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  • 1.
    Aaro, Fredrik
    Umeå University, Faculty of Science and Technology, Umeå Institute of Design.
    En intuitiv & lättillgänglig flyktmask för gruvmiljö2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    I have always lived around mines and around people work­ing with mines. They are a natural part of my life and, inev­itably, a great interest of mine. When time came to make a decision for a degree project, focusing on the mine context felt as natural as breathing.

    In LKABs underground mines, safety in fire accidents is a great priority. Of outmost importance for the escape is to have a personal gas filter for filtration of smoke and/or gas. My design project resulted in a concept which is aimed at shortening the user journey from the start of the accident until the user has applied the personal safety solution and is ready to escape.

    Throughout the project I’ve been working with a context which is heavily regulated, and all problems are serious, important ones. I have been striving towards keeping a high level of innovation during the process, whatever the result in the end might be. I’ve been heavily relying on scenarios/workflows, product testing, observation, and I’ve had the great joy to be able to take part of LKABs accident reports.

    The concept can be divided into three parts, but it is the way these collaborate that makes out the main part of the concept.

    1: An escape station, providing a standardized placement of escape hoods.

    2: A container for the vacuum sealed escape hood.

    3: An escape hood which enables a personalized fit for the user.

    Interactive surfaces are color coded with the goal to provide an intuitive workflow. When the container is opened, the vacuum seal is immediately broken and the user gains access to two handles, one white and one red. The handles are used to lift and apply the escape hood, and the red handle is then used, by pulling, to tighten the throat fit.

    Combined, these solutions help the user applying her escape hood in shorter time, and a large head size, glasses, beard and a thick neck are no longer problematic for the applica­tion

     

  • 2.
    Abbasi, Jasim Aftab
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Test of Rapid Control System Development using TargetLink2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of this thesis is to employ and evaluate an evaluation board with the standard microprocessor freescale MPC5554EVB board for implementation of control algorithms which are created in Matlab/Simulink instead of using dSPACE prototyping hardware. The Simulink real-time model shall be compiled to the MPC5554EVB board. TargetLink is a powerful software tool which allows an automatic generation of efficient C code from Simulink and facilitates model-based control design. The goal of this thesis is to learn how to use TargetLink in a control design workflow from model to real code and what are the limitations of a microprocessor platform and to evaluate the capabilities of TargetLink to generate a working code for a generic microprocessor.

  • 3.
    Abed, Ahmed Ghafel
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Energieffektivisering vid renovering av Lamellhus på Mariehemsvägen2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In Sweden more houses than ever before are being built, and the house production is moving forward. At the same time, awareness of the energy use of buildings and its accompanying impacts on climate and sustainability are increasing. Therefore, Boverket constantly raises the demands for the energy performance of newly built and refurbished buildings.

    According to current requirements from Boverket (BBR, 2017), the primary energy value for apartment buildings may not be more than 85 kWh per square meter of tempered floor space and year. This also applies according to future requirements in 2021, but with the difference that the average U-value will decrease from 0.4 to 0.35 W/m2 K which means that apartment buildings must be built in an efficient way to reduce energy use. A large part of new construction and newly refurbished apartment buildings must then implement energy efficiency measures on their buildings to meet future requirements.

    This degree project has been carried out in collaboration with Rikshem AB who wants to investigate the impact of various energy efficiency measures on their apartment building ”Lamellhus”. The aim is to theoretically reduce apartment buildings ”Lamellhusets” specific energy use from 187,4 to 70 kWh/m2 Atemp, year and thus reduce the primary energy enough to meet future requirements according to BBR near-zero energy building.

    To theoretically reduce specific energy use and thus primary energy value, the project through manual calculations and with the help of computer tools examined various energy efficiency measures on the building's construction and installation system.

    The results show that the measures on the property climate shell are sufficient to meet the requirements. If all the measures according to package 1 or 2 on the design are combined, specific energy use according to BBR 16 (2010) will be at 83-94 kWh/m2 Atemp, year and the primary energy value according to BBR 25 (2017) will be at 68-77 kWh/m2 Atemp, year.

    The results also show how much of a building's energy use is ventilated. Replacing the ventilation system from F-systems to FTX-systems on the reference house in the base case, is the measure that gives one of the greatest impacts with a heat saving of (25.5-26.7%). In combination FTX-system with district heating, specific energy consumption can be reduced as low as possible. If the operation with the FTX-system is applied together with the existing district heating and all measures on the construction according to package 1 or 2, this gives a reduction of approximately (70-75 %) compared to the base case corresponding to 42-51 kWh/m2 Atemp, year according to BBR 16 and according to BBR 25, the figures are even lower. If the calculation considers thermal bridges and air leakage in the house, the result will increase.

    The results also show that the investment repays itself after 15-16 years with a simplified payback. With a calculation rate of 5 %, it is profitable over 30-31 years or more, but with a calculation rate of 8 % it is not profitable.

  • 4.
    Abedan Kondori, Farid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Bring Your Body into Action: Body Gesture Detection, Tracking, and Analysis for Natural Interaction2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Due to the large influx of computers in our daily lives, human-computer interaction has become crucially important. For a long time, focusing on what users need has been critical for designing interaction methods. However, new perspective tends to extend this attitude to encompass how human desires, interests, and ambitions can be met and supported. This implies that the way we interact with computers should be revisited. Centralizing human values rather than user needs is of the utmost importance for providing new interaction techniques. These values drive our decisions and actions, and are essential to what makes us human. This motivated us to introduce new interaction methods that will support human values, particularly human well-being.

    The aim of this thesis is to design new interaction methods that will empower human to have a healthy, intuitive, and pleasurable interaction with tomorrow’s digital world. In order to achieve this aim, this research is concerned with developing theories and techniques for exploring interaction methods beyond keyboard and mouse, utilizing human body. Therefore, this thesis addresses a very fundamental problem, human motion analysis.

    Technical contributions of this thesis introduce computer vision-based, marker-less systems to estimate and analyze body motion. The main focus of this research work is on head and hand motion analysis due to the fact that they are the most frequently used body parts for interacting with computers. This thesis gives an insight into the technical challenges and provides new perspectives and robust techniques for solving the problem.

  • 5.
    Abedan Kondori, Farid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Human Motion Analysis for Creating Immersive Experiences2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    From an early age, people display the ability to quickly and effortlessly interpret the orientation and movement of human body parts, thereby allowing one to infer the intentions of others who are nearby and to comprehend an important nonverbal form of communication. The ease with which one accomplishes this task belies the difficulty of a problem that has challenged computational systems for decades, human motion analysis.

    Technological developments over years have resulted into many systems for measuring body segment positions and angles between segments. In these systems human body is typically considered as a system of rigid links connected by joints. The motion is estimated by the use of measurements from mechanical, optical, magnetic, or inertial trackers. Among all kinds of sensors, optical sensing encompasses a large and varying collection of technologies.

    In a computer vision context, human motion analysis is a topic that studies methods and applications in which two or more consecutive images from an image sequences, e.g. captured by a video camera, are processed to produce information based on the apparent human body motion in the images.

    Many different disciplines employ motion analysis systems to capture movement and posture of human body for applications such as medical diagnostics, virtual reality, human-computer interaction etc.

    This thesis gives an insight into the state of the art human motion analysissystems, and provides new methods for capturing human motion.

  • 6.
    Abedan Kondori, Farid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Yousefi, Shahrouz
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Smart Baggage in Aviation2011In: 2011 IEEE International Conferences on Internet of Things, and Cyber, Physical and Social Computing / [ed] Feng Xia, Zhikui Chen, Gang Pan, Laurence T. Yang, and Jianhua Ma, Los Alamitos: IEEE Computer Society, 2011, p. 620-623Conference paper (Refereed)
    Abstract [en]

    Nowadays, the Internet has dramatically changed the way people take the normal course of actions. By the recent growth of the Internet, connecting different objects to users through mobile phones and computers is no longer a dream. Aviation industry is one of the areas which have a strong potential to benefit from the Internet of Things. Among many problems related to air travel, delayed and lost luggage are the most common and irritating. Therefore, this paper suggests anew baggage control system, where users can simply track their baggage at the airport to avoid losing them. Attaching a particular pattern on the bag, which can be detected and localized from long distance by an ordinary camera, users are able to track their baggage. The proposed system is much cheaper than previous implementations and does not require sophisticated equipment.

