117 research outputs found
Detrended Fluctuation analysis of Bach's Inventions and Sinfonias pitches
Detrended Fluctuation Analysis (DFA), suitable for the analysis of
nonstationary time series, is used to investigate power law in some of the
Bach's pitches series. Using DFA method, which also is a well-established
method for the detection of long-range correlations, frequency series of Bach's
pitches have been analyzed. In this view we find same Hurts exponents in the
range (0.7-0.8) in his Inventions and sinfonia.Comment: 5 pages, 4 figure
Signature change from Schutz's canonical quantum cosmology and its classical analogue
We study the signature change in a perfect fluid Friedmann-Robertson-Walker
quantum cosmological model. In this work the Schutz's variational formalism is
applied to recover the notion of time. This gives rise to a
Schrodinger-Wheeler-DeWitt equation with arbitrary ordering for the scale
factor. We use the eigenfunctions in order to construct wave packets and
evaluate the time-dependent expectation value of the scale factor which
coincides with the ontological interpretation. We show that these solutions
exhibit signature transitions from a finite Euclidean to a Lorentzian domain.
Moreover, such models are equivalent to a classical system where, besides the
perfect fluid, a repulsive fluid is present.Comment: 15 pages, 4 figures, to appear in PR
Canonical wave packets in quantum cosmology
We discuss the construction of wave packets resulting from the solutions of a
class of Wheeler-DeWitt equations in Robertson-Walker type cosmologies, for
arbitrary curvature. We show that there always exists a ``canonical initial
slope" for a given initial wave function, which optimizes some desirable
properties of the resulting wave packet, most importantly good
classical-quantum correspondence. This can be properly denoted as a canonical
wave packet. We introduce a general method for finding these canonical initial
slopes which is generalization of our earlier work.Comment: 19 pages, 8 figure
Using Spectral Method as an Approximation for Solving Hyperbolic PDEs
We demonstrate an application of the spectral method as a numerical
approximation for solving Hyperbolic PDEs. In this method a finite basis is
used for approximating the solutions. In particular, we demonstrate a set of
such solutions for cases which would be otherwise almost impossible to solve by
the more routine methods such as the Finite Difference Method. Eigenvalue
problems are included in the class of PDEs that are solvable by this method.
Although any complete orthonormal basis can be used, we discuss two
particularly interesting bases: the Fourier basis and the quantum oscillator
eigenfunction basis. We compare and discuss the relative advantages of each of
these two bases.Comment: 19 pages, 14 figures. to appear in Computer Physics Communicatio
Accelerated gas-liquid visible light photoredox catalysis with continuous-flow photochemical microreactors
In this protocol, we describe the construction and use of an operationally simple photochemical microreactor for gas-liquid photoredox catalysis using visible light. The general procedure includes details on how to set up the microreactor appropriately with inlets for gaseous reagents and organic starting materials, and it includes examples of how to use it to achieve continuous-flow preparation of disulfides or trifluoromethylated heterocycles and thiols. The reported photomicroreactors are modular, inexpensive and can be prepared rapidly from commercially available parts within 1 h even by nonspecialists. Interestingly, typical reaction times of gas-liquid visible light photocatalytic reactions performed in microflow are lower (in the minute range) than comparable reactions performed as a batch process (in the hour range). This can be attributed to the improved irradiation efficiency of the reaction mixture and the enhanced gas-liquid mass transfer in the segmented gas-liquid flow regime
Signature Change in Noncommutative FRW Cosmology
The conditions for which the no boundary proposal may have a classical
realization of a continuous change of signature, are investigated for a
cosmological model described by FRW metric coupled with a self interacting
scalar field, having a noncommutative phase space of dynamical variables. The
model is then quantized and a good correspondence is shown between the
classical and quantum cosmology indicating that the noncommutativity does not
destruct the classical-quantum correspondence. It is also shown that the
quantum cosmology supports a signature transition where the bare cosmological
constant takes a vast continuous spectrum of negative values. The bounds of
bare cosmological constant are limited by the values of noncommutative
parameters. Moreover, it turns out that the physical parameters are constrained
by the noncommutativity parametres.Comment: 15 pages, 4 figures, Minor revision, references adde
Microstructure, mechanical and functional behavior
Funding Information:
JS acknowledges the China Scholarship Council for funding the Ph.D. grant (CSC NO. 201808320394). JPO acknowledges funding by national funds from FCT - Fundação para a Ciência e a Tecnologia, I.P., in the scope of the projects LA/P/0037/2020 of the Associate Laboratory Institute of Nanostructures, Nanomodelling and Nanofabrication – i3N. This activity has received funding from the European Institute of Innovation and Technology (EIT) – Project Smart WAAM: Microstructural Engineering and Integrated Non-Destructive Testing. This body of the European Union receives support from the European Union's Horizon 2020 research and innovation programme.
