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- Bundy, Kenneth, et al.
(författare)
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An electrochemical impedance spectroscopy method for prediction of the state of charge of a nickel-metal hydride battery at open circuit and during discharge
- 1998
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Ingår i: Journal of Power Sources. ; 72:2, s. 118-125
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Tidskriftsartikel (refereegranskat)abstract
- A multivariate method for predicting state of charge, from electrochemical data, of a nickel-metal hydride (NiMH)-battery is presented. Partial least square (PLS) regression is used to evaluate electrochemical impedance spectra and predict state of charge. The impedance spectra are analysed in the frequency range 239-0.6 Hz. The impedance is measured for different states of charge at open-circuit conditions and during continuous discharge at loads ranging between 0.2 C and 0.8 C. When measuring the impedance during discharge, the AC-current signal is imposed on the DC-current. The predictive capability of the method is tested by a cross validation procedure and the root mean square error of prediction is 7% when using the outlier identification capability of the PLS-regression method. The state of charge is evaluated with a single model, independently of whether the cell is subjected to open-circuit or polarised conditions. The predictive performance of the present model decreases at state of charge values less than 10%. © 1998 Elsevier Science S.A.
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| 5. |
- Davis, Paul A., et al.
(författare)
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Alpine Ski Coaches' and Athletes' Perceptions of Factors Influencing Adaptation to Stress in the Classroom and on the Slopes
- 2019
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Ingår i: Frontiers in Psychology. - : FRONTIERS MEDIA SA. - 1664-1078. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Research examining the student-athlete experience proposes a number of factors that can be both sources of stress and/or support. The dual career pathway offers a number of potential positive outcomes including psychological, social, and financial benefits; however, challenges including time management, fatigue, and restricted social activities are well documented. In consideration of the multidimensional student-athlete experience and the numerous factors that influence the complexity of potential stress, a mixed methods research study design was used in the study. First, data collected from surveys completed by 173 elite junior alpine skiers were analyzed to identify the degree to which athletes report experiencing stress associated with specific aspects pertaining to training, life, and organizational factors. These factors were then explored through semi-structured interviews with six coaches at the associated national elite sport schools. Taken collectively, athletes' reports of psychophysiological training stress on the Multidimensional Training Distress Scale were low. Scores on the college studentathletes' life stress scale revealed very low levels of general life stress; although the subscales associated with "performance demand" and "academic requirements" scored marginally higher. Scores on the Organizational Stressor Indicator for Sport Performers indicated low levels of organizational stress. The interviews with coaches elucidated the underlying factors potentially influencing athletes' positive adaptations to stress as they reported programming a number of strategies to reduce negative outcomes. Coaches aimed to teach athletes self-awareness and regulation strategies through the use of the training diaries and ongoing communication to promote positive adaptation to stress. A number of coaches also worked with sport psychology consultants to optimize athletes' training and study situations. Traditionally, research has noted high levels of stress in student-athletes due to co-occurring demands (school & sport); however, the data in the present study suggests that optimizing support mechanisms across domains can promote positive adaptations to potential sources of stress.
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| 7. |
- Lundqvist, Anton, et al.
(författare)
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Determination of the diffusion coefficient and phase-transfer rate parameter in LaNi5 and MmNi3.6Co0.8Mn0.4Al0.3 using microelectrodes
- 1998
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Ingår i: Journal of the Electrochemical Society. ; 145:11, s. 3740-3746
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Tidskriftsartikel (refereegranskat)abstract
- A potential-step method for determining the diffusion coefficient and phase-transfer parameter in metal hydrides by using microelectrodes was investigated. It was shown that a large potential step is not enough to ensure a completely diffusion-limited mass transfer if a surface-phase transfer reaction takes place at a finite rate. It was shown, using a kinetic expression for the surface phase-transfer reaction, that the slope of the logarithm of the current vs. time curve will be constant both in the case of the mass-transfer limited by diffusion or by diffusion and a surface-phase transfer The diffusion coefficient and phase-transfer rate parameter were accurately determined for MmNi2.4Co0.8Mn0.4Al0.3 using a fit to the whole transient. The diffusion coefficient was found to be (1.3 ± 0.3) × 10-13 m2/s. The fit was good and showed that a pure diffusion model was not enough to explain the observed transient. The diffusion coefficient and phase-transfer rate parameter were also estimated for pure LaNi5. A fit of the whole curve showed that neither a pure diffusion model nor a model including phase transfer could explain the whole transient.
