| 521. |
- Hagerhall, Caroline, et al.
(författare)
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Human eeg responses to exact and statistical fractal patterns.
- 2012
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Ingår i: Human experience in the natural and built environment: Implications for research policy & practice (Abstracts of Presentations).
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Konferensbidrag (refereegranskat)abstract
- Attention Restoration Theory point to nature as a particularly good candidate for restoring the ability to focus and inhibit distractions. However, little effort has been directed to elaborating on what makes nature's visual pattern unique for restoration purposes. One suggested explanation is the fractal properties of natural patterns (Hagerhall, 2005). Both perception studies (Hagerhall et al., 2004) and studies using quantitative electroencephalography, qEEG (Hagerhall et al., 2008) have pointed to that visual patterns with mid fractal dimension, D, seem to be the most relaxing and preferred. However, it has so far not been investigated if these responses are being driven by fractal geometry in general or by the specific form of fractal geometry found in nature. In natural scenery it is so called statistical fractals that are common because of nature's integration of randomness with the underlying fractal scaling properties. A natural fractal hence looks different from an artificial exact fractal (where the patterns repeating are identical at all scales), even if the two patterns have the same D value. We have here conducted the first study in which we consider both types of fractals and morph one type into the other.qEEG was recorded from 35 subjects viewing 9 images, combining 3 fractal dimensions and 3 levels of randomness. Each image was shown for 60 seconds, interspaced by 30 seconds of a neutral grey image. The data was mainly treated by analysis of variance (repeated measures design), including both within-group (fractal dimension, level of randomness) and between-group (order) variances. Bonferroni correction was carried out and the significance level set to p<.005. The study confirmed our hypotheses in that it showed that alpha power (an indicator of a wakefully relaxed state and internalized attention) was largest for fractals found in nature, i.e. fractals incorporating high randomness and mid to low fractal dimension. Statistically a majority of the results were tendencies (with p_.05) but the reaction patterns showed consistencies which point to that human response to the patterns, and the parameters randomness and fractal dimension, have some fundamental base. The results must be considered as preliminary, but encouraging given the relative visual simplicity of the patterns.
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| 522. |
- Haghbin, Saeid, 1977, et al.
(författare)
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An Integrated 20-kW Motor Drive and Isolated Battery Charger for Plug-In Vehicles
- 2013
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Ingår i: IEEE transactions on power electronics. - 0885-8993 .- 1941-0107. ; 28:8, s. 4013-4029
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Tidskriftsartikel (refereegranskat)abstract
- For vehicles using grid power to charge the battery, traction circuit components are not normally engaged during the charging time, so there is a possibility to use them in the charger circuit to have an on-board integrated motor drive and battery charger. An isolated high-power three-phase integrated motor drive and charger based on a split-phase permanent magnet motor is presented in this paper. The motor winding connections are reversible by a relay-based switching device for traction and battery charging. In traction mode, the motor is a classical three-phase motor, but in charging mode it is a rotating isolating transformer providing a three-phase voltage source for the inverter to charge the battery. A mathematical model of the motor with six stator windings is presented for an arbitrary phase shift in windings. For the charging mode, the split-phase motor grid synchronization process and charge control are explained including the developed controller. A 20-kW system is designed and implemented to verify the proper operation of the proposed system. Simulation and practical results are provided to show the system performance in terms of functionality, dynamic response, and efficiency. Moreover, some discussions, recommendations, and limitations are provided to give more practical insights.
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| 523. |
- Haghbin, Saeid, 1977, et al.
(författare)
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An Isolated High-Power Integrated Charger in Electrified-Vehicle Applications
- 2011
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Ingår i: IEEE Transactions on Vehicular Technology. - 1939-9359 .- 0018-9545. ; 60:9, s. 4115-4126
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Tidskriftsartikel (refereegranskat)abstract
- For electric and hybrid vehicles that use grid power to charge the battery, traction circuit components are not normally engaged during the charging time; hence, there is a possibility of using the traction circuit components in the charger circuit to have an onboard integrated charger. An isolated high-power integrated charger based on a special electrical machine with a double set of stator windings is described. Through the reconfiguration of the motor stator windings in the charging mode, a six-terminal machine is achieved. The so-called motor/generator acts as an isolated three-phase power source after synchronization with the utility grid in the charging mode. This rotary isolated power source constitutes a three-phase boost rectifier (battery charger) with full utilization of the inverter. The motor windings are reconfigured by a relay-based switching device for the charging and traction modes. This paper presents the mathematical model of the motor/generator and explains the system's functionality for the traction and charging modes. Furthermore, the charger grid synchronization and charge control are described. Finally, the simulation results are presented for a practically designed system with a traction power of 25 kW and a possible charge power of 12.5 kW.
