Non-periodic Variation Research Articles

Geração de séries sintéticas de vazão a partir de amostragem multivariada de saídas de modelo ARMA contemporâneo

ABSTRACT This work constitutes one of the outcomes of the “Evaluation of hydrological scenario generation models” activity initiated by the Hydrological Scenario Representation Working Group (GT CH) and coordinated by ONS and CCEE. We introduce the LYNX-Series model, a contemporaneous non-periodic and multivariate variation of the autoregressive moving average model (CARMA) for generating synthetic time series of average inflow discharges to reservoirs in the Brazilian National Interconnected System (SIN). Notably, LYNX-Series couples the synthetic series generator with a multivariate sampling process to select a group of synthetic hydrological scenarios based on a similarity criterion with recent historical data. In addition to reducing the computational burden of the hydrothermal dispatch optimization process, the solution aims to enhance the representativeness of synthetic hydrological scenarios. The paper expounds on the theoretical aspects of the model and presents numerical simulations that validate its ability to replicate hydrological behaviors in various Brazilian basins.

Study of COVID-19 epidemiological evolution in India with a multi-wave SIR model.

The global pandemic due to the outbreak of COVID-19 ravages the whole world for more than two years in which all the countries are suffering a lot since December 2019. In this article characteristics of a multi-wave SIR model have been studied which successfully explains the features of this pandemic waves in India. Origin of the multi-wave pattern in the solution of this model is explained. Stability of this model has been studied by identifying the equilibrium points as well as by finding the eigenvalues of the corresponding Jacobian matrices. In this model, a finite probability of the recovered people for becoming susceptible again is introduced which is found crucial for obtaining the oscillatory solution in other words. Which on the other hand incorporates the effect of new variants, like delta, omicron, etc in addition to the SARS-CoV-2 virus. The set of differential equations has been solved numerically in order to obtain the variation of susceptible, infected and removed populations with time. In this phenomenological study, some specific sets of parameters are chosen in order to explain the nonperiodic variation of infected population which is found necessary to capture the feature of epidemiological wave prevailing in India. The numerical estimations are compared with the actual cases along with the analytic results.

Acoustic waves in functionally graded rods with periodic longitudinal inhomogeneity

Acoustic waves in periodic functionally graded (FG) 1 D rods are studied by applying the modified Cauchy formalism previously developed for analyzing dispersion of the surface acoustic waves (SAW) in stratified media. In case of harmonic waves traveling in a semi-infinite rod with harmonic periodicity of acoustic properties several phenomena were observed, including the non-periodic spatial variation of the phase velocity and wave magnitude, but spatially periodic variation of kinetic and strain energy.

Climate-dependent malaria disease transmission model and its analysis

Malaria infection continues to be a major problem in many parts of the world including Africa. Environmental variables are known to significantly affect the population dynamics and abundance of insects, major catalysts of vector-borne diseases, but the exact extent and consequences of this sensitivity are not yet well established. To assess the impact of the variability in temperature and rainfall on the transmission dynamics of malaria in a population, we propose a model consisting of a system of non-autonomous deterministic equations that incorporate the effect of both temperature and rainfall to the dispersion and mortality rate of adult mosquitoes. The model has been validated using epidemiological data collected from the western region of Ethiopia by considering the trends for the cases of malaria and the climate variation in the region. Further, a mathematical analysis is performed to assess the impact of temperature and rainfall change on the transmission dynamics of the model. The periodic variation of seasonal variables as well as the non-periodic variation due to the long-term climate variation have been incorporated and analyzed. In both periodic and non-periodic cases, it has been shown that the disease-free solution of the model is globally asymptotically stable when the basic reproduction ratio is less than unity in the periodic system and when the threshold function is less than unity in the non-periodic system. The disease is uniformly persistent when the basic reproduction ratio is greater than unity in the periodic system and when the threshold function is greater than unity in the non-periodic system.

Adaptive tracking of a time-varying field with a quantum sensor

Sensors based on single spins can enable magnetic field detection with very high sensitivity and spatial resolution. Previous work has concentrated on sensing of a constant magnetic field or a periodic signal. Here, we instead investigate the problem of estimating a field with non-periodic variation described by a Wiener process. We propose and study, by numerical simulations, an adaptive tracking protocol based on Bayesian estimation. The tracking protocol updates the probability distribution for the magnetic field, based on measurement outcomes, and adapts the choice of sensing time and phase in real time. By taking the statistical properties of the signal into account, our protocol strongly reduces the required measurement time. This leads to a reduction of the error in the estimation of a time-varying signal by up to a factor 4 compared to protocols that do not take this information into account.

