large amount of space. The requirement for this project was to decrease the weight of the reflector by 50 percent and the transportation volume by 20 percent. The Bachelor thesis generated lots of different design and concepts with different choices of materials for the reflector, but only two concepts fulfilled all qualifications. The first concept was decided to have a body made completely out of Carbon fiber reinforced silicone (CFRS). This material is strong and robust once it unfolds and can stand external forces generated by strong winds, but it is very easy to fold it back and most important it is ultralight. The second concept was a reflector made of reflective fabric with an external shell construction made of polyethylene. Both of these concepts fulfill Datapath's requirements with aspect on weight, transportation volume and strength.

  • 326.
    ABDUL-JALIL, RICHARD
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    SELMAN, CHRISTOS
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    Effektivisering och optimering av transport och emballage för kretskort2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
  • 327.
    Abduljalil, Vian
    Mälardalen University, School of Innovation, Design and Engineering.
    Databasreplikering av kunddata i en DMZ miljö2013Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
  • 328.
    Abdulkadir, Hesho
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Kostov, Andrey Petrov
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Studie om energibesparing på OKQ8 i Häggvik samt andra energieffektiviserade byggnader2014Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The report begins with a brief description of some of the most common measures for energy savings in buildings with recess in the solar collectors and photovoltaic panels which lays a solid foundation for our study. Next comes the main part of the study consisting of detailed descriptions of three of the top streamlined Swedish buildings.

    The main purpose of this study is to investigate some of the energy efficiency improvements done on the OKQ8’s gasoline station in Häggvik with a calculate part. Part of the task is to calculate how many photovoltaic cell panels should be installed in order to cover the whole buildings energy need. After that have we calculated the payback time and profitability of some of the installations at the petrol station. We have also studied other energy optimized buildings and compared their specific energy need with that of OKQ8.

  • 329.
    Abdulla, Akar
    Blekinge Institute of Technology, School of Engineering.
    Estimating Erosion in Oil and Gas Pipe Line Due to Sand Presence2011Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Transporting solid particles in oil and gas flow cause erosion damage to the pipeline and fittings. The aim of this thesis is to study the effect of impact velocity on the erosion damage in 90 degree long elbow by using two different erosion models namely, Oka model and E/CRC model. Those correlation applied at air-borne sand eroding, methane-borne sand eroding, mixed gas-borne sand eroding, and multiphase (gas- oil) borne sand eroding Inconel 625. The commercial computational fluid dynamics (CFD) code STAR-CCM+ is used to obtain the average and maximum erosion rate by using the above mentioned models and compared them with the previous results.

  • 330.
    Abdulla, Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Delzanno, Giorgio
    Rezine, Ahmed
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Approximated Context-Sensitive Analysis for Parameterized Verification2009In: Formal Techniques for Distributed Systems: Joint 11th IFIP WG 6.1 International Conference FMOODS 2009 and 29th IFIP WG 6.1 International Conference FORTE 2009, Lisboa, Portugal, June 9-12, 2009. Proceedings / [ed] David Lee, Antónia Lopes and Arnd Poetzsch-Heffter, 2009, Vol. 5522, p. 41-56Conference paper (Other academic)
  • 331.
    Abdulla, Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Delzanno, Giorgio
    Rezine, Ahmed
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Approximated parameterized verification of infinite-state processes with global conditions2009In: Formal methods in system design, ISSN 0925-9856, E-ISSN 1572-8102, Vol. 34, no 2, p. 126-156Article in journal (Refereed)
  • 332.
    Abdulla, Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Delzanno, Giorgio
    Rezine, Ahmed
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Automatic Verification of Directory-Based Consistency Protocols2009In: Reachability Problems: 3rd International Workshop, RP 2009, Palaiseau, France, September 23-25, 2009. Proceedings / [ed] Olivier Bournez and Igor Potapov, 2009, Vol. 5797, p. 36-50Conference paper (Other academic)
  • 333.
    Abdulla, Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Delzanno, Giorgio
    Rezine, Ahmed
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Monotonic Abstraction in Parameterized Verification2008In: Electronical Notes in Theoretical Computer Science, ISSN 1571-0661, E-ISSN 1571-0661, Vol. 223, p. 3-14Article in journal (Refereed)
  • 334.
    Abdulla, Mohammad
    KTH, School of Information and Communication Technology (ICT).
    Modeling of Thermal Stresses and Analysis of Micro-Crack Formations in PCB Laminates2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This Master’s thesis has given me an opportunity to study how, where, when and why cracks appear in the Printed Circuit Board (PCB) laminate. Layout choices contribute to the likelihood of crack formation. Simulations were made on three different locations on one board, the results were then analyzed. Thermal simulation showed nearly no thermal gradient in the board, the temperature inside the board was almost the same as at the surface. This concluded that there was no need for linked thermal and structural simulation. Structural simulations showed that most of the stress and compressions in the laminate was around the vias.