  • 7.
    Abedan Kondori, Farid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Yousefi, Shahrouz
    KTH Royal Institute of Technology, Department of Media Technology and Interaction Design.
    Kouma, Jean-Paul
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Liu, Li
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    KTH Royal Institute of Technology, Department of Media Technology and Interaction Design.
    Direct hand pose estimation for immersive gestural interaction2015In: Pattern Recognition Letters, ISSN 0167-8655, E-ISSN 1872-7344, Vol. 66, p. 91-99Article in journal (Refereed)
    Abstract [en]

    This paper presents a novel approach for performing intuitive gesture based interaction using depth data acquired by Kinect. The main challenge to enable immersive gestural interaction is dynamic gesture recognition. This problem can be formulated as a combination of two tasks; gesture recognition and gesture pose estimation. Incorporation of fast and robust pose estimation method would lessen the burden to a great extent. In this paper we propose a direct method for real-time hand pose estimation. Based on the range images, a new version of optical flow constraint equation is derived, which can be utilized to directly estimate 3D hand motion without any need of imposing other constraints. Extensive experiments illustrate that the proposed approach performs properly in real-time with high accuracy. As a proof of concept, we demonstrate the system performance in 3D object manipulation On two different setups; desktop computing, and mobile platform. This reveals the system capability to accommodate different interaction procedures. In addition, a user study is conducted to evaluate learnability, user experience and interaction quality in 3D gestural interaction in comparison to 2D touchscreen interaction.

  • 8.
    Abedan Kondori, Farid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Yousefi, Shahrouz
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Direct three-dimensional head pose estimation from Kinect-type sensors2014In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 50, no 4, p. 268-270Article in journal (Refereed)
    Abstract [en]

    A direct method for recovering three-dimensional (3D) head motion parameters from a sequence of range images acquired by Kinect sensors is presented. Based on the range images, a new version of the optical flow constraint equation is derived, which can be used to directly estimate 3D motion parameters without any need of imposing other constraints. Since all calculations with the new constraint equation are based on the range images, Z(xyt), the existing techniques and experiences developed and accumulated on the topic of motion from optical flow can be directly applied simply by treating the range images as normal intensity images I(xyt). In this reported work, it is demonstrated how to employ the new optical flow constraint equation to recover the 3D motion of a moving head from the sequences of range images, and furthermore, how to use an old trick to handle the case when the optical flow is large. It is shown, in the end, that the performance of the proposed approach is comparable with that of some of the state-of-the-art approaches that use range data to recover 3D motion parameters.

  • 9.
    Abedan Kondori, Farid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Yousefi, Shahrouz
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Gesture Tracking for 3D Interaction in Augmented Environments2011Conference paper (Other academic)
  • 10.
    Abedan Kondori, Farid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Yousefi, Shahrouz
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Real 3D Interaction Behind Mobile Phones for Augmented Environments2011In: 2011 IEEE International Conference on Multimedia and Expo (ICME), IEEE conference proceedings, 2011, p. 1-6Conference paper (Refereed)
    Abstract [en]

    Number of mobile devices such as mobile phones or PDAs has been dramatically increased over the recent years. New mobile devices are equipped with integrated cameras and large displays which make the interaction with device easier and more efficient. Although most of the previous works on interaction between humans and mobile devices are based on 2D touch-screen displays, camera-based interaction opens a new way to manipulate in 3D space behind the device in the camera's field of view. This paper suggests the use of particular patterns from local orientation of the image called Rotational Symmetries to detect and localize human gesture. Relative rotation and translation of human gesture between consecutive frames are estimated by means of extracting stable features. Consequently, this information can be used to facilitate the 3D manipulation of virtual objects in various applications in mobile devices.

  • 11.
    Abedan Kondori, Farid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Yousefi, Shahrouz
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Sonning, Samuel
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Sonning, Sabina
    3D Head Pose Estimation Using the Kinect2011Conference paper (Refereed)
    Abstract [en]

    Head pose estimation plays an essential role for bridging the information gap between humans and computers. Conventional head pose estimation methods are mostly done in images captured by cameras. However accurate and robust pose estimation is often problematic. In this paper we present an algorithm for recovering the six degrees of freedom (DOF) of motion of a head from a sequence of range images taken by the Microsoft Kinectfor Xbox 360. The proposed algorithm utilizes a least-squares minimization of the difference between themeasured rate of change of depth at a point and the rate predicted by the depth rate constraint equation. We segment the human head from its surroundings and background, and then we estimate the head motion. Our system has the capability to recover the six DOF of the head motion of multiple people in one image. Theproposed system is evaluated in our lab and presents superior results.

  • 12.
    Abedan Kondori, Farid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Yousefi, Shahrouz
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Liu, Li
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Active human gesture capture for diagnosing and treating movement disorders2013Conference paper (Other academic)
    Abstract [en]

    Movement disorders prevent many people fromenjoying their daily lives. As with other diseases, diagnosisand analysis are key issues in treating such disorders.Computer vision-based motion capture systems are helpfultools for accomplishing this task. However Classical motiontracking systems suffer from several limitations. First theyare not cost effective. Second these systems cannot detectminute motions accurately. Finally they are spatially limitedto the lab environment where the system is installed. In thisproject, we propose an innovative solution to solve the abovementionedissues. Mounting the camera on human body, webuild a convenient, low cost motion capture system that canbe used by the patient in daily-life activities. We refer tothis system as active motion capture, which is not confinedto the lab environment. Real-time experiments in our labrevealed the robustness and accuracy of the system.

  • 13.
    Abedan Kondori, Farid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Yousefi, Shahrouz
    KTH Royal Institute of Technology, Department of Media Technology and Interaction Design.
    Liu, Li
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    KTH Royal Institute of Technology, Department of Media Technology and Interaction Design.
    Head operated electric wheelchair2014In: IEEE Southwest Symposium on Image Analysis and Interpretation (SSIAI 2014), IEEE , 2014, p. 53-56Conference paper (Refereed)
    Abstract [en]

    Currently, the most common way to control an electric wheelchair is to use joystick. However, there are some individuals unable to operate joystick-driven electric wheelchairs due to sever physical disabilities, like quadriplegia patients. This paper proposes a novel head pose estimation method to assist such patients. Head motion parameters are employed to control and drive an electric wheelchair. We introduce a direct method for estimating user head motion, based on a sequence of range images captured by Kinect. In this work, we derive new version of the optical flow constraint equation for range images. We show how the new equation can be used to estimate head motion directly. Experimental results reveal that the proposed system works with high accuracy in real-time. We also show simulation results for navigating the electric wheelchair by recovering user head motion.

  • 14.
    Abedan Kondori, Farid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Yousefi, Shahrouz
    Ostovar, Ahmad
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Liu, Li
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    A Direct Method for 3D Hand Pose Recovery2014In: 22nd International Conference on Pattern Recognition, 2014, p. 345-350Conference paper (Refereed)
    Abstract [en]

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

  • 15.
    Abedin, Reaz Ashraful
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Autonomous Object Category Learning for Service Robots Using Internet Resources2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the developments in the field of Artificial Intelligence (AI), robots are becoming smarter, more efficient and capable of doing more dififcult tasks than before. Recent progress in Machine Learning has revolutionized the field of AI. Rather than performing pre-programmed tasks, nowadays robots are learning things, and becoming more autonomous along the way. However, in most of the cases, robots need a certain level of human assistance to learn something. To recognize or classify daily objects is a very important skill that a service robot should possess. In this research work, we have implemented a fully autonomous object category learning system for service robots, where the robot uses internet resources to learn object categories. It gets the name of an unknown object by performing reverse image search in the internet search engines, and applying a verification strategy afterwards. Then the robot retrieves a number of images of that object from internet and use those to generate training data for learning classifiers. The implemented system is tested in actual domestic environment. The classification performance is examined against some object categories from a benchmark dataset. The system performed decently with 78:40% average accuracy on ve object categories taken from the benchmark dataset and showed promising results in real domestic scenarios. There are existing research works that deal with object category learning for robots using internet images. But those works use Human-in-the-loop models, where humans assist the robot to get the object name for using it as a search cue to retrieve training images from internet. Our implemented system eliminates the necessity of human assistance by making the task of object name determination automatic. This facilitates the whole process of learning object categories with full autonomy, which is the main contribution of this research.

