| 1. |
- Khodabakhshian, Mohammad, et al.
(författare)
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Fuel Saving Potential of Optimal Engine Cooling System
- 2014
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Konferensbidrag (refereegranskat)abstract
- The engine cooling system in trucks is one of the main sources of parasite load. Thus optimal control of the engine thermal management system with the objective of minimizing energy consumption can substantially improve fuel efficiency. Existing methods on the engine thermal control system concentrate mainly on regulating the engine coolant temperature within a safety range. This paper explicitly calculates the energy consumption of the cooling system using the optimal control methods to decide the trajectories of the control values of the cooling system. During the optimal operation, the engine cooling system serves as another energy buffer to balance the engine workload in conventional trucks. To expose the maximal fuel saving potential of the optimal engine thermal control system, we apply dynamic programming in the investigation and the results are compared with a simple state feedback controller.
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| 2. |
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| 3. |
- Pehlivan, Ilknur Bayrak, et al.
(författare)
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Ionic relaxation in polyethyleneimine-lithium bis(trifluoromethylsulfonyl) imide polymer electrolytes
- 2010
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 108:7, s. 074102-
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Tidskriftsartikel (refereegranskat)abstract
- Polymer electrolytes containing polyethyleneimine and different concentrations of lithium bis(trifluoromethylsulfonyl) imide were investigated by impedance spectroscopy at different temperatures. Two equivalent circuit models were compared for the bulk impedance response. The first one includes a conductive Havriliak-Negami (HN) element which represents ionic conductivity and ion pair relaxation in a single process, and the second model includes a dielectric HN element, which represents ion pair relaxation, in parallel with ion conductivity. Comparison of the two circuit models showed that the quality of the fit was similar and in some cases better for the conductive model. The experimental data follow the Barton-Nakajima-Namikawa relation, which relates the ion conductivity and the parameters of the relaxation. This indicates that ion conductivity and ion pair relaxation are two parts of the same process and should be described by the conductive model.
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| 4. |
- Pehlivan, Ilknur Bayrak, et al.
(författare)
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PEI-LiTFSI electrolytes for electrochromic devices : Characterization by differential scanning calorimetry and viscosity measurements
- 2010
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 94:12, s. 2399-2404
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Tidskriftsartikel (refereegranskat)abstract
- Polymer electrolytes containing poly(ethylene imine) (PEI) and lithium bis(trifluoromethylsulfonyl) imide (LiTFSI) can serve as model electrolytes for electrochromic devices. Such electrolytes were characterized by differential scanning calorimetry, conductivity, and viscosity measurements. The glass transition temperature (T-g) and viscosity of the PEI-LiTESI electrolytes have minima at a [N]:[Li] ratio of 100:1. Both T-g and viscosity increased at high salt concentrations. The temperature dependences of ionic conductivity and viscosity followed an Arrhenius equation with parameters depending only weakly on the salt concentration. The fluid behavior of the electrolytes could be reconciled with the Bingham plastic model with parameters being functions of salt concentration.
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| 5. |
- Pehlivan Rhodin, A., et al.
(författare)
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Accurate and experimentally validated transition data for Si I and Si II
- 2024
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 682
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Tidskriftsartikel (refereegranskat)abstract
- Aims. The aim of this study is to provide radiative data for neutral and singly ionised silicon, in particular for the first experimental oscillator strengths for near-infrared Si I lines. In addition, we aim to perform atomic structure calculations both for neutral and singly ionised silicon while including lines from highly excited levels. Methods. We performed large-scale atomic structure calculations with the relativistic multiconfiguration Dirac-Hartree-Fock method using the GRASP2K package to determine log(ð A) values of Si I and Si II lines, taking into account valence-valence and core-valence electron correlation. In addition, we derived oscillator strengths of near-infrared Si I lines by combining the experimental branching fractions with radiative lifetimes from our calculations. The silicon plasma was obtained from a hollow cathode discharge lamp, and the intensity-calibrated high-resolution spectra between 1037 and 2655 nm were recorded by a Fourier transform spectrometer. Results. We provide an extensive set of accurate experimental and theoretical log(ðA) values. For the first time, we derived 17 log(ðA) values of Si I lines in the infrared from experimental measurements. We report data for 1500 Si I lines and 500 Si II lines. The experimental uncertainties of our A-values vary between 5% for the strong lines and 25% for the weak lines. The theoretical log(ð A) values for Si I lines in the range 161 nm to 6340 nm agree very well with the experimental values of this study and complete the missing transitions involving levels up to 3s23p7s (61 970 cm' 1). In addition, we provide accurate calculated log(ðA) values of Si II lines from the levels up to 3s27f (122 483 cm' 1) in the range 81 nm to 7324 nm.
