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1.	Hamednia, Ahad, 1990, et al. (författare) Charge Planning and Thermal Management of Battery Electric Vehicles 2023 Ingår i: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 72:11, s. 14141-14154 Tidskriftsartikel (refereegranskat)abstract This paper studies optimal thermal management and charging of a battery electric vehicle driving over long-distance trips. The focus is on the potential benefits of including a heat pump in the thermal management system for waste heat recovery, and charging point planning, in a way to achieve optimality in time, energy, or their trade-off. An optimal control problem is formulated, in which the objective function includes the energy delivered by the charger(s), and the total charging time including the actual charging time and the detour time to and from the charging stop. To reduce the computational complexity, the formulated problem is then transformed into a hybrid dynamical system, where charging dynamics are modeled in the domain of normalized charging time. Driving dynamics can be modeled in either trip time or travel distance domains, as the vehicle speed is assumed to be known a priori, and the vehicle is only stopping at charging locations. Within the hybrid dynamical system, a binary variable is introduced for each charging location, in order to decide whether to use or skip a charger. This problem is solved numerically, and simulations are performed to evaluate the performance in terms of energy efficiency and time. The simulation results indicate that the time required for charging and total energy consumption are reduced up to $30.6\%$ and $19.4\%$, respectively, by applying the proposed algorithm.
2.	Hamednia, Ahad, 1990, et al. (författare) Optimal Thermal Management, Charging, and Eco-driving of Battery Electric Vehicles 2023 Ingår i: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 72:6, s. 7265-7278 Tidskriftsartikel (refereegranskat)abstract This paper addresses optimal battery thermal management, charging, and eco-driving of a battery electric vehicle (BEV) with the goal of improving its grid-to-meter energy efficiency. Thus, an optimization problem is formulated, aiming at finding the optimal trade-off between trip time and charging cost. The formulated problem is then transformed into a hybrid dynamical system, where the dynamics in driving and charging modes are modeled with different functions and with different state and control vectors. Moreover, to improve computational efficiency, we propose modeling the driving dynamics in a spatial domain, where decisions are made along the traveled distance. Charging dynamics are modeled in a temporal domain, where decisions are made along a normalized charging time. The actual charging time is modeled as a scalar variable that is optimized simultaneously with the optimal state and control trajectories, for both charging and driving modes. The performance of the proposed algorithm is assessed over a road with a hilly terrain, where two charging possibilities are considered along the driving route and the battery is soaked to the ambient before departure. According to the results, trip time including driving and charging times, is reduced by 44%, compared to a case without active heating/cooling of the battery.
3.	Pourabdollah, Mitra, 1984, et al. (författare) PHEV Energy Management: A Comparison of Two Levels of Trip Information 2012 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. Tidskriftsartikel (refereegranskat)abstract Plug-in hybrid electric vehicles (PHEVs) have rechargeable energy storage which can be used to run the vehicle on shorter range on electricity from the grid. In the absence of a priori information about the trip, a straightforward strategy is to first deplete the battery down to a minimum level and then keep the state of charge (SoC) around this level. However, largely due to the battery losses, the overall fuel economy can be improved if the battery is discharged gradually. This requires some a priori knowledge about the trip.This paper investigates the tradeoff between improved fuel economy and the need for a priori information. This investigation is done using a variant of telemetry equivalent consumption minimization strategy (T-ECMS) which is modified to be used for a PHEV. To implement this strategy, several parameters need to be tuned based on an assumption of the future trip. By studying two different levels of details, the tradeoff between fuel economy and a priori information is evaluated. It is shown that the proposed strategy improves the fuel economy considerably even when general information is available. However, increase in the details of the a priori information improves the fuel economy even further.
4.	Arvidsson, Rickard, 1985, et al. (författare) An Evaluation of Discharge Strategies for Plug-In Hybrid Electric Vehicles 2016 Ingår i: 25th Aachen Colloquium. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract Discharge strategies for known routes are tested in a Volvo XC90 T8 PHEV in order to evaluate fuel consumption for the drivetrain of a real commuting cycle. An approximate optimal solution is obtained by dynamic programming. The method is implemented in the vehicle control system and compared to a heuristic strategy. The work has been carried out at Volvo Cars test facilities in Gothenburg. Results show that for a known route both combustion engine and battery efficiency increases in both tested methods, with decreased charge transfer through the battery and less charge sustain operation. The dynamic programming strategy has previously been shown to outperform rule based strategies in terms of fuel consumption by comparing the methods in simulation studies. In this study the dynamic programming solution reduced the consumption with - 4 %, and the heuristic strategy decreased consumption even further to - 8 %.
5.	Braun, Robert, 1984-, et al. (författare) Hopsan: An Open-Source Tool for Rapid Modelling and Simulation of Fluid and Mechatronic Systems 2020 Ingår i: Proceedings of the BATH/ASME 2020 Symposium on Fluid Power and Motion Control (FPMC2020). - : American Society of Mechanical Engineers (ACME). - 9780791883754 Konferensbidrag (refereegranskat)abstract Hopsan is an open-source simulation package developed as a collaboration project between industry and academia. The simulation methodology is based on transmission line modelling, which provides several benefits such as linear model scalability, numerical robustness and parallel simulation. All sub-models are pre-compiled, so that no compilation is required prior to starting a simulation. Default component libraries are available for hydraulic, mechanic, pneumatic, electric and signal domains. Custom components can be written in C++ or generated from Modelica and Mathematica. Support for simulation-based optimization is provided using population-based, evolutionary or direct-search algorithms. Recent research has largely focused on co-simulation with other simulation tools. This is achieved either by using the Functional Mock-up Interface standard, or by tool-to-tool communications. This paper provides a description of the program and its features, the current status of the project, and an overview of recent and ongoing use cases from industry and academia.
