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  • 1.
    Mansouri, Sina Sharif
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Kanellakis, Christoforos
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Georgoulas, Georgios
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Kominiak, Dariusz
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    2D visual area coverage and path planning coupled with camera footprints2018In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 75, p. 1-16Article in journal (Refereed)
    Abstract [en]

    Unmanned Aerial Vehicles (UAVs) equipped with visual sensors are widely used in area coverage missions. Guaranteeing full coverage coupled with camera footprint is one of the most challenging tasks, thus, in the presented novel approach a coverage path planner for the inspection of 2D areas is established, a 3 Degree of Freedom (DoF) camera movement is considered and the shortest path from the taking off to the landing station is generated, while covering the target area. The proposed scheme requires a priori information about the boundaries of the target area and generates the paths in an offline process. The efficacy and the overall performance of the proposed method has been experimentally evaluated in multiple indoor inspection experiments with convex and non convex areas. Furthermore, the image streams collected during the coverage tasks were post-processed using image stitching for obtaining a single overview of the covered scene.

  • 2.
    Öhman, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    3D localization in digital holography from scattered light from micrometer-sized particles2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    When a particle is illuminated by a beam of light it will scatter and redistribute the light in all directions. How it scatters depends on the size, shape and refractive index of the particle. Additionally, it depends on the wavelength and polarization of the illuminating beam. The direction and distance to the observer relative the particle also needs to be considered.  A digital holographic imaging system is used to collect parts of the scattered light from micrometer-sized particles. By utilizing digital holography a three-dimensional reconstruction of the imaged scene is possible. Traditionally, particles are localized based on the intensity in the holographic reconstructions. In this licentiate thesis, the phase response of the scattered light is investigated and utilized. An alternative method for locating spherical particles is presented. The method locate particles based on a simple feature of a propagating wave, namely the fact that the wavefront curvature changes from converging to diverging at the axial location of the particle. The wavefront curvature is estimated using two different methods. The first method estimates the lateral phase-gradients using a finite-difference method. The second method uses a three-dimensional parametric model based on a Chebyshev polynomial expansion. The methods are demonstrated using both simulations and experimental measurements. The simulations are based on the Lorenz-Mie scattering theory for spherical particles and are combined with an imaging system model. Experiments are performed using an off-axis polarization sensitive digital holographic system with a coherent Nd:YAG laser. Measurements of stationary particles are made to validate and evaluate the proposed method. It is found that these methods estimate the true axial position and does not have the offset that is associated with intensity-based methods. Additionally, it is possible to exclude noise that shows up as false particles since noise does not have the same phase response as a real particle. The second method, that uses a parametric model, also improves the standard deviation in the positioning.

  • 3.
    Mishra, Madhav
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    van Riet, Maarten
    Alliander N.V., The Netherlands.
    A channel model for power line communication using 4PSK technology for diagnosis: Some lessons learned2018In: International Journal of Electrical Power & Energy Systems, ISSN 0142-0615, E-ISSN 1879-3517, Vol. 95, p. 617-634Article in journal (Refereed)
    Abstract [en]

    Modern smart grids and smart metering concepts are based on reliable digital communications. The absence of dedicated communications media, such as telephone lines or fibre optics within a power line network, can make transmission challenging. Electrical power companies are interested in implementing an overall communicating power line network. The power line communication (PLC) system uses the electric power distribution grid as a data transmission medium. The data transmission problem resulted due to poorly developed Medium Voltage Network of PLC Channel Model and challenges in data transmission technology, so this hampers better performance. This paper studies PLC over a medium voltage network with a goal of achieving greater bit rates and communication that is more reliable over power lines. It presents a complete channel model of a PLC system and evaluation of Bit Error Rate (BER) of Phase Shift Keying (PSK) when corrupted with noise. It calculates the number of sections between two substations to determine signal loss. The PSK modulation scheme in simulation is experimentally found to be more robust against such power line distortions as noise for point-to-point transmission. The model and calculations use Matlab and QUCS.

  • 4.
    Dai, Wenbin
    et al.
    Shanghai Jiao Tong University, Department of Automation.
    Riliskis, Laurynas
    Stanford University, Department of Computer Science.
    Wang, Peng
    Shenyang Institute of Automation, China Academy of Science.
    Vyatkin, Valeriy
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science. Aalto University, Espoo.
    Guan, Xinping
    Department of Automation, Shanghai Jiao Tong University, Shanghai.
    A Cloud-Based Decision Support System for Self-Healing in Distributed Automation Systems Using Fault Tree Analysis2018In: IEEE Transactions on Industrial Informatics, ISSN 1551-3203, E-ISSN 1941-0050, Vol. 14, no 3, p. 989-1000Article in journal (Refereed)
    Abstract [en]

    Downtime is a key performance index for industrial automation systems. An industrial automation system achieves maximum productivity when its downtime is reduced to the minimum. One approach to minimize downtime is to predict system faults and recover from them automatically. A cloud-based decision support system is proposed for rapid problem identifications and to assist the self-management processes. By running multiple parallel simulations of control software with real-time inputs ahead of system time, faults could be detected and corrected automatically using autonomous industrial software agents. Fault trees, as well as control algorithms, are modeled using IEC 61499 function blocks that can be directly executed on both physical controllers and cloud services. A case study of water heating process is used to demonstrate the self-healing process supported by the cloud-based decision support system.

  • 5.
    Sissakian, Varoujan K.
    et al.
    University of Kurdistan, Howler, KRG; Private Consultant Geologist, Erbil, Iraq.
    Adamo, Nasrat
    Al-Ansari, Nadhir
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Laue, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Elagely, Malik
    Private consultant, Baghdad, Iraq.
    A Comparative Study of Mosul and Haditha Dams, Iraq: Geological conditions2018In: Journal of Earth Sciences and Geotechnical Engineering, ISSN 1792-9040, E-ISSN 1792-9660, Vol. 8, no 2, p. 35-52Article in journal (Refereed)
    Abstract [en]

    Mosul and Haditha Dams are the largest dams on the Tigris and Euphrates Rivers in Iraq, respectively. Both dams are of earthfill type and constructed on sedimentary rocks, but have different geological conditions. Both of them suffer from karstification problems. The former; however, suffers from intense karstification, which has endangered the stability of the dam and possible failure. The karstification in both sites is of different origins, types, shapes, sizes and depths, as well as in different rocks and geological formations. In Mosul Dam site, the highly dissolved gypsum beds of the Fatha Formation has formed solution type sinkholes with cavities of different shapes and sizes at different depth; attaining to about 250 m upon which the foundations of the dam are located. In Haditha Dam site, the karstification occur in the limestone beds of the Euphrates Formation, the developed sinkholes are of collapse type with regular shapes; either circular or oval apertures. The thickness of the karstified sequence in the foundations is not more 50 m. This research work is to highlight the role of the geological conditions, especially when the karstification in the safety of both dams is concerned and its effect on the foundations of the dams.

  • 6.
    Filella, Montserrat
    et al.
    Department F.-A. Forel, University of Geneva.
    Rodushkin, Ilia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    A concise guide for the determination of less-studied technology-critical elements (Nb, Ta, Ga, In, Ge, Te) by inductively coupled plasma mass spectrometry in environmental samples2018In: Spectrochimica Acta Part B - Atomic Spectroscopy, ISSN 0584-8547, E-ISSN 1873-3565, Vol. 141, p. 80-84Article in journal (Refereed)
    Abstract [en]

    There is an increasing demand for analytical techniques able to measure so-called ‘technology-critical elements’, a set of chemical elements increasingly used in technological applications, in environmental matrices. Nowadays, inductively coupled plasma-mass spectrometry (ICP-MS) has become the technique of choice for measuring trace element concentrations. However, its application is often less straightforward than often assumed. The hints and drawbacks of ICP-MS application to the measurement of a set of less-studied technology-critical elements (Nb, Ta, Ga, In, Ge and Te) is discussed here and concise guidelines given.

  • 7.
    Hakima, Houman
    et al.
    Institute for Aerospace Studies, University of Toronto .
    Bazzocchi, Michael C. F.
    Institute for Aerospace Studies, University of Toronto.
    Emami, Reza
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Institute for Aerospace Studies, University of Toronto.
    A Deorbiter CubeSat for Active Orbital Debris Removal2018In: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 61, no 9, p. 2377-2392Article in journal (Refereed)
    Abstract [en]

    This paper introduces a mission concept for active removal of orbital debris based on the utilization of the CubeSat form factor. The CubeSat is deployed from a carrier spacecraft, known as a mothership, and is equipped with orbital and attitude control actuators to attach to the target debris, stabilize its attitude, and subsequently move the debris to a lower orbit where atmospheric drag is high enough for the bodies to burn up. The mass and orbit altitude of debris objects that are within the realms of the CubeSat’s propulsion capabilities are identified. The attitude control schemes for the detumbling and deorbiting phases of the mission are specified. The objective of the deorbiting maneuver is to decrease the semi-major axis of the debris orbit, at the fastest rate, from its initial value to a final value of about 6,471 km (i.e., 100 km above Earth considering a circular orbit) via a continuous low-thrust orbital transfer. Two case studies are investigated to verify the performance of the deorbiter CubeSat during the detumbling and deorbiting phases of the mission. The baseline target debris used in the study are the decommissioned KOMPSAT-1 satellite and the Pegasus rocket body. The results show that the deorbiting times for the target debris are reduced significantly, from several decades to one or two years.

