| 1. |
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| 2. |
- Beale, S. B., et al.
(författare)
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Stability Issues of Fuel Cell Models in the Activation and Concentration Regimes
- 2018
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Ingår i: Journal of Electrochemical Energy Conversion and Storage. - : ASME International. - 2381-6872 .- 2381-6910. ; 15:4
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Tidskriftsartikel (refereegranskat)abstract
- Code stability is a matter of concern for three-dimensional (3D) fuel cell models operating both at high current density and at high cell voltage. An idealized mathematical model of a fuel cell should converge for all potentiostatic or galvanostatic boundary conditions ranging from open circuit to closed circuit. Many fail to do so, due to (i) fuel or oxygen starvation causing divergence as local partial pressures and mass fractions of fuel or oxidant fall to near zero and (ii) nonlinearities in the Nernst and Butler-Volmer equations near open-circuit conditions. This paper describes in detail, specific numerical methods used to improve the stability of a previously existing fuel cell performance calculation procedure, at both low and high current densities. Four specific techniques are identified. A straight channel operating as a (i) solid oxide and (ii) polymer electrolyte membrane fuel cell is used to illustrate the efficacy of the modifications.
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| 3. |
- Brännström, André, et al.
(författare)
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Effects and mechanisms of tapering in maximizing muscular power
- 2013
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Ingår i: Sport and Art. - : Horizon Research Publishing. - 2331-6195 .- 2331-6233. ; 1:1, s. 18-23
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Forskningsöversikt (refereegranskat)abstract
- Muscle power is of great importance in most sports, and its development is one of the most fundamental physiological adaptations for improving physical performance. In order to optimize competition performance, athletes usually decrease training load before competition, the so-called tapering, to allow physiological and psychological recovery from accumulated training stress. Tapering could be conducted through changes in training volume, intensity and/or frequency, but training volume seems to be most effective in optimizing muscular power. There are two main types of tapering: progressive tapering and one-step tapering. Currently, there is no general conclusion on tapering duration. The physiological mechanisms regarding tapering effects on neuromuscular system are largely unknown. Generally, it is believed that sustained maximal muscular power after tapering is obtained through maintaining adaptations in muscle fiber size, fiber type and neural adaptations whereas increased maximal muscular power after tapering is assumed mainly through both physiological and psychological recovery. We believe that increased maximal muscular power after tapering may also rely on higher neural drive and increased muscle fiber cross sectional area (CSA), especially in type IIA muscle fibers. Complete rest is a special form of tapering and it usually only leads to sustained maximal power. This effect is believed to be associated with decreased muscle CSA and a transformation of muscle fibers from type IIA to type IIX.
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| 4. |
- Li, Shian, et al.
(författare)
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Wavy Surface Cathode Gas Flow Channel Effects on Transport Processes in a Proton Exchange Membrane Fuel Cell
- 2017
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Ingår i: Journal of Electrochemical Energy Conversion and Storage. - : ASME International. - 2381-6872 .- 2381-6910. ; 14:3
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Tidskriftsartikel (refereegranskat)abstract
- The flow field design of current collectors is a significant issue, which greatly affects the mass transport processes of reactants/products inside fuel cells. Especially for proton exchange membrane (PEM) fuel cells, an appropriate flow field design is very important due to the water balance problem. In this paper, a wavy surface is employed at the cathode flow channel to improve the oxygen mass transport process. The effects of wavy surface on transport processes are numerically investigated by using a three-dimensional anisotropic model including a water phase change model and a spherical agglomerate model. It is found that the wavy configurations enhance the oxygen transport and decrease the water saturation level. It is concluded that the predicted results and findings provide the guideline for the design and manufacture of fuel cells.
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| 5. |
- Sandgren, Evelina, et al.