6.	Cavalli, Luca, et al. (författare) Handcrafted Outlier Detection Revisited 2020 Ingår i: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics). - Cham : Springer International Publishing. - 1611-3349 .- 0302-9743. ; 12364 LNCS, s. 770-787 Konferensbidrag (refereegranskat)abstract Local feature matching is a critical part of many computer vision pipelines, including among others Structure-from-Motion, SLAM, and Visual Localization. However, due to limitations in the descriptors, raw matches are often contaminated by a majority of outliers. As a result, outlier detection is a fundamental problem in computer vision and a wide range of approaches, from simple checks based on descriptor similarity to geometric verification, have been proposed over the last decades. In recent years, deep learning-based approaches to outlier detection have become popular. Unfortunately, the corresponding works rarely compare with strong classical baselines. In this paper we revisit handcrafted approaches to outlier filtering. Based on best practices, we propose a hierarchical pipeline for effective outlier detection as well as integrate novel ideas which in sum lead to an efficient and competitive approach to outlier rejection. We show that our approach, although not relying on learning, is more than competitive to both recent learned works as well as handcrafted approaches, both in terms of efficiency and effectiveness. The code is available at https://github.com/cavalli1234/AdaLAM.
7.	Demaziere, Christophe, 1973, et al. (författare) Investigation of the MTC noise estimation with a coupled neutronic/thermal-hydraulic dedicated model – “Closing the loop” 2012 Ingår i: Proc. Int. Conf. on Advances in Reactor Physics – Linking Research, Industry, and Education (PHYSOR 2012), Knoxville, TN, USA, April 15-20, 2012, American Nuclear Society. - 9781622763894 ; 1, s. 361-375 Konferensbidrag (refereegranskat)abstract This paper investigates the reliability of different noise estimators aimed at determining the Moderator Temperature Coefficient (MTC) of reactivity in Pressurized Water Reactors. By monitoring the inherent fluctuations in the neutron flux and moderator temperature, an on-line monitoring of the MTC without perturbing reactor operation is possible. In order to get an accurate estimation of the MTC by noise analysis, the point-kinetic component of the neutron noise and the core-averaged moderator temperature noise have to be used. Because of the scarcity of the in-core instrumentation, the determination of these quantities is difficult, and several possibilities thus exist for estimating the MTC by noise analysis. Furthermore, the effect of feedback has to be negligible at the frequency chosen for estimating the MTC in order to get a proper determination of the MTC. By using an integrated neutronic/thermal-hydraulic model specifically developed for estimating the three-dimensional distributions of the fluctuations in neutron flux, moderator properties, and fuel temperature, different approaches for estimating the MTC by noise analysis can be tested individually. It is demonstrated that a reliable MTC estimation can only be provided if the core is equipped with a sufficient number of both neutron detectors and temperature sensors, i.e. if the core contain in-core detectors monitoring both the axial and radial distributions of the fluctuations in neutron flux and moderator temperature. It is further proven that the effect of feedback is negligible for frequencies higher than 0.1 Hz, and thus the MTC noise estimations have to be performed at higher frequencies.
8.	Furberg, Andreas, 1989, et al. (författare) Optimal Selection of Driving Modes along a Commuter Route for a Plug-in Hybrid Electric Vehicle 2014 Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - : Elsevier BV. - 1474-6670. - 9783902823625 ; 19, s. 7867-7872 Konferensbidrag (refereegranskat)abstract Many plug-in hybrid electric vehicles have predefined driving modes, e.g. electric drive and charge sustaining mode. For a driver it is not a trivial task to select a fuel optimal sequence of driving modes; a poor selection might even result in a severely degraded fuel economy. The purpose of this paper is therefore to investigate optimal mode selection along a well known commuter route. To obtain a predictable driving behaviour it is assumed that the driving mode is only allowed to change at a limited number of decision points, located where the driving conditions along the route changes. The optimal mode selection is computed using the well known Dynamic Programming algorithm. However, the results show that the optimal mode selection might be perceived as counterintuitive, as a mode is not necessarily optimal over a connected set with respect to battery state of charge, at a given decision point. To mitigate this type of behaviour a suboptimal algorithm is proposed, in which a mode is associated with one unique interval of state of charge at any decision point along the route. The results indicate that the proposed algorithm is only marginally suboptimal with respect to the optimal solution.
