Evolution Of Agreements Research Articles

Dynamical systems analysis of an interacting scalar field model in an anisotropic universe

In this paper, we investigate a non-canonical scalar field model in the background dynamics of anisotropic Locally Rotationally Symmetric (LRS) Bianchi type I universe where gravity is coupled minimally to scalar field which is taken as dark energy and pressureless dust as dark matter are the main matter content of the universe. We perform dynamical system analysis to characterize the cosmological evolution of the model with and without interaction in the dark sector separately. First, we convert the evolution equation into an autonomous system of ordinary differential equations by using a suitable choice of dimensionless variables, which are normalized over the Hubble scale. We choose scalar field coupling and potential in such a way that the autonomous system converted to a 2D system. Linear stability theory is employed to the extracted critical points to find the nature. From the analysis, we find some interesting cosmological scenarios, such as late-time scalar-field dominated solutions, which evolve in the quintessence era, cannot solve the coincidence problem. Accelerated scaling attractors are also obtained that correspond to the late phase evolution in agreement with present observational data, and these solutions also provide possible mechanisms to alleviate the coincidence problem. A complete cosmic evolution is obtained from early inflation to a late-time dark energy-dominated phase, connecting through a matter-dominated transient phase of the universe. Furthermore, we find that for different values of the interaction parameter α, the evolutionary trajectories of the Hubble parameter, and the distance modulus forecasted by the model are in quite well agreement with observational datasets.

Representative grain boundaries during anisotropic grain growth

Conventional grain growth models do not account for the variability in grain boundary (GB) mobility, GB energy, and solute segregation energy that depend in detail on the GB structure. Instead, these parameters are typically determined empirically from experimental measurements. In this study, we present a systematic quantitative analysis that accounts for anisotropic GB properties, i.e., GB mobility and solute drag pressure to rationalize the average grain size evolution using representative GB properties under normal grain growth conditions in a non–textured system. We perform two–dimensional phase field simulations to analyze the role of (1) anisotropic mobility, (2) anisotropic segregation, and (3) combined anisotropic mobility and segregation on the average grain size evolution. A corresponding “representative GB” is introduced for each case considering a phenomenological grain growth model that fits the simulated average grain size evolution. A relationship is proposed to determine the representative GB properties for an arbitrary distribution of anisotropic GB properties in the initial microstructure. Simulations with the combined variation of GB mobility and segregation energy suggest that the representative GB mobility and segregation energy determined from independent simulations with varying either GB mobility or segregation energy can be superimposed to determine the average grain size evolution in agreement with the phase field simulations. The limits of validity, i.e., the range of moderate anisotropies, are identified where the phenomenological model with representative GB properties may be applicable, i.e., as long as a mean grain size is an appropriate descriptor of the grain structure.

Ostwald ripening of aqueous microbubble solutions.

Bubble solutions are of growing interest because of their various technological applications in surface cleaning, water treatment, and agriculture. However, their physicochemical properties, such as the stability and interfacial charge of bubbles, are not fully understood yet. In this study, the kinetics of radii in aqueous microbubble solutions are experimentally investigated, and the results are discussed in the context of Ostwald ripening. The obtained distributions of bubble radii scaled by mean radius and total number were found to be time-independent during the observation period. Image analysis of radii kinetics revealed that the average growth and shrinkage speed of each bubble is governed by diffusion-limited Ostwald ripening, and the kinetic coefficient calculated using the available physicochemical constants in the literature quantitatively agrees with the experimental data. Furthermore, the cube of mean radius and mean volume exhibit a linear time evolution in agreement with the Lifshitz-Slezov-Wagner (LSW) theory. The coefficients are slightly larger than those predicted using the LSW theory, which can be qualitatively explained by the effect of finite volume fraction. Finally, the slowdown and pinning of radius in the shrinkage dynamics of small microbubbles are discussed in detail.