(författare)
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Correlation analysis between soccer game world ranking and player league distribution
- 2013
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Ingår i: Sport and Art. - : Horizon Research Publishing Co., Ltd.. - 2331-6233. ; 1:2, s. 34-40
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Tidskriftsartikel (refereegranskat)abstract
- Nowadays professional soccer player trading between clubs/leagues is very common. Soccer players could be employed in foreign clubs/leagues, but when international competitive events come, the elite players are recruited to compose a national team. One can expect that the higher ranking of a national team, the more players are employed by the top soccer leagues. However, the relationship between the two issues has never been studied early. In the study, seven national soccer teams were selected from a list of the world top 35 soccer teams of year 2010[created by the Federation of International Football Association (FIFA)]. The 7 teams are Spain, England, Argentina, Germany, USA, Ghana and Sweden, across the full range of the list, thus, representing different levels of the world. On basis of the position of the 7 teams in the world ranking, an order ranking for the 7 teams was created. To identify player distribution of the 7 teams in different quality/level of soccer leagues, a league ranking including the top 25 soccer leagues in the world created by the International Federation of Football History and Statistics (IFFHS) was used. For each of the 7 teams, its player distribution in different soccer leagues was classified. On basis of the league ranking and the number of player(s) of each team in different leagues, calculated team point was calculated for each team. According to the amount of the calculated point, a calculated team ranking was obtained. Correlation analysis was performed between the two rankings: the order ranking and the calculated team ranking. The results showed a high and positive correlation between the two variables. We concluded that the more players are employed in higher ranking leagues the higher world ranking of a national team.
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| 6. |
- Schlesak, Saskia, et al.
(författare)
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Addendum to Hypnum subcomplanatum Hedenäs, Schlesak, D. Quandt
- 2019
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Ingår i: Bryophyte Diversity and Evolution. - : Magnolia Press. - 2381-9685 .- 2381-9677. ; 41, s. 1-1
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Tidskriftsartikel (refereegranskat)abstract
- In our recent paper on the relationships of 21 European Hypnum taxa we introduced the name Hypnum subcomplanatum Hedenäs, Schlesak & D. Quandt as a new name at the species level, based on the basionym Hypnum cupressiforme var. subjulaceum Molendo (Schlesak et al. 2018). We were aware that H. cupressiforme var. subjulaceum had already been elevated and combined at the species rank (Stereodon subjulaceum (Molendo) Loeske & Osterwald [Verh. Bot. Vereins Prov. Brandenburg 49: 65. 1907)], but unfortunately overlooked that Hypnum subjulaceum Besch. was not validly published. The latter therefore cannot block a species level combination in Hypnum based on H. cupressiforme var. subjulaceum Molendo (Art. 53.1 of the Code). Because no homonym issues exist, the epithet ’subjulaceum’ has priority when combined under Hypnum. The new combination follows:
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| 7. |
- Schlesak, Saskia, et al.
(författare)
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Cleaning a taxonomic dustbin: placing the European Hypnum species in a phylogenetic context!
- 2018
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Ingår i: Bryophyte Diversity and Evolution. - : Magnolia Press. - 2381-9685 .- 2381-9677. ; 40, s. 37-54
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Tidskriftsartikel (refereegranskat)abstract
- The pleurocarpous moss genus Hypnum s.l. is a species-rich (> 40 species) cosmopolitan genus, of which 21 taxa occur in Europe. Although several of these species show high morphological resemblance there are strong indications that the genus is highly paraphyletic, which may be masked by convergent morphological evolution. Using molecular information, we analyse whether the morphological similarity of gametophytes of the European Hypnum taxa is explained by common ancestry or convergence. We provide a phylogenetic reconstruction of the relationships of the currently recognized European Hypnum taxa in a broad pleurocarpous moss context (192 taxa) using the nuclear ITS1-5.8S-ITS2, the plastid rps4 gene and trnL-F, and the mitochondrial nad5 intron. Bayesian tree topologies show that the genus is polyphyletic, and we retain only the Hypnum cupressiforme complex within Hypnum. The genus originally represented half of the moss species diversity, as it accommodated basically all pleurocarpous mosses; here we retain only seven species and one variety. The remainder of the species where resolved either within the three families Amblystegiaceae, Entodontaceae, and Pylaisiaceae, or in an independent clade that we describe as the new family Stereodontaceae. The Stereodontaceae includes five European species, all in the genus Stereodon, where they were already placed in the 18th century. In addition, we describe the four new genera Aquilonium, Insomniella, Jochenia, and Lignocariosa, and make new combinations for several Hypnum species.