  • 16. Abel, Olubunmi
    et al.
    Shatunov, Aleksey
    Jones, Ashley R.
    Andersen, Peter M.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurology.
    Powell, John F.
    Al-Chalabi, Ammar
    Development of a Smartphone App for a Genetics Website: The Amyotrophic Lateral Sclerosis Online Genetics Database (ALSoD)2013In: JMIR mhealth and uhealth, E-ISSN 2291-5222, Vol. 1, no 2, article id e18Article in journal (Refereed)
    Abstract [en]

    Background: The ALS Online Genetics Database (ALSoD) website holds mutation, geographical, and phenotype data on genes implicated in amyotrophic lateral sclerosis (ALS) and links to bioinformatics resources, publications, and tools for analysis. On average, there are 300 unique visits per day, suggesting a high demand from the research community. To enable wider access, we developed a mobile-friendly version of the website and a smartphone app. Objective: We sought to compare data traffic before and after implementation of a mobile version of the website to assess utility. Methods: We identified the most frequently viewed pages using Google Analytics and our in-house analytic monitoring. For these, we optimized the content layout of the screen, reduced image sizes, and summarized available information. We used the Microsoft. NET framework mobile detection property (HttpRequest. IsMobileDevice in the Request. Browser object in conjunction with HttpRequest. UserAgent), which returns a true value if the browser is a recognized mobile device. For app development, we used the Eclipse integrated development environment with Android plug-ins. We wrapped the mobile website version with the WebView object in Android. Simulators were downloaded to test and debug the applications. Results: The website automatically detects access from a mobile phone and redirects pages to fit the smaller screen. Because the amount of data stored on ALSoD is very large, the available information for display using smartphone access is deliberately restricted to improve usability. Visits to the website increased from 2231 to 2820, yielding a 26% increase from the pre-mobile to post-mobile period and an increase from 103 to 340 visits (230%) using mobile devices (including tablets). The smartphone app is currently available on BlackBerry and Android devices and will be available shortly on iOS as well. Conclusions: Further development of the ALSoD website has allowed access through smartphones and tablets, either through the website or directly through a mobile app, making genetic data stored on the database readily accessible to researchers and patients across multiple devices.

  • 17.
    Abouhachem, Khalil
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Implementering av Lean Production på Hedson Technologies AB2014Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report is the conclusion of my bachelor degree in mechanical engineering at Umeå University. The report is the result of the work that has been done at Hedson Technologies AB in Malmö. Hedson is the number one on the market for producing wheel washers, dry equipment and car lifts. They have two constructions in Sweden and one in Germany. This work is limited to the building in Malmö, Sweden.

    To continue being the market leading company Hedson have realized that they need to improve the production line. To obtain a more efficient flow companies usually use Lean Production. Lean is a philosophy that permeates the whole company, from supply delivery until the product has reached the customer. The purpose of this thesis is to begin a work within Lean at Hedson. The work is supposed to act as groundwork for a Lean initiative that the company later can build on to get the production as efficient as possible.

    I have through an analysis of the production line and interviews with the market and the product manager shaped an overall picture of how the company operates. I have then done a pilot study and manipulated the information I have gathered to find the optimal course of action for Hedson to begin their work within Lean.

    It was thanks to a great cooperation with the staff of the company that a successful result was possible. Since the production was much unorganized and disordered the implementation of the 5S method was a perfect start for a long and successful journey through Lean Production. At last an introduction to Lean and 5S was done through a presentation to create an understanding at the company.

  • 18.
    Abrahamsson, Erik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Värmeöverföring från smälta till vattenkyld tapputrustning2011Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis work is done on behalf of Boliden Mineral AB at Rönnskärsverken.

    Kopparhyttan is an electric copper furnace for melting of copper concentrates and secondary materials in the form of ashes, metal scrap, crushed matte, slag and sludge.

    Depending on how the input material varies, the chemical composition of the melt will vary as well. Variations in the chemical composition of the melt also imply that the physical properties of the melt vary and the heat transfer between melt and tap block.

    A high heat load on the tap block during tapping of matte, results in increased wear and severe erosion of the tap channel and therefore the need of an understanding of the underlying causes to prevent and if possible avoid the high heat load.

    The completed analysis shows that a high heat load on the tap equipment mainly is associated with the copper content. A lower copper content leads to the melting point is lowered and also reduces the viscosity, leading to an increased mass flow. The increased heat load thus indicate an increased mass flow in combination with a reduced melting point, which means that the freezing of an erosion protective coating of matte on the inside of tapping channel walls becomes more difficult and thus increases the erosion on the tap equipment. Sulphur deficit, which is calculated from a chemical analysis of matte, showed no correlation to a high heat load and no connection between the sulfur deficit and the erosion of the tap equipment were successfully concluded.

    Measures proposed to reduce the wear on the tap equipment are increasing the flow of cooling water and a possible reduction of the tap channel diameter.

  • 19.
    Abrahamsson, Matilda
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Metoder för utredning av inomhusmiljö: En studie inom hälsoskyddet med delsyfte att utföra dammätningar i skolor2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Methods for inspection of the indoor environment – a study within health protection where a part of the aim is to perform measurements of dust in schools

    In Sweden the communities are responsible for the health protection in many agencies. The control of the indoor environment can be done in different ways and with different means. The aim of this report was to study in which way the inspectors made this kind of inspections and if there was anything in their approach that could be developed. A part of the aim of the report was to study how fast a clean surface in a school become dusty. Interviewes with healthinspectors in Uppsala, Håbo and Tierp was made. Together with them also some inspections were performed. To get a larger view of methods to investigate the indoor environment some inspections of schools and dwellings were done with an employee at the unit of Arbets- och miljömedicin at the University Hospital in Uppsala. The dust study was performed at two schools in Knivsta. The results were that the inspectors had well developed methods for assessings of the indoor environment. The approach differed in some matters between the larger and the smaller communities. Regardless of the size of the communities the inspectors rarely used instruments as a tool for the inspections. The communication and agreement between the inspectors was also shown as an important part in their work. In general the inspectors felt secure in their role and to make decisions. It appeared some shortcomings in the general advice and guidelines from the national board of health and welfare, which is the national supervisory authority that shall guide inspection of health protection. For example there was shown a lack in the guidelines regarding cleaning in schools and kindergardens. The study of dust in schools showed that there was more dust after five days than after one day.

  • 20.
    Abrahamsson, Mattias
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Elkvalitet på ett industrinät2016Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    En tung industri har oftast utrustning installerad som kan bidra till övertoner på ett elnät. Samtidigt är oftast elnäten starka inom dessa industrier vilket ska bidra till att reducera spänningsövertonerna som går att finna på respektive fas.Studien har arbetat med de villkor och föreskrifter som gäller både för en ansluten elanläggning till Vattenfalls elnät, men även hur en elkvalitetsmätning ska genomföras och vilka krav som behöver uppfyllas.Åkers Sweden AB, där studien har ägt rum, har induktionsugnar för smältning av metaller. Det förekommer olika tekniska lösningar samt 3 olika fabrikat. Mätningar har genomförts på samtliga dessa fabrikat för att kontrollera om någon av dessa urskiljer sig gentemot de övriga.Genomförda mätningar indikerar att spänningsövertoner förekommer men inte i sådan utsträckning att man inte uppfyller gällande regelverk. Det finns dock anledning till att fortsätta arbetet och utöka mätningarna till övriga objekt inom företaget som inte har ingått i denna studie.Företaget har ett effektabonnemang och en kontroll av detta med avseende på nu gällande effekt och förbrukning under 2015 har genomförts för att kunna ge förslag på eventuella förändringar. Eftersom företaget har ungefär samma produktionsvolym 2016 som 2015 finns anledning till att se över nu gällande avtal för att kunna erhålla en kostnadsreducering.En enkät har skickats ut till samtliga anställda inom företaget med syfte att både upplysa de anställda om vilka kvalitetsproblem som kan förekomma inom ett elnät, men även få en återkoppling på hur de anställda upplever nuvarande situation. Enkäten fick låg svarsfrekvens men svaren som inkom indikerade att de anställda upplever att företaget har en god elkvalitet.

  • 21.
    Abrahamsson, Simon
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Ny lösning för uppvärmning av Nordanås provbana2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    BAE Systems Hägglunds testbana är belägen i Nordanås nordväst om Örnsköldsvik. Detta projekt hade till avsikt att på BAE Systems förfrågan inventera testanläggningens nuvarande oljebaserade värmesystem för att finna ett mer ekonomiskt och miljövänligt alternativ. Utifrån en omfattande litteraturstudie samt kontakt med flera olika leverantörer, undersöktes vilka eventuella värmesystem som skulle kunna vara intressanta utifrån de krav som fanns i Nordanås.

    De alternativa värmesystemen som ansågs vara tekniskt hållbara var följande; bergvärme med lätt biooljepanna, tung biooljepanna eller pelletspanna; pelletspanna, lätt biooljepanna och tung biooljepanna. Dessa alternativ är de som undersökts noggrant i studien och därefter jämförts med det nuvarande värmesystemet i form av ekonomi och miljöpåverkan.

    I en ekonomisk kalkyl jämfördes de olika alternativens kapitalvärde och återbetalningstid. För att jämföra deras miljöpåverkan skapades en kalkyl som utifrån framtagna värden på olika bränslens utsläpp beräknade varje alternativs förväntade årliga utsläpp i form av koldioxidekvivalenter.

