1,635 research outputs found
A review on the complementarity of renewable energy sources: concept, metrics, application and future research directions
It is expected, and regionally observed, that energy demand will soon be
covered by a widespread deployment of renewable energy sources. However, the
weather and climate driven energy sources are characterized by a significant
spatial and temporal variability. One of the commonly mentioned solutions to
overcome the mismatch between demand and supply provided by renewable
generation is a hybridization of two or more energy sources in a single power
station (like wind-solar, solar-hydro or solar-wind-hydro). The operation of
hybrid energy sources is based on the complementary nature of renewable
sources. Considering the growing importance of such systems and increasing
number of research activities in this area this paper presents a comprehensive
review of studies which investigated, analyzed, quantified and utilized the
effect of temporal, spatial and spatio-temporal complementarity between
renewable energy sources. The review starts with a brief overview of available
research papers, formulates detailed definition of major concepts, summarizes
current research directions and ends with prospective future research
activities. The review provides a chronological and spatial information with
regard to the studies on the complementarity concept.Comment: 34 pages 7 figures 3 table
Huge First-Order Metamagnetic Transition in the Paramagnetic Heavy-Fermion System CeTiGe
We report on the observation of large, step-like anomalies in the
magnetization (\,/Ce), in the magnetostriction
(), and in the magnetoresistance in
polycrystals of the paramagnetic heavy-fermion system CeTiGe at a critical
magnetic field 12.5\,T at low temperatures. The size of
these anomalies is much larger than those reported for the prototypical
heavy-fermion metamagnet CeRuSi. Furthermore, hysteresis between
increasing and decreasing field data indicate a real thermodynamic, first-order
type of phase transition, in contrast to the crossover reported for
CeRuSi. Analysis of the resistivity data shows a pronounced decrease of
the electronic quasiparticle mass across . These results establish CeTiGe
as a new metamagnetic Kondo-lattice system, with an exceptionally large,
metamagnetic transition of first-order type at a moderate field.Comment: 5 pages, 4 figure
Exploring high temperature magnetic order in CeTi_1-xSc_xGe
Most of magnetic transitions related to Ce ordering are found below
T_ord~12K. Among the few cases exceeding that temperature, two types of
behaviors can be distinguished. One of them is related to the rare cases of Ce
binary compounds formed in BCC structures, with a quartet ground state, whose
degeneracy is reduced by undergoing different types of transitions mostly
structural. The other group shows evidences of itinerant character with the
outstanding example of CeRh_3B_2 showing the highest T_ord=115K. The second
highest ordering temperature has been reported for CeScGe with T_ord=47K, but
the nature of this magnetic state has not been investigated very deeply. In
order to shed more light into this unusual high temperature ordering we studied
the structural, magnetic, transport and thermal properties of CeTi_1-xSc_xGe
alloys in the stability range of the CeScSi-type structure 0.25<x<1 This system
presents a rich variety of magnetic behaviors along this concentration range,
with the magnetic ordering growing from ferromagnetic (FM) T_C~7K up to an
antiferromagnetic (AFM) transition at T_N=47K. The different regions show the
following characteristics: i) on the Ti rich side (0.25<x<0.50) it exhibits a
FM ground state (GS) with large saturation magnetization values M_sat up to
~1.15 mu_B. ii) Around x=0.60, the first crystal electric field excited doublet
starts to contribute to the GS magnetic properties. Furthermore an AFM
component with a connected metamagnetic transition appears. iii) At x=0.65 a
clear change in the GS nature is associated to a critical point above which the
GS properties can be described like for an itinerant system (with decreasing
M_sat) and an effective GS degeneracy N_eff=4. iv) For x>0.65, the magnetic
phase boundary splits into two transitions, with an intermediate phase
presenting incommensurate spin density waves features.Comment: 8 pages, 10 figure
Text as signal. A tutorial with case studies focusing on social media (Twitter)
Sentiment analysis is the automated coding of emotions expressed in text. Sentiment analysis and other types of analyses focusing on the automatic coding of textual documents are increasingly popular in psychology and computer science. However, the potential of treating automatically coded text collected with regular sampling intervals as a signal is currently overlooked. We use the phrase "text as signal" to refer to the application of signal processing techniques to coded textual documents sampled with regularity. In order to illustrate the potential of treating text as signal, we introduce the reader to a variety of such techniques in a tutorial with two case studies in the realm of social media analysis. First, we apply finite response impulse filtering to emotion-coded tweets posted during the US Election Week of 2020 and discuss the visualization of the resulting variation in the filtered signal. We use changepoint detection to highlight the important changes in the emotional signals. Then we examine data interpolation, analysis of periodicity via the fast Fourier transform (FFT), and FFT filtering to personal value-coded tweets from November 2019 to October 2020 and link the variation in the filtered signal to some of the epoch-defining events occurring during this period. Finally, we use block bootstrapping to estimate the variability/uncertainty in the resulting filtered signals. After working through the tutorial, the readers will understand the basics of signal processing to analyze regularly sampled coded text
Some cases of anatomic variations observed in dissections
En el presente trabajo, los autores detallan una variación de la arteria toracodorsal en el vacuno y otra del músculo peroné largo en el cerdo.In this work the authors give detail of a variation found in the dorsal thoracic artery (Toraco Dorsalis) in Bovines. Another variation was found in the long perone muscle (Peroneus Longus) of swine.Facultad de Ciencias Veterinaria
Persistence and Eventual Demise of Oxygen Molecules at Terapascal Pressures
Computational searches for structures of solid oxygen under high pressures in the multi-TPa range are carried out using density-functional-theory methods. We find that molecular oxygen persists to about 1.9 TPa at which it transforms into a semiconducting square-spiral-like polymeric structure (I41/acd) with a band gap of ∼3.0  eV. Solid oxygen forms a metallic zigzag chainlike structure (Cmcm) at about 3.0 TPa, but the chains in each layer gradually merge as the pressure is increased and a structure of Fmmm symmetry forms at about 9.3 TPa in which each atom has four nearest neighbors. The superconducting properties of molecular oxygen do not vary much with compression, although the structure becomes more symmetric. The electronic properties of oxygen have a complex evolution with pressure, swapping between insulating, semiconducting, and metallic
Dry Juan de Fuca slab revealed by quantification of water entering Cascadia subduction zone
Author Posting. © The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Nature Geoscience 10 (2017): 864-870, doi:10.1038/ngeo3050.Water is carried by subducting slabs as a pore fluid and in structurally bound
minerals, yet no comprehensive quantification of water content and how it is stored
and distributed at depth within incoming plates exists for any segment of the global
subduction system. Here we use seismic data to quantify the amount of pore and
structurally bound water in the Juan de Fuca plate entering the Cascadia
subduction zone. Specifically, we analyse these water reservoirs in the sediments,
crust and lithospheric mantle, and their variations along the central Cascadia
margin. We find that the Juan de Fuca lower crust and mantle are drier than at any
other subducting plate, with most of the water stored in the sediments and upper
crust. Variable but limited bend faulting along the margin limits slab access to
water, and a warm thermal structure resulting from a thick sediment cover and
young plate age prevents significant serpentinization of the mantle. The dryness of
the lower crust and mantle indicates that fluids that facilitate episodic tremor and
slip must be sourced from the subducted upper crust, and that decompression
rather than hydrous melting must dominate arc magmatism in central Cascadia.
Additionally, dry subducted lower crust and mantle can explain the low levels of
intermediate-depth seismicity in the Juan de Fuca slab.This research was funded by the US NSF
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