  • 8.
    Yin, Lihua
    et al.
    State Key Laboratory of Information Security, Institute of Information Engineering, Chinese Academy of Sciences, Beijing, .
    Guo, Yunchuan
    State Key Laboratory of Information Security, Institute of Information Engineering, Chinese Academy of Sciences, Beijing.
    Li, Fenghua
    State Key Laboratory of Information Security, Institute of Information Engineering, Chinese Academy of Sciences, Beijing.
    Sun, Yanwei
    State Key Laboratory of Information Security, Institute of Information Engineering, Chinese Academy of Sciences, Beijing .
    Qian, Junyan
    Guangxi Key Laboratory of Trusted Software, Guilin University of Electronic Technology, Guilin.
    Vasilakos, Athanasios
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    A game-theoretic approach to advertisement dissemination in ephemeral networks2018In: World wide web (Bussum), ISSN 1386-145X, E-ISSN 1573-1413, Vol. 21, no 2, p. 241-260Article in journal (Refereed)
    Abstract [en]

    In ephemeral networks, disseminating advertisements faces two dilemmatic problems: on the one hand, disseminators own the limited resources and have privacy concerns, thus, often preferring to avoid disseminating advertisements without enough incentives; Even if advertisements are disseminated, their dissemination accuracy is lower. On the other hand, false advertisements may flood in ephemeral networks if too many incentives but no punishments are given. Thus, it is a challenge to design an effective scheme to guarantee rational disseminators have sufficient impetus to forward true advertisements to the interested consumers and report false advertisements, despite facing the limitation of resources and the risk of privacy leakage. To solve this problem, in this paper, a bargaining-based scheme is proposed to motive disseminators to forward the true advertisements to the interested node and a semi-grim policy is designed for punishing the disseminators who releases and disseminates false advertisements. Acknowledging the assumption of incomplete information, a repeated dissemination game is proposed to help disseminators to decide whether to forward advertisements or report false advertisements. Simulation results demonstrate that our scheme not only provides disseminators a strong impetus to disseminate the advertisements with higher dissemination accuracy, but also effectively prevents disseminators from forwarding false advertisements.

  • 9.
    Jouybari, Nima
    et al.
    Department of Mechanical Engineering, Tarbiat Modares University.
    Maerefat, Mehdi
    Department of Mechanical Engineering, Tarbiat Modares University.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Eshagh Nimvari, Majid
    Faculty of Engineering Technologies, Amol University of Special Modern Technologies, Amol.
    Gholami, Zahra
    Department of Food and Agriculture, Standard Research Institute, Karaj.
    A General Macroscopic Model for Turbulent Flow in Porous Media2018In: Journal of Fluids Engineering - Trancactions of The ASME, ISSN 0098-2202, E-ISSN 1528-901X, Vol. 140, no 1, article id 011201Article in journal (Refereed)
    Abstract [en]

    The present study deals with the generalization of a macroscopic turbulence model in porous media using a capillary model. The additional source terms associated with the production and dissipation of turbulent kinetic energy due to the presence of solid matrix are calculated using the capillary model. The present model does not require any prior pore scale simulation of turbulent flow in a specific porous geometry in order to close the macroscopic turbulence equations. Validation of the results in packed beds, periodic arrangement of square cylinders, synthetic foams and longitudinal flows such as pipes, channels and rod bundles against available data in the literature reveals the ability of the present model in predicting turbulent flow characteristics in different types of porous media. Transition to the fully turbulent regime in porous media and different approaches to treat this phenomenon are also discussed in the present study. Finally, the general model is modified so that it can be applied to lower Reynolds numbers below the range of fully turbulent regime in porous media.

  • 10.
    Kohlbacher, Anton
    et al.
    Luleå University of Technology.
    Eliasson, Jens
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Acres, Kevin
    Monash Swarm Robotics Laboratory, Monash University.
    Chung, Hoam
    Monash Swarm Robotics Laboratory, Monash University.
    Barca, Jan Carlo
    Monash Swarm Robotics Laboratory, Monash University.
    A Low Cost Omnidirectional Relative Localization Sensor for Swarm Applications2018In: IEEE 4th World Forum on Internet of Things, 2018Conference paper (Refereed)
    Abstract [en]

    By enabling coordinated task execution and movement, robotic swarms can achieve efficient exploration of unknown environments. In this paper, we propose a relative localization sensor system using Ultra-wideband (UWB) radio technology for ranging. This system is light-weight and relatively indifferent to the types of surrounding environments. Infrastructure dependency such as the requirement of beacons at known locations is eliminated by making an array of sensors on a swarm agent. In this paper, a novel algorithm is implemented on hardware with limited resources and compared to a more traditional trilateration approach. Both utilize Particle Swarm Optimization (PSO) to be more robust against noise and to achieve similar accuracy. The experimental results show that the proposed algorithm runs up to ten times faster than the existing trilateration approach. The sensor array which forms the localization system weighs only 56g, and achieves around 0.5m RMSE with a 10Hz update rate. Experiments show that the accuracy can be further improved if the rotational bias observed in the UWB devices are compensated for.

  • 11.
    Lideskog, Håkan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    A Methodology for Automation of Mechanized Forest Regeneration2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    High quality forest regeneration is typically performed by a combination of site preparation through mounding and deep planting. These operations are performed either by mounders with subsequent manual planting, or by mechanized tree planting devices that creates mounds and, simultaneously, plant seedlings. These forest regeneration strategies are sustainably beneficial and have high development potential particularly regarding efficiency. Recent development in digitalization, sensing, IoT etc. has enabled new forest regeneration strategies. Hence, the objective of this thesis is therefore to develop a methodology for how automation can be used to improve sustainability in forestry and in forest regeneration operations in particular. The research has followed the Design Research Methodology in which success criteria was identified concurrently with analysis of the as-is situation. Then different sub-solutions forming the automation methodology was prescribed and validated in subsequent descriptive studies. To enable automation, it was found that data needs to be retrieved from surroundings while performing mounding or mechanized planting, whereby analyses of this data need to be used to make improved decisions of the machines’ working procedures. First, properties and characteristics of the surroundings on a clearcut were defined. Then, different ways to retrieve data from the surroundings were tested and evaluated. In addition, several ways of analyzing such data for improved decision making were found and validated. The information gained from data collection of surroundings and subsequent analyses further has potential to be improve activities beyond forest regeneration e.g. smart forwarding, customer adapted assortments, history tracking etc. To use as support for how decision making can be improved from such information, an experimental terrain vehicle platform for researchers and machine developers was developed to enable tests and validation of new solutions with special focus on autonomy and robotics, which requires a variety of data collected from both exteroceptive and proprioceptive sensors. The resulting methodology shows how forest regeneration can be automated in the short-term. Developed methods for data collection and analysis can enhance obstacle avoidance for mounding significantly, and thus contribute to increasing the share of continuously intermittent mounding conducted in Fennoscandia.