Publisher Copyright:
© 2023 The AuthorsShape memory alloys (SMA) are a class of smart materials with inherent shape memory and superelastic characteristics. Unlike other SMAs, iron-based SMAs (Fe-SMA) offer cost-effectiveness, weldability, and robust mechanical strength for the construction industry. Thus, applying these promising materials to advanced manufacturing processes is of considerable industrial and academic relevance. This study aims to present a pioneer application of a Fe–Mn–Si–Cr–Ni–V-C SMA to arc-based directed energy deposition additive manufacturing, namely wire and arc additive manufacturing (WAAM), examining the microstructure evolution and mechanical/functional response. The WAAM-fabricated Fe-SMAs presented negligible porosity and high deposition efficiency. Microstructure characterization encompassing electron microscopy and high energy synchrotron X-ray diffraction revealed that the as-deposited material is primarily composed by γ FCC phase with modest amounts of VC, ε and σ phases. Tensile and cyclic testing highlighted the Fe-SMA's excellent mechanical and functional response. Tensile testing revealed a yield strength and fracture stress of 472 and 821 MPa, respectively, with a fracture strain of 26%. After uniaxial tensile loading to fracture, the γ → ε phase transformation was clearly evidenced with post-mortem synchrotron X-ray diffraction analysis. The cyclic stability during 100 load/unloading cycles was also evaluated, showcasing the potential applicability of the fabricated material for structural applications.publishersversionpublishe
Resistance to acid attack, abrasion and leaching behavior of alkali-activated mine waste binders
This paper report results of a research
project on the development of alkali-activated binders using mine wastes. Abrasion and acid resistance of two
ordinary Portland cement (OPC) strength class concrete mixtures (C20/25 and C30/37) and several mine waste (MW) mixtures were compared. This study
indicates that MW binders possess higher acid and abrasion resistance than OPC based concrete mixtures.The leaching assessment of the MW binders shows it
can be considered an inert material which indicates that it could be used as a building material
Durability of Mortar Incorporating Ferronickel Slag Aggregate and Supplementary Cementitious Materials Subjected to Wet–Dry Cycles
This paper presents the strength and durability of cement mortars using 0–100% ferronickel slag (FNS) as replacement of natural sand and 30% fly ash or ground granulated blast furnace slag (GGBFS) as cement replacement. The maximum mortar compressive strength was achieved with 50% sand replacement by FNS. Durability was evaluated by the changes in compressive strength and mass of mortar specimens after 28 cycles of alternate wetting at 23 °C and drying at 110 °C. Strength loss increased by the increase of FNS content with marginal increases in the mass loss. Though a maximum strength loss of up to 26% was observed, the values were only 3–9% for 25–100% FNS contents in the mixtures containing 30% fly ash. The XRD data showed that the pozzolanic reaction of fly ash helped to reduce the strength loss caused by wet–dry cycles. Overall, the volume of permeable voids (VPV) and performance in wet–dry cycles for 50% FNS and 30% fly ash were better than those for 100% OPC and natural sand
An expression analysis of markers of radiation-induced skin fibrosis and angiogenesis in wound healing disorders of the head and neck
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