Now showing items 461-480 of 926

    • Atmospheric Contamination of Coastal Cities by the Exhaust Emissions of Docked Marine Vessels: the case of Tromsø 

      Zubiaga, Asier; Madsen, Synne; Khawaja, Hassan; Boiger, Gernot (Journal article; Tidsskriftartikkel, 2021-08-04)
      Docked ships are a source of contamination for the city while they keep their engine working. Plumes emissions from large boats can carry a number of pollutants to the nearby cities causing a detrimental effect on the life quality and health of local citizens and ecosystems. A computational fluid dynamics model of the harbour area of Tromsø has been built in order to model the deposition of CO2 gas ...
    • A New Development of the Classical Single Ladder Problem via Converting the Ladder to a Staircase 

      Høibakk, Ralph; Lukkassen, Dag; Meidell, Annette; Persson, Lars Erik (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-08)
      Our purpose is to shed some new light on problems arising from a study of the classical Single Ladder Problem (SLP). The basic idea is to convert the SLP to a corresponding Single Staircase Problem. The main result (Theorem 1) shows that this idea works fine and new results can be obtained by just calculating rational solutions of an algebraic equation. Some examples of such concrete calculations ...
    • A Class-E-Based Resonant AC-DC Converter With Inherent PFC Capability 

      Al-Sallami, Hussein; M. Ammar, Ahmed; Nour, Yasser; A. E. Andersen, Michael (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-03-22)
      This paper investigates the use of the class-E inverter for power factor correction (PFC) applications. Analytical and state-space models are derived showing the class-E inverter’s capability of achieving inherent PFC operation with a constant duty cycle. The inherent PFC operation limits the controller responsibility to the regulation of the output voltage, which is key for resonant converters with ...
    • Improving Geopolymer Characteristics with Addition of Poly-Vinyl Alcohol (PVA) Fibers 

      Ekaputri, Januarti Jaya; Fujiyama, Chikako; Chijiwa, Nobuhiro; Ho, Tu Dac; Nguyen, Hung Thanh (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-20)
      This paper presents the benefits of PVA fibers in improving the mechanical properties of class F fly-ash-based geopolymer concrete. The activator used in the geopolymer was 8M sodium hydroxide (NaOH) and sodium silicate (Na<sub>2</sub>SiO<sub>3</sub>), with a mass ratio of Na<sub>2</sub>SiO<sub>3</sub> to NaOH varied from 1.5 to 2.5. Cylindrical specimens with a diameter of 100 mm and a height of ...
    • Finite element simulation of ductile fracture in polycrystalline materials using a regularized porous crystal plasticity model 

      Khadyko, Mikhail; Frodal, Bjørn Håkon; Hopperstad, Odd Sture (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-18)
      In the present study, a hypoelastic–plastic formulation of porous crystal plasticity with a regularized version of Schmid’s law is proposed. The equation describing the effect of the voids on plasticity is modified to allow for an explicit analytical solution for the effective resolved shear stress. The regularized porous crystal plasticity model is implemented as a material model in a finite element ...
    • Modeling of Pressure and Temperature Profiles for the Flow of CO2 through a Restriction 

      Leyli, Amir Nadem; Jackson, Steven; Khawaja, Hassan; Moatamedi, Mojtaba (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-19)
      CO<sub>2</sub> emissions due to massive industrialization have led to several environmental issues. Carbon Capture and Storage (CCS) is one of the most important technologies that can be used to reduce anthropogenic CO<sub>2</sub> emissions worldwide. CCS projects mainly involve three processes: carbon capture, transportation, and storage. In the transportation process, the modeling of the flow in ...
    • Solving a Real-World Urban Postal Service Network Redesign Problem 

      Yu, Hao; Sun, Xu; Solvang, Wei Deng; Laporte, Gilbert (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-28)
      Due to recent technological advancements, more diversified customer demand, and increasingly harder competition, traditional postal service systems have experienced significant changes all over the world. In Norway, through a strategic reform called post-in-shop, undertaken in 2013, most postal services are now provided at postal service counters located in retailer stores in order to improve ...
    • Characteristics of fragmented aurora-like emissions (FAEs) observed on Svalbard 

      Dreyer, Joshua; Partamies, Noora; Whiter, Daniel; Ellingsen, Pål Gunnar; Baddeley, Lisa; Buchert, Stephan C. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-03-04)
      This study analyses the observations of a new type of small-scale aurora-like feature, which is further referred to as fragmented aurora-like emission(s) (FAEs). An all-sky camera captured these FAEs on three separate occasions in 2015 and 2017 at the Kjell Henriksen Observatory near the arctic town of Longyearbyen, Svalbard, Norway. A total of 305 FAE candidates were identified. They seem to appear ...
    • Recognizing Potential of LiDAR for Comprehensive Measurement of Sea Spray Flux for Improving the Prediction of Marine Icing in Cold Conditions - A Review 

      Dhar, Sushmit; Khawaja, Hassan (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-06)
      Marine icing phenomenon depends on multiple variables like vessel characteristics and uncertain factors like environmental parameters, developing an accurate model for its forecasting, evaluation, and estimation is very challenging. Commonly, most severe ice accretion is caused due to sea spray. The past attempts to measure impinging sea spray flux were carried out on specific parts of the spray ...
    • Path planning and collision avoidance for autonomous surface vehicles I: a review 