STEREO observations of HD90386 (RX Sex): a δ-Scuti or a hybrid star?

HD90386 is a rarely studied bright A2V type δ Scuti star (V = 6.66 mag). It displays short-term light curve variations which are originated due to either a beating phenomenon or a non-periodic variation. In this paper, we presented high-precision photometric data of HD90386 taken by the STEREO satellite between 2007 and 2011 to shed light on its internal structure and evolution stage. From the frequency analysis of the four-year data, we detected that HD90386 had at least six different frequencies between 1 and 15 c d-1. The most dominant frequencies were found at around 10.25258 c d-1 (A ∼ 1.92 mmag) and 12.40076 c d-1 (A ∼ 0.61 mmag). Based on the ratio between these frequencies, the star was considered as an overtone pulsator. The variation in pulsation period over 35 years was calculated to be dP/Pdt = 5.39(2) x 10-3 yr-1. Other variabilities at around 1.0 c d-1 in the amplitude spectrum of HD90386 were also discussed. In order to explain these variabilities, possible rotational effects and γ Dor type variations were focused. Consequently, depending on the rotation velocity of HD90386, we speculated that these changes might be related to γ Dor type high-order g-modes shifted to the higher frequencies and that HD90386 might be a hybrid star.

Azimuthal anisotropy beneath north central Africa from shear wave splitting analyses

AbstractThis study represents the first multistation investigation of azimuthal anisotropy beneath the interior of north central Africa, including Libya and adjacent regions, using shear wave splitting (SWS) analysis. Data used in the study include recently available broadband seismic data obtained from 15 stations managed by the Libyan Center for Remote Sensing and Space Science, and those from five other stations at which data are publicly accessible. A total of 583 pairs of high‐quality SWS measurements utilizing the PKS, SKKS, and SKS phases demonstrate primarily N‐S fast orientations with an average splitting delay time of approximately 1.2 s. An absence of periodic azimuthal variation of the observed splitting parameters indicates the presence of simple anisotropy, and lack of correlation between surficial features and the splitting parameters suggests that the origin of the observed anisotropy is primarily asthenospheric. This conclusion is enhanced by nonperiodic azimuthal variation of the splitting parameters observed at one of the stations located near the boundary of areas with different anisotropic properties. We interpret the observed anisotropy to be the consequence of northward movement of the African plate relative to the asthenosphere toward the Hellenic and Calabrian subduction zones. Local variance in fast orientations may be attributable to flow deflection by the northern edge of the African continental root. The observations provide critical and previously lacking constraints on mantle dynamic models in the vicinity of the convergent boundary between the African and Eurasian plates.

Soliton dynamics in complex potentials

Soliton propagation dynamics under the presence of a complex potential are investigated. Cases of both symmetric and non-symmetric potentials are studied in terms of their effect on soliton dynamics. The existence of an invariant of soliton propagation under specific symmetry conditions for the real and the imaginary part of the potential is shown. The rich set of dynamical features of soliton propagation include dynamical trapping, periodic and nonperiodic soliton mass variation and non-reciprocal dynamics. These features are systematically investigated with the utilization of an effective particle phase space approach which is shown in remarkable agreement with direct numerical simulations. The generality of the results enables the consideration of potential applications where the inhomogeneity of the gain and loss is appropriately engineered in order to provide desirable soliton dynamics.

Soliton dynamics in symmetric and non-symmetric complex potentials

Soliton propagation dynamics under the presence of a complex potential are investigated. A large variety of qualitatively different potentials, including periodic, semi-infinite periodic and localized potentials, is considered. Cases of both symmetric and non-symmetric potentials are studied in terms of their effect on soliton dynamics. The rich set of dynamical features of soliton propagation includes dynamical trapping, periodic and non-periodic soliton mass variation and non-reciprocal scattering dynamics. These features are systematically investigated with the utilization of an effective particle phase space approach which is shown in remarkable agreement with direct numerical simulations. The generality of the results enables the consideration of potential applications where the inhomogeneity of the gain and loss is appropriately engineered in order to provide desirable soliton dynamics.