  • 12.
    Fernández-Remolar, David
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Banerjee, Neil
    Centre for Planetary Science and Exploration (CPSX), Department of Earth Sciences, University of Western Ontario.
    Gómez-Ortiz, David
    ESCET-Área de Geología, Universidad Rey Juan Carlos.
    Izawa, Matthew
    4Institute for Planetary Materials, Okayama University, Misasa.
    Amils, Ricardo
    Planetology and Habitability Department, Center of Astrobiology (INTA-CSIC) .
    A mineralogical archive of the biogeochemical sulfur cycle preserved in the subsurface of the Río Tinto system2018In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 103, no 3, p. 394-411Article in journal (Refereed)
    Abstract [en]

    The search for extinct and extant life on Mars is based on the study of biosignatures that could be preserved under Mars-like, extreme conditions that are replicated in different terrestrial analog environments. The mineral record in the subsurface of the Río Tinto system is one example of a Mars analog site that has been exposed to weathering conditions, including the biogeochemical activity of Fe and S chemolithotrophic bacteria, for millions of years. The SEM-EDAX analysis of different samples recovered in the Peña de Hierro area from four boreholes, ranging from 166 to 610 m in depth, has provided the identification of microbial structures that have affected a suite of hydrothermal minerals (~345 Ma) as well as minerals likely produced by biological activity in more recent times (<7 Ma). The hydrothermal minerals correspond to reduced sulfur or sulfate-bearing compounds (e.g., pyrite and barite) that are covered by bacilli- or filamentous-like microbial structures and/or secondary ferrous carbonates (e.g., siderite) with laminar to spherical structures. The secondary iron carbonates can be in direct contact or above an empty interphase with the primary hydrothermal minerals following a wavy to bent contact. Such an empty interphase is usually filled with nanoscale, straight filamentous structures that have a carbonaceous composition. The occurrence of a sulfur and iron chemolithotrophic community in the Río Tinto basement strongly suggests that the association between sulfur-bearing minerals, dissolution scars and secondary minerals of biological origin is a complex process involving the microbial attack on mineral surfaces by sulfur reducing bacteria followed by the precipitation of iron-rich carbonates. In this scenario, iron sulfide compounds such as pyrite would act as electron donors under microbial oxidation, while sulfate minerals such as barite would act as electron acceptors through sulfate reduction. Furthermore, the formation of siderite would have resulted from carbonate biomineralization of iron chemoheterotrophic organims or other microorganisms that concentrate carbonate through metabolic pathways. Although the distribution of the mineral biosignatures at depth clearly follows a redox gradient, they show some irregular allocation underground, suggesting that the geochemical conditions governing the microbial activity are affected by local changes associated with the fracturing pattern of the Río Tinto basement. The abundance of sulfur- and iron-bearing minerals in the Mars crust suggests that the Río Tinto mineral biosignatures can be useful in the search for extant and extinct subsurface life on the red planet

  • 13.
    Lindström, John
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Hermansson, Anders
    Adage AB, C/O BnearIT.
    Blomstedt, Fredrik
    BnearIT AB.
    Kyösti, Petter
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems. Luleå University of Technology, Department of Applied Physics and Mechanical Engineering, Fastelaboratoriet.
    A multi-usable cloud service platform: a case study on improved development pace and efficiency2018In: Applied Sciences, E-ISSN 2076-3417, Vol. 8, no 2, article id 316Article in journal (Refereed)
    Abstract [en]

    The case study, spanning three contexts, concerns a multi-usable cloud service platform for big data collection and analytics and how the development pace and efficiency of it has been improved 50-75% by using the Arrowhead framework and changing development processes/practices. Further, additional results captured during the case study are related to technology, competencies and skills, organization, management, infrastructure, and service and support. A conclusion is that when offering a complex offer such as an Industrial Product-Service System, comprising sensors, hardware, communications, software, cloud service platform, etc., it is necessary that the technology, business model, business set up and organization all go hand in hand during the development and later operation, as all “components” are required for a successful result.

  • 14.
    Espinilla, Macarena
    et al.
    Department of Computer Science, University of Jaén, Jaén, Spain.
    Medina, Javier
    Department of Computer Science, University of Jaén, Jaén, Spain.
    Hallberg, Josef
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Nugent, Chris
    School of Computing and Mathematics, Ulster University, Coleraine, UK.
    A new approach based on temporal sub-windows for online sensor-based activity recognition2018In: Journal of Ambient Intelligence and Humanized Computing, ISSN 1868-5137, E-ISSN 1868-5145Article in journal (Refereed)
    Abstract [en]

    Usually, approaches driven by data proposed in literature for sensor-based activity recognition use the begin label and the end label of each activity in the dataset, fixing a temporal window with sensor data events to identify the activity carried out in this window. This type of approach cannot be carried out in real time because it is not possible to predict the start time of an activity, i.e., the class of the future activity that an inhabitant will perform, neither when he/she will begin to carry out this activity. However, an activity can be marked as finished in real time only with the previous observations. Therefore, there is a need of online activity recognition approaches that classify activities using only the end label of the activity. In this paper, we propose and evaluate a new approach for online activity recognition with three temporal sub-windows that uses only the end label of the activity. The advantage of our approach is that the temporal sub-windows keep a partial order in the sensor data stream from the end time of the activity in a short-term, medium-term, long-term. The experiments conducted to evaluate our approach suggest the importance of the use of temporal sub-windows versus a single temporal window in terms of accuracy, using only the end time of the activity. The use of temporal sub-windows has improved the accuracy in the 98.95% of experiments carried out.

  • 15.
    Islam, Raihan Ul
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Hossain, Mohammad Shahadat
    Department of Computer Science and Engineering, University of Chittagong, Chittagong 4331, Bangladesh.
    Andersson, Karl
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    A novel anomaly detection algorithm for sensor data under uncertainty2018In: Soft Computing - A Fusion of Foundations, Methodologies and Applications, ISSN 1432-7643, E-ISSN 1433-7479, Vol. 22, no 5, p. 1623-1639Article in journal (Refereed)
    Abstract [en]

    It is an era of Internet of Things, where various types of sensors, especially wireless, are widely used to collect huge amount of data to feed various systems such as surveillance, environmental monitoring, and disaster management. In these systems, wireless sensors are deployed to make decisions or to predict an event in a real-time basis. However, the accuracy of such decisions or predictions depends upon the reliability of the sensor data. Unfortunately, erroneous data are received from the sensors. Consequently, it hampers the appropriate operations of the mentioned systems, especially in making decisions and prediction. Therefore, the detection of anomaly that exists with the sensor data drew significant attention and hence, it needs to be filtered before feeding a system to increase its reliability in making decisions or prediction. There exists various sensor anomaly detection algorithms, but few of them are able to address the uncertain phenomenon, associated with the sensor data. If these uncertain phenomena cannot be addressed by the algorithms, the filtered data into the system will not be able to increase the reliability of the decision-making process. These uncertainties may be due to the incompleteness, ignorance, vagueness, imprecision and ambiguity. Therefore, in this paper we propose a new belief-rule-based association rule (BRBAR) with the ability to handle the various types of uncertainties as mentioned.The reliability of this novel algorithm has been compared with other existing anomaly detection algorithms such as Gaussian, binary association rule and fuzzy association rule by using sensor data from various domains such as rainfall, temperature and cancer cell data. Receiver operating characteristic curves are used for comparing the performance of our proposed BRBAR with the aforementioned algorithms. The comparisons demonstrate that BRBAR is more accurate and reliable in detecting anomalies from sensor data under uncertainty. Hence, the use of such algorithm to feed the decision-making systems could be beneficial. Therefore, we have used this algorithm to feed appropriate sensor data to our recently developed belief-rule-based expert system to predict flooding in an area. Consequently, the reliability and the accuracy of the flood prediction system increase significantly. Such novel algorithm (BRBAR) can be used in other areas of applications. 

  • 16.
    Liu, Yanan
    et al.
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, .
    Cai, Xiaoping
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou .
    Sun, Zhi
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou .
    Jiao, Xinyang
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Akhtar, Farid
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Wang, Jianzhong
    State Key Laboratory of Porous Metal Materials, Northwest Institute for Non-ferrous Metal Research, Xi'an .
    Feng, Peizhong
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    A novel fabrication strategy for highly porous FeAl/Al2O3 composite by thermal explosion in vacuum2018In: Vacuum, ISSN 0042-207X, Vol. 149, p. 225-230Article in journal (Refereed)
    Abstract [en]

    The high porosity of FeAl/Al2O3 composites was successfully prepared via a low-energy consumption method of thermal explosion (TE) in vacuum from reactant mixtures of Fe, Al and Fe2O3. The temperature profiles, phase compositions, microstructure, porosity and pore size of the products were investigated. The TE reactions were ignited between 639 and 648 °C and maximum combustion temperatures reached to 1196–1867 °C. XRD patterns showed that FeAl, Fe2Al5 and Al2O3 were formed via TE reaction, and FeAl and Al2O3 were evolved as dominant phase after the final sintering at 1100 °C. The FeAl/Al2O3 composites exhibited an interconnected pore structure with porosities and pore size of 52–61% and 27–32 μm, respectively.

