19,529 research outputs found
A ’feasibility space’ as a goal to be achieved in the development of new technologies for converting renewable energies
This method article proposes the establishment of a feasibility space as an objective to be achieved during the development of new technologies to convert energy from renewable resources. The feasibility space can also be a reference when designing an energy system based on renewable resources. The feasibility space is a set of parameter values for the design stage that define the economic and technical feasibility of an energy system or a new technology, which must be satisfied when the energy system comes into operation or when the new technology for converting power goes into operation. The study of possible feasibility spaces allows characterizing energy systems or new technologies as attractive investments, or on the other hand, as unfeasible ventures. - The method proposes to establish a goal to achieve during the development of technologies for energy conversion. - The method provides a benchmark for both the stages of design and development of generation systems and new technologies. - The feasibility space constitutes a planning tool for power systems based on renewable resources of any size
Ensemble Forecasts of Solar Wind Connectivity to 1 Rs using ADAPT-WSA
The solar wind which arrives at any location in the solar system is, in
principle, relatable to the outflow of solar plasma from a single source
location. This source location, itself usually being part of a larger coronal
hole, is traceable to 1 Rs along the Sun's magnetic field, in which the entire
path from 1 Rs to a location in the heliosphere is referred to as the solar
wind connectivity. While not directly measurable, the connectivity between the
near-Earth solar wind is of particular importance to space weather. The solar
wind solar source region can be obtained by leveraging near-sun magnetic field
models and a model of the interplanetary solar wind. In this article we present
a method for making an ensemble forecast of the connectivity presented as a
probability distribution obtained from a weighted collection of individual
forecasts from the combined Air Force Data Assimilative Photospheric Flux
Transport - Wang Sheeley Arge (ADAPT-WSA) model. The ADAPT model derives the
photospheric magnetic field from synchronic magnetogram data, using flux
transport physics and ongoing data assimilation processes. The WSA model uses a
coupled set of potential field type models to derive the coronal magnetic
field, and an empirical relationship to derive the terminal solar wind speed
observed at Earth. Our method produces an arbitrary 2D probability distribution
capable of reflecting complex source configurations with minimal assumptions
about the distribution structure, prepared in a computationally efficient
manner.Comment: Accepted to the journal "Space Weather
Emergence of pseudogap from short-range spin-correlations in electron doped cuprates
Electron interactions are pivotal for defining the electronic structure of
quantum materials. In particular, the strong electron Coulomb repulsion is
considered the keystone for describing the emergence of exotic and/or ordered
phases of quantum matter as disparate as high-temperature superconductivity and
charge- or magnetic-order. However, a comprehensive understanding of
fundamental electronic properties of quantum materials is often complicated by
the appearance of an enigmatic partial suppression of low-energy electronic
states, known as the pseudogap. Here we take advantage of ultrafast
angle-resolved photoemission spectroscopy to unveil the temperature evolution
of the low-energy density of states in the electron-doped cuprate
NdCeCuO, an emblematic system where
the pseudogap intertwines with magnetic degrees of freedom. By photoexciting
the electronic system across the pseudogap onset temperature T*, we report the
direct relation between the momentum-resolved pseudogap spectral features and
the spin-correlation length with an unprecedented sensitivity. This transient
approach, corroborated by mean field model calculations, allows us to establish
the pseudogap in electron-doped cuprates as a precursor to the incipient
antiferromagnetic order even when long-range antiferromagnetic correlations are
not established, as in the case of optimal doping.Comment: 17 pages, 3 figure
Transition from Knudsen to molecular diffusion in activity of absorbing irregular interfaces
We investigate through molecular dynamics the transition from Knudsen to
molecular diffusion transport towards 2d absorbing interfaces with irregular
geometry. Our results indicate that the length of the active zone decreases
continuously with density from the Knudsen to the molecular diffusion regime.
In the limit where molecular diffusion dominates, we find that this length
approaches a constant value of the order of the system size, in agreement with
theoretical predictions for Laplacian transport in irregular geometries.
Finally, we show that all these features can be qualitatively described in
terms of a simple random-walk model of the diffusion process.Comment: 4 pages, 4 figure
Collapse of superconductivity in cuprates via ultrafast quenching of phase coherence
The possibility of driving phase transitions in low-density condensates
through the loss of phase coherence alone has far-reaching implications for the
study of quantum phases of matter. This has inspired the development of tools
to control and explore the collective properties of condensate phases via phase
fluctuations. Electrically-gated oxide interfaces, ultracold Fermi atoms, and
cuprate superconductors, which are characterized by an intrinsically small
phase-stiffness, are paradigmatic examples where these tools are having a
dramatic impact. Here we use light pulses shorter than the internal
thermalization time to drive and probe the phase fragility of the
BiSrCaCuO cuprate superconductor, completely melting
the superconducting condensate without affecting the pairing strength. The
resulting ultrafast dynamics of phase fluctuations and charge excitations are
captured and disentangled by time-resolved photoemission spectroscopy. This
work demonstrates the dominant role of phase coherence in the
superconductor-to-normal state phase transition and offers a benchmark for
non-equilibrium spectroscopic investigations of the cuprate phase diagram.Comment: 24 pages, 9 figures, Main Text and Supplementary Informatio
The Ammount of Interstellar Carbon Locked in Solid Hydrogenated Amorphous Carbon
We review the literature and present new experimental data to determine the
amount of carbon likely to be locked in form of solid hydrogenated amorphous
carbon (HAC) grains. We conclude on the basis of a thorough analysis of the
intrinsic strength of the C-H stretching band at 3.4 micron that between 10 and
80 ppM H of carbon is in the form of HAC grains. We show that it is necessary
to know the level of hydrogenation (H/C) of the interstellar HAC to determine
more precisely the amount of carbon it ties up. We present optical constants,
photoluminescence spectroscopy, and IR absorption spectroscopy for a particular
HAC sample that is shown to have a 3.4 micron absorption feature that is
quantatively consistent with that observed in the diffuse interstellar medium.Comment: This paper is 14 pages long with 5 figures and will appear in the 1
December 1999 issue of Ap
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High-resolution adaptive optics scanning laser ophthalmoscope with dual deformable mirrors for large aberration correction
Scanning laser ophthalmoscopes with adaptive optics (AOSLO) have been shown previously to provide a noninvasive, cellular-scale view of the living human retina. However, the clinical utility of these systems has been limited by the available deformable mirror technology. In this paper, we demonstrate that the use of dual deformable mirrors can effectively compensate large aberrations in the human retina, making the AOSLO system a viable, non-invasive, high-resolution imaging tool for clinical diagnostics. We used a bimorph deformable mirror to correct low-order aberrations with relatively large amplitudes. The bimorph mirror is manufactured by Aoptix, Inc. with 37 elements and 18 {micro}m stroke in a 10 mm aperture. We used a MEMS deformable mirror to correct high-order aberrations with lower amplitudes. The MEMS mirror is manufactured by Boston Micromachine, Inc with 144 elements and 1.5 {micro}m stroke in a 3 mm aperture. We have achieved near diffraction-limited retina images using the dual deformable mirrors to correct large aberrations up to {+-} 3D of defocus and {+-} 3D of cylindrical aberrations with test subjects. This increases the range of spectacle corrections by the AO systems by a factor of 10, which is crucial for use in the clinical environment. This ability for large phase compensation can eliminate accurate refractive error fitting for the patients, which greatly improves the system ease of use and efficiency in the clinical environment
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