Study of fouling in graphite blocks (cross flow) heat exchanger of phosphoric acid concentration process

Fouling in phosphoric acid concentration process of preheat exchangers is a chronic operational problem that compromises energy recovery in these systems. Progress is hindered by the lack of quantitative knowledge of the dynamic effects of fouling on heat exchanger transfer. The subject of this work is an experimental determination of the thermal fouling resistance in the graphite blocks heat exchanger installed in a phosphoric acid concentration process. By measuring the inlet and outlet temperatures and mass flows of fluids, the overall heat transfer coefficient has been determined. Determining the overall heat transfer coefficient for the heat exchanger with clean and fouled surfaces, the fouling resistance was calculated. The results obtained from the heat exchanger studied, show that the fouling resistance increase with time presenting an exponential evolution in agreement with the model suggested by Kern and Seaton, with the existence of fluctuation caused by the instability of the flow rate and the temperature. Bad cleaning of the heat exchanger involves the absence of the induction period and consequently, causes high values of the fouling resistance and of the deposit fouling during a relatively short period of time.

On the extraction of the power-law parts of probability density functions in star-forming clouds

ABSTRACT We present a new approach to extract the power-law part of a density/column-density probability density function (ρ-pdf/N-pdf) in star-forming clouds. This approach is based on the mathematical method bPlfit of Virkar & Clauset (2014, Annals of Applied Statistics, 8, 89) and it assesses the power-law part of an arbitrary distribution, without any assumptions about the other parts of this distribution. The slope and deviation point are derived as averaged values as the number of bins is varied. Neither parameter is sensitive to spikes and other local features of the tail. This adapted bPlfit method is applied to two different sets of data from numerical simulations of star-forming clouds at scales 0.5 and 500 pc, and it displays ρ-pdf and N-pdf evolution in agreement with a number of numerical and theoretical studies. Applied to Herschel data on the regions Aquila and Rosette, the method extracts pronounced power-law tails, consistent with those seen in simulations of evolved clouds.

Automated mining of the ALMA archive in the COSMOS field (A3 COSMOS): Cold molecular gas evolution

AbstractWe present new constraints on the cosmic cold molecular gas evolution out to redshift 6 based on systematic mining of the public ALMA archive in the COSMOS field (A3 COSMOS). Our A3 COSMOS dataset contains ∼ 700 galaxies (0.3 ≲ z ≲ 6) with high-confidence ALMA detection and multi-wavelength SEDs. Combining with ∼ 1,200 CO-observed galaxies at 0 ≲ z ≲ 4 (75% at z < 0.1) in the literature, we parameterize galaxies’ molecular gas depletion time and gas fraction each as a function of stellar mass, offset from the star-forming main-sequence and cosmic age. We propose a new functional form which provides a better fit and implies a “downsizing” effect and “mass-quenching”. By adopting galaxy stellar mass functions and applying our gas fraction function, we obtain a cosmic cold molecular gas density evolution in agreement with recent CO blind field surveys as well as semi-analytic modeling. These together provide us a coherent picture of galaxy cold molecular gas, SFR and stellar mass evolution.

Phase portraits of general f(T) cosmology

We use dynamical system methods to explore the general behaviour of f(T) cosmology. In contrast to the standard applications of dynamical analysis, we present a way to transform the equations into a one-dimensional autonomous system, taking advantage of the crucial property that the torsion scalar in flat FRW geometry is just a function of the Hubble function, thus the field equations include only up to first derivatives of it, and therefore in a general f(T) cosmological scenario every quantity is expressed only in terms of the Hubble function. The great advantage is that for one-dimensional systems it is easy to construct the phase space portraits, and thus extract information and explore in detail the features and possible behaviours of f(T) cosmology. We utilize the phase space portraits and we show that f(T) cosmology can describe the universe evolution in agreement with observations, namely starting from a Big Bang singularity, evolving into the subsequent thermal history and the matter domination, entering into a late-time accelerated expansion, and resulting to the de Sitter phase in the far future. Nevertheless, f(T) cosmology can present a rich class of more exotic behaviours, such as the cosmological bounce and turnaround, the phantom-divide crossing, the Big Brake and the Big Crunch, and it may exhibit various singularities, including the non-harmful ones of type II and type IV. We study the phase space of three specific viable f(T) models offering a complete picture. Moreover, we present a new model of f(T) gravity that can lead to a universe in agreement with observations, free of perturbative instabilities, and applying the Om(z) diagnostic test we confirm that it is in agreement with the combination of SNIa, BAO and CMB data at 1σ confidence level.