  • 17.
    Lee, Cheng-Chi
    et al.
    Department of Library and Information Science, Fu Jen Catholic University, New Taipei City, Taiwan, Republic of China; Department of Photonics and Communication Engineering, Asia University, Taichung, Taiwan, Republic of China.
    Li, Chun-Ta
    Department of Information Management, Tainan University of Technology, Tainan, Taiwan, Republic of China.
    Cheng, Chung-Lun
    Department of Library and Information Science, Fu Jen Catholic University, New Taipei City, Taiwan, Republic of China.
    Lai, Yan-Ming
    Department of Computer Science and Information Engineering, National Taiwan University, Taipei, Taiwan, Republic of China.
    Vasilakos, Athanasios V.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    A Novel Group Ownership Delegate Protocol for RFID Systems2018In: Information Systems Frontiers, ISSN 1387-3326, E-ISSN 1572-9419Article in journal (Refereed)
    Abstract [en]

    In recent years, Radio Frequency Identification (RFID) applications of various kinds have been blooming. However, along with the stunning advancement have come all sorts of security and privacy issues, for RFID tags oftentimes store private data and so the permission to read a tag or any other kind of access needs to be carefully controlled. Therefore, of all the RFID-related researches released so far, a big portion focuses on the issue of authentication. There have been so many cases where the legal access to or control over a tag needs to be switched from one reader to another, which has encouraged the development of quite a number of different kinds of ownership transfer protocols. On the other hand, not only has the need for ownership transfer been increasing, but a part of it has also been evolving from individual ownership transfer into group ownership transfer. However, in spite of the growing need for practical group ownership transfer services, little research has been done to offer an answer to the need. In this paper, we shall present a new RFID time-bound group ownership delegate protocol based on homomorphic encryption and quadratic residues. In addition, in order to provide more comprehensive service, on top of mutual authentication and ownership delegation, we also offer options for the e-th time verification as well as the revocation of earlier delegation.

  • 18.
    Mohamad, Medhat
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nilsson, Rickard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    van de Beek, Jaap
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    A Novel Transmitter Architecture for Spectrally-Precoded OFDM2018In: IEEE Transactions on Circuits and Systems Part 1: Regular Papers, ISSN 1549-8328, E-ISSN 1558-0806Article in journal (Refereed)
    Abstract [en]

    Frequency nulling spectral precoding is an approachthat suppresses the out-of-band emission in OFDM systems.In this paper, we discuss the transmitter architecture of thespectrally precoded OFDM systems. We design a novel precoderthat matches the practical implementation of the OFDM modulator.We show that spectral precoding can relax the analog lowpass filtering requirements of the OFDM system transmitter. Weexamine the effect of spectral precoding on the PAPR as wellas the effect of the PA on the spectral precoding suppressionperformance. We also study the compliance of the spectrallyprecoded OFDM transmitter with the 3GPP standardizationmeasures and analyze its computation complexity. At the receiverside, we analyze the in-band interference and BER performanceof the suggested precoding approach.

  • 19.
    Wibron, Emelie
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    A Numerical and Experimental Study of Airflow in Data Centers2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Airflow management is crucial for the performance of cooling systems in data centers. The amount of energy consumed by data centers is huge and a large amount is related to the cooling. In attempts to develop energy efficient data centers, numerical methods are important for several reasons. Experimental procedures are more expensive and time consuming but when done carefully, experiments provide trustful results that can be used to validate simulations and give additional insights. Numerical methods in their turn have the advantage that they can be applied to proposed designs of data centers before they are built and not only to already existing data centers.In this study, Computational Fluid Dynamics (CFD) is used to study the airflow in data centers. The aim is to use an experimentally validated CFD model to investigate the effects of using different designs in data centers with respect to the performance of the cooling systems. Important parameters such as quality of the computational grid, boundary conditions and choice of turbulence model must be carefully considered in order for the results from simulations to be reliable.In Paper A, a hard floor configuration where the cold air is supplied directly into the data center is compared to a raised floor configuration where the cold air is supplied into an under-floor space instead and enters the data center through perforated tiles in the floor. In Paper B, the performance of different turbulence models are investigated and velocity measurements are used to validate the CFD model. In Paper C, the performance of different cooling systems is further investigated by using an experimentally validated CFD model. The effects of using partial aisle containment in the design of data centers are evaluated for both hard and raised floor configurations.Results show that the flow fields in data centers are very complex with large velocity gradients. The k − ε model fails to predict low velocity regions. Reynolds Stress Model (RSM) and Detached Eddy Simulation (DES) produce very similar results and based on solution times, it is recommended to use RSM to model the turbulent airflow in data centers. Based on a combination of performance metrics where both intake temperatures for the server racks and airflow patterns are considered, the airflow management is significantly improved in raised floor configurations. Using side covers to partially enclose the aisles performs better than using top covers or open aisles.

  • 20.
    Svartsjaern, Mikael
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering. Itasca Consultants AB Luleå .
    A Prognosis Methodology for Underground Infrastructure Damage in Sublevel Cave Mining2018In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453XArticle in journal (Refereed)
    Abstract [en]

    In sublevel caving (SLC), the caving of the hangingwall due to ore extraction emphasises placement of the mining infrastructure in the footwall. While the footwall in general is less affected by ground settlement compared to the hangingwall, the changes in stress field from mining are significant. The footwall infrastructure must thus be positioned sufficiently far into the footwall to avoid damage from the mining-induced stress; however, placing the infrastructure farther into the footwall increases costs associated with additional drifting and operational distances. This paper presents a case study in which a robust prognosis tool for predicting infrastructure damage associated with SLC mining is developed. The concept of the proposed methodology was developed for the Luossavaara-Kiirunavaara Aktiebolag Kiirunavaara SLC mine. Initial steps are data collection through systematic damage mapping followed by conceptual modelling of the general rock mass response to mining. The results of the conceptual models are used as the basis for refined calibrated models detailing the damage development and failure mechanisms. The main system behaviour, failure mechanism and associated damage evolution are incorporated into a bilinear equation using the studied depth and local ore width as input to estimate the final horizontal damage extent from the footwall contact after mining of any specific level. The proposed relationship accurately replicates the current damage pattern within 40 m for more than 70% of the recorded observations up until current mining. The anticipated future damage extent is also shown to be well correlated with current micro-seismic event locations. The connection between seismic rock mass damage and subsequent infrastructure damage during de-confinement suggests that current seismic records from operations, which currently experience no stability issues, might become important at later mining stages.

  • 21.
    Jafri, Yawer
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Kirtania, Kawnish
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Gebart, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Granberg, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    A study of black liquor and pyrolysis oil co-gasification in pilot scale2018In: Biomass Conversion and Biorefinery, ISSN 2190-6815, E-ISSN 2190-6823, Vol. 8, no 1, p. 113-124Article in journal (Refereed)
    Abstract [en]

    The effect of the blend ratio and reactor temperature on the gasification characteristics of pyrolysis oil (PO) and black liquor (BL) blends with up to 20 wt% PO was studied in a pilot-scale entrained-flow gasifier. In addition to unblended BL, three blends with PO/BL ratios of 10/90, 15/85, and 20/80 wt% were gasified at a constant load of 2.75 MWth. The 15/85 PO/BL blend was used to investigate the effect of temperature in the range 1000–1100 °C. The decrease in fuel inorganic content with increasing PO fraction resulted in more dilute green liquor (GL), and a greater portion of the feedstock carbon ended up in syngas as CO. As a consequence, the cold gas efficiency increased by about 5%-units. Carbon conversion was in the range 98.8–99.5% and did not vary systematically with either fuel composition or temperature. Although the measured reactor temperatures increased slightly with increasing PO fraction, both unblended BL and the 15% PO blend exhibited largely similar behavior in response to temperature variations. The results from this study show that blending BL with the more energy-rich PO can increase the cold gas efficiency and improve the process carbon distribution without adversely affecting either carbon conversion or the general process performance.

  • 22.
    Hammarberg, Samuel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    A Study on Structural Cores for Lightweight Steel Sandwiches2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Lightweight materials and structures are essential building blocks for a future with sustainable transportation and automotive industries. Incorporating lightweight materials and structures in today's vehicles, reduces weight and energy consumption while maintaining, or even improving, necessary mechanical properties and behaviors. Due to this, the environmental footprint can be reduced through the incorporation of lightweight structures and materials. 

    Awareness of the negative effects caused by pollution from emissions is ever increasing. Legislation, forced by authorities, drives industries to find better solutions with regard to the environmental impact. For the automotive industry, this implies more effective vehicles with respect to energy consumption. This can be achieved by introducing new, and improve current, methods of turning power into motion. An additional approach is reducing weight of the body in white (BIW) while maintaining crash worthiness to assure passenger safety. In addition to the structural integrity of the BIW, passenger safety is further increased through electrical systems integrated into the modern vehicle. Besides these safety systems, customers are also able to choose from a long list of gadgets to be fitted to the vehicle. As a result, the curb weight of vehicles are increasing, partly due to customer demands. In order to mitigate the increasing weights the BIW must be optimized with respect to weight, while maintaining its structural integrity and crash worthiness. To achieve this, new and innovative materials, geometries and structures are required, where the right material is used in the right place, resulting in a lightweight structure which can replace current configurations. 

    A variety of approaches are available for achieving lightweight, one of them being the press-hardening method, in which a heated blank is formed and quenched in the same process step. The result of the process is a component with greatly enhanced properties as compared to those of mild steel. Due to the properties of press hardened components they can be used to reduce the weight of the body-in-white. The process also allows for manufacturing of components with tailored properties, allowing the right material properties in the right place. 