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| 524. |
- Haghbin, Saeid, 1977, et al.
(författare)
-
Grid-Connected Integrated Battery Chargers in Vehicle Applications: Review and New Solution
- 2013
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Ingår i: IEEE Transactions on Industrial Electronics. - 0278-0046 .- 1557-9948. ; 60:2, s. 459-473
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Tidskriftsartikel (refereegranskat)abstract
- For vehicles using grid power to charge the battery, traction circuit components are not engaged during the charging time, so there is a possibility to use them in the charger circuit to have an onboard integrated charger. The battery charger can be galvanically isolated or nonisolated from the grid. Different examples of isolated or nonisolated integrated chargers are reviewed and explained. Moreover, a novel isolated-high-power three-phase battery charger based on a split-phase permanent-magnet motor and its winding configuration is presented in this paper. The proposed charger is a bidirectional high-power charger with a unity power factor operation capability that has high efficiency.
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| 525. |
- Haghighatafshar, Salar, et al.
(författare)
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Laboratory-scale assessment of vacuum-degassed activated sludge for improved settling properties
- 2017
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Ingår i: Environmental Technology (United Kingdom). - : Informa UK Limited. - 1479-487X .- 0959-3330. ; 38:17, s. 2193-2201
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Tidskriftsartikel (refereegranskat)abstract
- Vacuum degassing of activated sludge was tested at eight different Swedish wastewater treatment plants with laboratory-scale equipment in batch mode in order to evaluate its efficiency on improvement of sludge compaction and settling properties. The results show that the efficiency of the degassing technique is mainly dependent on the initial sludge volume index (SVI) of the target sludge which was found to be related to its process configuration. Facilities with full activated sludge-based nitrogen removal processes, including both nitrification and denitrification, had high SVIs (>300 mL g(-1)) and were strongly affected by vacuum degassing with reduction of SVI up to 30%. Nitrogen removal facilities also including biological phosphorus removal showed better compaction and settling properties with relatively lower SVIs and were affected to a lesser extent by degassing with SVI reduction of 10-20%. Wastewater treatment plants without full biological nitrogen removal, lacking either nitrification or denitrification (or both) processes in the activated sludge had the lowest SVIs observed with almost no effect of vacuum degassing.
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| 526. |
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| 527. |
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| 528. |
- Haglund Stignor, Caroline, et al.
(författare)
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Energy-efficient flat-tube heat exchangers for indirectly cooled display cabinets
- 2009
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Ingår i: International Journal of Refrigeration. - : Elsevier BV. - 0140-7007. ; 32:6, s. 1460-1471
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Tidskriftsartikel (refereegranskat)abstract
- Different designs of flat-tube heat exchangers with plain fins have been evaluated theoretically in a parameter study in order to evaluate their performance potential in indirectly cooled display cabinets. Two different types of flat-tube heat exchangers were considered; one with serpentine fins and one with continuous plate fins. Both flat-tube heat exchanger types were adapted to the laminar flow regime on the liquid as well as on the air side. The performance of the two heat exchanger types had previously been verified experimentally under dehumidifying conditions. The results from this parameter study show that considerable savings in the required electric drive power to compressors, pumps and fans can be obtained in comparison with the traditional cooling coil. The savings may be up to 15%. In addition, the required temperature difference for the flat-tube heat exchangers is so small that frost-free operation is possible, which would result in even larger savings. (C) 2009 Elsevier Ltd and IIR. All rights reserved.
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| 529. |
- Haglund Stignor, Caroline, et al.
(författare)
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Heat Transfer and Pressure Drop Under Dry and Humid Conditions in Flat-Tube Heat Exchangers With Plain Fins
- 2010
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Ingår i: Heat Transfer Engineering. - : Informa UK Limited. - 0145-7632 .- 1521-0537. ; 31:3, s. 179-192
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Tidskriftsartikel (refereegranskat)abstract
- Flat-tube heat exchangers could be an interesting alternative to make indirect cooling of display cabinets more energy-efficient. This application involves low air velocities in combination with condensation of water vapor on the air side, so plain fins could be suitable. Two different heat exchangers having flat tubes and plain fins on the air side were evaluated experimentally. One of the heat exchangers had continuous plate fins, and the other had serpentine fins. The performances during dry and wet test conditions were compared and related to theoretical predictions for different assumptions. The influence of air velocity, air humidity, and inclination angle was investigated. The results show that, in most cases, the heat transfer performance is somewhat reduced under wet conditions in comparison with dry test conditions, and that wet heat transfer surfaces lead to an increased pressure drop. At the lower air velocity range that was investigated, the heat exchanger having continuous plate fins drained better than the one with serpentine fins.
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| 530. |
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