    Slutligen konstaterades att om BAE Systems Hägglunds ska byta ut nuvarande systemet bör man antingen investera i ett bergvärmesystem med en lätt biooljepanna som spetspanna eller en konvertering till lätt biooljepanna. Med priser från den tid då rapporten skrevs skulle alternativet med bergvärme ha en beräknad återbetalningstid på ca 6,4 år och kapitalvärdet 1,0 Mkr. Motsvarande värden för alternativet med enbart en lätt biooljepanna uppgick till 1,0 års återbetalningstid samt 0,8 Mkr i kapitalvärde. Den stora skillnaden i återbetalningstid berodde på bergvärmesystemets höga investeringskostnad. Att investera i ett bergvärmesystem ansågs trots detta som ett bra alternativ på grund av den förväntade prisökningen av eldningsolja.

  • 22.
    Abu-Hamam, Anas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Georgakis, Apostolos
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Understanding Web Users Behaviour From A Web Video Camera2003Report (Other academic)
    Abstract [en]

    To develop a Real-Time system, which can capture and track the web user’s head motion. Based on the head motion information, the system should be able to identify whether the user is interested in the current homepage or not. A future system property would be to find out in which area of the homepage the user’s interest is moving.

  • 23.
    Adebiyi, Abdulafeez
    et al.
    Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506, USA.
    Alkandari, Rawan
    Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506, USA.
    Valiev, Damir
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Center for Combustion Energy, Key Laboratory for Thermal Science and Power Engineering of the Ministry of Education of China, Department of Energy and Power Engineering, Tsinghua University, Beijing, China.
    Akkerman, V’yacheslav
    Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia, USA.
    Effect of surface friction on ultrafast flame acceleration in obstructed cylindrical pipes2019In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 9, no 3, article id 035249Article in journal (Refereed)
    Abstract [en]

    The Bychkov model of ultrafast flame acceleration in obstructed tubes [Valiev et al., “Flame Acceleration in Channels with Obstacles in the Deflagration-to-Detonation Transition,” Combust. Flame 157, 1012 (2010)] employed a number of simplifying assumptions, including those of free-slip and adiabatic surfaces of the obstacles and of the tube wall. In the present work, the influence of free-slip/non-slip surface conditions on the flame dynamics in a cylindrical tube of radius R, involving an array of parallel, tightly-spaced obstacles of size αR, is scrutinized by means of the computational simulations of the axisymmetric fully-compressible gasdynamics and combustion equations with an Arrhenius chemical kinetics. Specifically, non-slip and free-slip surfaces are compared for the blockage ratio, α, and the spacing between the obstacles, ΔZ, in the ranges 1/3 ≤ α ≤ 2/3 and 0.25 ≤ ΔZ/R ≤ 2.0, respectively. 

    For these parameters, an impact of surface friction on flameacceleration is shown to be minor, only 1-4%, slightly facilitating acceleration in a tube with ΔZ/R = 0.5 and moderating acceleration in thecase of ΔZ/R = 0.25. Given the fact that the physical boundary conditions are non-slip as far as the continuum assumption is valid, the presentwork thereby justifies the Bychkov model, employing the free-slip conditions, and makes its wider applicable to the practical reality. Whilethis result can be anticipated and explained by a fact that flame propagation is mainly driven by its spreading in the unobstructed portion ofan obstructed tube (i.e. far from the tube wall), the situation is, however, qualitatively different from that in the unobstructed tubes, wheresurface friction modifies the flame dynamics conceptually.

  • 24.
    Adebiyi, Abdulafeez
    et al.
    Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV 26506-6106, United States.
    Idowu, Gbolahan
    Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV 26506-6106, United States.
    Valiev, Damir
    Center for Combustion Energy, Tsinghua University, Beijing 100084, China.
    Akkerman, V'yacheslav
    Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV 26506-6106, United States.
    Computational simulations of nonequidiffusive premixed flames in obstructed pipes2018Conference paper (Refereed)
    Abstract [en]

    The impact of the Lewis number, Le, on the dynamics and morphology of a premixed flame front, spreading through a toothbrush-like array of obstacles in a semi-open channel, is studied by means of the computational simulations of the reacting flow equations with fully-compressible hydrodynamics and Arrhenius chemical kinetics. The computational approach employs a cell-centered, finite-volume numerical scheme, which is of the 2nd-order accuracy in time, 4th-order in space for the convective terms, and of the 2nd-order in space for the diffusive terms. The channels of blockage ratios 0.33∼0.67 are considered, with the Lewis numbers in the range 0.2≤Le≤2.0 employed. It is shown that the Lewis number influences the flame evolution substantially. Specifically, flame acceleration weakens for Le>1 (inherent to fuel-lean hydrogen or fuel-rich hydrocarbon burning), presumably, due to a thickening of the flame front. In contrast, Le<1 flames (such as that of rich hydrogen or lean hydrocarbon) acquire an extra strong folding of the front and thereby accelerate even much faster. The later effect can be devoted to the onset of the diffusional-Thermal combustion instability. © 2018 Eastern States Section of the Combustion Institute. All rights reserved.

  • 25.
    Adjeiwaah, Mary
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Quality assurance for magnetic resonance imaging (MRI) in radiotherapy2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Magnetic resonance imaging (MRI) utilizes the magnetic properties of tissues to generate image-forming signals. MRI has exquisite soft-tissue contrast and since tumors are mainly soft-tissues, it offers improved delineation of the target volume and nearby organs at risk. The proposed Magnetic Resonance-only Radiotherapy (MR-only RT) work flow allows for the use of MRI as the sole imaging modality in the radiotherapy (RT) treatment planning of cancer. There are, however, issues with geometric distortions inherent with MR image acquisition processes. These distortions result from imperfections in the main magnetic field, nonlinear gradients, as well as field disturbances introduced by the imaged object. In this thesis, we quantified the effect of system related and patient-induced susceptibility geometric distortions on dose distributions for prostate as well as head and neck cancers. Methods to mitigate these distortions were also studied.

    In Study I, mean worst system related residual distortions of 3.19, 2.52 and 2.08 mm at bandwidths (BW) of 122, 244 and 488 Hz/pixel up to a radial distance of 25 cm from a 3T PET/MR scanner was measured with a large field of view (FoV) phantom. Subsequently, we estimated maximum shifts of 5.8, 2.9 and 1.5 mm due to patient-induced susceptibility distortions. VMAT-optimized treatment plans initially performed on distorted CT (dCT) images and recalculated on real CT datasets resulted in a dose difference of less than 0.5%.

     The magnetic susceptibility differences at tissue-metallic,-air and -bone interfaces result in local B0 magnetic field inhomogeneities. The distortion shifts caused by these field inhomogeneities can be reduced by shimming.  Study II aimed to investigate the use of shimming to improve the homogeneity of local  B0 magnetic field which will be beneficial for radiotherapy applications. A shimming simulation based on spherical harmonics modeling was developed. The spinal cord, an organ at risk is surrounded by bone and in close proximity to the lungs may have high susceptibility differences. In this region, mean pixel shifts caused by local B0 field inhomogeneities were reduced from 3.47±1.22 mm to 1.35±0.44 mm and 0.99±0.30 mm using first and second order shimming respectively. This was for a bandwidth of 122 Hz/pixel and an in-plane voxel size of 1×1 mm2.  Also examined in Study II as in Study I was the dosimetric effect of geometric distortions on 21 Head and Neck cancer treatment plans. The dose difference in D50 at the PTV between distorted CT and real CT plans was less than 1.0%.

    In conclusion, the effect of MR geometric distortions on dose plans was small. Generally, we found patient-induced susceptibility distortions were larger compared with residual system distortions at all delineated structures except the external contour. This information will be relevant when setting margins for treatment volumes and organs at risk.  

    The current practice of characterizing MR geometric distortions utilizing spatial accuracy phantoms alone may not be enough for an MR-only radiotherapy workflow. Therefore, measures to mitigate patient-induced susceptibility effects in clinical practice such as patient-specific correction algorithms are needed to complement existing distortion reduction methods such as high acquisition bandwidth and shimming.

  • 26.
    Adolfsson, Sebastian
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Expanding operation ranges using active flow control in Francis turbines2014Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report contains an investigation of fluid injection techniques used in the purpose of reducing deleterious flow effects occurring in the draft tube of Francis turbines when operating outside nominal load. There is a focus on implement ability at Jämtkrafts hydroelectric power plants and two power plants were investigated, located in series with each other named Lövhöjden and Ålviken. The only profitable scenario found with some degree of certainty was an increase in the operating range upwards to allow overload operation.

    Findings show that both air and water can be introduced in various locations to improve hydraulic efficiency around the turbine parts as well as reduce pressure pulsations in harmful operating regions. Investments in such systems have proven useful and profitable at several facilities with poorly adapted operating conditions. But due to losses in efficiency when operating injection systems, it turns out unprofitable in situations where it does not improve the operating range in a way that is resulting in increased annual or peak production.