    The present work aims to investigate, develop and in the end bring forth two types of light weight sandwiches; one intended for crash applications (Type I) and another for stiffness applications (Type II). Type I, based on press hardened boron steel, consists of a perforated core in between two face plates. To evaluate Type I's ability to absorb energy for crash applications a hat profile geometry is utilized. The hat profile is numerically subjected to loading from which the required energy to deform it can be found. These results are compared to those from a reference test, consisting of a hat profile based on solid steel and with an equivalent weight to that of the Type I hat profile. The aim is to minimize the weight of the core while maximizing the energy absorption. Type II consists of a bidirectional corrugated steel plate, placed in between two face plates. The geometry of the bidirectional core requires a large amount of finite elements for discretization causing a small time step and long simulation times. In order to reduce computational time a homogenization approach is suggested where the aim is to be able to predict stiffness of a planar sandwich at a reduced computational cost. 

    The numerical results from Type I show that it is possible to obtain a higher energy absorption per unit weight by introducing perforated cores in sandwich panels. Typically, energy absorption of such a panels were 20% higher as compared to a solid hat profile of equivalent weight, making it an attractive choice for reducing weight while maintaining performance. However, these results are awaiting experimental validation. The results from Type II show that it is possible, by introducing a homogenization procedure, to predict stiffness at a reduced computational cost. Validation by experiments were carried out as a sandwich panel was subjected to a three point bend in the laboratory. Numerical and experimental results agreed quite well, showing the possibilities of incorporating such panels into larger structure for stiffness applications.

  • 23.
    Frady, E. Paxon
    et al.
    Redwood Center for Theoretical Neuroscience, University of California, Berkeley.
    Kleyko, Denis
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Sommer, Friedrich T.
    Redwood Center for Theoretical Neuroscience, University of California, Berkeley.
    A Theory of Sequence Indexing and Working Memory in Recurrent Neural Networks2018In: Neural Computation, ISSN 0899-7667, E-ISSN 1530-888XArticle in journal (Refereed)
    Abstract [en]

    To accommodate structured approaches of neural computation, we propose a class of recurrent neural networks for indexing and storing sequences of symbols or analog data vectors. These networks with randomized input weights and orthogonal recurrent weights implement coding principles previously described in vector symbolic architectures (VSA) and leverage properties of reservoir computing. In general, the storage in reservoir computing is lossy, and cross-talk noise limits the retrieval accuracy and information capacity. A novel theory to optimize memory performance in such networks is presented and compared with simulation experiments. The theory describes linear readout of analog data and readout with winner-take-all error correction of symbolic data as proposed in VSA models. We find that diverse VSA models from the literature have universal performance properties, which are superior to what previous analyses predicted. Further, we propose novel VSA models with the statistically optimal Wiener filter in the readout that exhibit much higher information capacity, in particular for storing analog data. The theory we present also applies to memory buffers, networks with gradual forgetting, which can operate on infinite data streams without memory overflow. Interestingly, we find that different forgetting mechanisms, such as attenuating recurrent weights or neural nonlinearities, produce very similar behavior if the forgetting time constants are aligned. Such models exhibit extensive capacity when their forgetting time constant is optimized for given noise conditions and network size. These results enable the design of new types of VSA models for the online processing of data streams.

  • 24.
    Atashipour, Seyed Rasoul
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Department of Architecture and Civil Engineering, Division of Structural Engineering, Chalmers University of Technology.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Challamel, Noël
    Université de Bretagne Sud, UBS – Institut Dupuy de Lôme, Centre de Recherche.
    A weak shear web model for deflection analysis of deep composite box-type beams2018In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 155, p. 36-49Article in journal (Refereed)
    Abstract [en]

    Deep box-type beams, consisting of framing members and sheathings, are sensitive to shear deformations and hence appropriate refined theories or complicated magnification factors are needed to be used to obtain accurate results. For sheathings or webs between the framing members that are weak in shear, additional shear deformations occur corresponding to the relative axial displacement between the framing members. These sandwich-type or partial interaction-type of in-plane shear behaviour between the framing members, needs to be taken into account, especially when the web shear stiffness is very low. The composite box-type beam treated here is composed of three framing members with sheathings on both sides. To incorporate effects of the sheathings shear deformations between the framing members on the deflection, the sheathings, here called web interlayers, are modelled as shear media with equivalent slip moduli corresponding to a partially interacting composite beam model. Governing equilibrium equations of the model are obtained using the minimum total potential energy principle and solved explicitly. The obtained results are compared with those based on different conventional beam theories and 3-D finite element (FE) simulations. It is shown that the model is capable of predicting accurately the deflection for a wide range of geometry and property parameters. It is demonstrated that the deflection of such deep box-type beams can be expressed as the summation of three different effects, namely bending deformations, conventional shear deformations in the framing members and sheathings, and additional in-plane shear deformations or shear slips of the weak web causing relative axial displacements between the framing members.

  • 25.
    Lindqvist, Maria
    et al.
    Department of Clinical Sciences, Obstetrics and Gynecology, Umeå University.
    Persson, Margareta
    Department of Nursing, Umeå University.
    Nilsson, Margareta
    Department of Clinical Sciences, Obstetrics and Gynaecology, Umeå University.
    Uustal, Eva
    Department of Molecular and Clinical Medicine, Division of obstetrics and Gynaecology, Linköping university.
    Lindberg, Inger
    Luleå University of Technology, Department of Health Sciences, Nursing Care.
    “A worse nightmare than expected”: a Swedish qualitative study of women's experiences two months after obstetric anal sphincter muscle injury2018In: Midwifery, ISSN 0266-6138, E-ISSN 1532-3099, Vol. 61, p. 22-28Article in journal (Refereed)
    Abstract [en]

    Objective

    This study explores women's experiences of the first two months after obstetric anal sphincter injury (OASIS) during childbirth with a focus on problematic recovery.

    Methods

    This qualitative study used inductive qualitative content analysis to investigate open-ended responses from 1248 women. The data consists of short and comprehensive written responses to open-ended questions focusing on recovery in the national quality register, the Perineal Laceration Register, two months after OASIS at childbirth.

    Results

    The theme “A worse nightmare than expected” illustrated women's experiences of their life situation. Pain was a constant reminder of the trauma, and the women had to face physical and psychological limitations as well as crushed expectations of family life. Furthermore, navigating healthcare services for help added further stress to an already stressful situation.

    Conclusions

    We found that women with problematic recovery two months after OASIS experienced their situation as a worse nightmare than expected. Extensive pain resulted in physical and psychological limitations, and crushed expectations of family life. Improved patient information for women with OASIS regarding pain, psychological and personal aspects, sexual function, and subsequent pregnancy delivery is needed. Also, there is a need for clear organizational structures and information to guide help-seeking women to needed care.

  • 26.
    Rutberg, Stina
    et al.
    Luleå University of Technology, Department of Health Sciences, Health and Rehabilitation.
    Lindqvist, Anna-Karin
    Luleå University of Technology, Department of Health Sciences, Health and Rehabilitation.
    Active School Transportation is an Investment in School Health2018In: Health Behavior and Policy Review, ISSN 2326-4403, Vol. 5, no 2, p. 88-97Article in journal (Refereed)
    Abstract [en]

    Objective: In this study, we aimed to explore the experiences of schoolchildren and teachers participating in an empowerment- and gamification-inspired program to promote children's active school transportation. Methods: Data were collected using focus groups with 32 schoolchildren and 2 teachers. Content analysis revealed 2 themes and 5 subthemes. Results: Integrating learning into the program increased student engagement and enhanced learning outcomes. The program also created additional value beyond physical activity, such as togetherness, readiness to learn, and changed parental attitudes. Conclusions: Combining learning with physical activity through gamification is a promising method for promoting active school transportation. The time and energy spent increasing active school transportation enrich learning activities and health and are therefore well invested

  • 27.
    Zhang, Liangwei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Lin, Janet
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Karim, Ramin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Adaptive Kernel Density-based Anomaly Detection for Nonlinear Systems2018In: Knowledge-Based Systems, ISSN 0950-7051, E-ISSN 1872-7409, Vol. 139, no 1, p. 50-63Article in journal (Refereed)
    Abstract [en]

    This paper presents an unsupervised, density-based approach to anomaly detection. The purpose is to define a smooth yet effective measure of outlierness that can be used to detect anomalies in nonlinear systems. The approach assigns each sample a local outlier score indicating how much one sample deviates from others in its locality. Specifically, the local outlier score is defined as a relative measure of local density between a sample and a set of its neighboring samples. To achieve smoothness in the measure, we adopt the Gaussian kernel function. Further, to enhance its discriminating power, we use adaptive kernel width: in high-density regions, we apply wide kernel widths to smooth out the discrepancy between normal samples; in low-density regions, we use narrow kernel widths to intensify the abnormality of potentially anomalous samples. The approach is extended to an online mode with the purpose of detecting anomalies in stationary data streams. To validate the proposed approach, we compare it with several alternatives using synthetic datasets; the approach is found superior in terms of smoothness, effectiveness and robustness. A further experiment on a real-world dataset demonstrated the applicability of the proposed approach in fault detection tasks.