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| 6. |
- Pehlivan Rhodin, Asli
(författare)
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Experimental and Computational Atomic Spectroscopy for Astrophysics : Oscillator strengths and lifetimes for Mg I, Si I, Si II, Sc I, and Sc II
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Atomic data such as oscillator strengths and wavelengths are important for astrophysical applications as they have a crucial role in determining abundances of specific elements in a star, a galaxy, or any object emitting radiation in the space. Stars in the Galaxy mostly keep the composition of the interstellar gas from which they were formed, therefore studying stellar abundances helps us understand how the Milky Way was formed and how it evolved. However, atomic data of most chemical elements are incomplete and/or have low quality, particularly for the infrared wavelength region and for the highly excited levels. This PhD project focuses on completing missing atomic data for the infrared region in addition to the optical and UV regions, and improving the existing data. In order to achieve this, I have performed both laboratory measurements and large scale atomic structure calculations.Experimental oscillator strengths have been derived by combining measured branching fractions with radiative lifetimes. A hollow cathode discharge lamp has been used as a light source to produce free atoms in a plasma and a Fourier transform spectrometer has recorded the intensity-calibrated high-resolution spectra. In addition, atomic structure calculations have been performed using the multiconfiguration Hartree-Fock programmes ATSP2K and GRASP2K to determine oscillator strengths and lifetimes. Combining the experimental work with the computational approach allows determining a large set of accurate and validated atomic data.In this thesis, an evaluated set of atomic data for Mg I, Si I, Si II, Sc I, and Sc II has been provided for astrophysical applications. The experimental oscillator strengths in the infrared region have been measured for the first time. The uncertainties in the experimental oscillator strengths are as low as 5% for strong transitions. The theoretical oscillator strengths are validated with the experimental values and with internal investigations of the length and velocity forms. The small uncertainties in the values allow accurate astrophysical abundance determinations within the 0.1dex uncertainty.
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| 7. |
- Poulikakos, L., et al.
(författare)
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In Situ Measurements of the Environmental Footprint of Freight Vehicles in Switzerland
- 2008
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Ingår i: Transportation Research Part D. - : Elsevier BV. - 1361-9209 .- 1879-2340. ; 13:4, s. 274-282
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Tidskriftsartikel (refereegranskat)abstract
- Eureka Logchain Footprint is an ongoing European cooperative project aimed at developing methods to identify road and rail vehicles through their environmental "footprint" as characterised by their dynamic load, noise, ground borne vibrations, and gaseous emissions. Part of the project involves the installation of road and rail footprint monitoring stations throughout Europe. This paper reports the results of the first road station built on the A1 motorway in Switzerland on a flexible asphalt pavement. Individual vehicle data on weigh in motion, noise and vibration sensors were measured in situ. Methods for the incorporation of gaseous emissions from vehicles are discussed. The results indicate that the various footprint parameters need to be assessed separately to determine the environmental impact of heavy vehicles.
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| 8. |
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| 9. |
- Djurle, Annika
(författare)
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The disease cycle and lifestyles
- 2020
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Ingår i: Plant pathology and plant diseases. - 9781789243185 ; , s. 19-35
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 10. |
- Gopalakrishnan, Maheshwaran, 1987, et al.
(författare)
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Data-driven machine criticality assessment – maintenance decision support for increased productivity
- 2022
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Ingår i: Production Planning and Control. - : Informa UK Limited. - 0953-7287 .- 1366-5871. ; 33:1, s. 1-19
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Tidskriftsartikel (refereegranskat)abstract
- Data-driven decision support for maintenance management is necessary for modern digitalized production systems. The data-driven approach enables analyzing the dynamic production system in realtime. Common problems within maintenance management are that maintenance decisions are experience-driven, narrow-focussed and static. Specifically, machine criticality assessment is a tool that is used in manufacturing companies to plan and prioritize maintenance activities. The maintenance problems are well exemplified by this tool in industrial practice. The tool is not trustworthy, seldom updated and focuses on individual machines. Therefore, this paper aims at the development and validation of a framework for a data-driven machine criticality assessment tool. The tool supports prioritization and planning of maintenance decisions with a clear goal of increasing productivity. Four empirical cases were studied by employing a multiple case study methodology. The framework provides guidelines for maintenance decision-making by combining the Manufacturing Execution System (MES) and Computerized Maintenance Management System (CMMS) data with a systems perspective. The results show that by employing data-driven decision support within the maintenance organization, it can truly enable modern digitalized production systems to achieve higher levels of productivity.
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