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| 8. |
- Lundqvist, Anton, et al.
(författare)
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Kinetic study of a porous metal hydride electrode
- 1999
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Ingår i: Electrochimica Acta. ; 44:15, s. 2523-2542
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Tidskriftsartikel (refereegranskat)abstract
- A physio-chemical approach has been used to describe the behaviour of a porous metal hydride electrode. The metal hydride alloy MmNi3.6Co0.8Mn0.4Al0.3, was studied. Electrochemical impedance spectroscopy (EIS) and a potential ramp were used to study the applicability of the model close to and far from its equilibrium state. An EIS model was developed and took into account a finite conductivity in the solid or liquid phase together with a distribution in characteristic diffusion length, for the hydrogen diffusion, caused by a distribution in particle size. It was shown that the impedance in the low frequency region could not be described by an average particle size, if the particle size was distributed. The EIS model was used to determine different parameters as a function of relative concentration of hydrogen. The change within the parameters could not be explained by a single phase model. The parameters were also tested by a comparison with the result of a single particle's EIS measurement, and a good agreement was found. The potential ramp showed that the present model could not fully describe the transient behaviour of the respective material, far from its equilibrium state. The reason for this could be that the expression describing the surface phase and its connection to the bulk phase is too simplified. © 1999 Elsevier Science Ltd. All rights reserved.
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| 10. |
- Lundqvist, Anton
(författare)
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Transient electrochemical methods for investigation of porous battery electrodes
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis treats electrochemical methods used to studybattery materials. Two different types of materials are used asmodel systems in this study, metal hydride alloys used in thenickel-metal hydride battery and LiMn2O4suggested for use in the lithium-ion battery. Thetwo model systems are used to critically analyse differentexperimental methods. The three methods under study have beenelectrochemical impedance spectroscopy (eis), potential step and linear sweep voltammetry. Threedifferent experimental systems are studied, the singleparticle, the porous electrode and the cell.Using a commonly accepted kinetic model for the metalhydride, it was shown that a surface phase transfer reactionhas to be included in the analysis of potential step data. Theconsequences of this are discussed. The local kinetics of LiMn2O4were studied in order to investigate thepossibility to use a simplified mathematical model. It washowever found that this model had limited applicability.Methods suitable to study porous electrodes are also developed.It is shown that an average particle size cannot replace thatof a size distributed model in eithereisor potential step investigations. The potentialdistribution in the porous structure was investigated and amethod that makes it easier to separate between effects of theporous electrode and the local kinetic reaction is presented.This method utilises the impedance measured at the back of theporous electrode in addition to that measured at the front. Themethod was applied both to a porous metal hydride- and a LiMn2O4-electrode.Five different metal hydride materials were investigated andit was found that the material properties of metal hydridematerials are strongly influenced by production method.Important rate constants such as diffusion coefficient andsurface phase transfer parameter were determined both frommeasurements on porous electrodes and single particles. It wasfound that the values were distributed within a sample ofsingle particles. It was concluded that one reason is particlecracking and that this will have consequences for the studiesof porous electrodes. Important differences were also found bystudying single particles and porous electrodes and it wasconcluded that there are differences in material behaviourwhere additional processes seem to take place in the porouselectrode.Eiswas also used for determination of state of chargein commercial nickel-metal hydride cells. A statisticalevaluation that makes it possible to determine state of chargeboth at open circuit and during discharge is presented.Keywords: Electrochemical impedance spectroscopy, LiMn2O4,mathematical modelling, metal hydride,microelectrode, porous electrode, potential step, State ofcharge.
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| 14. |
- Tersmeden, Fredrik, et al.
(författare)
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Fäktmästarna vid Lunds universitet
- 2012
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Ingår i: LUGI Fäktförening 100 år 1912-2012. - 9789163715730 ; , s. 55-75
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Bokkapitel (populärvet., debatt m.m.)abstract
- Historik över fäktmästarinstitutionen vid Lunds universitet, dess lokaler och andra yttre förutsättningar samt kortbiografier över samtliga ämbetets innehavare.
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