  • 28.
    Khan, Zaheer
    et al.
    Centre for Wireless Communications, University of Oulu.
    Lehtomäki, Janne
    Centre for Wireless Communications, University of Oulu.
    Vasilakos, Athanasios V.
    Centre for Wireless Communications, University of Oulu.
    MacKenzie, Allen B.
    Centre for Wireless Communications, University of Oulu.
    Juntti, Markku
    Centre for Wireless Communications, University of Oulu.
    Adaptive wireless communications under competition and jamming in energy constrained networks2018In: Wireless networks, ISSN 1022-0038, E-ISSN 1572-8196, Vol. 24, no 1, p. 151-171Article in journal (Refereed)
    Abstract [en]

    We propose a framed slotted Aloha-based adaptive method for robust communication between autonomous wireless nodes competing to access a channel under unknown network conditions such as adversarial disruptions. With energy as a scarce resource, we show that in order to disrupt communications, our method forces the reactive adversary to incur higher energy cost relative to a legitimate node. Consequently, the adversary depletes its energy resources and stops attacking the network. Using the proposed method, a transmitter node changes the number of selected time slots and the access probability in each selected time slot based on the number of unsuccessful transmissions of a data packet. On the receiver side, a receiver node changes the probability of listening in a time slot based on the number of unsuccessful communication attempts of a packet. We compare the proposed method with two other framed slotted Aloha-based methods in terms of average energy consumption and average time required to communicate a packet. For performance evaluation, we consider scenarios in which: (1) Multiple nodes compete to access a channel. (2) Nodes compete in the presence of adversarial attacks. (3) Nodes compete in the presence of channel errors and capture effect.

  • 29.
    Lindwall, Angelica
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Human and technology.
    Additive Manufacturing in Product Design for Space Applications: Opportunities and Challenges for Design Engineers2018Licentiate thesis, comprehensive summary (Other academic)
  • 30.
    Cenamor, Javier
    et al.
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Parida, Vinit
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Oghazi, Pejvak
    School of Social Sciences, Södertörn University.
    Pesämaa, Ossi
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Business Administration and Industrial Engineering.
    Wincent, Joakim
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Addressing dual embeddedness: The roles of absorptive capacity and appropriabilitymechanisms in subsidiary performance2018In: Industrial Marketing Management, ISSN 0019-8501, E-ISSN 1873-2062Article in journal (Refereed)
    Abstract [en]

    This study examines how subsidiaries can manage dual embeddedness with both local partners and a multinational enterprise. Specifically, we examine the role of absorptive capacity and appropriability mechanisms on subsidiary performance. We analyse how absorptive capacity and appropriability enable subsidiaries to successfully address knowledge challenges related to internal and external networks. We conducted an empirical analysis on a sample of 165 subsidiaries. Our results suggest that absorptive capacity has a direct, positive effect on subsidiary performance, which is greater in emerging countries. The study also found an indirect effect of absorptive capacity on subsidiary performance, which is mediated through appropriability mechanisms. These findings extend the literature on international networks, dual embeddedness and absorptive capacity

  • 31.
    Frishammar, Johan
    et al.
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Ericson, ÅsaLuleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Addressing societal challenges2018Collection (editor) (Refereed)
  • 32.
    Lugnet, Johan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Wenngren, Johan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Ericson, Åsa
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Addressing team based innovation for small firms: Create, Build, Test & Learn2018In: Proceedings of International Design Conference: Design 2018, Dubrovnik: Faculty of Mechanical Engineering and Naval Architecture , 2018Conference paper (Refereed)
    Abstract [en]

    The Create-Build-Test-Learn supports toolbox for engineering concept development motivates not only experimentation, but also instils design thinking in teams. By offering tools and methods for reconstruction of the design challenge, the approach prevents teams to jump into a solution too quickly. When using prototyping as a team resource, reframing of the problem becomes part of the process, ensuring that efforts are put on solving the right problem. The article describes the contents of the toolbox as well as exemplifies how to use it. CBTL has been designed in particular to support SMEs.

  • 33.
    Escamilla-Roa, Elizabeth
    et al.
    Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR).
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR).
    Sainz-Díaz, C. Ignacio
    Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR).
    Adsorption of methane and CO2 onto olivine surfaces in Martian dust conditions2018In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 153, p. 163-171Article in journal (Refereed)
    Abstract [en]

    Methane has been detected on all planets of our Solar System, and most of the larger moons, as well as in dwarf-planets like Pluto and Eric. The presence of this molecule in rocky planets is very interesting because its presence in the Earth's atmosphere is mainly related to biotic processes. Space instrumentation in orbiters around Mars has detected olivine on the Martian soil and dust. On the other hand the measurements of methane from the Curiosity rover report detection of background levels of atmospheric methane with abundance that is lower than model estimates of ultraviolet degradation of accreted interplanetary dust particles or carbonaceous chondrite material. Additionally, elevated levels of methane about this background have been observed implying that Mars is episodically producing methane from an additional unknown source, making the reasons of these temporal fluctuations of methane a hot topic in planetary research. The goal of this study is to investigate at atomic level the interactions during the adsorption processes of methane and other Mars atmospheric species (CO2, H2O) on forsterite surfaces, through electronic structure calculations based on the Density Functional Theory (DFT). We propose two models to simulate the interaction of adsorbates with the surface of dust mineral, such as binary mixtures (5CH4+5H2O/5CH4+5CO2) and as a semi-clathrate adsorption. We have obtained interesting results of the adsorption process in the mixture 5CH4+5CO2. Associative and dissociative adsorptions were observed for water and CO2 molecules. The methane molecules were only trapped and held by water or CO2 molecules. In the dipolar surface, the adsorption of CO2 molecules produced new species: one CO from a CO2 dissociation, and, two CO2 molecules chemisorbed to mineral surface forming a carbonate group. Our results suggest that CO2 has a strong interaction with the mineral surface when methane is present. These results could be confirmed after the analysis of the data from the upcoming remote and in-situ observations on Mars, as those to be performed by instruments on the ESA's ExoMars Trace Gas Orbiter and ExoMars rover.

  • 34.
    Leijonhufvud, Susanna
    Luleå University of Technology, Department of Arts, Communication and Education, Music and dance.
    Affordances of Music Streaming based on Exploratory Media Archaeology: A presentation of the completed PhD-project Liquid Streaming focusing the affordance of musicking for the public via the Spotify streaming service with an emphasis on method2018Conference paper (Refereed)
    Abstract [en]

    In my dissertation, I have accounted for the affordances of musicking brought about by streamed music with the case example of Spotify. In order to perform a study orbiting the realm of music streaming, mainly digital sources have been used; Internet sources and software program of the streaming service. In the presentation, I will focus on issues concerning those two major roots. Within the latter I will present, problematize and conclude how; the Internet can be used as a field of sources, and on what terms the Internet can be regarded as an Archive. Also, what alternatives researchers can depend on when practising research within the realm of the Internet. The sources have, over time, been shown to change content, update, disappear, change resolution or package, which means that digital sources such as source material as well as methodology operating in such a field need to be problematized. First of all, I will account for how a phenomenon such as the Spotify streaming service is a multidimensional feature where appearance and featured functions depend on a number of things such as geographical market zone, subscription zone, the digital device used for access, and previous user-generated history. Researching a platform based software program like this brings particular issues for the researcher. I will present how these issues have been recognised and managed in my research. Secondly, I will address Internet as a base for research. The Internet provides a plethora of available sources, and as such Internet brings the affordance of accessing a tremendous amount of data opening up for possibilities that were not available prior to digitalisation. For instance, interviews and talks by interesting people might be available on-line whereas the same persons may be difficult or impossible to reach in ordinary life. Contemporary culture on the Internet, characterised by free culture and shared content further supply massive amount of data to be researched. Further, many services on the Internet provide access to local archives where content can be searched for, and a great number of sources can be screened regarding particular content. The popular phrase: “Once on the Internet, always on the Internet” has been found to be a truth with modification. I will present four different examples of issues concerning using the Internet as an archive and how such issues can be tackled within research concerning questions of reliability and trustworthiness. The first (i) example is how content many times are personalised, why an "objective" or public view can be impossible to gain. Further, it can be impossible to gain access to how personalisation is conducted. The second (ii) example is how sources, such as music, can be limited to certain geographical restrictions and thus only accessed from certain IP-addresses for the researcher. The third (iii) example is how sources may be removed and deleted. This is the case with some personal information as individuals have a right to be forgotten. Another example is how documents from the government offices are removed when there is a new government in office. The fourth (iv) example addresses the issue where a source might remain on the Internet but presented in a different digital format than the original content.

