173 research outputs found
Exchange bias and training effects in antiferromagnetically coupled La0.7Sr0.3MnO3 / SrRuO3 superlattices
Exchange bias (EB) and the training effects (TE) in an antiferromagnetically
coupled La0.7Sr0.3MnO3 / SrRuO3 superlattices were studied in the temperature
range 1.8 - 150 K. Strong antiferromagnetic (AFM) interlayer coupling is
evidenced from AC - susceptibility measurements. Below 100 K, vertical
magnetization shifts are present due to the two remanent states corresponding
to the two ferromagnetic (FM) layers at FM and AFM coupling condition. After
field cooling (FC), significant decrease in the exchange bias field (HEB) is
observed when cycling the system through several consecutive hysteresis loops.
Quantitative analysis for the variation of HEB vs. number of field cycles (n)
indicates an excellent agreement between the theory, based on triggered
relaxation phenomena, and our experimental observations. Nevertheless, the
crucial fitting parameter K indicates smooth training effect upon repeated
field cycling, in accordance with our observation.Comment: Accepted Europhysics Letter
Room temperature soft ferromagnetism in the nanocrystalline form of YCo2 - a well-known bulk Pauli paramagnet
The Laves phase compound, YCo2, is a well-known exchange-enahnced Pauli
paramagnet. We report here that, in the nanocrystalline form, this compound
interestingly is an itinerant ferromagnet at room temperature with a low
coercive-field. The magnitude of the saturation moment (about 1 Bohr-magneton
per formula unit) is large enough to infer that the ferromagnetism is not a
surface phenomenon in these nanocrystallites. Since these ferromagnetic
nanocrystallines are easy to synthesize with a stable form in air, one can
explore applications, particularly where hysteresis is a disadvantage
Exploring wind direction and SO2 concentration by circular-linear density estimation
The study of environmental problems usually requires the description of
variables with different nature and the assessment of relations between them.
In this work, an algorithm for flexible estimation of the joint density for a
circular-linear variable is proposed. The method is applied for exploring the
relation between wind direction and SO2 concentration in a monitoring station
close to a power plant located in Galicia (NW-Spain), in order to compare the
effectiveness of precautionary measures for pollutants reduction in two
different years.Comment: 17 pages, 7 figures, 2 table
Planar localisation analyses: a novel application of a centre of mass approach
Sound localisation is one of the key roles for listening, and measuring localisation performance is a mainstay of the hearing research laboratory. Such measurements consider both accuracy and, for incorrect trials, the size of the error. In terms of error analysis, localisation studies have frequently used general univariate techniques in conjunction with either mean signed or unsigned error measurements. This approach can make inappropriate distributional assumptions and so more suitable alternatives based on directional statistics (e.g. based on von Mises distributed data) have also been used. However these are not readily computed using most commercially available, commonly used statistical software, and are generally only defined for simple experimental designs. We describe a novel use of a 'centre of mass' approach for describing localisation data jointly in terms of accuracy and size of error. This spatial method offers powerful, yet flexible, statistical analysis using standard multivariate analysis of variance (MANOVA)
Predictive Influence of Unavailable Values of Future Explanatory Variables in a Linear Model
Projected changes of rainfall seasonality and dry spells in a high greenhouse gas emissions scenario
In this diagnostic study we analyze changes of rainfall seasonality and dry spells by the end of the twenty-first century under the most extreme IPCC5 emission scenario (RCP8.5) as projected by twenty-four coupled climate models contributing to Coupled Model Intercomparison Project 5 (CMIP5). We use estimates of the centroid of the monthly rainfall distribution as an index of the rainfall timing and a threshold-independent, information theory-based quantity such as relative entropy (RE) to quantify the concentration of annual rainfall and the number of dry months and to build a monsoon dimensionless seasonality index (DSI). The RE is projected to increase, with high inter-model agreement over Mediterranean-type regions---southern Europe, northern Africa and southern Australia---and areas of South and Central America, implying an increase in the number of dry days up to 1Ă‚ month by the end of the twenty-first century. Positive RE changes are also projected over the monsoon regions of southern Africa and North America, South America. These trends are consistent with a shortening of the wet season associated with a more prolonged pre-monsoonal dry period. The extent of the global monsoon region, characterized by large DSI, is projected to remain substantially unaltered. Centroid analysis shows that most of CMIP5 projections suggest that the monsoonal annual rainfall distribution is expected to change from early to late in the course of the hydrological year by the end of the twenty-first century and particularly after year 2050. This trend is particularly evident over northern Africa, southern Africa and western Mexico, where more than 90% of the models project a delay of the rainfall centroid from a few days up to 2Ă‚ weeks. Over the remaining monsoonal regions, there is little inter-model agreement in terms of centroid changes
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