Blar i USN Open Archive på forfatter "Lie, Bernt"
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A Sensor Fusion Algorithm for Filtering Pyrometer Measurement Noise in the Czochralski Crystallization Process
Komperød, Magnus; Bones, John Atle; Lie, Bernt (Journal article; Peer reviewed, 2011)The Czochralski (CZ) crystallization process is used to produce monocrystalline silicon for solar cell wafers and electronics. Tight temperature control of the molten silicon is most important for achieving high crystal ... -
A solution method for one-dimensional shallow water equations using flux limiter centered scheme for open Venturi channels
Welahettige, Prasanna Kumara Welahetti; Vågsæther, Knut; Lie, Bernt (Journal article; Peer reviewed, 2018)The one-dimensional shallow water equations were modified for a Venturi contraction and expansion in a rectangular open channel to achieve more accurate results than with the conventional one-dimensional shallow water ... -
Adapting dynamic mathematical models to a pilot anaerobic digestion reactor
Haugen, Finn; Bakke, Rune; Lie, Bernt (Journal article; Peer reviewed, 2013)A dynamic model has been adapted to a pilot anaerobic reactor fed diarymanure. Both steady-state data from online sensors and laboratory analysis anddynamic operational data from online sensors are used in the model ... -
Algorithm with improved accuracy for real-time measurement of flow rate in open channel systems
Agu, Cornelius Emeka; Hjulstad, Åsmund; Elseth, Geir; Lie, Bernt (Journal article; Peer reviewed, 2017)Most methods for flow rate measurement in open channels usually have low accuracy over a range of flow rates due to varying fluid properties, flow conditions and channel length. This paper suggests an algorithm to improve ... -
Combining measurements with models for superior information in hydropower plants
Vytvytskyi, Liubomyr; Lie, Bernt (Peer reviewed; Journal article, 2019)Water flow and pressure measurements play essential roles in the operation of hydropower plants. For all methods of measuring flow and pressure, there is a level of uncertainty with regards to sensor noise and sensor ... -
Comparison of elastic vs. inelastic penstock model using OpenModelica
Vytvytskyi, Liubomyr; Lie, Bernt (Journal article; Peer reviewed, 2017)The possibility for modelling and simulating hydropower systems as accurately as possible take an important role in order to develop a control structure and to make efficient analysis tools for testing a designed controller ... -
Comparison of Linear Controllers for Nonlinear, Open-loop Unstable Reactor
Khalili, Mohammad; Lie, Bernt (Journal article; Peer reviewed, 2018)Many industrially important reactors are operated over a regime where they exhibit nonlinear behavior. Exothermal reactors are often open-loop unstable. For such reactors, safe operation with good performance requires good ... -
Comparison of simulation tools for dynamic models
Sund, Sveinung Martinius; Plouvier, Marianne; Lie, Bernt (Journal article; Peer reviewed, 2018)Macroscopic models are used extensively in process engineering, and can often be posed as DAE (Differential Algebraic Equation) models. Three generic tools for solving such DAEs are compared: OpenModelica, Julia, and MATLAB. ... -
Computational fluid dynamics study of flow depth in an open Venturi channel for Newtonian fluid
Welahettige, Prasanna Kumara Welahetti; Lie, Bernt; Vågsæther, Knut (Journal article; Peer reviewed, 2017)Open Venturi channel flow measurement could be a cheap method to be used in drill bit pressure control. The main objective of this study is to identify the factors related with the flow depth in an open Venturi channel. A ... -
Computational Fluid Dynamics Study of Shear Thinning Fluid (Drilling Fluid) Viscosity Models in an Open Venturi Channel
Welahettige, Prasanna Kumara Welahetti; Lie, Bernt; Vågsæther, Knut (Journal article; Peer reviewed, 2019)We aim to develop an improved kick/loss detection technology by developing smart flow-sensor technology for returned flow from the oil well in open Venturi channels. This is a detailed study about a capacity of use of ... -
Computational Fluid Dynamics Study of the Effects of Drill Cuttings on the Open Channel Flow
Welahettige, Prasanna Kumara Welahetti; Berg, Christian; Lundberg, Joachim; Lie, Bernt; Vågsæther, Knut (Peer reviewed; Journal article, 2019)A three-dimensional computational fluid dynamics (CFD) study was carried out for drilling fluid flow with drill cuttings in open channels. The flow is similar to the return flow when drilling, stream containing drilling ... -
Control Relevant Model of Synchronous Generator Attached to Turbine and Grid
Bhusal, Khemraj (Master thesis, 2021)A synchronous generator is one of the important units in the hydropower plant that plays a key role in the production of electricity. Much effort has been done for designing more accurate models of synchronous machines ... -
Controller Design for a Magnetic Levitation Kit using OpenModelica’s Integration with the Julia Language
Thiele, Bernhard; Lie, Bernt; Sjölund, Martin; Pop, Adrian; Fritzson, Peter (Peer reviewed; Journal article, 2019)This paper presents a practical application of computer aided control systems design using a new OpenModelica API (OMJulia) which allows to conveniently operate on Modelica models from the Julia language. Julia is a rather ... -
Dynamic Model of an Ammonia Synthesis Reactor Based on Open Information
Jinasena, Asanthi; Lie, Bernt; Glemmestad, Bjørn (Chapter; Peer reviewed, 2016)Ammonia is a widely used chemical, hence the ammonia manufacturing process has become a standard case study in the scientific community. In the field of mathematical modeling of the dynamics of ammonia synthesis reactors, ... -
Electric Submersible Pump Lifted Oil Field: Basic Model for Control, and Comparison of Simulation Tools
Lie, Bernt (Peer reviewed; Journal article, 2024)Early childhood educationOptimal operation of petroleum production is important in a transition from energy systems based on fossil fuel to sustainable systems. One sub-process in petroleum production deals with transport ... -
Empirical Modeling of Heating Element Power for the Czochralski Crystallization Process
Komperød, Magnus; Lie, Bernt (Journal article, 2010)The Czochralski (CZ) crystallization process is used to produce monocrystalline silicon. Monocrystalline silicon is used in solar cell wafers and in computers and electronics. The CZ process is a batch process, where ... -
Enhanced Power Capability of Generator Units for Increased Operational Security using NMPC
Øyvang, Thomas; Nøland, Jonas Kristiansen; Sharma, Roshan; Hegglid, Gunne John; Lie, Bernt (Peer reviewed; Journal article, 2019)The ever-increasing penetration of intermittent energy sources introduces new demanding operating regimes for the bulk power generation in the power grid. During a worst-case power system disturbance scenario, the generator ... -
ESP Lifted Oil Field: Core Model, and Comparison of Simulation Tools
Lie, Bernt (Peer reviewed; Journal article, 2023)Optimal operation of petroleum production is important in a transition from energy systems based on fossil fuel to sustainable systems. One sub-process in petroleum production deals with transport from the (subsea) well-bore ... -
Estimating uncertainty of model parameters obtained using numerical optimisation
Brastein, Ole Magnus; Lie, Bernt; Pfeiffer, Carlos Fernando; Skeie, Nils-Olav (Peer reviewed; Journal article, 2019)Obtaining accurate models that can predict the behaviour of dynamic systems is important for a variety of applications. Often, models contain parameters that are difficult to calculate from system descriptions. Hence, ... -
Flood Control of Lake Toke: Model Development and Model Fitting
Kvam, Kristian D.; Furenes, Beathe; Hasaa, Åsmund; Gjerseth, Alexander Zhang; Skeie, Nils-Olav; Lie, Bernt (Journal article; Peer reviewed, 2017)