9.	Larsson, Viktor, 1984, et al. (författare) A coupled neutronics/thermal–hydraulics tool for calculating fluctuations in Pressurized Water Reactors 2012 Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 43, s. 68-76 Tidskriftsartikel (refereegranskat)abstract This paper describes a tool for estimating fluctuations in neutron flux, fuel temperature, moderator density and flow velocity in Pressurized Water Reactors by coupling a dynamic thermal–hydraulic module and a dynamic neutron kinetic module. The code calculates the static solution first, giving the profile of the static fuel temperature, moderator density, velocity and neutron flux. The fluctuations (called noise in this work) are the differences between the actual time-dependent values and the corresponding mean values. The fluctuations are in general induced by perturbations in the thermal–hydraulic parameters, e.g. moderator temperature or density, at the inlet of the core. There is also a possibility to directly define the perturbations in the macroscopic cross-sections and to supply them to the neutronic part of the model. The model was validated against two separate calculations using two different commercial tools.
10.	Larsson, Viktor, 1984, et al. (författare) Analytic Solutions to the Dynamic Programming sub-problem in Hybrid Vehicle Energy Management 2015 Ingår i: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 64:4, s. 1458-1467 Tidskriftsartikel (refereegranskat)abstract The computationally demanding Dynamic Programming(DP) algorithm is frequently used in academic research tosolve the energy management problem of an Hybrid ElectricVehicle (HEV). This paper is focused exclusively on how thecomputational demand of such a computation can be reduced.The main idea is to use a local approximation of the griddedcost-to-go and derive an analytic solution for the optimal torquesplit decision at each point in the time and state grid. Therebyit is not necessary to quantize the torque split and identifythe optimal decision by interpolating in the cost-to-go. Twodifferent approximations of the cost-to-go are considered in thepaper: i) a local linear approximation, and ii) a quadratic splineapproximation. The results indicate that computation time can bereduced by orders of magnitude with only a slight degradation insimulated fuel economy. Furthermore, with a spline approximatedcost-to-go it is also possible to significantly reduce the memorystorage requirements. A parallel Plug-in HEV is considered inthe paper but the method is also applicable to an HEV.
11.	Larsson, Viktor, 1984, et al. (författare) Benefit of Route Recognition in Energy Management of Plug-in Hybrid Electric Vehicles 2012 Ingår i: Proceedings of the American Control Conference. - : IEEE. - 0743-1619. - 9781457710940 ; , s. 1314-1320 Konferensbidrag (refereegranskat)abstract This paper investigates the benefit of an energymanagement system that autonomously can recognize when aplug-in hybrid electric vehicle is driven along known commutingroutes. The presented route recognition algorithm comparesthe GPS trajectory of the ongoing trip with stored commutingroutes using the well known cross-correlation operation. If aroute is recognized the energy management system switchesfrom a charge depleting charge sustaining discharge strategyto a strategy where the battery discharge rate is adapted to thelength of the recognized route, thereby decreasing the averagedischarge current and the resistive losses.The proposed system is evaluated using simulations onone month of logged commuter driving data. The resultsfor an energy management system based on the equivalentconsumption minimization strategy indicate an overall fuel costreduction of 1.5% compared to an system that only utilize acharge depleting charge sustaining strategy.
12.	Larsson, Viktor, 1984, et al. (författare) Calculation of the neutron noise using the Analytical Nodal Method 2009 Ingår i: REACTOR PHYSICS CALCULATIONS IN THE NORDIC COUNTRIES. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract In this study, the neutron noise, i.e. the stationary fluctuations of the neutron flux around its mean value, iscalculated in 2-group diffusion theory for a 2-dimensional reactor using the Analytical Nodal Method. Abrief description of the calculation of the static flux is also included. The same calculational scheme for theneutron noise as for the static flux is used. As a benchmark, the calculated neutron noise for a 2-dimensionalfully homogeneous reactor is compared with the analytical solution which can easily be determined for homogeneousreactors. The result of the benchmark is that the numerically calculated neutron noise accuratelymatches the analytically calculated neutron noise.
13.	Larsson, Viktor, 1984, et al. (författare) Commuter Route Optimized Energy Management of Hybrid Electric Vehicles 2014 Ingår i: IEEE Transactions on Intelligent Transportation Systems. - 1524-9050 .- 1558-0016. ; 15:3, s. 1145-1154 Tidskriftsartikel (refereegranskat)abstract Optimal energy management of hybrid electric vehicles requires a priori information regarding future driving conditions; the acquisition and processing of this information is nevertheless often neglected in academic research. This paper introduces a commuter route optimized energy management system, where the bulk of the computations are performed on a server. The idea is to identify commuter routes from historical driving data, using hierarchical agglomerative clustering, and then precomputean optimal solution to the energy management controlproblem with dynamic programming; the obtained solution canthen be transmitted to the vehicle in the form of a lookup table. To investigate the potential of such a system, a simulation study is performed using a detailed vehicle model implemented in the Autonomie simulation environment for MATLAB/Simulink. The simulation results for a plug-in hybrid electric vehicle indicate that the average fuel consumption along the commuter route(s) can be reduced by 4%–9% and battery usage by 10%–15%.
