Using spin-polarized low energy electron microscopy, we discovered a new type of domain wall structure in perpendicularly magnetized Fe/Ni bilayers grown epitaxially on Cu(100). Specifically, we ...observed unexpected Néel-type walls with fixed chirality in the magnetic stripe phase. Furthermore, we find that the chirality of the domain walls is determined by the film growth order with the chirality being right handed in Fe/Ni bilayers and left handed in Ni/Fe bilayers, suggesting that the underlying mechanism is the Dzyaloshinskii-Moriya interaction at the film interfaces. Our observations may open a new route to control chiral spin structures using interfacial engineering in transition metal heterostructures.
•A fuel cell system integrating PEMFC and MH hydrogen tank is analyzed.•A mathematical model set is proposed for simulating the fuel cell system.•Database from real operation vehicles is used to ...valid the simulation results.•2.5% of voltage degradation of PEMFC is reduced with proposed thermal management strategy.•3% of fuel efficiency and 10% of fuel economy of the system is saved.
A fuel cell power system integrating proton-exchange-membrane fuel cell (PEMFC) and metal hydride (MH)-based hydrogen storage tank presents great potential in transportation applications. The embedded PEMFC and MH tank are thermally coupled through a heat ex-changer and control system. The hydrogen generating and supplying rate from the MH tank to PEMFC is strongly influenced by the transferred heat, which affects the performance of long-term operation as well. In this work, the dynamic behavior of the fuel cell system is simulated with a mathematical model set and validated using a database from the real operation vehicles. Thanks to the heat ex-changer combined by fan, radiator and circulation water, the hydrogen flow rate from MH tank to PEMFC is well controlled to meet the requirement of power load. The simulated model describes the response of each component including the power and heat generated by PEMFC, the hydrogen desorption kinetics and the heat transfer in the system. A thermal management strategy with a PID controller is proposed to reduce the degradation and extend the lifespan of PEMFC. The results demonstrate that an optimized performance of PEMFC after 1000 h is realized. In spite of the MH tank degradation rate has been raised 0.3%, 2.5% of voltage degradation of PEMFC is reduced. Meanwhile, for the integration fuel cell system, more than 3% of fuel efficiency and 10% of fuel economy is saved.
Plants must respond to environmental cues and schedule their development in order to react to periods of abiotic stress and commit fully to growth and reproduction under favorable conditions. This ...study was initiated to identify SNP markers for characters expressed from the seedling stage to plant maturity in spring and winter wheat (Triticum aestivum L.) genotypes adapted to western Canada. Three doubled haploid populations with the winter cultivar 'Norstar' as a common parent were developed and genotyped with a 90K Illumina iSelect SNP assay and a 2,998.9 cM consensus map with 17,541 markers constructed. High heritability's reflected large differences among the parents and relatively low genotype by environment interactions for all characters considered. Significant QTL were detected for the 15 traits examined. However, different QTL for days to heading in controlled environments and the field provided a strong reminder that growth and development are being orchestrated by environmental cues and caution should be exercised when extrapolating conclusions from different experiments. A QTL on chromosome 6A for minimum final leaf number, which determines the rate of phenological development in the seedling stage, was closely linked to QTL for low-temperature tolerance, grain quality, and agronomic characters expressed up to the time of maturity. This suggests phenological development plays a critical role in programming subsequent outcomes for many traits. Transgressive segregation was observed for the lines in each population and QTL with additive effects were identified suggesting that genes for desirable traits could be stacked using Marker Assisted Selection. QTL were identified for characters that could be transferred between the largely isolated western Canadian spring and winter wheat gene pools demonstrating the opportunities offered by Marker Assisted Selection to act as bridges in the identification and transfer of useful genes among related genetic islands while minimizing the drag created by less desirable genes.
In this work, the dynamic responses of the on board hydrogen storage system with commercially available metal hydride tanks are investigated based on the database collected from fuel cell electric ...vehicles operation experiments. A mathematical model considering the heat transfer measured by the temperature control system is developed to analyze the absorption and desorption reaction during operation. As a seal container filled with unknown metal hydride, the practical used hydrogen storage tank is a gray box in the embedded storage system. Without the information about characteristics of material, current operation state and degradation degree, the parameters of the model are uncertain. Particle swarm optimization (PSO) algorithm is applied to search for the optimal parameter set. The simulation results of the hydrogen storage system model using these parameters show great agreements with the real operating data under different temperature conditions; the maximal error is lower than 9%.
•The applied system is constituted of metal hydride tank and heat exchange.•A dynamic modeling process is proposed for the embedded hydrogen storage system.•PSO algorithm is used to identify the parameters of the proposed dynamic model.•The dynamic model is validated by the database of real operation FC vehicles.
Magnetic domain structure and spin-dependent reflectivity measurements on cobalt thin films intercalated at the graphene/Ir(111) interface are investigated using spin-polarised low-energy electron ...microscopy. We find that graphene-covered cobalt films have surprising magnetic properties. Vectorial imaging of magnetic domains reveals an unusually gradual thickness-dependent spin reorientation transition, in which magnetisation rotates from out-of-the-film plane to the in-plane direction by less than 10° per cobalt monolayer. During this transition, cobalt films have a meandering spin texture, characterised by a complex, three-dimensional, wavy magnetisation pattern. In addition, spectroscopy measurements suggest that the electronic band structure of the unoccupied states is essentially spin-independent already a few electron-Volts above the vacuum level. These properties strikingly differ from those of pristine cobalt films and could open new prospects in surface magnetism.
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