Manifestations of Non‐Planar Adsorption Geometries of Lead Pyrenocyanine at the Liquid‐Solid Interface

In this work, we provide evidence for multiple non-planar adsorption geometries of a novel pyrenocyanine derivative at the liquid-solid interface under ambient conditions. When adsorbed at the organic liquid-solid interface, lead pyrenocyanine forms well-ordered monolayers that exhibit peculiar non-periodic contrast variation. The different contrast of the adsorbed molecules is attributed to dissimilar adsorption geometries which arise from the non-planar conformation of the molecules. The non-planarity of the molecular backbone in turn arises due to a combination of the angularly extended pyrene subunits and the presence of the large lead ion, which is too big to fit inside the central cavity and thus is located out of the aromatic plane. The two possible locations of the lead atom, namely below and above the aromatic plane, could be identified as depression and protrusion in the central cavity, respectively. The manifestation of such multiple adsorption geometries on the structure of the resultant monolayer is discussed in detail. The packing density of these 2D arrays of molecules could be tuned by heating of the sample wherein the molecular packing changes from a low-density, pseudo six-fold symmetric to a high-density, two-fold symmetric arrangement. Finally, a well-ordered two-component system could be constructed by incorporating C60 molecules in the adlayer of lead pyrenocyanine at the liquid-solid interface.

The Effect of Strong Heterogeneity and Strong Throughflow on the Onset of Convection in a Porous Medium: Non-Periodic Global Variation

The effect of strong throughflow and strong heterogeneity on the onset of convection induced by a vertical density gradient in a saturated porous medium governed by Darcy’s law is investigated with the aid of a computer package. The general case, where there is heterogeneity in both the vertical and horizontal directions, and where there is heterogeneity in permeability, thermal conductivity, and applied temperature gradient, is considered. Previous work on the case of non-periodic global variation is now extended to the case of either periodic variation or localized variation.

Empirical Modeling and Impact of Transient Effects on the Mean Sea Level Trend Estimates from the Global Tide Gauge Data

Empirical Modeling and Impact of Transient Effects on the Mean Sea Level Trend Estimates from the Global Tide Gauge Data The mean sea level trend estimates from shorter records (less than 50 years) are easily influenced by a number of additional transient effects including atmospheric pressure variations, interannual and decadal changes in the mean sea level or various station dependent disturbances, which are not always accounted for in previous studies because their influences may be negligible for stations longer than 100 years or simply such information may not have been available. In this study, we detected and modeled 8,072 transient changes (a nearly periodic, or non-periodic variation, a shift or an episodic change in the mean sea level that may last several months or longer) from all of the globally distributed 1,862 tide gauge stations with approximately 47,000 years of tide gauge data in the Permanent Service Mean Sea Level repository. It was shown that 1,264 out of 1,862 globally distributed tide gauge station solutions were affected significantly by modeling transient changes in the mean sea level. The solutionsR2 values improved at a 95% confidence level with the inclusion of new empirical model parameters representing transient changes as mean shifts as well as the trend estimates that fall within [-1 to +3] mm/year interval.

A nanometre-scale non-periodic structural variation in high temperature superconducting ceramics and the implications for properties.

Non-periodic structural variation has been found in the high Tc cuprates, YBa2Cu3O7-x and Hg0.67Pb0.33Ba2Ca2Cu3O8+delta, by image analysis of high resolution transmission electron microscope (HRTEM) images. We use two methods for analysis of the HRTEM images. The first method is a means for measuring the bending of lattice fringes at twin planes. The second method is a low-pass filter technique which enhances information contained by diffuse-scattered electrons and reveals what appears to be an interference effect between domains of differing lattice parameter in the top and bottom of the thin foil. We believe that these methods of image analysis could be usefully applied to the many thousands of HRTEM images that have been collected by other workers in the high temperature superconductor field. This work provides direct structural evidence for phase separation in high Tc cuprates, and gives support to recent stripes models that have been proposed to explain various angle resolved photoelectron spectroscopy and nuclear magnetic resonance data. We believe that the structural variation is a response to an opening of an electronic solubility gap where holes are not uniformly distributed in the material but are confined to metallic stripes. Optimum doping may occur as a consequence of the diffuse boundaries between stripes which arise from spinodal decomposition. Theoretical ideas about the high Tc cuprates which treat the cuprates as homogeneous may need to be modified in order to take account of this type of structural variation.