14.	Larsson, Viktor, 1984, et al. (författare) Comparative study of 2-group P1 and diffusion theories for the calculation of the neutron noise in 1D 2-region systems 2009 Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 36:10, s. 1574-1587 Tidskriftsartikel (refereegranskat)abstract In this paper, the neutron noise, i.e. the stationary fluctuations of the neutron flux around its meanvalue, is calculated in 2-group P1 and diffusion theories for a 2-region slab reactor using Green’sfunction technique. The applicability of diffusion theory for different types and locations of the perturbation,as well as different frequencies, is assessed. Material data, i.e. nuclear cross-sections and kineticparameters, representative of a Light Water Reactor (LWR) and of a Heavy Water Reactor (HWR),respectively, are used in this work. It is demonstrated that for practical situations in LWRs and HWRs,there is no significant advantage to use P1 theory since diffusion theory gives acceptable results. Thelargest deviations between the two formalisms are observed in regions of large gradients of the staticneutron flux, such as close to the reflector interface and close to the perturbation. Such observationsare in agreement with theoretical expectations. This study also indicates that neglecting the effect ofcross-section perturbation on the diffusion coefficient gives a rather small impact on the solution. Thisallows drastically simplifying the determination of the neutron noise. When using numericaltechniques for such a determination the memory requirements and computational effort can be significantlyreduced.
15.	Larsson, Viktor, 1984, et al. (författare) Comparing two approaches to precompute discharge strategies for plug-in hybrid electric vehicles 2013 Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - 1474-6670. - 9783902823434 ; , s. 121-126 Konferensbidrag (refereegranskat)abstract This paper investigates two alternative approaches to precompute a discharge strategy for the main commuter route of a plug-in hybrid electric vehicle. The first approach is based on the idea of computing a state of charge reference trajectory by solving a convex program; while the second approach utilizes dynamic programming to determine an optimal cost-to-go function. During real-time operation the torque split is decided by an equivalent consumption minimization strategy where the main difference between the two approaches is how the equivalence factor is determined. With the first approach it is adapted to track the state of charge reference trajectory and in the second approach it is given by the partial derivative of the cost-to-go function with respect to state of charge. To evaluate the two approaches a simulation study is performed in the dynamic vehicle modelling software Autonomie using logged commuter driving data. The simulation results indicate no clear difference between the two approaches in terms of fuel economy and battery usage. Both approaches are, however, significantly better than a charge depleting charge sustaining discharge strategy.
16.	Larsson, Viktor, 1984, et al. (författare) Comparison of the calculated neutron noise using finite differences and the Analytical Nodal Method 2012 Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 43, s. 176-182 Tidskriftsartikel (refereegranskat)abstract In this paper, a comparison of the calculated neutron noise, i.e. the fluctuation of the neutron flux around its average value assuming that all processes are stationary, is conducted, where the neutron noise is calculated using finite differences alone and with finite differences where the Analytical Nodal Method is used to correct the neutron currents, respectively. It is seen that the lower the frequency of the noise source, the larger difference between the two solutions. The main conclusion from this work is that the gain of calculating the neutron noise using the more sophisticated Analytical Nodal Method compared to the increase of the corresponding computational burden is too little to motivate the use of the ANM.
17.	Larsson, Viktor, 1984, et al. (författare) Cubic Spline Approximations of the Dynamic Programming Cost-to-go in HEV Energy Management Problems 2014 Ingår i: 13th European Control Conference, ECC 2014; Strasbourg Convention and Exhibition CenterPlace de BordeauxStrasbourg; France; 24 June 2014 through 27 June 2014. - 9783952426913 ; , s. 1699-1704 Konferensbidrag (refereegranskat)abstract The energy management problem of a hybridelectric vehicle (HEV) is a non-linear and mixed integeroptimization problem. The problem can be solved with DynamicProgramming (DP), but the algorithm requires the problem tobe gridded in time, states and control signals. To ensure a highaccuracy of the solution the grid must be dense, meaning thatthe cost-to-go can require several megabytes of memory. Thescope of this paper is therefore twofold. The first topic is asensitivity study, where the effect of a sparsely gridded state isinvestigated, both for an HEV and a plug-in HEV (PHEV). Thestudy shows that it is possible to use a sparse grid for an HEV,but not for a PHEV. The second topic and the main contributionis a method to approximate the DP cost-to-go with cubic splines.The results indicate that it is possible to use only a few splines,if the knot points are determined based on the characteristicsof the cost-to-go. Thereby it is possible to significantly reducethe memory requirements, without any noticeable increase insimulated fuel consumption.
18.	Larsson, Viktor, 1984, et al. (författare) Cubic Spline Approximations of the Dynamic Programming Value Function in HEV Energy Management Problems 2013 Ingår i: Workshop for new energy vehicle dynamic system and control technology. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract Energy management of a hybrid electric powertrain is a non-linear and mixed integer optimization problem that often is solved with Dynamic Programming (DP); thus requiring the problem to be gridded both in time, control signals and the states. To ensure a high accuracy of the solution the grid must be dense, meaning that the resulting value function can require several megabytes of memory. The first contribution of the paper is therefore a sensitivity study where the effect of a sparsely gridded state is investigated, both for a hybrid electric vehicle (HEV) and a plug-in HEV (PHEV). The study shows that it is possible to use a sparse grid for an HEV, but not for a PHEV. The second contribution is a method to approximate the DP value function with cubic splines. The results indicate that it is possible to useonly a few splines, if the knot points are determined based on the characteristics of the value function. Thereby it is possible to significantly reduce the memory requirements of the PHEV value function, without any noticeable increase in fuel consumption.