  • 335.
    Abdulla, Nardien
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Ali, Mohammed
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Ett modernare sätt att dimensionera: En jämförelse för Huvudstaprojektet, FEM-design eller handberäkning ?2014Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This theses has been conducted in collaboration with Peab where the students had Tomas Schäfer and Peter Jansson as supervisors.

    This report addresses how a specific secondary build up, located in Huvudsta Centrum, could had been designed differently. The original frame was designed with the old BKR construction rules. But at the construction start a new construction standard was applied, the Eurocode. Therefore, the house got decreased in weight to meet the stricter Eurocode requirements.

    The current frame was designed using manual methods, which were compared with the results from the same frame calculated with a computer programme, FEM-Design 3D Structure. The report is based on the know-how of how a designer should proceed to join the production model and the analytical model. This to be able to designed in a BIM environment.

    The difference in results, between the two methods, was about 50% reeducation in purchased steel and about 40% in design-engineer costs. We have estimated a total saving of 141000 SEK for Peab.

  • 336.
    Abdulla, Parosh
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Aronis, Stavros
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Jonsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Sagonas, Konstantinos
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Optimal dynamic partial order reduction2014In: Proc. 41st ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages, New York: ACM Press, 2014, p. 373-384Conference paper (Refereed)
    Abstract [en]

    Stateless model checking is a powerful technique for program verification, which however suffers from an exponential growth in the number of explored executions. A successful technique for reducing this number, while still maintaining complete coverage, is Dynamic Partial Order Reduction (DPOR). We present a new DPOR algorithm, which is the first to be provably optimal in that it always explores the minimal number of executions. It is based on a novel class of sets, called source sets, which replace the role of persistent sets in previous algorithms. First, we show how to modify an existing DPOR algorithm to work with source sets, resulting in an efficient and simple to implement algorithm. Second, we extend this algorithm with a novel mechanism, called wakeup trees, that allows to achieve optimality. We have implemented both algorithms in a stateless model checking tool for Erlang programs. Experiments show that source sets significantly increase the performance and that wakeup trees incur only a small overhead in both time and space.

  • 337.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Computer Systems.
    Annichini, A
    Bouajjani, A
    Symbolic verification of lossy channel systems: Application to the bounded retransmission protocol1999In: Tools and Algorithms for the Construction and Analysis of Systems: Proceddings of TACAS'99 / [ed] W. Rance Cleaveland, 1999, Vol. 1579, p. 208-222Conference paper (Refereed)
    Abstract [en]

    We consider the problem of verifying automatically infinite- state systems that are systems of finite machines that communicate by exchanging messages through unbounded lossy fifo channels. In a previous work [1], we proposed an algorithmic approach based on constructing a symbolic representation of the set of reachable configurations of a system by means of a class of regular expressions (SREs). The construction of such a representation consists of an iterative computation with an acceleration technique which enhances the chance of convergence. This technique is based on the analysis of the effect of iterating control loops. In the work we present here, we experiment our approach and show how it can be effectively applied. For that, we developed a tool prototype based on the results in [1]. Using this tool, we provide an automatic verification of (the parameterized version of) the Bounded Retransmission Protocol.

  • 338.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Bouajjani, Ahmed
    Ngo, Tuan Phong
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Context-bounded analysis for POWER2017In: Tools and Algorithms for the Construction and Analysis of Systems: Part II, Springer, 2017, p. 56-74Conference paper (Refereed)
  • 339.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Bui, Phi Diep
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Counter-Example Guided Program Verification2016In: FM 2016: Formal Methods, Springer, 2016, p. 25-42Conference paper (Refereed)
  • 340.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Chen, Yu-Fang
    Institute of Information Science, Academia Sinica .
    Holik, Lukas
    Brno University.
    Rezine, Ahmed
    Linköping University.
    Rümmer, Philipp
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    String Constraints for Verification2014In: Computer Aided Verification - 26th International Conference, {CAV} 2014, Held as Part of the Vienna Summer of Logic, {VSL} 2014, Vienna, Austria, July 18-22, 2014. Proceedings, Springer, 2014, p. 150-166Conference paper (Refereed)
    Abstract [en]

    We present a decision procedure for a logic that combines (i) word equations over string variables denoting words of arbitrary lengths, together with (ii) constraints on the length of words, and on (iii) the regular languages to which words belong. Decidability of this general logic is still open. Our procedure is sound for the general logic, and a decision procedure for a particularly rich fragment that restricts the form in which word equations are written. In contrast to many existing procedures, our method does not make assumptions about the maximum length of words. We have developed a prototypical implementation of our decision procedure, and integrated it into a CEGAR-based model checker for the analysis of programs encoded as Horn clauses. Our tool is able to automatically establish the correctness of several programs that are beyond the reach of existing methods.