  • 35.
    Perišić, Marija Majda
    et al.
    University of Zagreb, Faculty of Mechanical Engineering and Naval Architectur.
    Štorga, Mario
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Human and technology. University of Zagreb, Faculty of Mechanical Engineering and Naval Architectur.
    Podobnik, Vedran
    University of Zagreb, Faculty of Electrical Engineering and Computing.
    Agent-Based Modelling and Simulation of Product Development Teams2018In: Technical Gazzete, ISSN 1330-3651, Vol. 25Article in journal (Refereed)
    Abstract [en]

    The success of product development highly depends on the quality of cooperation among members of a team involved in the process. Thus, a tool capable of simulating product development team may be beneficial for researchers interested in teamwork, as well as useful for managers struggling with team formation during process planning phase. This work aims at providing a detailed overview of agent-based simulators of product development teams. Specifically, the scientific databases Web of Science, Scopus, ACM DL, and IEEE were searched to extract relevant agent-based models of teamwork in mechanical engineering and aerospace context and obtained models were reviewed to identify their key advantages and limitations. 

  • 36.
    Ljunggren, Fredrik
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Simmons, Christian
    Simmons akustik och utveckling, Chalmers Teknikpark, Gothenburg, Sweden.
    Airborne sound insulation between dwellings, from 50 vs. 100 Hz: a compilation of Swedish field surveys2018In: Applied Acoustics, ISSN 0003-682x, Vol. 133, p. 58-63Article in journal (Refereed)
    Abstract [en]

    It has for long been debated whether 50 or 100 Hz is the proper lower frequency limit when evaluating airborne sound insulation between dwellings. Although 100 Hz is the lowest third-octave band within most regulations, there is an ongoing interest in paying more attention to lower frequencies. In Sweden, evaluation from 50 Hz became mandatory already in 1999 wherefore unique experiences are available by now. In this paper, extensive data in terms of field measurements and questionnaire surveys from in total 46 building objects of various constructions have been compiled. A number of single number quantities, standardized by ISO as well as alternatives, are compared concerning their correlation against the subjectively rated annoyance responded by the residents. The statistical evidence for a 50 Hz limit was found to be small considering the total database but when the lightweight buildings were analyzed by their own, the importance of frequencies below 100 Hz became clearer. The overall recommendation is to include frequencies from 50 Hz in order to achieve good sound protection against a broad variety of sound sources, including music and other possible items generating low frequencies.

  • 37.
    Singh, Anshu A.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Geng, Shiyu
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Herrera Vargas, Natalia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Aligned plasticized polylactic acid cellulose nanocomposite tapes: Effect of drawing conditions2018In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 104, p. 101-107Article in journal (Refereed)
    Abstract [en]

    Aligned nanocomposite tapes based on plasticized polylactic acid (PLA) and 1 wt.% cellulose nanofibers (CNF) were prepared using uniaxial solid-state drawing, and the effects of drawing conditions including temperature, speed and draw ratio on the material were studied. Microscopy studies confirmed alignment and the formation of ‘shish-kebab’ morphology in the drawn tape. Mechanical properties demonstrate that the solid-state drawing is a very effective way to produce stronger and tougher PLA nanocomposites, and the toughness can be improved 60 times compared to the undrawn tape. Additionally, the thermal properties, i.e. storage modulus, glass transition temperature and degree of crystallinity were improved. These improvements are expected due to the synergistic effect of CNF in the nanocomposite and orientations induced by the solid-state drawing.

  • 38.
    Geng, Shiyu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Yao, Kun
    Division of Glycoscience, School of Biotechnology, Royal Institute of Technology, SE-100 44, Stockholm, Sweden.
    Zhou, Qi
    Division of Glycoscience, School of Biotechnology, Royal Institute of Technology, SE-100 44, Stockholm, Sweden.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Aligned polylactic acid based nanocomposite reinforced using a tiny amount of functionalized cellulose nanofibers2018Conference paper (Refereed)
    Abstract [en]

    Due to the challenges of the cost of nanocellulose materials and the dispersion of them in polymer matrix, small amount and well-dispersed nanocellulose materials are desired as reinforcement to achieve environmentally-friendly nanocomposites with high performance. In this study, an aligned polylactic acid (PLA) based nanocomposite reinforced by 0.1 wt% of functionalized cellulose nanofibers (CNFs) was investigated. The CNFs were covalently grafted by polyethylene glycol (PEG), which improves the dispersion of the CNFs in the PLA significantly compared to the native CNFs. The improved dispersion was examined by scanning electron microscopy (SEM), polarized optical microscopy (POM) and mechanical testing. Furthermore, it was found that the alignment can improve mechanical properties of the nanocomposite dramatically. The strength of the aligned nanocomposite reaches 343 MPa with a draw ratio of 8, meanwhile the toughness is about 30 times enhanced compared to the isotropic material. The aligned nanocomposite also exhibits light scattering behavior, indicating that it has the potential to be used in optical applications.

  • 39.
    Carvalho, Lara
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ma, Chunyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Lundgren, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Wetterlund, Elisabeth
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Alkali enhanced biomass gasification with in situ S capture and a novel syngas cleaning: Part 2: Techno-economic analysis2018In: Energy Journal, ISSN 0195-6574, E-ISSN 1944-9089Article in journal (Refereed)
  • 40.
    Goetz, Lee
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Naseri, Narges
    Department of Materials and Environmental Chemistry, Stockholm University.
    Nair, Santhosh S.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Karim, Zoheb
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Materials and Environmental Chemistry, Stockholm University.
    All cellulose electrospun water purification membranes nanotextured using cellulose nanocrystals2018In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882XArticle in journal (Refereed)
    Abstract [en]

    Cellulose acetate (CA) fibers were electrospun on a mesh template to create specific surface and pore structures for membrane applications. The mesh template CA fiber mats were impregnated with cellulose nanocrystals at varying weight percentages. The membranes showed nanotextured surfaces and improved mechanical properties post impregnation. More importantly, the hydrophilicity of the original CA fibers was increased from a hydrophobic contact angle of 102°–0° thereby creating an anti-fouling membrane surface structure. The membranes showed rejection of 20–56% for particles of 0.5–2.0 μm, indicating potential of these membranes in rejecting microorganisms from water. Furthermore, high rejection of dyes (80–99%) by adsorption and potential application as highly functional affinity membranes was demonstrated. These membranes can therefore be utilized as all-cellulose, green, scalable and low cost high flux membranes (> 20,000 LMH) for water cleaning applications in food industry where microorganisms and charged contaminants are to be removed.

  • 41.
    Tanpichai, Supachok
    et al.
    Learning Institute King Mongkut's University of Technology Thonburi Bangkok .
    Witayakran, Suteera
    Kasetsart Agricultural and Agro-Industrial Product Improvement Institute Kasetsart University Bangkok.
    All-cellulose composites from pineapple leaf microfibers: Structural, thermal, and mechanical properties2018In: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 39, no 3, p. 895-903Article in journal (Refereed)
    Abstract [en]

    Pineapple leaf microfibers (PALM) were used to prepare all‐cellulose composites using the surface selective dissolution method. Effect of dissolution times on mechanical and physical properties of the all‐cellulose composites was investigated. The structural transformation from cellulose I to cellulose II was observed when the fibers were dissolved in a mixed solution of lithium chloride (LiCl) and N,N‐dimethylacetamide (DMAc). Values of 42.8 MPa and 1.2 GPa for tensile strength and Young's modulus, respectively, were obtained from the composites with 120 min dissolution time in the LiCl/DMAc solution, whereas the tensile strength and Young's modulus of the undissolved PALM mats were found to be only 1.5 MPa and 0.1 GPa, respectively. The failure mechanism of the composites was changed from the fiber pull‐out to the fiber breakage when the dissolution time was longer. However, lower thermal stability and degree of crystallinity of the composites were caused by the change of the cellulose structure. The composites prepared in this work can be called as biodegradable materials, and could be the potential candidates to replace nonbiodegradable materials.