In silico phylogenomics using complete genomes: a case study on the evolution of hominoids.

The increasing availability of complete genome data is facilitating the acquisition of phylogenomic data sets, but the process of obtaining orthologous sequences from other genomes and assembling multiple sequence alignments remains piecemeal and arduous. We designed software that performs these tasks and outputs anonymous loci (AL) or anchored enrichment/ultraconserved element loci (AE/UCE) data sets in ready-to-analyze formats. We demonstrate our program by applying it to the hominoids. Starting with human, chimpanzee, gorilla, and orangutan genomes, our software generated an exhaustive data set of 292 ALs (∼1 kb each) in ∼3 h. Not only did analyses of our AL data set validate the program by yielding a portrait of hominoid evolution in agreement with previous studies, but the accuracy and precision of our estimated ancestral effective population sizes and speciation times represent improvements. We also used our program with a published set of 512 vertebrate-wide AE “probe” sequences to generate data sets consisting of 171 and 242 independent loci (∼1 kb each) in 11 and 13 min, respectively. The former data set consisted of flanking sequences 500 bp from adjacent AEs, while the latter contained sequences bordering AEs. Although our AE data sets produced the expected hominoid species tree, coalescent-based estimates of ancestral population sizes and speciation times based on these data were considerably lower than estimates from our AL data set and previous studies. Accordingly, we suggest that loci subjected to direct or indirect selection may not be appropriate for coalescent-based methods. Complete in silico approaches, combined with the burgeoning genome databases, will accelerate the pace of phylogenomics.

APPLICATION OF LiDAR DATE TO ASSESS THE LANDSLIDE SUSCEPTIBILITY MAP USING WEIGHTS OF EVIDENCE METHOD – AN EXAMPLE FROM PODHALE REGION (SOUTHERN POLAND)

Abstract. Podhale is a region in southern Poland, which is the northernmost part of the Central Carpathian Mountains. It is characterized by the presence of a large number of landslides that threaten the local infrastructure. In an article presents application of LiDAR data and geostatistical methods to assess landslides susceptibility map. Landslide inventory map were performed using LiDAR data and field work. The Weights of Evidence method was applied to assess landslides susceptibility map. Used factors for modeling: slope gradient, slope aspect, elevation, drainage density, faults density, lithology and curvature. All maps were subdivided into different classes. Then were converted to grid format in the ArcGIS 10.0. The conditional independence test was carried out to determine factors that are conditionally independent of each other with landslides. As a result, chi-square test for further GIS analysis used only five factors: slope gradient, slope aspect, elevation, drainage density and lithology. The final prediction results, it is concluded that the susceptibility map gives useful information both on present instability of the area and its possible future evolution in agreement with the morphological evolution of the area.

APPLICATION OF LiDAR DATE TO ASSESS THE LANDSLIDE SUSCEPTIBILITY MAP USING WEIGHTS OF EVIDENCE METHOD – AN EXAMPLE FROM PODHALE REGION (SOUTHERN POLAND)

Podhale is a region in southern Poland, which is the northernmost part of the Central Carpathian Mountains. It is characterized by the presence of a large number of landslides that threaten the local infrastructure. In an article presents application of LiDAR data and geostatistical methods to assess landslides susceptibility map. Landslide inventory map were performed using LiDAR data and field work. The Weights of Evidence method was applied to assess landslides susceptibility map. Used factors for modeling: slope gradient, slope aspect, elevation, drainage density, faults density, lithology and curvature. All maps were subdivided into different classes. Then were converted to grid format in the ArcGIS 10.0. The conditional independence test was carried out to determine factors that are conditionally independent of each other with landslides. As a result, chi-square test for further GIS analysis used only five factors: slope gradient, slope aspect, elevation, drainage density and lithology. The final prediction results, it is concluded that the susceptibility map gives useful information both on present instability of the area and its possible future evolution in agreement with the morphological evolution of the area.