19.	Larsson, Viktor, 1984, et al. (författare) Development of a numerical tool for calculating the fluctuations in PWRs 2011 Ingår i: Proc. of XV MEETING ON REACTOR PHYSICS CALCULATIONS IN THE NORDIC COUNTRIES. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract This paper describes the development of a tool for estimating fluctuations in neutron flux, fuel temperature, moderator density and flow velocity in Pressurized Water Reactors by coupling a dynamic thermal-hydraulic module and a dynamic neutron kinetic module. The code calculates the static solution first, giving the profile of the static fuel temperature, moderator density, velocity and neutron flux. The fluctuations (called noise in this work) are the differences between the actual time-dependent values and the corresponding mean values. The fluctuations are in general induced by perturbations in the thermal-hydraulic parameters, e.g. moderator temperature or density, at the inlet of the core. There is also a possibility to directly define the perturbations in the macroscopic cross-sections and to supply them to the neutronic part of the model.
20.	Larsson, Viktor, 1984 (författare) Development of a Numerical Tool for Estimating the Neutron Noise in Nuclear Reactors 2009 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract The neutron noise, i.e. the time-variations of the neutron flux around its meanvalue, can be used for obtaining important safety parameters in a nuclear reactor,e.g. the decay ratio for a boiling water reactor and the moderator temperature coefficientfor a pressurized water reactor. The main benefit of using the neutron noiseis that it can be taken from the existing detectors and there is therefore no need forperturbing reactor operation. It would thus be advantageous to be able to calculatethe neutron noise with a relatively simple model with a relatively small computationaleffort, a work initiated earlier at the Department of Nuclear Engineering,Chalmers University of Technology.The objectives of this report are thus to validate some of the assumptions inthe previously developed model and to evaluate various ways of improving it. Acomparison is thus conducted between P1 and diffusion theories with two energygroups for a 1-dimensional 2-region reactor. The previous model used the FiniteDifference Method, a method which is simple and easy to implement for spatialdiscretization of the equations. The drawback is that the accuracy is low unlessthe size of the nodes of the reactor model is small. To enhance the neutronics whilekeeping the size of the nodes in the range of 15-20 cm, theAnalytical Nodal Methodwas implemented for the calculation of the neutron noise.The results fromthis study are that there is no need in practical situations for usinghigher order theory for neutron noise calculations since diffusion theory givesresults that are accurate enough. The implemented Analytical Nodal Method alsoshows high agreement with the analytically calculated neutron noise.
21.	Larsson, Viktor, 1984 (författare) Development of an integrated neutronic/thermal-hydraulic tool for estimating fluctuations in PWRs 2011 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Monitoring and diagnostics of a reactor core at a given state is very important for detecting potential problems and anomalies at an early stage. Several methods exist for these purposes, but the majority of them require a disruption of the plant operation, e.g. by shut-down or by perturbation of the system. The knowledge of the noise, i.e. the fluctuations of a parameter around its time-averaged value, can be used for on-line/off-line core monitoring and diagnostics without any disruption of normal operation. Measurements of reactor parameters can be used for estimating dynamical parameters, as the Moderator Temperature Coefficient (MTC) in a Pressurized Water Reactor (PWR), or for detecting anomalies, as unseated fuel assemblies in Boiling Water Reactors (BWRs) or flow blockages.Since the interpretation of the neutron noise aims at finding the driving perturbation responsible for the observed noise in the system and the limited number of detectors makes this attempt difficult, it would be beneficial to be able to numerically estimate in-core noise for any arbitrary noise source so that the comparison between the measured and calculated noise would allow finding the root cause of the observed fluctuations. The intention of this work is thus to calculate the in-core noise for commercial systems using coupled thermal-hydraulic/neutronic models. This includes the determination of the neutron noise, as well as of fluctuations in fuel temperature, moderator density and flow velocity.The work is divided into two main parts, neutron kinetics and thermal-hydraulics. On the neutron kinetic side, P1 and diffusion theories were compared with the conclusion that diffusion theory was accurate enough for noise calculations. The spatial discretization was also tested through the finite difference method and the Analytical Nodal Method (ANM), where it was concluded that both could be used for calculating the neutron noise. The comparisons between those two methods revealed that finite differences seems to be accurate enough for most practical applications. Both methods were successfully validated against analytical solutions.The other part covered in this work was the development for PWRs of a thermal-hydraulic model coupled to the neutronic model. This model was validated against calculations by the commercial Computational Fluid Dynamics (CFD) code FLUENT.The integrated neutronic/thermal-hydraulic model was proven viable and was also benchmarked against a RELAP5/PARCS model of a commercial PWR with mostly good results.
22.	Larsson, Viktor, 1984, et al. (författare) Impact of Trip Length Uncertainty on Optimal Discharging Strategies for PHEVs 2010 Ingår i: Proceedings of the 6th IFAC Symposium Advances in Automotive Control, Munich; 12 July 2010 through 14 July 2010. - 1474-6670. - 9783902661722 ; 43, s. 55-60 Konferensbidrag (refereegranskat)abstract When charged from the electric grid, plug-in Hybrid Electric Vehicles can be expected to have an all electric range of 10 - 60 km depending on battery size. In order to minimize the fuel cost it is vital to fully deplete the battery between two charging occasions. However, when driving distances exceeding the electric range it is in many cases energy efficient to turn on the engine at an early stage and blend power from the battery with power from the combustion engine. This paper studies how uncertainties regarding the predicted trip length affect the optimal discharging strategy of a parallel plug-in Hybrid Electric Vehicle. The predicted trip length along an otherwise perfectly known speed profile is modeled as a normally distributed stochastic variable and Dynamic Programming is used to calculate the optimal discharging strategy. Calculations are carried out for varying standard deviations on three different speed profiles. The results indicate that it is possible to decrease the fuel costs with 1-4 % even with relatively little knowledge regarding the future trip length.