  • 27.
    af Geijerstam, Klas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    CONGESTION-CONTROLLED AUTOTUNING OF OPENMP PROGRAMS2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Parallelisation is becoming more and more important as the single core performance increase is stagnating while the amount of cores is increasing with every new generation of hardware. ŒThe traditional approach of manual parallelisation has an alternative in parallel frameworks, such as OpenMP, which can simplify the creation of parallel code. Optimising this code can, however, be cumbersome and difficult. Automating the optimisation or tuning of parallel code and computations is a very interesting alternative to manually optimising algorithms and programs. Previous work has shown that intricate systems can eff‚ectively autotune parallel programs with potentially the same eff‚ectiveness as human experts. ThŒis study suggests using an approach with the main algorithm used inspired from the congestion control algorithms from computer networks, namely AIMD. By applying the algorithm on top of an OpenMP program the parallel parameters such as grain size can be controlled. TheŒe simpli€ed algorithm is shown to be able to achieve a 19% speedup compared to a naive static parallel implementation

  • 28.
    Afzaal, Qasim
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Ahmad, Usman
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Audio Video Streaming Solution for Bambuser2012Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Audio/Video streaming has widely been used in different applications but the social communication applications have especially raised its usage. The aim of this thesis is to design and develop an improved Audio/Video streaming solution for a Swedish company Bambuser and can easily be extended with new features where necessary. Currently Bambuser is using the Flash Media Server (FMS) for streaming the media, but it is license based and adds the extra cost to the company's budget. It does not support a wide range of platforms (e.g. OpenBSD and various Linux distributions) and also has limited options for the streaming. There is no real time monitoring and controlling functionality, which can show the status of essential services to the user, needed for the streaming (for example if the camera is working, microphone is turned on, battery power status. etc.).

    In order to solve these issues the GStreamer is used, which is an Open source multimedia streaming framework. The GStreamer environment was tested on different Linux distributions. The research and implementation includes the creation of the streaming pipeline and analyzing which options (i.e. GStreamer elements and plugins) are required to stream the media. It also includes the testing of different pipeline parameters (for example video rate, audio rate etc.) and noting their effects in a real working environment. Python binding with GStreamer is used to have better control over the pipeline. Another requirement of this project was to add the functionality of monitoring and control that shows the status of essential services to the user. Implementation of this part is done by using server and client side coding. Further improvements and suggestions are also proposed in this report.

  • 29. Agogo, George O.
    et al.
    van der Voet, Hilko
    van 't Veer, Pieter
    Ferrari, Pietro
    Muller, David C.
    Sanchez-Cantalejo, Emilio
    Bamia, Christina
    Braaten, Tonje
    Knuppel, Sven
    Johansson, Ingegerd
    Umeå University, Faculty of Medicine, Department of Odontology.
    van Eeuwijk, Fred A.
    Boshuizen, Hendriek C.
    A method for sensitivity analysis to assess the effects of measurement error in multiple exposure variables using external validation data2016In: BMC Medical Research Methodology, ISSN 1471-2288, E-ISSN 1471-2288, Vol. 16, article id 139Article in journal (Refereed)
    Abstract [en]

    Background: Measurement error in self-reported dietary intakes is known to bias the association between dietary intake and a health outcome of interest such as risk of a disease. The association can be distorted further by mismeasured confounders, leading to invalid results and conclusions. It is, however, difficult to adjust for the bias in the association when there is no internal validation data. Methods: We proposed a method to adjust for the bias in the diet-disease association (hereafter, association), due to measurement error in dietary intake and a mismeasured confounder, when there is no internal validation data. The method combines prior information on the validity of the self-report instrument with the observed data to adjust for the bias in the association. We compared the proposed method with the method that ignores the confounder effect, and with the method that ignores measurement errors completely. We assessed the sensitivity of the estimates to various magnitudes of measurement error, error correlations and uncertainty in the literature-reported validation data. We applied the methods to fruits and vegetables (FV) intakes, cigarette smoking (confounder) and all-cause mortality data from the European Prospective Investigation into Cancer and Nutrition study. Results: Using the proposed method resulted in about four times increase in the strength of association between FV intake and mortality. For weakly correlated errors, measurement error in the confounder minimally affected the hazard ratio estimate for FV intake. The effect was more pronounced for strong error correlations. Conclusions: The proposed method permits sensitivity analysis on measurement error structures and accounts for uncertainties in the reported validity coefficients. The method is useful in assessing the direction and quantifying the magnitude of bias in the association due to measurement errors in the confounders.

  • 30.
    Agrell, Daniel
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Optimerad design och tillverkningsmetod av koncentrerande solfångare2015Independent thesis Advanced level (degree of Master (Two Years)), 300 HE creditsStudent thesis
    Abstract [en]

    The sun is our most important source of energy for us to be able to cope with the evermore pressuring climate threats. This has always been very clear for Absolicon Solar Collector AB in Härnösand, developers of concentrating solar collectors. The company has so far produced solar collectors which can produce both thermal and electrical power for mid-sized installations such as hotels and hospital. Now however, they are changing direction. Absolicon wants to address the many bigger industries with a demand for steam, in countries rich with solar radiation. Absolicon also wants to develop a production line for production of their solar collector, for deployment in the countries where the demand is the biggest.

     

    In a project partially financed by the Swedish energy department, a demonstrational production line will be built in Härnösand. The production line will be used to build a demonstrational field at HEMAB (Härnösands Energi och Miljö AB) with a new generation of solar collectors, optimized for steam production. The solar collectors built today has a problem with the reflector not getting an optimized shape throughout the whole collector. This has to be rectified since the demand on the shape of the reflector is higher on the new generation of solar collectors. This Is due to the use of a smaller receiver. Furthermore a mounting carriage using a new production method is to be developed for the production line. The mounting carriage should, by using vacuum, form and fixate the reflector of the collector while it also optimizes its shape.

     

    Tests was performed to examine how to optimize the shape of the reflector. A test rig was used to examine how a thin sheet of metal can be formed and fixated using vacuum while developing an optimized production method. A prototype carriage for production of 2 m long collectors using the new method was designed and constructed for evaluation.

     

    The results of the evaluation showed that the developed method is working well and that a receiver diameter of 19 mm can be used. The method is based on letting the edges of the reflector sheet hang free, which eliminates unwanted tensions in the reflector.

     

    The prototype which was built is ready for upscaling to a 6 m mounting carriage which will be able to produce the new generation of solar collectors for the demonstration field. A mounting process for production of solar collectors in a production line has been proposed which can shorten the mounting time and work load to less than 45 minutes and 1-2 persons per collector.

    The full text will be freely available from 2025-09-01 20:46
  • 31.
    Agrell, Elias
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Analys av massapumps- och mixerarbete vid Metsä Board Sverige AB, Husums Fabriker: Energibesparingsåtgärder vid blekeri 4 & 5 med jämförelse mot ny utrustning2014Independent thesis Basic level (university diploma), 180 HE creditsStudent thesis
    Abstract [en]

    Husums plant has a selection of different pulp pumps at bleaching plant 4 and 5. The displacement- (HC-pump, Sund Defibrator PTD-60) and centrifugalpumps (MC-pump, MCA 42-200, MCP 30/20) are of interest in this report. The centrifugal pumps are controlled by throttle valves, which result in an energy loss. Chemical mixers are used to mix ClO2 into the pulp before proceeding into a holding tower where the bleaching process occurs.

    The energy demand of the different positions has been measured or calculated to be used in comparisons against new equipment. Quotations were requested and delivered from Valmet and Sulzer. The quotations were made with a production increase of 10 ADMt/h and plant compared to current equipment. Therefore energy need of the equipment in the quotation had to be recalculated to the same production output as when measurements were conducted to be comparable. Quotation of the pumps assumes the use of frequency inverters.

    A deeper investigation was made for 441PU255 which is located at bleaching plant 4. The drop leg level of the pump is controlled via a throttle valve. A frequency inverter is installed but not utilized to maintain constant pulp level in the drop leg. This was due to physical changes in the process not being compensated for in the control system. This caused the drop leg level to oscillate when automatic control was used. As a workaround the drive had been set at a constant speed. To investigate the potential savings, an attempt was made in which the speed was lowered from 1520 rpm to 1100 rpm, resulting in a power reduction of 82 kW or 342,081 Sek per year at a production of 36 ADMT/h. The experiment was done with slightly lower production output than desirable; because of this, savings will decrease slightly at higher outputs.

    Comparisons showed that considerable amounts of energy could be saved at all positions. However the investment cost is high and therefore favorable payback times can only be seen for some of the positions. The MC-pumps are oversized and in need of constant throttling therefore the majority of the energy savings is made through the installation of frequency inverters and not the pump upgrade.