      Vagale, Anete; Oucheikh, Rachid; Bye, Robin Trulssen; Osen, Ottar Laurits; Fossen, Thor I. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-29)
      Autonomous surface vehicles are gaining increasing attention worldwide due to the potential benefits of improving safety and efficiency. This has raised the interest in developing methods for path planning that can reduce the risk of collisions, groundings, and stranding accidents at sea, as well as costs and time expenditure. In this paper, we review guidance, and more specifically, path planning ...
    • Path planning and collision avoidance for autonomous surface vehicles II: a comparative study of algorithms 

      Vagale, Anete; Bye, Robin Trulssen; Oucheikh, Rachid; Osen, Ottar; Fossen, Thor I. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-06)
      Artificial intelligence is an enabling technology for autonomous surface vehicles, with methods such as evolutionary algorithms, artificial potential fields, fast marching methods, and many others becoming increasingly popular for solving problems such as path planning and collision avoidance. However, there currently is no unified way to evaluate the performance of different algorithms, for example ...
    • Investigating the affordances of a flipped mathematics classroom from an activity theoretical perspective 

      Fredriksen, Helge (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-11-20)
      Flipped Classroom as a pedagogical framework has gained popularity at secondary and tertiary levels of mathematics education, but there is a lack of research based on a solid theoretical foundation. This article considers the flipped mathematics classroom from the perspective of affordances and cultural–historical activity theory. The empirical background is based on semi-structured interview data ...
    • Using Deep Learning Methods to Monitor Non-Observable States in a Building 

      Tangrand, Kristoffer; Bremdal, Bernt Arild (Conference object; Konferansebidrag, 2020-02-06)
      This paper presents results from ongoing research with a goal to use a combination of time series from non-intrusive ambient sensors and deep recurrent neural networks to predict room usage at a university campus. Training data was created by collecting measurements from ambient sensors measuring room CO2, humidity, temperature, light, motion and sound, while the ground-truth counts was created ...
    • Exploring Realistic Mathematics Education in a Flipped Classroom Context at the Tertiary Level 

      Fredriksen, Helge (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-01)
      Flipped classroom (FC) pedagogical frameworks have recently gained considerable popularity, especially at secondary school levels. However, there are rich opportunities to explore FC at tertiary levels, but progress on the area requires instructors’ attention to well-designed tasks for students’ collaborative learning. Realistic Mathematics Education (RME) provides a foundation for the development ...
    • User-Friendly MES Interfaces: Recommendations for an AI-Based Chatbot Assistance in Industry 4.0 Shop Floors 

      Mantravadi, Soujanya; Jansson, Andreas Dyrøy; Møller, Charles (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-04)
      The purpose of this paper is to study an Industry 4.0 scenario of ‘technical assistance’ and use manufacturing execution systems (MES) to address the need for easy information extraction on the shop floor. We identify specific requirements for a user-friendly MES interface to develop (and test) an approach for technical assistance and introduce a chatbot with a prediction system as an interface layer ...
    • Frequency Support of Fast-Multi-Energy Storage Systems in Low Rotational Inertia Scenarios 

      Ersdal, Anne Mai; Acosta Montalvo, Martha Nohemi; Gonzalez-Longatt, Francisco; Torres, José Luis Rueda; Palenski, Peter (Peer reviewed; Chapter, 2020-11-10)
      Modern power systems are increasing the connection of power electronic converters (PECs), and new inertia-less technologies displace the synchronous generation units. Therefore, the total rotational system inertia is reduced, creating new problems related to the system frequency control and stability. Several mechanisms to enable the PECs with frequency sensible control loops have been proposed in ...
    • Proactive Learning for Intelligent Maintenance in Industry 4.0 

      Noureddine, Rami; Solvang, Wei Deng; Johannessen, Espen; Yu, Hao (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-03)
      Manufacturing companies require efficient maintenance practices in order to improve business performance, ensure equipment availability and reduce process downtime. With the advent of new technology, manufacturing processes are evolving from the traditional ways into digitalized manufacturing. This transformation enables systems and machines to be connected in complex networks as a collaborative ...
    • Solving the Location Problem of Printers in a University Campus Using p-Median Location Model and AnyLogic Simulation 

      Sun, Xu; Yu, Hao; Solvang, Wei Deng (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-03)
      The location decision on service facilities is of significant importance in determining the accessibility of the service provided. Due to this reason, it has been extensively focused over the past decades by both researchers and practitioners. This paper investigates a novel two-phase hybrid method combining both optimization model and agent-based simulation in order to solve the location problem ...
    • A Stochastic Closed-Loop Supply Chain Network Optimization Problem Considering Flexible Network Capacity 

      Yu, Hao; Solvang, Wei Deng; Sun, Xu (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-03)
      Nowadays, due to the concern of environmental challenges, global warming and climate change, companies across the globe have increasingly focused on the sustainable operations and management of their supply chains. Closed-loop supply chain (CLSC) is a new concept and practice, which combines both traditional forward supply chain and reverse logistics in order to simultaneously maximize the utilization ...
    • An Introduction of the Role of Virtual Technologies and Digital Twin in Industry 4.0 

      Azarian, Mohammad; Yu, Hao; Solvang, Wei Deng; Shu, Beibei (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-03)
      It is inevitable that technological improvements have affected human’s life in any aspect to a large extent. Automation, artificial intelligence, robotics, etc., are some advances contributed to the fourth industrial revolution: Industry 4.0. Despite there are still many arguments, Internet of Things (IoT) and Cyber Physical Systems (CPS) have been widely acknowledged as the main fundaments of ...