  • 341.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Hofman, Piotr
    Mayr, Richard
    Kumar, K. Narayan
    Chennai Mathematical Institute, Chennai, India.
    Totzke, Patrick
    Infinite-state energy games2014In: Joint Meeting of the Twenty-Third EACSL Annual Conference on Computer Science Logic (CSL) and the Twenty-Ninth Annual ACM/IEEE Symposium on Logic in Computer Science (LICS), CSL-LICS '14, Vienna, Austria, July 14 - 18, 2014, New York: ACM Press, 2014Conference paper (Refereed)
    Abstract [en]

    Energy games are a well-studied class of 2-player turn-based games on a finite graph where transitions are labeled with integer vectors which represent changes in a multidimensional resource (the energy). One player tries to keep the cumulative changes non-negative in every component while the other tries to frustrate this.

    We consider generalized energy games played on infinite game graphs induced by pushdown automata (modelling recursion) or their subclass of one-counter automata.

    Our main result is that energy games are decidable in the case where the game graph is induced by a one-counter automaton and the energy is one-dimensional. On the other hand, every further generalization is undecidable: Energy games on one-counter automata with a 2-dimensional energy are undecidable, and energy games on pushdown automata are undecidable even if the energy is one-dimensional. Furthermore, we show that energy games and simulation games are inter-reducible, and thus we additionally obtain several new (un)decidability results for the problem of checking simulation preorder between pushdown automata and vector addition systems.

  • 342.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Rezine, Othmane
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Verification of Directed Acyclic Ad Hoc Networks2013In: Formal Techniques for Distributed Systems: FORTE 2013, Springer Berlin/Heidelberg, 2013, p. 193-208Conference paper (Refereed)
  • 343.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Stenman, Jari
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Computing optimal reachability costs in priced dense-timed pushdown automata2014In: Language and Automata Theory and Applications: LATA 2014, Springer Berlin/Heidelberg, 2014, p. 62-75Conference paper (Refereed)
  • 344.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Stenman, Jari
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Zenoness for Timed Pushdown Automata2014In: Proceedings 15th International Workshop on Verification of Infinite-State Systems, {INFINITY} 2013, Hanoi, Vietnam, 14th October 2013., 2014, p. -47Conference paper (Refereed)
    Abstract [en]

    Timed pushdown automata are pushdown automata extended with a finite set of real-valued clocks. Additionaly, each symbol in the stack is equipped with a value representing its age. The enabledness of a transition may depend on the values of the clocks and the age of the topmost symbol. Therefore, dense-timed pushdown automata subsume both pushdown automata and timed automata. We have previously shown that the reachability problem for this model is decidable. In this paper, we study the zenoness problem and show that it is EXPTIME-complete.

  • 345.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Computer Systems.
    Bouajjani, A
    Jonsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Computer Systems.
    On-the-fly analysis of systems with unbounded, lossy FIFO channels1998In: Computer Aided Verification: Proceedings of 10th International Conference, CAV'98 / [ed] Alan J. Hu, Moshe Y. Vardi, 1998, Vol. 1427, p. 305-318Conference paper (Refereed)
    Abstract [en]

    We consider symbolic on-the-fly verification methods for systems of finite-state machines that communicate by exchanging messages via unbounded and lossy FIFO queues. We propose a novel representation formalism, called simple regular expressions (SREs), for representing sets of states of protocols with lossy FIFO channels. We show that the class of languages representable by SREs is exactly the class of downward closed languages that arise in the analysis of such protocols. We give methods for (i) computing inclusion between SREs, (ii) an SRE representing the set of states reachable by executing a single transition in a system, and (iii) an SRE representing the set of states reachable by an arbitrary number of executions of a control loop of a program. All these operations are rather simple and can be carried out in polynomial time. With these techniques, one can construct a semi-algorithm which explores the set of reachable states of a protocol, in order to check various safety properties.

