24,137 research outputs found
Real space mapping of topological invariants using artificial neural networks
Topological invariants allow to characterize Hamiltonians, predicting the
existence of topologically protected in-gap modes. Those invariants can be
computed by tracing the evolution of the occupied wavefunctions under twisted
boundary conditions. However, those procedures do not allow to calculate a
topological invariant by evaluating the system locally, and thus require
information about the wavefunctions in the whole system. Here we show that
artificial neural networks can be trained to identify the topological order by
evaluating a local projection of the density matrix. We demonstrate this for
two different models, a 1-D topological superconductor and a 2-D quantum
anomalous Hall state, both with spatially modulated parameters. Our neural
network correctly identifies the different topological domains in real space,
predicting the location of in-gap states. By combining a neural network with a
calculation of the electronic states that uses the Kernel Polynomial Method, we
show that the local evaluation of the invariant can be carried out by
evaluating a local quantity, in particular for systems without translational
symmetry consisting of tens of thousands of atoms. Our results show that
supervised learning is an efficient methodology to characterize the local
topology of a system.Comment: 9 pages, 6 figure
Supergiant Barocaloric Effects in Acetoxy Silicone Rubber over a Wide Temperature Range: Great Potential for Solid-state Cooling
Solid-state cooling based on caloric effects is considered a viable
alternative to replace the conventional vapor-compression refrigeration
systems. Regarding barocaloric materials, recent results show that elastomers
are promising candidates for cooling applications around room-temperature. In
the present paper, we report supergiant barocaloric effects observed in acetoxy
silicone rubber - a very popular, low-cost and environmentally friendly
elastomer. Huge values of adiabatic temperature change and reversible
isothermal entropy change were obtained upon moderate applied pressures and
relatively low strains. These huge barocaloric changes are associated both to
the polymer chains rearrangements induced by confined compression and to the
first-order structural transition. The results are comparable to the best
barocaloric materials reported so far, opening encouraging prospects for the
application of elastomers in near future solid-state cooling devices.Comment: 19 pages, 7 figures, 2 table
Processamento e caracterização de snack extrudado a partir de farinhas de quirera de arroz e de bandinha de feijão.
Este trabalho teve por objetivo desenvolver nova formulação de snack por extrusão termoplástica a partir de mistura de farinhas de quirera de arroz e de bandinha de feijão, bem como avaliar o potencial nutricional, tecnológico e sensorial do novo produto. A farinha de bandinha de feijão carioca foi incorporada à farinha de quirera de arroz na proporção de 30%. O snack foi produzido em extrusora monorrosca, escala piloto. Os parâmetros de extrusão foram fixos, utilizando-se três zonas de extrusão com temperaturas de 40, 60 e 85 °C; velocidade do parafuso de 177 rpm; taxa de alimentação de 292 g.min?1, e matriz circular de 3,85 mm de diâmetro. A amostra de snack foi submetida a caracterizações fisicoquímica, tecnológica e sensorial. Observou-se efeito significativo da farinha de bandinha de feijão no aumento dos teores proteico e de fibras no snack obtido, quando comparada à farinha de quirera de arroz. Em relação às características tecnológicas do produto, obteve-se 0,17 g.cm?3 para densidade aparente, 7,75 para o índice de expansão e 435, g.f para a dureza instrumental. A formulação estudada foi aceita sensorialmente, com índice de aceitação para impressão global de 76%. Conclui-se que é possível produzir snacks por extrusão a partir da incorporação de 30% de farinha de bandinha de feijão à farinha de quirera de arroz, resultando em produto aceito sensorialmente e com adequado valor nutricional
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Aplicação de Análise e Modelagem Multidimensional para o Monitoramento de Resíduos Sólidos Industriais
The Power of Non-Determinism in Higher-Order Implicit Complexity
We investigate the power of non-determinism in purely functional programming
languages with higher-order types. Specifically, we consider cons-free programs
of varying data orders, equipped with explicit non-deterministic choice.
Cons-freeness roughly means that data constructors cannot occur in function
bodies and all manipulation of storage space thus has to happen indirectly
using the call stack.
While cons-free programs have previously been used by several authors to
characterise complexity classes, the work on non-deterministic programs has
almost exclusively considered programs of data order 0. Previous work has shown
that adding explicit non-determinism to cons-free programs taking data of order
0 does not increase expressivity; we prove that this - dramatically - is not
the case for higher data orders: adding non-determinism to programs with data
order at least 1 allows for a characterisation of the entire class of
elementary-time decidable sets.
Finally we show how, even with non-deterministic choice, the original
hierarchy of characterisations is restored by imposing different restrictions.Comment: pre-edition version of a paper accepted for publication at ESOP'1
Adubação NPK do algodoeiro em cultivo adensado de safrinha no Cerrado de Goiás - safra 2010/11.
O objetivo desse trabalho foi definir doses de NPK para adubação de manutenção do algodão de safrinha adensado, nas condições do Cerrado de Goiás, em função da fertilidade do solo, da expectativa de produtividade e das quantidades exportadas desses nutrientes pela cultura
Zero-mode analysis of quantum statistical physics
We present a unified formulation for quantum statistical physics based on the
representation of the density matrix as a functional integral. We identify the
stochastic variable of the effective statistical theory that we derive as a
boundary configuration and a zero mode relevant to the discussion of infrared
physics. We illustrate our formulation by computing the partition function of
an interacting one-dimensional quantum mechanical system at finite temperature
from the path-integral representation for the density matrix. The method of
calculation provides an alternative to the usual sum over periodic
trajectories: it sums over paths with coincident endpoints, and includes
non-vanishing boundary terms. An appropriately modified expansion into
Matsubara modes provides a natural separation of the zero-mode physics. This
feature may be useful in the treatment of infrared divergences that plague the
perturbative approach in thermal field theory.Comment: 9 pages, 5 figure
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