23.	Larsson, Viktor, 1984, et al. (författare) Influence of State of Charge Estimation Uncertainty on Energy Management Strategies for Hybrid Electric Vehicles 2011 Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - 1474-6670. - 9783902661937 ; 18:PART 1, s. 9703-9708 Konferensbidrag (refereegranskat)abstract This paper studies how the optimal energy management of a hybrid electric vehicle and a plug-in hybrid electric vehicle is affected by uncertain estimates of the battery state of charge. A simple model for the battery dynamics and the state of charge estimation is postulated, inspired by the known characteristics of previously proposed estimation schemes. Based on the assumption that the drive cycle is perfectly known, the effects of state of charge estimation uncertainty is studied by including the estimation uncertainty in the optimization of the energy management strategy. The simulations indicate lower battery usage and higher fuel consumption as the estimation uncertainty increases.
24.	Larsson, Viktor, 1984, et al. (författare) NEUTRON NOISE CALCULATIONS IN THREE-DIMENSIONAL SYSTEMS 2011 Ingår i: Proc. of International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering 2011. - 9788563688002 Konferensbidrag (refereegranskat)abstract In this paper, the neutron noise, i.e. the stationary fluctuations of the neutron flux around its mean value, is calculated in three dimensions and two energy groups using diffusion theory. Cross-sections and other reactor parameters are realistic data coming from a commercial PWR. This work is an extension of a previous model which used finite differences in two dimensions for the spatial discretization. In this work, the calculations are still performed using finite differences for the spatial discretization, but the neutron currents and neutron noise currents are corrected using the Analytical Nodal Method. Another correction is performed by introducing discontinuity factors to improve the modelling of leakages at the face between the fuel assemblies.
25.	Larsson, Viktor, 1984, et al. (författare) Neutron Noise Calculations Using the Analytical Nodal Method 2010 Ingår i: Proc of PHYSOR 2010 - Advances in Reactor Physics to Power the Nuclear Renaissance, Pittsburgh May 9-14 2010. - 9781617820014 ; 2, s. 939-950 Konferensbidrag (refereegranskat)abstract In this study, the neutron noise, i.e. the stationary fluctuations of the neutron flux around its mean value, is calculated in 2-group diffusion theory using the Analytical Nodal Method. A brief description of the calculation of the static flux is also included. The static solution is benchmarked against a reference solution in the case of a homogeneous core. The same calculational scheme for the neutron noise as for the static flux is used. As a dynamical benchmark, the calculated neutron noise for a 2D fully homogeneous reactor is compared with the analytical solution, which can easily be determined for homogeneous reactors, at different frequencies. The result of the benchmarks is that the numerical calculations using ANM accurately match the analytical solutions.
26.	Larsson, Viktor, 1984, et al. (författare) Neutron noise calculations using the Analytical Nodal Method and comparisons with analytical solutions 2011 Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 38:4, s. 808-816 Tidskriftsartikel (refereegranskat)abstract In this study, the neutron noise, i.e. the stationary fluctuations of the neutron flux around its mean value, is calculated in 2-group diffusion theory using the Analytical Nodal Method. A brief description of the calculation of the static flux is also included. The static solution is benchmarked against a reference solution in the case of a homogeneous core. The same calculational scheme for the neutron noise as for the static flux is used. As a dynamical benchmark, the calculated neutron noise for a 2D fully homogeneous reactor is compared with the analytical solution of a centered noise source at different frequencies. The numerical solution is also benchmarked to an off-centered source where the analytical solution is determined using the power reactor approximation, extended to two energy groups. The results of the benchmarks are that the numerical calculations using ANM accurately match the analytical solutions.
27.	Larsson, Viktor, 1984 (författare) On Discharge Strategies for Plug-in Hybrid Electric Vehicles 2011 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract During recent years electrification of vehicles has emerged as a promisingtechnology to reduce oil dependency and CO2 emissions within the transportationsector. At the present day several automotive manufacturers areabout to introduce plug-in hybrid electric vehicles to the market, i.e. hybridelectric vehicles with high capacity batteries that are grid rechargeable.As with most new technologies this introduces new control problems to besolved by engineers and researchers.This thesis investigates one of these new control problems, namely howto optimally discharge the battery of a plug-in hybrid electric vehicle ontrips that exceed the electric range. Rather than using the trivial dischargestrategy, which is to operate as an electric vehicle until the battery is depletedand then proceed in charge sustaining operation as a conventionalhybrid electric vehicle, it is possible to improve powertrain efficiency if thebattery is discharged gradually throughout the trip. A gradual dischargelowers the average discharge current, thereby lowering the resistive lossesthat are quadratic in current. However, to find a suitable discharge ratesome a priori information regarding the future trip is required.In the thesis it is shown that the a priori information needed can beobtained using route recognition; an algorithm with low computational demandis proposed and evaluated using simulations on logged commuter drivingdata. The results suggest that notable fuel cost reductions are possiblefor commuters that frequently drive along routes that exceed the electricrange. Furthermore, the impact of trip length uncertainty on the optimaldischarge rate is also studied and results indicate that it is preferable tounderestimate rather than overestimate the trip length. A separate investigationconcludes that uncertain estimates of the battery state of chargeonly has minor effects on the optimal discharge rate.
