116 research outputs found
Effect of wind turbine generator model and siting on wind power changes out of large WECS arrays
Methods of reducing the WECS generation change through selection of the wind turbine model for each site, selection of an appropriate siting configuration, and wind array controls are discussed. An analysis of wind generation change from an echelon and a farm for passage of a thunderstorm is presented. Reduction of the wind generation change over ten minutes is shown to reduce the increase in spinning reserve, unloadable generation and load following requirements on unit commitment when significant WECS generation is present and the farm penetration constraint is satisfied. Controls on the blade pitch angle of all wind turbines in an array or a battery control are shown to reduce both the wind generation change out of an array and the effective farm penetration in anticipation of a storm so that the farm penetration constraint may be satisfied
Calorimetric Measurements of Magnetic-Field-Induced Inhomogeneous Superconductivity Above The Paramagnetic Limit
We report the first magneto-caloric and calorimetric observations of a
magnetic-field-induced phase transition within a superconducting state to the
long-sought exotic "FFLO" superconducting state first predicted over 50 years
ago. Through the combination of bulk thermodynamic calorimetric and
magnetocaloric measurements in the organic superconductor -
(BEDT-TTF)Cu(NCS), as a function of temperature, magnetic field
strength, and magnetic field orientation, we establish for the first time that
this field-induced first-order phase transition at the paramagnetic limit
for traditional superconductivity is to a higher entropy superconducting phase
uniquely characteristic of the FFLO state. We also establish that this
high-field superconducting state displays the bulk paramagnetic ordering of
spin domains required of the FFLO state. These results rule out the alternate
possibility of spin-density wave (SDW) ordering in the high field
superconducting phase. The phase diagram determined from our measurements ---
including the observation of a phase transition into the FFLO phase at
--- is in good agreement with recent NMR results and our own earlier
tunnel-diode magnetic penetration depth experiments, but is in disagreement
with the only previous calorimetric report.Comment: 5 pages, 5 figure
Calorimetric Measurements of Magnetic-Field-Induced Inhomogeneous Superconductivity Above The Paramagnetic Limit
We report the first magnetocaloric and calorimetric observations of a magnetic-field-induced phase transition within a superconducting state to the long-sought exotic Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconducting state, first predicted over 50 years ago. Through the combination of bulk thermodynamic calorimetric and magnetocaloric measurements in the organic superconductor κ−(BEDT−TTF)2Cu(NCS)2 as a function of temperature, magnetic field strength, and magnetic field orientation, we establish for the first time that this field-induced first-order phase transition at the paramagnetic limit Hp is a transition to a higher-entropy superconducting phase, uniquely characteristic of the FFLO state. We also establish that this high-field superconducting state displays the bulk paramagnetic ordering of spin domains required of the FFLO state. These results rule out the alternate possibility of spin-density wave ordering in the high-field superconducting phase. The phase diagram determined from our measurements—including the observation of a phase transition into the FFLO phase at Hp—is in good agreement with recent NMR results and our own earlier tunnel-diode magnetic penetration depth experiments but is in disagreement with the only previous calorimetric report
The PHENIX Experiment at RHIC
The physics emphases of the PHENIX collaboration and the design and current
status of the PHENIX detector are discussed. The plan of the collaboration for
making the most effective use of the available luminosity in the first years of
RHIC operation is also presented.Comment: 5 pages, 1 figure. Further details of the PHENIX physics program
available at http://www.rhic.bnl.gov/phenix
Negative Impacts of Human Land Use on Dung Beetle Functional Diversity
The loss of biodiversity caused by human activity is assumed to alter ecosystem
functioning. However our understanding of the magnitude of the effect of these
changes on functional diversity and their impact on the dynamics of ecological
processes is still limited. We analyzed the functional diversity of
copro-necrophagous beetles under different conditions of land use in three
Mexican biosphere reserves. In Montes Azules pastures, forest fragments and
continuous rainforest were analyzed, in Los Tuxtlas rainforest fragments of
different sizes were analyzed and in Barranca de Metztitlán two types of
xerophile scrub with different degrees of disturbance from grazing were
analyzed. We assigned dung beetle species to functional groups based on food
relocation, beetle size, daily activity period and food preferences, and as
measures of functional diversity we used estimates based on multivariate
methods. In Montes Azules functional richness was lower in the pastures than in
continuous rainforest and rainforest fragments, but fragments and continuous
forest include functionally redundant species. In small rainforest fragments
(<5 ha) in Los Tuxtlas, dung beetle functional richness was lower than in
large rainforest fragments (>20 ha). Functional evenness and functional
dispersion did not vary among habitat types or fragment size in these reserves.
In contrast, in Metztitlán, functional richness and functional dispersion
were different among the vegetation types, but differences were not related to
the degree of disturbance by grazing. More redundant species were found in
submontane than in crassicaule scrub. For the first time, a decrease in the
functional diversity in communities of copro-necrophagous beetles resulting from
changes in land use is documented, the potential implications for ecosystem
functioning are discussed and a series of variables that could improve the
evaluation of functional diversity for this biological group is proposed
Biodiversity, Disparity and Evolvability
A key problem in conservation biology is how to measure biological diversity. Taxic diversity (the number of species in a community or in a local biota) is not necessarily the most important aspect, if what most matters is to evaluate how the loss of the different species may impact on the future of the surviving species and communities. Alternative approaches focus on functional diversity (a measure of the distribution of the species among the different 'jobs' in the ecosystem), others on morphological disparity, still others on phylogenetic diversity. There are three major reasons to prioritize the survival of species which provide the largest contributions to the overall phylogenetic diversity. First, evolutionarily isolated lineages are frequently characterized by unique traits. Second, conserving phylogenetically diverse sets of taxa is valuable because it conserves some sort of trait diversity, itself important in so far as it helps maintain ecosystem functioning, although a strict relationships between phylogenetic diversity and functional diversity cannot be taken for granted. Third, in this way we maximize the "evolutionary potential" depending on the evolvability of the survivors. This suggests an approach to conservation problems focussed on evolvability, robustness and phenotypic plasticity of developmental systems in the face of natural selection: in other terms, an approach based on evolutionary developmental biology
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