91,772 research outputs found
Food security and sustainable agriculture in India: The water management challenge
Sustainable agriculture / Food security / Water management / Water scarcity / Groundwater depletion / Waterlogging / Salinity / Soil degradation / Water use efficiency / Productivity / Equity / Irrigation water / Pricing
Two quantum spin models on the checkerboard lattice with an exact two-fold degenerate Shastry-Sutherland ground state
Two quantum spin models with bilinear-biquadratic exchange interactions are
constructed on the checkerboard lattice. It is proved that, under certain
sufficient conditions on the exchange parameters, their ground states consist
of two degenerate Shastry-Sutherland singlet configurations. The constructions
are studied for arbitrary spin-S. The sufficient conditions for the existence
of ferromagnetic ground state are also found exactly. The approximate quantum
phase diagrams are presented using the exact results, together with a
variational estimate for the N\'eel antiferromagnetic phase. A two-leg spin-1/2
ladder model, based on one of the above constructions, is considered which
admits exact solution for a large number of eigenstates. The ladder model is
shown to have exact level-crossing between the rung-singlet state and the AKLT
state in the singlet ground state. Also introduced is the notion of
perpendicularity for quantum spin vectors, which appears in the discussion on
one of the two checkerboard models, and is discussed in the Appendix.Comment: Revtex, 10 pages, 6 figures, 3 table
Insightful classification of crystal structures using deep learning
Computational methods that automatically extract knowledge from data are
critical for enabling data-driven materials science. A reliable identification
of lattice symmetry is a crucial first step for materials characterization and
analytics. Current methods require a user-specified threshold, and are unable
to detect average symmetries for defective structures. Here, we propose a
machine-learning-based approach to automatically classify structures by crystal
symmetry. First, we represent crystals by calculating a diffraction image, then
construct a deep-learning neural-network model for classification. Our approach
is able to correctly classify a dataset comprising more than 100 000 simulated
crystal structures, including heavily defective ones. The internal operations
of the neural network are unraveled through attentive response maps,
demonstrating that it uses the same landmarks a materials scientist would use,
although never explicitly instructed to do so. Our study paves the way for
crystal-structure recognition of - possibly noisy and incomplete -
three-dimensional structural data in big-data materials science.Comment: Nature Communications, in press (2018
Laminate comprising fibers embedded in cured amine terminated bis-imide
Amine terminated bisaspartimides are prepared by a Michael type reaction of an aromatic bismaleimide and an aromatic diamine in an aprotic solvent. These bisaspartimides are thermally polymerized to yield tough, resinous polymers crosslinked through -NH- groups. Such polymers are useful in applications requiring materials with resistance to change at elevated temperatures
Maleimido substituted aromatic cyclotriphosphazenes
4-Aminophenoxy cyclotriphosphazenes are reacted with maleic anhydride to produce maleamic acids which are converted to the maleimides. The maleimides are polymerized. By selection of starting materials (e.g., hexakis amino or trisaminophenoxy-trisphenoxy-cyclo-triphosphazenes), selection of molar proportions of reactants, use of mixtures of anhydrides and use of dianhydrides as bridging groups a variety of maleimides and polymers are produced. The polymers have high limiting oxygen indices, high char yields and other useful heat and fire resistant properties making them useful as, for example, impregnants of fabrics
Amine terminated bisaspartimide polymer
Novel amine terminated bisaspartimides are prepared by a Michael-type reaction of an aromatic bismalteimide and an aromatic diamine in an aprotic solvent. These bisaspartimides are thermally polymerized to yield tough, resinous polymers cross-lined through -NH- groups. Such polymers are useful in applications requiring materials with resistance to change at elevated temperatures, e.g., as lightweight laminates with graphite cloth, molding material prepregs, adhesives and insulating material
The Vanishing Role of Money in the Macroeconomy - An Empirical Investigation Based On Spectral and Wavelet Analysis
The recent de-emphasizing of the role of money in both theoretical macroeconomics as well as in the practical conduct of monetary policy sits uneasily with the idea that inflation is a monetary phenomenon. Empirical evidence has, however, been accumulating, pointing to an important leading indicator role for money and credit aggregates with respect to long term inflationary trends. Such a role could arise from monetary aggregates furnishing a nominal anchor for inflationary expectations, from their influence on the term structure of interest rates and from their affecting transactions costs in markets. Our paper attempts to assess the informational content role of money in the Indian economy by a separation of these effects across time scales and frequency bands, using the techniques of wavelet analysis and band spectral analysis respectively. Our results indicate variability of causal relations across frequency ranges and time scales, as also occasional causal reversals.Money, inflation, Cointegration, Causality, Decomposition, band spectra, wavelets
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