  • 346.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Computer Systems.
    Cerans, K
    Simulation is decidable for one-counter nets1998In: CONCUR'98 Concurrency Theory: Proceedings of the 9th International Conference, 1998, Vol. 1466, p. 253-268Conference paper (Refereed)
    Abstract [en]

    We prove that the simulation preorder is decidable for the class of one-counter nets. A one-counter net consists of a finite-state machine operating on a variable (counter) which ranges over the natural numbers. Each transition can increase or decrease the value of the counter. A transition may not be performed if this implies that the value of the counter becomes negative. The class of one-counter nets is computationally equivalent to the class of Petri nets with one unbounded place, and to the class of pushdown automata where the stack alphabet is restricted to one symbol. To our knowledge, this is the first result in the literature which gives a positive answer to the decidability of simulation preorder between pairs of processes in a class whose elements are neither finite-state nor allow finite partitioning of their state spaces.

  • 347.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Clemente, Lorenzo
    Mayr, Richard
    Sandberg, Sven
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Stochastic Parity Games on Lossy Channel Systems2014In: Logical Methods in Computer Science, ISSN 1860-5974, E-ISSN 1860-5974, Vol. 10, no 4, article id 21Article in journal (Refereed)
    Abstract [en]

    We give an algorithm for solving stochastic parity games with almost-sure winning conditions on lossy channel systems, under the constraint that both players are restricted to finitememory strategies. First, we describe a general framework, where we consider the class of 21/2-player games with almost-sure parity winning conditions on possibly infinite game graphs, assuming that the game contains a finite attractor. An attractor is a set of states (not necessarily absorbing) that is almost surely re-visited regardless of the players' decisions. We present a scheme that characterizes the set of winning states for each player. Then, we instantiate this scheme to obtain an algorithm for stochastic game lossy channel systems.

  • 348.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Delzanno, Giorgio
    Rezine, Ahmed
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Automatic verification of directory-based consistency protocols with graph constraints2011In: International Journal of Foundations of Computer Science, ISSN 0129-0541, Vol. 22, no 4, p. 761-782Article in journal (Refereed)
    Abstract [en]

    We propose a symbolic verification method for directory-based consistency protocols working for an arbitrary number of controlled resources and competing processes. We use a graph-based language to specify in a uniform way both client/server interaction schemes and manipulation of directories that contain the access rights of individual clients. Graph transformations model the dynamics of a given protocol. Universally quantified conditions defined on the labels of edges incident to a given node are used to model inspection of directories, invalidation loops and integrity conditions. Our verification procedure computes an approximated backward reachability analysis by using a symbolic representation of sets of configurations. Termination is ensured by using the theory of well-quasi orderings.

  • 349.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Dwarkadas, Sandhya
    University of Rochester, U.S.A..
    Rezine, Ahmed
    Linköping University.
    Shriraman, Arrvindh
    Simon Fraser University, Canada .
    Yunyun, Zhu
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Verifying safety and liveness for the FlexTM hybrid transactional memory2013Conference paper (Refereed)
    Abstract [en]

    We consider the verification of safety (strict serializability and abort consistency) and liveness obstruction and livelock freedom) for the hybrid transactional memory framework FlexTM. This framework allows for flexible implementations of transactional memories based on an adaptation of the MESI coherence protocol. FlexTM allows for both eager and lazy conflict resolution strategies. Like in the case of Software Transactional Memories, the verification problem is not trivial as the number of concurrent transactions, their size, and the number of accessed shared variables cannot be a priori bounded. This complexity is exacerbated by aspects that are specific to hardware and hybrid transactional memories. Our work takes into account intricate behaviours such as cache line based conflict detection, false sharing, invisible reads or non-transactional instructions. We carry out the first automatic verification of a hybrid transactional memory and establish, by adopting a small model approach, challenging properties such as strict serializability, abort consistency, and obstruction freedom for both an eager and a lazy conflict resolution strategies. We also detect an example that refutes livelock freedom. To achieve this, our prototype tool makes use of the latest antichain based techniques to handle systems with tens of thousands of states.

  • 350.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Haziza, Frédéric
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Holík, Lukás
    Block me if you can!: Context-sensitive parameterized verification2014In: Static Analysis: SAS 2014, Springer, 2014, p. 1-17Conference paper (Refereed)
    Abstract [en]

    We present a method for automatic verification of systems with a parameterized number of communicating processes, such as mutual exclusion protocols or agreement protocols. To that end, we present a powerful abstraction framework that uses an efficient and precise symbolic encoding of (infinite) sets of configurations. In particular, it generalizes downward-closed sets that have successfully been used in earlier approaches to parameterized verification. We show experimentally the efficiency of the method, on various examples, including a fine-grained model of Szymanski’s mutual exclusion protocol, whose correctness, to the best of our knowledge, has not been proven automatically by any other existing methods.

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