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| 8. |
- Zaccaria, Valentina, 1989-, et al.
(författare)
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Fuel Cell Temperature Control with a Pre-Combustor in SOFC Gas Turbine Hybrids during Load Changes
- 2017
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Ingår i: Journal of electrochemical energy conversion and storage. - : ASME International. - 2381-6872 .- 2381-6910. ; 14, s. 031006-031014
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Tidskriftsartikel (refereegranskat)abstract
- The use of high temperature fuel cells, such as Solid Oxide Fuel Cells (SOFCs), for power generation is considered a very efficient and clean solution to conservation of energy resources. When the SOFC is coupled with a gas turbine, the global system efficiency can go beyond 70% on natural gas LHV. However, durability of the ceramic material and system operability can be significantly penalized by thermal stresses due to temperature fluctuations and non-even temperature distributions. Thermal management of the cell during load following is therefore essential.The purpose of this work was to develop and test a pre-combustor model for real-time applications in hardware-based simulations, and to implement a control strategy to keep constant cathode inlet temperature during different operative conditions. The real-time model of the pre-combustor was incorporated into the existing SOFC model and tested in a hybrid system facility, where a physical gas turbine and hardware components were coupled with a cyber-physical fuel cell for flexible, accurate, and cost-reduced simulations.The control of the fuel flow to the pre-combustor was proven to be effective in maintaining a constant cathode inlet temperature during a step change in fuel cell load. With a 20 A load variation, the maximum temperature deviation from the nominal value was below 0.3% (3K). Temperature gradients along the cell were maintained below 10 K/cm. An efficiency analysis was performed in order to evaluate the impact of the pre-combustor on the overall system efficiency.
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| 9. |
- Abbassi, Nasrollah, et al.
(författare)
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Avian ichnia and other vertebrate trace fossils from the Neogene Red Beds of Tarom valley in north-western Iran
- 2016
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Ingår i: Historical Biology. - : Informa UK Limited. - 0891-2963 .- 1029-2381. ; 28:8, s. 1075-1089
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Tidskriftsartikel (refereegranskat)abstract
- The Neogene Red Beds of the Tarom valley (north-western Iran) include conglomerate, sandstone, marl and gypsum. Avian and mammal footprints were discovered in one of the sandstone layers at the base of a third Miocene stratigraphical unit in the Gilankesheh area located in the east Tarom valley. The avian ichnia include Aviadactyla vialovi, Avipeda filiportatis, Charadriipeda disjuncta, Charadriipeda isp. A and B and cf. Ornithotarnocia lambrechti. Bird feeding traces are preserved as bilobate, loop-shaped, sinusoidal and ring-like traces. We have also identified a reticulate texture of sole scale imprints in some of the avian ichnia. Two mammal footprints of camelid-like artiodactyls are also present with the avian ichno-assemblage.
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| 10. |
- Acquaviva, Alessandro, 1987
(författare)
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Analytical Electromagnetic Sizing of Inner Rotor Brushless PM Machines Based on Split Ratio Optimization
- 2018
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Ingår i: 2018 XIII International Conference on Electrical Machines (ICEM). - 2381-4802. - 9781538624777 ; , s. 576-582
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Konferensbidrag (refereegranskat)abstract
- This paper presents an analytical procedure to size brushless PM Machines from a set of required performance specifications. The sizing is obtained by optimizing the machine's split ratio, defined as the ratio of the stator inner to outer diameter. This ratio is key in the design of the machine and it is a compromise among several performance factors, and in particular it is shown to be a trade-off between efficiency and torque density. The split ratio also affects the volume of each material and in turn the cost of the machine. The algorithm outputs the machine performance and cost curves as a function of the split ratio, giving the possibility to the user to decide the best compromise for a certain application. The analytical sizing procedure is built and integrated with a 2D FEM simulator for refinement and verification of the design. A case study is presented and validated to prove the effectiveness of the sizing procedure.
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