  • 32. Aguilar, Luis T.
    et al.
    Boiko, Igor M.
    Fridman, Leonid M.
    Freidovich, Leonid B.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Generating oscillations in inertia wheel pendulum via two-relay controller2012In: International Journal of Robust and Nonlinear Control, ISSN 1049-8923, E-ISSN 1099-1239, Vol. 22, no 3, p. 318-330Article in journal (Refereed)
    Abstract [en]

    The problem of generating oscillations of the inertia wheel pendulum is considered. We combine exact feedback linearization with two-relay controller, tuned using frequency-domain tools, such as computing the locus of a perturbed relay system. Explicit expressions for the parameters of the controller in terms of the desired frequency and amplitude are derived. Sufficient conditions for orbital asymptotic stability of the closed-loop system are obtained with the help of the Poincare map. Performance is validated via experiments. The approach can be easily applied for a minimum phase system, provided the behavior of the states of the zero dynamics is of no concern. Copyright (C) 2011 John Wiley & Sons, Ltd.

  • 33.
    Aguilar, Luis T.
    et al.
    CITEDI, National Polytechnic Institute, Tijuana, BC, Mexico.
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Orlov, Yury
    CICESE Research Center, Ensenada, Baja California, Mexico.
    Merida, Jovan
    CITEDI, National Polytechnic Institute, Tijuana, BC, Mexico.
    Performance Analysis of Relay Feedback Position Regulators for Manipulators with Coulomb Friction2013In: Proc. 12th European Control Conference, NEW YORK, NY 10017 USA: IEEE , 2013, p. 3754-3759Conference paper (Refereed)
    Abstract [en]

    The purpose of the paper is to analyze the performance of several global position regulators for robot manipulators with Coulomb friction. All the controllers include a proportional-differential part and a switched part whereas the difference between the controllers is in the way of compensation of the gravitational forces. Stability analysis is also revisited within the nonsmooth Lyapunov function framework for the controllers with and without gravity pre-compensation. Performance issues of the proposed controllers are evaluated in an experimental study of a five degrees-of-freedom robot manipulator. In the experiments, we choose two criteria for performance analysis. In the first set of experiments, we set the same gains to all the controllers. In the second set of experiments, the gains of the controller were chosen such that the work done by the manipulator is similar.

  • 34. Aguirre-Hernandez, Baltazar
    et al.
    Campos-Canton, Eric
    Villafuerte-Segura, Raul
    Vazquez, Carlos
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Loredo-Villalobos, Carlos-Arturo
    Open Challenges on the Stability of Complex Systems: Insights of Nonlinear Phenomena with or without Delay2019In: Complexity, ISSN 1076-2787, E-ISSN 1099-0526, article id 5209636Article in journal (Other academic)
  • 35.
    Ahlgren, Benjamin
    et al.
    Umeå University.
    Tian, Zhiyong
    Perers, Bengt
    Dragsted, Janne
    Johansson, Emma
    Umeå University.
    Lundberg, Kajsa
    Umeå University.
    Mossegard, Jonatan
    Bystrom, Joakim
    Olsson, Olle
    A simplified model for linear correlation between annual yield and DNI for parabolic trough collectors2018In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 174, p. 295-308Article in journal (Refereed)
    Abstract [en]

    This paper proposes a simple method for estimating annual thermal performance of parabolic trough collectors (PTCs) based on a linear relation with annual DNI for a certain latitude. A case study with simulations for a novel concentrating solar collector in 316 locations for three operating temperature scenarios worldwide was carried out and showed promising results for the latitudes and continents investigated. For a certain latitude and mean operating temperature, the annual yield of a PTC was found to be linearly proportional to yearly DNI. The proposed method will serve as a simplified alternative to the steady-state and quasi-dynamic methods already used. Estimating performance based on yearly DNI can be used by design engineers to do quick preliminary planning of solar plants. Customers can also use this method to evaluate existing solar collector installations. A TRNSYS/TRNSED tool that uses a steady-state model has been developed to carry out the simulations and it has been validated against a PTC array at Technical University of Denmark (DTU). The results show that the simplified method can give reliable estimates of long-term performance of parabolic trough collectors.

  • 36.
    Ahlgren, Ulf
    et al.
    Umeå University, Faculty of Medicine, Umeå Centre for Molecular Medicine (UCMM).
    Kostromina, Elena
    Umeå University, Faculty of Medicine, Umeå Centre for Molecular Medicine (UCMM).
    Imaging the pancreatic beta cell: chapter 132011In: Type 1 diabetes: pathogenesis, genetics and immunotherapy / [ed] David Wagner, InTech, 2011Chapter in book (Refereed)
    Abstract [en]

    This book is a compilation of reviews about the pathogenesis of Type 1 Diabetes. T1D is a classic autoimmune disease. Genetic factors are clearly determinant but cannot explain the rapid, even overwhelming expanse of this disease. Understanding etiology and pathogenesis of this disease is essential. A number of experts in the field have covered a range of topics for consideration that are applicable to researcher and clinician alike. This book provides apt descriptions of cutting edge technologies and applications in the ever going search for treatments and cure for diabetes. Areas including T cell development, innate immune responses, imaging of pancreata, potential viral initiators, etc. are considered.

  • 37.
    Ahlqvist, Emil
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Implementing a Resume Database with Online Learning to Rank2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Learning to Rank is a research area within Machine Learning. It is mainly used in Information Retrieval and has been applied to, among other systems, web search engines and in computational advertising. The purpose of the Learning to Rank model is to rank a list of items, placing the most relevant at the top of the list, according to the users' requirements. Online Learning to Rank is a type of this model, that learns directly from the users' interactions with the system.

    In this thesis a resume database is implemented, where the search engine applies an Online Learning to Rank algorithm, to rank consultant's resumes, when queries with required skills and competences are issued to the system. The implementation of the Resume Database and the ranking algorithm, as well as an evaluation, is presented in this report. Results from the evaluation indicates that the performance of the search engine, with the Online Learning to Rank algorithm, could be desirable in a production environment.

  • 38.
    Ahmed, Shibbir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Micro-wave synthesis of co-doped transition metal oxides anchored on reduced graphene oxide and their implementation as catalysts for water oxidation2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Abstract: Artificial photosynthesis is a very attractive and a desirable way to solve the rising energy demand. In order to harvest energy directly from sunlight catalyst for oxygen reduction and evolution reaction are at the core of key renewable-energy technologies including fuel cells and water splitting. Herein, tungsten oxide-reduced graphene oxide (WO3-rGO), cobalt oxide-reduced graphene oxide (Co3O4-rGO) and tungsten oxide-cobalt oxide-reduced graphene oxide (WO3-Co3O4-rGO) nano-composites were synthesized via a facile, efficient, one-pot microwave assisted method as an efficient electro-catalyst for water oxidation. The structural and chemical compositions of the produced nano-structures were investigated by Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), Raman Spectroscopy as well as thremogravimetric analysis. Catalytic performances of the engineered nano hybrids for the oxygen evolution reaction (OER) were evaluated using a standard three electrode system in 0.1 M KOH aqueous solution, with a coiled Pt wire as the counter electrode and an Ag/AgCl as the reference electrode. In the produced nano-composites, WO3 and Co3O4 nano-particles are uniformly decorated on the reduced graphene oxide sheets without any agglomeration. The WO3-Co3O4-rGO hybrids afforded current density 1 mA/cm2 at 1.693 V vs RHE and the Co3O4-rGO reached the current density 1 mA/cm2 at 1.769 V vs RHE regarding the catalytic performance for OER in alkaline solution. The over potential was significantly reduced by 76 mV after co-doping of WO3 with Co3O4-rGO nano hybrids. The WO3-Co3O4-rGO gives current density 1 mA/cm2 at 1.658 V vs RHE. We also show that the over potential for oxygen evolution of the WO3-Co3O4-rGO was further reduced by illuminating the catalyst to visible light thus manifesting the photo-catalytic properties of the hybrid catalyst.

  • 39.
    Aimaiti, Nuerrennisahan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    A Comparison of Rotation Parameterisations for Bundle Adjustment2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Bundle Adjustment is an iterative process where 3D information is estimated from 2D image measurements. Typically, the position of object points are estimated simultaneously with the position and orientation of the cameras. While the object points and camera positions have a straightforward "natural" parameterisation, several possibilities exist for the rotation. In this thesis, seven parameterisation of the rotation were investigated; Euler angles (two variants), the Rodriguez representation, the axis-and-angle representation, unit quaternions, and two variants of the direction cosine matrix (DCM). The Euler and Rodriguez parameterisation are common in photogrammetry and each has three parameters. The other parameterisations have more parameters and one or more constraint between them.

