Width and extremal height distributions of fluctuating interfaces with window boundary conditions

We present a detailed study of squared local roughness (SLRDs) and local extremal height distributions (LEHDs), calculated in windows of lateral size $l$, for interfaces in several universality classes, in substrate dimensions $d_s = 1$ and $d_s = 2$. We show that their cumulants follow a Family-Vicsek type scaling, and, at early times, when $\xi \ll l$ ($\xi$ is the correlation length), the rescaled SLRDs are given by log-normal distributions, with their $n$th cumulant scaling as $(\xi/l)^{(n-1)d_s}$. This give rise to an interesting temporal scaling for such cumulants $\left\langle w_n \right\rangle_c \sim t^{\gamma_n}$, with $\gamma_n = 2 n \beta + {(n-1)d_s}/{z} = \left[ 2 n + {(n-1)d_s}/{\alpha} \right] \beta$. This scaling is analytically proved for the Edwards-Wilkinson (EW) and Random Deposition interfaces, and numerically confirmed for other classes. In general, it is featured by small corrections and, thus, it yields exponents $\gamma_n$'s (and, consequently, $\alpha$, $\beta$ and $z$) in nice agreement with their respective universality class. Thus, it is an useful framework for numerical and experimental investigations, where it is, usually, hard to estimate the dynamic $z$ and mainly the (global) roughness $\alpha$ exponents. The stationary (for $\xi \gg l$) SLRDs and LEHDs of Kardar-Parisi-Zhang (KPZ) class are also investigated and, for some models, strong finite-size corrections are found. However, we demonstrate that good evidences of their universality can be obtained through successive extrapolations of their cumulant ratios for long times and large $l$'s. We also show that SLRDs and LEHDs are the same for flat and curved KPZ interfaces.Comment: 11 pages, 10 figures, 4 table

Big Data on Decision Making in Energetic Management of Copper Mining

Indexado en: Web of Science; Scopus.It is proposed an analysis of the related variables with the energetic consumption in the process of concentrate of copper; specifically ball mills and SAG. The methodology considers the analysis of great volumes of data, which allows to identify the variables of interest (tonnage, temperature and power) to reach to an improvement plan in the energetic efficiency. The correct processing of the great volumen of data, previous imputation to the null data, not informed and out of range, coming from the milling process of copper, a decision support systems integrated, it allows to obtain clear and on line information for the decision making. As results it is establish that exist correlation between the energetic consumption of the Ball and SAG Mills, regarding the East, West temperature and winding. Nevertheless, it is not observed correlation between the energetic consumption of the Ball Mills and the SAG Mills, regarding to the tonnages of feed of SAG Mill. In consequence, From the experimental design, a similarity of behavior between two groups of different mills was determined in lines process. In addition, it was determined that there is a difference in energy consumption between the mills of the same group. This approach modifies the method presented in [1].(a)http://www.univagora.ro/jour/index.php/ijccc/article/view/2784/106

Level and length of cyclic solar activity during the Maunder minimum as deduced from the active day statistics

The Maunder minimum (MM) of greatly reduced solar activity took place in 1645-1715, but the exact level of sunspot activity is uncertain as based, to a large extent, on historical generic statements of the absence of spots on the Sun. Here we aim, using a conservative approach, to assess the level and length of solar cycle during the Maunder minimum, on the basis of direct historical records by astronomers of that time. A database of the active and inactive days (days with and without recorded sunspots on the solar disc respectively) is constructed for three models of different levels of conservatism (loose ML, optimum MO and strict MS models) regarding generic no-spot records. We have used the active day fraction to estimate the group sunspot number during the MM. A clear cyclic variability is found throughout the MM with peaks at around 1655--1657, 1675, 1684 and 1705, and possibly 1666, with the active day fraction not exceeding 0.2, 0.3 or 0.4 during the core MM, for the three models. Estimated sunspot numbers are found very low in accordance with a grand minimum of solar activity. We have found, for the core MM (1650-1700), that: (1) A large fraction of no-spot records, corresponding to the solar meridian observations, may be unreliable in the conventional database. (2) The active day fraction remained low (below 0.3-0.4) throughout the MM, indicating the low level of sunspot activity. (3) The solar cycle appears clearly during the core MM. (4) The length of the solar cycle during the core MM appears $9\pm 1$ years, but there is an uncertainty in that. (5) The magnitude of the sunspot cycle during MM is assessed to be below 5-10 in sunspot numbers; A hypothesis of the high solar cycles during the MM is not confirmed.Comment: Accepted to Astron. Astrophy

Magnetism of NaFePO4 and related polyanionic compounds

Magnetic properties of maricite (m) and triphlyte (t) polymorphs of NaFePO4 are investigated by combining ab initio density functional theory with a model Hamiltonian approach, where a realistic Hubbard-type model for magnetic Fe 3d states in NaFePO4 is constructed entirely from first-principles calculations. For these purposes, we perform a comparative study based on the pseudopotential and linear muffin-tin orbital methods while tackling the problem of parasitic non-sphericity of the exchange-correlation potential. Upon calculating the model parameters, magnetic properties are studied by applying the mean-field Hartree-Fock approximation and the theory of superexchange interactions to extract the corresponding interatomic exchange parameters. Despite some differences, the two methods provide a consistent description of the magnetic properties of NaFePO4. On the one hand, our calculations reproduce the correct magnetic ordering for t-NaFePO4 allowing for magnetoelectric effect, and the theoretical values of Néel and Curie-Weiss temperatures are in fair agreement with reported experimental data. Furthermore, we investigate the effect of chemical pressure on magnetic properties by substituting Na with Li and, in turn, we explain how a noncollinear magnetic alignment induced by an external magnetic field leads to magnetoelectric effect in NaFePO4 and other transition-metal phosphates. However, the origin of a magnetic superstructure with q = (1/2, 0, 1/2) observed experimentally in m-NaFePO4 remains puzzling. Instead, we predict that competing exchange interactions can lead to the formation of magnetic superstructures along the shortest orthorhombic c axis of m-NaFePO4, similar to multiferroic manganites. © 2018 the Owner Societies.Oier Arcelus and Javier Carrasco acknowledge the financial support of the Ministerio de Economía y Competitividad of Spain through the project ENE2016-81020-R. The SGI/IZO-SGIker UPV/EHU (Arina cluster), the i2BASQUE academic network, and the Barcelona Supercomputer Center are acknowledged for computational resources. Oier Arcelus acknowledges support by the Basque Government through a PhD grant (Reference No. PRE-2016-1-0044)

Damage detection and quantification in composite beam structure using strain energy and vibration data

10.1088/1742-6596/842/1/012027Journal of Physics: Conference Series84211202

Data Deluge in Astrophysics: Photometric Redshifts as a Template Use Case

Astronomy has entered the big data era and Machine Learning based methods have found widespread use in a large variety of astronomical applications. This is demonstrated by the recent huge increase in the number of publications making use of this new approach. The usage of machine learning methods, however is still far from trivial and many problems still need to be solved. Using the evaluation of photometric redshifts as a case study, we outline the main problems and some ongoing efforts to solve them.Comment: 13 pages, 3 figures, Springer's Communications in Computer and Information Science (CCIS), Vol. 82