| 1. |
- Bayrak Pehlivan, Ilknur, et al.
(författare)
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NiMoV and NiO-based catalysts for efficient solar-driven water splitting using thermally integrated photovoltaics in a scalable approach
- 2021
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Ingår i: iScience. - : Cell Press. - 2589-0042. ; 24:1
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Tidskriftsartikel (refereegranskat)abstract
- In this work, a trimetallic NiMoV catalyst is developed for the hydrogen evolution reaction and characterized with respect to structure, valence, and elemental distribution. The overpotential to drive a 10 mA cm−2 current density is lowered from 94 to 78 mV versus reversible hydrogen electrode by introducing V into NiMo. A scalable stand-alone system for solar-driven water splitting was examined for a laboratory-scale device with 1.6 cm2 photovoltaic (PV) module area to an up-scaled device with 100 cm2 area. The NiMoV cathodic catalyst is combined with a NiO anode in alkaline electrolyzer unit thermally connected to synthesized (Ag,Cu) (In,Ga)Se2 ((A)CIGS) PV modules. Performance of 3- and 4-cell interconnected PV modules, electrolyzer, and hydrogen production of the PV electrolyzer are examined between 25°C and 50°C. The PV-electrolysis device having a 4-cell (A)CIGS under 100 mW cm−2 illumination and NiMoV-NiO electrolyzer shows 9.1% maximum and 8.5% averaged efficiency for 100 h operation.
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| 2. |
- Brabie, Dan, 1975-
(författare)
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On the Influence of Rail Vehicle Parameters on the Derailment Process and its Consequences
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis aims at systematically studying the possibilities of minimising devastatingconsequences of high-speed derailments by appropriate measures and features in thetrain design, including the running gear. The course of events immediately afterderailments is studied with respect to whether the train stays upright and close to thetrack centre line or deviates laterally with probably serious consequences. There is abelief in the railway community that some trains can better cope with derailment thenothers, although this superiority is apparently hard to quantify.Firstly, an empirical database has been established containing as much relevantinformation as possible of past incidents and accidents occurred at higher speeds due tomechanical failure close to the interface between the running gear and the track, as wellas other causes that ultimately brought the train into a derailed condition. Although nevertwo derailments are the same, certain patterns appeared to crystallise after analysing thecourse of events immediately after the failure based on the descriptions available in eachincident or accident report. Ultimately, this led to that several critical vehicle parameterscould be distinguished as capable to influence the outcome of a derailment.Secondly, two of the critical vehicle features found in the first stage have been subject todetailed analysis by means of multi-body system (MBS) simulations. The first phase ofthe computer simulation program focused on studying the tendency of a wheelset toderail as a result of an axle journal failure on the outside of the wheel. The prederailmentcomputer simulation model has been validated with good results for twoauthentic Swedish events of axle journal failure.Thereafter, one of the newly found critical vehicle feature, the wheelset mechanicalrestrictions relative to the bogie frame, have been extensively studied on an X 2000power unit and trailer car model. The results show that a vertical mechanical restrictionof the wheelset relative to the bogie frame of approximately 50 to 60 mm is capable ofkeeping the wheelsets on the rails after an axle journal failure, for the studied conditions.An axle mounted brake disc constitutes the second critical vehicle feature that has thepotential to favourably influence the sequence of events in cases of wheel flangeclimbing. A minimal range of geometrical parameters for which the rail would safely fillthe gap between the brake disc and the wheel has been calculated.The third and last part of the thesis establishes the prerequisites necessary in order tostudy the remaining of the critical vehicle parameters found in the first part, whichrequires complete MBS simulations of derailed vehicles rolling on track structures, i.e.concrete sleepers. To accomplish this task, hysteresis data for the force as function ofconcrete material indentation, are aimed to be acquired by means of finite element (FE)simulations. Therefore, the intended FE model of wheel-concrete sleeper impact issubjected to a tentative validation procedure. A good agreement is observed whencomparing the FE model results with an authentic accident in terms of concrete sleeperindentation. Furthermore, preliminary results in terms of a wheelset tendency to reboundafter concrete sleeper impact are presented.
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| 3. |
- Calnan, Sonya, et al.
(författare)
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Development of Various Photovoltaic‐Driven Water Electrolysis Technologies for Green Solar Hydrogen Generation
- 2021
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Ingår i: Solar RRL. - : John Wiley & Sons. - 2367-198X. ; 6:5
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Tidskriftsartikel (refereegranskat)abstract
- Direct solar hydrogen generation via a combination of photovoltaics (PV) and water electrolysis can potentially ensure a sustainable energy supply while minimizing greenhouse emissions. The PECSYS project aims at demonstrating asolar-driven electrochemical hydrogen generation system with an area >10 m2 with high efficiency and at reasonable cost. Thermally integrated PV electrolyzers(ECs) using thin-film silicon, undoped, and silver-doped Cu(In,Ga)Se2 and silicon heterojunction PV combined with alkaline electrolysis to form one unit are developed on a prototype level with solar collection areas in the range from 64 to2600 cm2 with the solar-to-hydrogen (StH) efficiency ranging from 4 to 13%. Electrical direct coupling of PV modules to a proton exchange membrane EC test the effects of bifacially (730 cm2 solar collection area) and to study the long-term operation under outdoor conditions (10 m2 collection area) is also investigated. In both cases, StH efficiencies exceeding 10% can be maintained over the test periods used. All the StH efficiencies reported are based on measured gas outflow using mass flow meters.
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| 4. |
- Ekengren Oscarsson, Henrik, et al.