28.	Larsson, Viktor, 1984, et al. (författare) Parametric study of the influence of heterogeneous boron concentration and coolant density on cross section generation in BWRs 2008 Ingår i: International Conference on the Physics of Reactors 2008, PHYSOR 08; Interlaken; Switzerland; 14 September 2008 through 19 September 2008. - 9781617821219 ; 2, s. 966-973 Konferensbidrag (refereegranskat)abstract In this paper, we investigate the effect of heterogeneous boron concentration and coolant density distribution on nodal macroscopic cross sections, which could potentially arise in an Anticipated Transient Without Control rods of a boiling water reactor. All calculations are made with the 2-D transport code PHOENIX4. Full core simulators, such as POLCA7, often have simple models for handling such heterogeneities with the basic requirement that conservative results are obtained simulating such core conditions. We have found that this is not always the case and that the errors can potentially be quite high.
29.	Larsson, Viktor, 1984 (författare) Route Optimized Energy Management of Plug-in Hybrid Electric Vehicles 2014 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Plug-in hybrid electric vehicles have the potential to significantly reducethe oil dependence within the transportation sector. However, there willalways be some trips that exceed the electric driving range, meaning thatboth electric energy and fuel must be used. For such trips the fuel economyis intimately connected with the energy management system and its abilityto schedule the use of the battery. The fundamental problem is that theoptimal fuel economy can be reached only if the future trip is known a priori.It is therefore desirable to have a system that can perform three principaltasks: i) acquire a prediction of the future trip, ii) given the predictionprecompute feedforward information for the real-time level, and iii) at thereal-time level identify the optimal operating points in the powertrain.This thesis investigates all three of the mentioned tasks. It is shown thatfrequently travelled routes can be identified from logged driving data usinghierarchical clustering. Based on the historical driving conditions along theroute, it is then possible to precompute an optimal strategy that can be usedas feedforward information for the real-time level. Two different methods forsuch a precomputation are investigated, convex optimization and DynamicProgramming. Particular attention is given to the implementation of acomputationally efficient Dynamic Programming algorithm.A real-time control strategy that is based on a closed-form minimizationof the Hamiltonian is also presented. The strategy is derived for a power-train with two degrees of freedom, and is implemented in a dynamic vehiclemodel that is used by a vehicle manufacturer. Simulations with a linearlydecreasing battery state of charge reference indicate that the fuel economycan be improved with up to 10%, compared to a depleting-sustaining strat-egy. Real-time compatible controller code is also generated and tested in aproduction vehicle. The vehicle behaviour during a test drive is similar tosimulated behaviour
30.	Larsson, Viktor, 1984, et al. (författare) Semi-analytical calculations of the neutron noise in 2-group theory for 1-D homogeneous systems 2008 Ingår i: International Conference on the Physics of Reactors 2008, PHYSOR 08; Interlaken; Switzerland; 14 September 2008 through 19 September 2008. - 9781617821219 ; 2, s. 1235-1242 Konferensbidrag (refereegranskat)abstract In this paper, 2-group diffusion and P1 theories are compared via semi-analytical calculations of the neutronnoise in a 1-D 2-region slab reactor using the Green’s function technique. The neutron noise, i.e. the timevariationsof the neutron flux around its mean value, is useful for core diagnostics and monitoring of a reactor.For a 2-region system, the Green’s function can be calculated in a semi-analytical manner as a function offrequency and space, for various positions of the perturbation. This work demonstrates that for practicalsituations in a Light Water Reactor, there is no significant advantage to use P1 theory since diffusion theorygives acceptable results. The largest deviations between the two formalisms are observed in the reflector region.This study also shows that neglecting the effect of cross-section perturbations on the diffusion coefficient has arather strong impact on the solution in the reflector.
31.	Le Du-Carrée, Jessy, et al. (författare) Cocktail effects of tire wear particles leachates on diverse biological models : A multilevel analysis 2024 Ingår i: Journal of Hazardous Materials. - : Elsevier. - 0304-3894 .- 1873-3336. ; 471 Tidskriftsartikel (refereegranskat)abstract Tire wear particles (TWP) stand out as a major contributor to microplastic pollution, yet their environmental impact remains inadequately understood. This study delves into the cocktail effects of TWP leachates, employing molecular, cellular, and organismal assessments on diverse biological models. Extracted in artificial seawater and analyzed for metals and organic compounds, TWP leachates revealed the presence of polyaromatic hydrocarbons and 4-tert-octylphenol. Exposure to TWP leachates (1.5 to 1000 mg peq L-1) inhibited algae growth and induced zebrafish embryotoxicity, pigment alterations, and behavioral changes. Cell painting uncovered pro-apoptotic changes, while mechanism-specific gene-reporter assays highlighted endocrine-disrupting potential, particularly antiandrogenic effects. Although heavy metals like zinc have been suggested as major players in TWP leachate toxicity, this study emphasizes water-leachable organic compounds as the primary causative agents of observed acute toxicity. The findings underscore the need to reduce TWP pollution in aquatic systems and enhance regulations governing highly toxic tire additives.