Oscillatory Behavior during Methanol Oxidation on Mo–Ca–O/SiO2Catalyst

The authors have recently reported on the observation of an oscillatory behavior during mild methanol oxidation on a silica-supported molybdenum catalyst (1). This unusual behavior in mild oxidation on oxide catalysts is nevertheless well known for CO total oxidation on platinum or palladium catalysts (2-5). The oscillatory behavior appears as a periodic or nonperiodic (chaotic) variation in the reaction rate and selectivities, although the external conditions of the reaction (oven reactor temperature, flow rate, and feed composition) are constant. This phenomenon was extensively studied for total oxidation reactions occurring on metallic catalysts (5) and comparatively, only a few number of examples of mild oxidation reaction on oxide catalysts are reported in the literature (6-9). Nevertheless, the diversity of the catalytic reactions showing an oscillatory behavior suggests that this phenomena is rather common in the complex system formed by catalyst, products, and reactants. The authors here on the study of an oscillatory behavior observed during methanol oxidation on a calcium molybdate catalyst supported on silica. 21 refs., 7 figs., 4 tabs.

The coalescence of magnetic flux ropes and reconnection in the magnetotail

We have used magnetohydrodynamic simulation methods to investigate the characteristics and relevance of the magnetic island coalescence instability for magnetotail reconnection. The study was carried out under a wide range of parameters with different initial conditions. Periodic and nonperiodic island chains in or near equilibrium were considered and their linear and nonlinear evolution compared and contrasted. We found that for the periodic two‐island configuration the reconnection rate showed little dependence on resistivity and increased with lower plasma β. For the nonperiodic case, which resembled a two‐dimensional magnetotail configuration, a chain of magnetic flux ropes whose size decreased down the magnetotail was initialized. The coalescence process led to the formation of a large magnetic island whose motion down the tail drove reconnection at an x type neutral line. In the nonperiodic case variation of parameters had different effects than in the periodic case: a lower plasma β lowered the growth rate while the rate of energy conversion was higher for lower resistivity. Our results indicate that coalescence is an efficient mode of reconnection in long island chains, and in a finite system it can help drive reconnection on a scale larger than the original islands.

NON-LINEAR DYNAMIC INSTABILITY OF TWO DIMENSIONAL SLAB SYMMETRIC DISSIPATIVE DISTURBANCES ON ROTATING EARTH

The non-linear instability of the two-dimensional slab symmetric disturbances of the dis- sipative system on the rotating earth subject to the forcing of the mean temperature field is investigated by means of the 5 modes low order truncated spectrum. We get the catastrophe of the butterfly type. For a given definite value to the horizontal temperature gradient, with the decrease of the static stability, the equilibrium state of the system generally proceeds start- ing from a quiescent single stable state, then abruptly jumping to the single stable state with a circulation of a certain strength, hereafter again residing stably in the double stable state of strong circulation. Moreover, there does not appear the periodic and non-periodic variation. Without temperature gradient, only a definite and comparatively weak vertical eddy viscosity in conjunction with the non-linear mechanism of the system itself and the linear static insta- bility of the environment can lead to the periodic or non-periodic variation.

Signal processing in a nonperiodically time-varying magnetoelastic medium

Wave propagation in a nonperiodically time-varying medium provides a means for realizing in simple physical structures a variety of signal-processing operations, such as frequency translation and coding, variable delay recall, gating, time-scale stretching or shrinking, and time reversal. The use of low-velocity modes, such as acoustic, spin, or magnetoelastic waves in solids, reduces the length of the propagation structure required to less than an inch. A general review is given of the principles of wave propagation in a spatially uniform medium with nonperiodic time variation. Both abrupt and gradual time variations are discussed. Illustrations are given for the cases of spin-wave and magnetoelastic-wave propagation and signal processing operations in these media are explained. Consideration is given to the problem of spin-wave propagation in a time-and space-varying magnetic field of the form encountered in experiments; and it is shown that a simple separated variable solution exists. For the more difficult problem of magnetoelastic propagation with both space and time variations, an approximate space-time ray theory is described. Experimental results for pulsed-field processing of spin and magnetoelastic waves are given and related to the theory.

VII.—The Clear-Day Barometric Curve at Ben Nevis

SummaryAn examination of the Ben Nevis barometric records shows that, when the non-periodic convex variation is eliminated, the clear-day barometric curve differs but little from the normal curve obtained from all days. The results prove that the clear-day excess found by Buchan and Omond is mainly (though not entirely) due to bias in the selection of data.

The Probable Error of the Amplitudes in a Fourier Series Obtained from a Given Set of Observations

To express a periodic variation by one or more terms of a Fourier series is such a common and convenient method that it is of importance to know the extent to which the constants are trustworthy. This is particularly the case when the quantity is subject to a large casual and therefore non-periodic variation as well.