(författare)
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Politisk polarisering behövs i en levande demokrati
- 2021
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Ingår i: Dagens nyheter. - Stockholm : AB Dagens nyheter. - 1101-2447.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Fyra forskare i SNS Demokratiråd 2021: Vi ifrågasätter föreställningen om att vi lever i en särskilt polariserad tid. Det gäller även påståendet att polarisering enbart är av ondo. Stark polarisering har varit ett grundackord i svenskt politiskt liv. Den intressanta frågan är hur vi så framgångsrikt har kunnat hantera mycket djupa samhällskonflikter och en hög grad av polarisering.
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| 5. |
- Eriksson K., Susanna, et al.
(författare)
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Geometrical and energetical structural changes in organic dyes for dye-sensitized solar cells probed using photoelectron spectroscopy and DFT
- 2016
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 18:1, s. 252-260
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Tidskriftsartikel (refereegranskat)abstract
- The effects of alkoxy chain length in triarylamine based donor acceptor organic dyes are investigated with respect to the electronic and molecular surface structures on the performance of solar cells and the electron lifetime. The dyes were investigated when adsorbed on TiO2 in a configuration that can be used for dye sensitized solar cells (DSCs). Specifically, the two dyes D35 and D45 were compared using photoelectron spectroscopy (PES) and density functional theory (DFT) calculations. The differences in solar cell characteristics when longer alkoxy chains are introduced in the dye donor unit are attributed to geometrical changes in dye packing while only minor differences were observed in the electronic structure. A higher dye load was observed for D45 on TiO2. However, D35 based solar cells result in higher photocurrent although the dye load is lower. This is explained by different geometrical structures of the dyes on the surface.
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| 6. |
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| 7. |
- Gabrielsson, Erik, et al.
(författare)
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Dipicolinic acid : a strong anchoring group with tunable redox and spectral behavior for stable dye-sensitized solar cells
- 2015
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 51:18, s. 3858-3861
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Tidskriftsartikel (refereegranskat)abstract
- Dipicolinic acidwas investigated as a new anchoring group for DSSCs. A pilot dye (PD2) bearing this new anchoring group was found to adsorb significantly stronger to TiO2 than its cyanoacrylic acid analogue. The electrolyte composition was found to have a strong effect on the photoelectrochemical properties of the adsorbed dye in the device, allowing the dye LUMO energy to be tuned by 0.5 eV. Using a pyridine-free electrolyte, panchromatic absorption of the dye on TiO2 extending to 900 nm has been achieved. Solar cells using PD2 and a Co(bpy)(3) based electrolyte showed unique stability under simulated sunlight and elevated temperatures.
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| 8. |
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| 9. |
- Hoiseth, G., et al.
(författare)
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Evaluating the hip-flask defence using analytical data from ethanol and ethyl glucuronide. A comparison of two models
- 2020
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Ingår i: Forensic Science International. - : ELSEVIER IRELAND LTD. - 0379-0738 .- 1872-6283. ; 316
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Tidskriftsartikel (refereegranskat)abstract
- Aim: Claimed intake of alcohol after a traffic incident, called the hip-flask defence, can be objectively assessed by different methods. One of them is the use of two consecutive ethanol concentrations in urine and the ratio between ethanol concentrations in urine and blood. Another one is the concentrations of ethyl glucuronide (EtG) and ethyl sulphate (EtS) in blood and their ratio to ethanol. The experimental basis for both these models is from single dose studies only. The aim of this study was therefore to describe the kinetics of ethanol, EtG and EtS after ingestion of two repeated doses of ethanol and to investigate the usefulness of the different models for the assessment of the hip-flask defence. Methods: Thirty-five subjects ingested a first dose of 0.51 g of ethanol per kilo body weight, and two hours later a second dose (the hip-flask drink) of 0.25, 0.51 or 0.85 g of ethanol per kilo body weight. Ten urine and 17 blood samples were collected and analysed for ethanol, EtG and EtS using fully validated methods. It was investigated if all subjects fulfilled the criteria for recent drinking, according to the two different models, when using the samples collected 180-240 minutes after start of first dose drinking. According to the first model, increase in urinary ethanol concentrations and a ratio UAC/BAC below 1.3 indicated recent drinking. According to the second model, increase in blood EtG concentrations and a ratio ethanol (g/kg)/EtG (mg/L) above 1 indicated recent drinking. Results: All subjects in the high dose group fulfilled all criteria for recent drinking. One subject in the medium dose group and nine subjects in the low dose group failed to show increasing UAC and/or a UAC/ BAC ratio below 1.3. One subject in the low dose group failed to show increasing concentrations of blood EtG, but all subjects showed a ratio ethanol/EtG above 1. Conclusions: The present study showed, by the use of experimental data, that both two models used to investigate the hip-flask defence can be used, but only when the hip-flask dose is sufficiently high. (C) 2020 The Author(s). Published by Elsevier B.V.
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| 10. |
- Lee, Wei Chuang, et al.
(författare)
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Monolayer calibration of endofullerenes with x-ray absorption from implanted keV ion doses
- 2024
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Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Institute of Physics (AIP). - 0734-2101 .- 1520-8559. ; 42:2
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Tidskriftsartikel (refereegranskat)abstract
- X-ray absorption spectroscopy (XAS) has the highest sensitivity for chemical element detection on surfaces. With this approach, small amounts of lanthanide-containing endofullerene molecules (Ho3N@C80) have been measured by total electron yield at a low flux bending magnet beamline. The monolayer coverage is calibrated by extrapolating the signals of constant doses (3 x 1014 cm-2) of Ho ions implanted into SiO2 with energies between 2 and 115 keV. At room temperature, the Ho XAS spectra of the molecules and implanted ions indicate trivalent but not identical Ho ground states. Still, this approach demonstrates a way for calibration of small coverages of molecules containing open core-shell elements.
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