32.	Lin, Yukai, et al. (författare) Infrastructure-Based Multi-camera Calibration Using Radial Projections 2020 Ingår i: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics). - Cham : Springer International Publishing. - 1611-3349 .- 0302-9743. ; 12361 LNCS, s. 327-344 Konferensbidrag (refereegranskat)abstract Multi-camera systems are an important sensor platform for intelligent systems such as self-driving cars. Pattern-based calibration techniques can be used to calibrate the intrinsics of the cameras individually. However, extrinsic calibration of systems with little to no visual overlap between the cameras is a challenge. Given the camera intrinsics, infrastructure-based calibration techniques are able to estimate the extrinsics using 3D maps pre-built via SLAM or Structure-from-Motion. In this paper, we propose to fully calibrate a multi-camera system from scratch using an infrastructure-based approach. Assuming that the distortion is mainly radial, we introduce a two-stage approach. We first estimate the camera-rig extrinsics up to a single unknown translation component per camera. Next, we solve for both the intrinsic parameters and the missing translation components. Extensive experiments on multiple indoor and outdoor scenes with multiple multi-camera systems show that our calibration method achieves high accuracy and robustness. In particular, our approach is more robust than the naive approach of first estimating intrinsic parameters and pose per camera before refining the extrinsic parameters of the system. The implementation is available at https://github.com/youkely/InfrasCal.
33.	Olsson, Carl, 1978, et al. (författare) A quasiconvex formulation for radial cameras 2021 Ingår i: Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition. - 1063-6919. ; , s. 14571-14580 Konferensbidrag (refereegranskat)abstract In this paper we study structure from motion problems for 1D radial cameras. Under this model the projection of a 3D point is a line in the image plane going through the principal point, which makes the model invariant to radial distortion and changes in focal length. It can therefore effectively be applied to uncalibrated image collections without the need for explicit estimation of camera intrinsics. We show that the reprojection errors of 1D radial cameras are examples of quasiconvex functions. This opens up the possibility to solve a general class of relevant reconstruction problems globally optimally using tools from convex optimization. In fact, our resulting algorithm is based on solving a series of LP problems. We perform an extensive experimental evaluation, on both synthetic and real data, showing that a whole class of multiview geometry problems across a range of different cameras models with varying and unknown intrinsic calibration can be reliably and accurately solved within the same framework.
34.	Rist, Sinja, et al. (författare) Cumulative Impacts of Oil Pollution, Ocean Warming, and Coastal Freshening on the Feeding of Arctic Copepods 2024 Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 58:7, s. 3163-3172 Tidskriftsartikel (refereegranskat)abstract The Arctic is undergoing rapid changes, and biota are exposed to multiple stressors, including pollution and climate change. Still, little is known about their joint impact. Here, we investigated the cumulative impact of crude oil, warming, and freshening on the copepod species Calanus glacialis and Calanus finmarchicus. Adult females were exposed to ambient conditions (control; 0 °C + 33 psu) and combined warming and freshening: 5 °C + 27 psu (Scenario 1), 5 °C + 20 psu (Scenario 2) for 6 days. All three conditions were tested with and without dispersed crude oil. In Scenario 1, fecal pellet production (FPP) significantly increased by 40-78% and 42-122% for C. glacialis and C. finmarchicus, respectively. In Scenario 2, FPP decreased by 6-57% for C. glacialis, while it fluctuated for C. finmarchicus. For both species, oil had the strongest effect on FPP, leading to a 68-83% reduction. This overshadowed the differences between climatic scenarios. All variables (temperature, salinity, and oil) had significant single effects and several joint effects on FPP. Our results demonstrate that Arctic copepods are sensitive to environmentally realistic concentrations of crude oil and climate change. Strong reductions in feeding can reduce the copepods' energy content with potential large-scale impacts on the Arctic marine food web.
35.	Schops, Thomas, et al. (författare) Why Having 10,000 Parameters in Your Camera Model Is Better Than Twelve 2020 Ingår i: Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition. - 1063-6919. ; , s. 2532-2541 Konferensbidrag (refereegranskat)abstract Camera calibration is an essential first step in setting up 3D Computer Vision systems. Commonly used parametric camera models are limited to a few degrees of freedom and thus often do not optimally fit to complex real lens distortion. In contrast, generic camera models allow for very accurate calibration due to their flexibility. Despite this, they have seen little use in practice. In this paper, we argue that this should change. We propose a calibration pipeline for generic models that is fully automated, easy to use, and can act as a drop-in replacement for parametric calibration, with a focus on accuracy. We compare our results to parametric calibrations. Considering stereo depth estimation and camera pose estimation as examples, we show that the calibration error acts as a bias on the results. We thus argue that in contrast to current common practice, generic models should be preferred over parametric ones whenever possible. To facilitate this, we released our calibration pipeline at https://github.com/puzzlepaint/camera_calibration, making both easy-to-use and accurate camera calibration available to everyone.

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