  • 42.
    Kohtamäki, Marko
    et al.
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design. Department of Management, University of Vaasa.
    Rabetino, Rodrigo
    Department of Management, University of Vaasa.
    Möller, Kristian
    Department of Marketing, Aalto University School of Business.
    Alliance capabilities: A systematic review and future research directions2018In: Industrial Marketing Management, ISSN 0019-8501, E-ISSN 1873-2062, Vol. 68, p. 188-201Article in journal (Refereed)
    Abstract [en]

    The ability to manage, integrate and learn from strategic alliances is essential in today's interconnected and globalized economy. Despite the managerial relevance of alliance capability, there remain several open questions related to the conceptualization of alliance capabilities, their antecedents, processes and outcomes, and future research needs. We address these issues through a systematic review of 94 articles from top-tier journals focused on alliance capabilities. This study makes three contributions. The study (1) defines the concept of alliance capabilities when operating in a dyadic relational context by reviewing the rich alliance capability literature, acknowledging and bridging the works conducted in different fields. We (2) identify the main processes, antecedents and outcomes of alliance capabilities and, through this analysis, pave the way for (3) the creation of a comprehensive research agenda to direct future research efforts. Overall, this study extends the existing literature by providing an integrative view of alliance capability research in various fields.

  • 43.
    Wårell, Linda
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Social Sciences.
    An analysis of iron ore prices during the latest commodity boom2018In: Mineral Economics, ISSN 2191-2203, E-ISSN 2191-2211Article in journal (Refereed)
    Abstract [en]

    This paper performs a quantitative analysis of iron ore prices, and is an extension of Wårell (2014), which analyzed the change in iron ore pricing regime on iron ore prices using data from 2003 until September 2012. However, considering that the iron ore market still was characterized by surging prices in 2012, it is of interest to see if the same conclusions hold today when the latest commodity boom has come to an end. The quantitative analysis uses monthly data between January 2003 and June 2017, and performs both statistical tests for structural breaks and a reduced price regression of the most important factors for iron ore prices during the time period. The overall results indicate that the change in pricing regime does not have a significant impact on the iron ore prices when extending the time period; rather, it is the end of the commodity boom in 2014 that is picked up as a structural break in the price series. Furthermore, results regarding whether the variables are cointegrated are more inconclusive when analyzing the entire commodity boom. However, the result that GDP growth in China has had the strongest impact on iron ore prices is though robust when extending the time period. To conclude, even though the commodity boom now has come to an end the developments in China still seems to be the most influential factor determining international iron ore prices.

  • 44.
    Ramanenka, Dmitrij
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    An Approach for Evaluation of Brick Lining's Mechanical State in Rotary Kilns2018Doctoral thesis, comprehensive summary (Other academic)
  • 45.
    Olofsson, Elias
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Social Sciences.
    An economic study on forest resource competition: How market imperfections and increased competition affect woody feedstock markets2018Licentiate thesis, comprehensive summary (Other academic)
  • 46.
    Salehi, Saeed
    et al.
    Hydraulic Machinery Research Institute, School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran.
    Raisee, Mehrdad
    Hydraulic Machinery Research Institute, School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics. Water Power Laboratory, Norwegian University of Science and Technology, Trondheim, Norway.
    Nourbakhsh, Ahmad
    Hydraulic Machinery Research Institute, School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran.
    An efficient multifidelity ℓ1-minimization method for sparse polynomial chaos2018In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 334, p. 183-207Article in journal (Refereed)
    Abstract [en]

    The Polynomial Chaos Expansion (PCE) methodology is widely used for uncertainty quantification of stochastic problems. The computational cost of PCE increases exponentially with the number of input uncertain variables (known as curse of dimensionality). Therefore, use of PCE for uncertainty quantification of industrial applications with large number of uncertain variables is challenging. In this paper, a novel methodology is presented for efficient uncertainty quantification of stochastic problems with large number of input random variables. The proposed method is based on PCE with combination of ℓ1-minimization and multifidelity methods. The developed method employs the ℓ1-minimization method to recover important coefficients of PCE using low-fidelity computations. The low-fidelity evaluations should be accurate enough to capture the physical trends well. After that the multifidelity PCE method is utilized to correct a subset of recovered coefficients using high-fidelity computations. A threshold parameter is defined in order to select the subset of recovered coefficients to be corrected. Two challenging analytical and CFD test cases namely, the Ackley function and the transonic RAE2822 airfoil with combined operational and geometrical uncertainties are considered to examine the performance of the methodology. It is shown that the proposed method can reproduce accurate results with much lower computational cost than the classical full Polynomial Chaos (PC), and ℓ1-minimization methods. It is observed that for the considered examples, the present method can achieve comparable accuracy with respect to the full PC and the ℓ1-minimization methods with significantly lower number of samples.

  • 47.
    Guay, Martin
    et al.
    Department of Chemical Engineering, Queen's University, Kingston, ON, K7L 3N6, Canada.
    Atta, Khalid
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    An extremum-seeking control observer design technique for nonlinear systems2018In: 2017 IEEE 56th Conference on Decision and Control, CDC, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2018Conference paper (Refereed)
    Abstract [en]

    In this study, we propose an extremum-seeking control approach for the design on nonlinear observers for a general class of detectable nonlinear systems. The extremum-seeking control approach provides a mechanism to compute an observer gain that minimizes the squared output error. The technique extends and generalizes an earlier extremum seeking control observer design approach that was limited to systems in observer normal form with a linear state to output map. The analysis provides conditions for the application of the technique and establishes a semi-global practical stability property of the error dynamics. Two simulation examples are presented to demonstrate the effectiveness of the technique

  • 48.
    Shadram, Farshid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Mukkavaara, Jani
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    An Integrated BIM-based framework for the optimization of the trade-off between embodied and operational energy2018In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 158, p. 1189-1205Article in journal (Refereed)
    Abstract [en]

    Design choices with a unilateral focus on the reduction of operational energy for developing energy-efficient and near-zero energy building practices can increase the impact of the embodied energy, as there is a trade-off between embodied and operational energy. Multi-objective optimization approaches enable exploration of the trade-off problems to find sustainable design strategies, but there has been limited research in applying it to find optimal design solution(s) considering the embodied versus operational energy trade-off. Additionally, integration of this approach into a Building Information Modeling (BIM) for facilitating set up of the building model toward optimization and utilizing the benefits of BIM for sharing information in an interoperable and reusable manner, has been mostly overlooked. To address these issues, this paper presents a framework that supports the making of appropriate design decisions by solving the trade-off problem between embodied and operational energy through the integration of a multi-objective optimization approach with a BIM-driven design process. The applicability of the framework was tested by developing a prototype and using it in a case study of a low energy dwelling in Sweden, which showed the potential for reducing the building’s Life Cycle Energy (LCE) use by accounting for the embodied versus operational energy trade-off to find optimal design solution(s). In general, the results of the case study demonstrated that in a low energy dwelling, depending on the site location, small reductions in operational energy (i.e. 140 GJ) could result in larger increases in embodied energy (i.e. 340 GJ) and the optimization process could yield up to 108 GJ of LCE savings relative to the initial design. This energy saving was equivalent to up to 8 years of the initial design’s operational energy use for the dwelling, excluding household electricity use.

  • 49.
    Santillán Martínez, Gerardo
    et al.
    Department of Electrical Engineering and Automation, Aalto University.
    Karhela, Tommi
    VTT Technical Research Centre of Finland .
    Ruusu, Reino
    VTT Technical Research Centre of Finland Ltd, Espoo.
    Sierla, Seppo A.
    Department of Electrical Engineering and Automation, Aalto University.
    Vyatkin, Valeriy
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science. Department of Electrical Engineering and Automation, Aalto University.
    An Integrated Implementation Methodology of a Lifecycle-Wide Tracking Simulation Architecture2018In: IEEE Access, E-ISSN 2169-3536, Vol. 6, p. 15391-15407Article in journal (Refereed)
    Abstract [en]

    A tracking simulator is a decision support application in which dynamic estimation is used to continuously align the results of an online first principle simulation model with the measurements of the targeted plant. They are a holistic application where current and future plant information is available for operation support of process plants. Existing tracking simulators have focused on the application of online and offline methods for estimation of their underlying first principle models (FPMs). However, these systems have been less attractive than similar alternatives based on empirical modeling, due to the lack of systematic approaches that address challenges across the tracking simulation lifecycle, such as laborious development of FPMs and high integration costs with the process or with other systems and simulation methods. In contrast, the approach presented in this paper integrates a tracking simulation architecture and various simulation methods to address the described challenges as follows. In order to tackle time-consuming development of FPMs, a method for generating tracking simulation models from models created during design phase is proposed. The process of connecting the tracking simulator to the physical plant and initializing the tracking simulator is automated. An optimization method for tracking simulation applications is developed to overcome drawbacks of available methods. The simulation architecture developed applies the proposed methodology during the various phases of tracking simulation. Furthermore, it exploits industrial communication standards to avoid the need for point-to-point integration of various simulators and other systems used over the course of the tracking simulator lifecycle. The work is demonstrated with laboratory process equipment.

  • 50.
    Risberg, Daniel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Analysis of the Thermal Indoor Climate with Computational Fluid Dynamics for Buildings in Sub-arctic Regions2018Doctoral thesis, comprehensive summary (Other academic)
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