    The parameterisations were analyzed with respect to singularities, i.e. well-defined rotations that do not have any bounded and/or unique set of parameters. Four bundle adjustment experiments were setup, each corresponding to a singularity for one or more parameterisations. A fitth, singularity-free, experiment was also added. The experiments were perturbation studies that investigated the convergence properties of each parameterisation. The unconstrained parameterisations were solved by a damped and undamped Gauss-Newton algorithm, whereas the parameterisations with constraints were solved using damped and undamped algorithms based on the Gauss-Helmert estimation model.

    As expected, the parameterisations corresponding to the constructed singularity had higher failure rates and required more iterations and execution time than the others when it did converge. Excluding their singular cases, the Euler xyz and Rodriguez representations were the fastest with about 37% of the dcm. Of the singularity-free parameterisation, the unit quaternion was the fastest with 79% of the dcm.

    Surprisingly, the undamped bundle algorithms converged more often and faster than the damped bundle algorithms, even close to singularities. However, the undamped convergence was to a higher degree associated with numerical warnings and convergence toward angular values outside the nominal 2 range.

    The results suggest that if singularities are not expected, the Euler xyz and Rodriguez representations are the best of the tested parameterisations. Otherwise, the unit quaternion is the best. As an alternative to the latter case, the switching algorithm by Singla may be used, at the expense of a more complex algorithm.

  • 40.
    Akkerman, Vyacheslav
    et al.
    West Virginia University, Morgantown, WV, United States.
    Bilgili, Serdar
    West Virginia University, Morgantown, WV, United States.
    Bychkov, Vitaly
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Valiev, Damir
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Demir, Sinan
    West Virginia University, Morgantown, WV, United States.
    Morella, Haley
    West Virginia University, Morgantown, WV, United States.
    Impacts of the Lewis and Markstein numbers effects on the flame acceleration in channels2016Conference paper (Other academic)
    Abstract [en]

    The effects of flame stretch and thermal/molecular diffusion on the flame acceleration in channels are quantified by means of the analytical and computational endeavours. The internal transport flame properties are accounted in the theory by means of the Markstein number, Mk. Being a positive or negative function of the thermal-chemical combustion parameters, such as the thermal expansion ratio and the Lewis and Zeldovich numbers, the Markstein number either moderates or promotes the flame acceleration. While Mk may provide a substantial impact on the flame acceleration rate in narrow channels, this effects diminishes with the increase of the channel width. The analysis is accompanied by extensive computational simulations of the Navier-Stokes combustion equations, which clarify the impact of the Lewis number on the flame acceleration. It is obtained that, for Le below a certain critical value, at the initial stage of flame acceleration, a globally-convex flame front is splits into two or more "fingers", accompanied by a drastic increase in the flame surface area and associated enhancement of the flame acceleration. Overall, the thermal-diffusive effects substantially facilitate the flame acceleration scenario, thereby advancing a potential deflagration-to-detonation transition. 

  • 41.
    Akkerman, V'yacheslav
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Bychkov, Vitaly
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Bastiaans, R. J. M.
    de Goey, L. P. H.
    van Oijen, J. A.
    Eriksson, L. E.
    Flow-flame interaction in a closed chamber2008In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 20, no 5, p. 055107-055121Article in journal (Refereed)
    Abstract [en]

    Numerous studies of flame interaction with a single vortex andrecent simulations of burning in vortex arrays in open tubesdemonstrated the same tendency for the turbulent burning rate$\propto U_{rms}\lambda^{2/3}$, where  $U_{rms}$ is theroot-mean-square velocity and $\lambda$ is the vortex size. Here itis demonstrated that this tendency is not universal for turbulentburning. Flame interaction with vortex arrays is investigated forthe geometry of a closed burning chamber using direct numericalsimulations of the complete set of gas-dynamic combustion equations.Various initial conditions in the chamber are considered, includinggas at rest and several systems of vortices of different intensitiesand sizes. It is found that the burning rate in a closed chamber(inverse burning time) depends strongly on the vortex intensity; atsufficiently high intensities it increases with $U_{rms}$approximately linearly in agreement with the above tendency. On thecontrary, dependence of the burning rate on the vortex size isnon-monotonic and qualitatively different from the law$\lambda^{2/3}$. It is shown that there is an optimal vortex size ina closed chamber, which provides the fastest total burning rate. Inthe present work the optimal size is 6 times smaller than thechamber height.

  • 42.
    Akkerman, V’yacheslav
    et al.
    Nuclear Safety Institute of Russian Academy of Sciences B. Tulskaya 52, 115191 Moscow, Russia.
    Ivanov, Mikhail
    Department of Physics and Power Engineering, Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Moscow Region, Russia.
    Bychkov, Vitaly
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Turbulent flow produced by Piston Motion in a Spark-ignition engine2009In: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987, Vol. 82, no 3, p. 317-337Article in journal (Refereed)
    Abstract [en]

    Turbulence produced by the piston motion in spark-ignition engines is studied by 2D axisymmetric numerical simulations in the cylindrical geometry as in the theoretical and experimental work by Breuer et al (Flow Turb. Combust. 74 (2005) 145, Ref. [1]). The simulations are based on the Navier-Stokes gas-dynamic equations including viscosity, thermal conduction and non-slip at the walls. Piston motion is taken into account as a boundary condition. The turbulent flow is investigated for a wide range of the engine speed, 1000-4000 rpm, assuming both zero and non-zero initial turbulence. The turbulent rms-velocity and the integral length scale are investigated in axial and radial directions. The rms-turbulent velocity is typically an order-of-magnitude smaller than the piston speed. In the case of zero initial turbulence, the flow at the top-dead-center may be described as a combination of two large-scale vortex rings of a size determined by the engine geometry. When initial turbulence is strong, then the integral turbulent length demonstrates self-similar properties in a large range of crank angles. The results obtained agree with the experimental observations of [1].

  • 43.
    Akkerman, Vyacheslav
    et al.
    Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV, United States .
    Valiev, Damir
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Effect of gas compression on flame acceleration in obstructed cylindrical tubes2016Conference paper (Other academic)
    Abstract [en]

    The role of gas compression on the process of extremely fast flame acceleration in obstructed cylindrical tubes is studied analytically and validated by computational simulations. The acceleration leading to a deflagration-to-detonation transition is associated with a powerful jet-flow produced by delayed combustion in spaces between the obstacles. This acceleration mechanism is Reynolds-independent and conceptually laminar, with turbulence playing only a supplementary role. In this particular work, the incompressible formulation [Combust. Flame 157 (2010) 1012], Ref. 15 is extended to account for small but finite initial Mach number up to the first-order terms. While flames accelerate exponentially during the initial stage of propagation, when the compressibility is negligible, with continuous increase in the flame velocity with respect to the tube wall, the flame-generated compression waves subsequently moderate the acceleration process by affecting the flame shape and velocity, as well as the flow driven by the flame. It is demonstrated that the moderation effect is substantial, and as soon as gas compression is relatively small, the present theory is in good quantitative agreement with the computational simulations. The limitations of the incompressible theory are thereby underlined, and a critical blockage ratio for with this acceleration mechanism can be evaluated.

  • 44.
    Al Khodor, Rami
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Rörelseanalyssystem2014Independent thesis Basic level (professional degree), 180 HE creditsStudent thesis
    Abstract [sv]

    Idag ses ett ökat intresse för användandet av rörelseanalys inom olika sammanhang t.ex. övervakning, dataspel och diagnostisk undersökning av personers rörelsemönster med mera. Optisk rörelseanalys är den teknik som finns mest idag, men de systemen är dyra och saknar lämplig mjukvara för klinisk användning.

    En forskargrupp vid centrum för medicinsk teknik och strålningsfysik (CMTS) forskning och utvecklings avdelning (MT-FoU) vid Norrlands universitetssjukhus har sedan 2007 jobbat med en produktidé som bygger på att skapa ett nytt mobilt system för rörelseanalys som kan användas i medicinska undersökningar. Ett Arduino pro mini kort samt ett 9-axligt prototypkort som består av MPU-6000 och en magnetometer HMC5883L är anskaffat för att tillverka ett system i detta syfte.

    Syftet med projektet har varit att skapa ett verktyg som kan samla in rörelsemönster för att sedan presentera resultatet i ett diagram. Systemet skulle kunna samla in data från en sensor som inkluderar en 3D-accelerometer ett 3D-gyroskop och en 3D magnetometer för att därefter skicka det vidare till en dator där mätdata presenteras visuellt och sparas undan i en textfil.

    En viktig detalj att ta hänsyn till vid konstruktionen av det nya systemet var att konstruktionen gjordes med hjälp av billiga standardkomponenter och kretskort. Projektet har genomförts och några testmätningar har gjorts. Ett resultat sparades undan i en textfil och ett diagram har tagits fram som beskriver ett lårs rörelsemönster vid normal gång.

  • 45.
    Alaa, Alaqra
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    The Thing about gaming experience2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Despite the increasing popularity in the academic and practical fields of digital gaming, little has been explored and documented about gaming experience, especially firsthand account. This study uses Bruno Latour’s concept of the Thing while investigating digital gaming experience from frequent gamers’ standpoint using focus groups methodology. Additionally in-depth interviews were conducted with developers in order to gain a business perspective on the status of digital games development with regard to gamers. From the findings, Reality, Game, and Player were identified as agencies and their associations with the experiences of the gamers were gathered in making the Thing about gaming experience a matter of concern providing new meanings and further understandings of the abstract sets of experiences.

  • 46.
    Al-Alosi, Muhammed
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Framtidsmöjligheter med 5G mobilnät2014Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report introduces various mobile network technologies, 1G to 5G. Focus is on the future 5G mobile networks, how it works and what opportunities will come with it. The report also covers the base stations that will be used in the future mobile network, with a brief description of the terminal in 5G network and the services that will be available with it. The protocol stack in 5G network is also covered. Moreover the report presents the Wi-Fi 802.11u standard that will be a part of the future mobile network. We can also read about how the 5G network will solve certain problems that are related to today's networks technologies. Finally, the report describes different access technologies that are used in the telecommunications systems.

  • 47.
    Alam, Md Khorshed
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Fabrication of surface enhanced Raman spectroscopy (SERS) active substrates based on vertically aligned nitrogen doped carbon nanotube forest2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis work describes the fabrication and surface enhanced Raman spectroscopy (SERS) characterization of vertically aligned nitrogen (N) doped multi walled carbon nanotube (MWCNT) forests coated by silver (Ag) and gold (Au) nanoparticles. In the present work, the CNT forests were grown from a catalyst metal layer by the chemical vapor deposition (CVD) process at temperature of 800 oC and a physical vapor deposition (PVD) and annealing processes were applied subsequently for the evaporation and diffusion of noble metal nanoparticles on the forest.

    Transistor patterning of 20, 50 and 100 μm were made onto the silicon-oxide (SiO2) wafers through the photolithography process with and without depositing a thickness of 10 nm titanium (Ti) buffer layer on the Si-surfaces. Iron (Fe) and cobalt (Co) were used together to deposite a thickness of 5 nm catalyst layer onto the Single Side Polished (SSP) wafers. As carbon and nitrogen precursor for the CNT growth was used pyridine. Two different treatment times (20 and 60 minutes) in the CVD process determined the CNT forest height. Scanning Electron Microscopy (SEM) imaging was employed to characterize the CNT forest properties and Ag and Au nanoparticle distribution along the CNT walls.

    The existence of “hot spots” created by the Ag and Au nanoparticles through the surface roughness and plasmonic properties was demonstrated by the SERS measurements. Accordingly, the peak intensity at wave number of 1076 cm-1 was picked up from each SERS spectra to establish the Ag- and Au-trend curves with different concentrations of 4-ATP solution. The SERS mapping was also carried out to study the Ag- and Au-coated CNT surface homogeneity and “hot spots” distribution on the CNT surface. The SERS enhancement factors (EF) were calculated by applying an analyte solution of ethanolic 4-ATP on the CNT surface. The calculated values of EF from Ag- and Au-coated CNT forests were 9×106 and 2.7×105 respectively. 

  • 48.
    Albano, Amanda
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Exploratory statistical study of long-term variability in echocardiographic indices (echocardiovariability) in healthy and diseased1987Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Heart rate variability, HRV, has been well researched for some decades. The oscillations of the heart rate is studied over a time period of some minutes up to 24 hours, it is measured with electrocardiography, ECG. From this one has concluded that the heart rate signal oscillates in accordance with the respiration, the resistance in the vessels etc.

    The most frequently used examination method of the heart is done with ultrasound, called echocardiography. One interesting variable at a time is measured and it is measured for a single heartbeat. With inspiration ofthe HRV studies this project focuses on some of the variables measured with ultrasound but over time andsimultaneously. The variables of interest are the myocardial motion and the blood flow in the left part ofthe heart, they are measured over two minutes. To complement these variables the well known variables HRand Resp are measured with ECG and added to the analysis.

    The methods used for analysing the variables are first of all descriptive statistics like mean and standard deviation. Secondly spectral analysis is performed to investigate in which frequencies the variables oscillates. Through coherence this is compared with the spectrum for HR where the three peaks have known origin. Finally principal component analysis, PCA, is performed as a method to compare all variables at the same time.

    The analyses are performed on seven measurements from five (5) healthy persons and five measurementsfrom four (4) patients with the disease FAP (“Skelleftesjukan”). The variables are investigated and described for the healthy persons first, then the healthy persons and patients are compared.

    The result from the study shows that most of the echo-variables oscillate in accordance with the respirationand the heart rate. For a healthy person the oscillations are within normal values and the relative deviation isaround 10%. The patients with FAP are most affected in the variables connected to the myocardium apartfrom HR, which is known since before.

    The coherence between the echo-variables and HR is low in one of VLF, very low frequency, or LF, lowfrequency, region and high in the other. In HF, high frequency, region the coherence is high for all variables.

    Finally the PCA was conducted on measurements from all healthy persons as one data set, from one ofthe healthy persons and from one of the patients with FAP. The analysis showed that for healthy personsrespiration is the process causing most variation and all of the echo-variables have a correlation to therespiration. For a patient with FAP the respiration is not as salient. A PCA over blocks of data at different time points however show that the signals are not oscillating in the same way multivariately over the wholetime series.

  • 49.
    Albán Reyes, Diana Carolina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden .
    Svedberg, Anna
    Eliasson, Bertil
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sundman, Ola
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    The influence of different parameters on the mercerisation of cellulose for viscose production2016In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 2, p. 1061-1072Article in journal (Refereed)
    Abstract [en]

    A quantitative analysis of degree of transformation from a softwood sulphite dissolving pulp to alkalised material and the yield of this transformation as a function of the simultaneous variation of the NaOH concentration, denoted [NaOH], reaction time and temperature was performed. Samples were analysed with Raman spectroscopy in combination with multivariate data analysis and these results were confirmed by X-ray diffraction. Gravimetry was used to measure the yield. The resulting data were related to the processing conditions in a Partial Least Square regression model, which made it possible to explore the relevance of the three studied variables on the responses. The detailed predictions for the interactive effects of the measured parameters made it possible to determine optimal conditions for both yield and degree of transformation in viscose manufacturing. The yield was positively correlated to the temperature from room temperature up to 45 A degrees C, after which the relation was negative. Temperature was found to be important for the degree of transformation and yield. The time to reach a certain degree of transformation (i.e. mercerisation) depended on both temperature and [NaOH]. At low temperatures and high [NaOH], mercerisation was instantaneous. It was concluded that the size of fibre particles (mesh range 0.25-1 mm) had no influence on degree of transformation in viscose processing conditions, apparently due to the quick reaction with the excess of NaOH.

  • 50.
    Albán Reyes, Diana Carolina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Stridh, Kjell
    AkzoNobel, Stenungsund, Sverige.
    de Wit, Paul P.
    AkzoNobel, Arnhem, The Netherlands.
    Sundman, Ola
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Is there a diffusion of alkali in the activation of dissolving cellulose pulp at low NAOH stoichiometric excess?2019In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 2, p. 1297-1308Article in journal (Refereed)
    Abstract [en]

    We conducted a quantitative study, following the degree of activation (i.e. the transformation to alkali cellulose, denoted as DoA) over time for dissolving cellulose pulp treated with different [NaOH] at low NaOH/anhydroglucose unit stoichiometric ratio (denoted as (r) ≤ 2.6). Our quantitative approach was based on Raman spectroscopy data, evaluated by partial least squares regression modelling. The results show strong influence of the (r) on DoA (increasing from DoA= 45% at (r) = 0.8, to DoA = 85% at (r) = 2.6), and its complex dependence on [NaOH]. At (r) = 0.8 the highest DoA (DoA ≳ 60%) was found at 30% [NaOH], while at (r) =1.3 it was found at 20% [NaOH] (DoA ≳ 80%). Although activation of cellulose happens in minutes at the studied temperature (30 °C), it was found that the reaction may be slow when a low (r) is used. A gradual increase of the DoA from ≈ 30% to ≈ 70% in time was seen when samples were activated with 30% [NaOH] at (r) = 0.8. At the same (r), a similar increase of DoA from ≈ 30 % to ≈ 60 % was also observed when 40% [NaOH] was used. Slow diffusion of NaOH through poorly swollen cellulose fibres is proposed as an explanation for this phenomenon. Lastly, solid-state CP/MAS NMR measurements suggest that at a fixed temperature, the Na-Cell allomorph mostly depends on [NaOH]. However, in the transition area between Na-Cell I and Na-Cell II, its influence might be affected by (r). 

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