Bi-scalar modified gravity and cosmology with conformal invariance

We investigate the cosmological applications of a bi-scalar modified gravity that exhibits partial conformal invariance, which could become full conformal invariance in the absence of the usual Einstein-Hilbert term and introducing additionally either the Weyl derivative or properly rescaled fields. Such a theory is constructed by considering the action of a non-minimally conformally-coupled scalar field, and adding a second scalar allowing for a nonminimal derivative coupling with the Einstein tensor and the energy-momentum tensor of the first field. At a cosmological framework we obtain an effective dark-energy sector constituted from both scalars. In the absence of an explicit matter sector we extract analytical solutions, which for some parameter regions correspond to an effective matter era and/or to an effective radiation era, thus the two scalars give rise to “mimetic dark matter” or to “dark radiation” respectively. In the case where an explicit matter sector is included we obtain a cosmological evolution in agreement with observations, that is a transition from matter to dark energy era, with the onset of cosmic acceleration. Furthermore, for particular parameter regions, the effective dark-energy equation of state can transit to the phantom regime at late times. These behaviors reveal the capabilities of the theory, since they arise purely from the novel, bi-scalar construction and the involved couplings between the two fields.

The fouling in the tubular heat exchanger of Algiers refinery

Crude oil fouling in refinery preheat exchangers is a chronic operational problem that compromises energy recovery in these systems. Progress is hindered by the lack of quantitative knowledge of the dynamic effects of fouling on heat exchanger transfer and pressure drops. In subject of this work is an experimental determination of the thermal fouling resistance in the tubular heat exchanger of the crude oil preheats trains installed in an Algiers refinery. By measuring the inlet and outlet temperatures and mass flows of the two fluids, the overall heat transfer coefficient has been determined. Determining the overall heat transfer coefficient for the heat exchanger with clean and fouled surfaces, the fouling resistance was calculated. The results obtained from the two cells of exchangers studies, showed that the fouling resistance increased with time presented an exponential evolution in agreement with the model suggested by Kern and Seaton, with the existence of fluctuation caused by the instability of the flow rate and the impact between the particles. The bad cleaning of the heat exchangers involved the absence of the induction period and caused consequently, high values of the fouling resistance in a relatively short period of time.

RAINOVA Approach on Vocational Institutions

Innovation is regarded as essential for the vocational institution performance. Not only does the competitive environment make any vocational institution innovate but its entire evolution in agreement with the purpose and the objectives of the group of interest. It is not enough to recognize, to highlight and to make this relevant, because the respective institution must put into practice a whole device, accompanied by a specific philosophy in order to make the innovation effective.For the real success of any vocational institute, we want to implement the RAINOVA Innovation Management Model. In its design, many references have been taken into account, both at European and international levels, paying particular attention to the newest existing approaches in both innovation and advanced management.

Modeling lattice strain evolution at finite strains and experimental verification for copper and stainless steel using in situ neutron diffraction

An elasto-plastic self-consistent (EPSC) polycrystal model is extended to account, in an approximate fashion, for the kinematics of large strains, rigid body rotations, texture evolution and grain shape evolution. In situ neutron diffraction measurements of the flow stress, internal strain, texture and diffraction peak intensity evolutions were performed on polycrystalline copper and stainless steel, up to true tensile strains of ε = 0.3. Suitably adjusted slip system hardening model parameters enable the model to quantitatively describe the flow stress of the polycrystalline aggregate. Quantitative predictions of the texture evolution and the internal strain evolution along the stress axis are good, while predictions of transverse internal strains (perpendicular to the tensile loading direction) are less satisfactory. The latter exhibit a large dispersion from grain to grain around a macroscopic average, and the implications of this finding for the interpretation of in situ neutron diffraction method are explored. Finally, as a demonstration of the applicability of the model to problems involving finite rotation, as well as deformation, simulations of simple shear were conducted which predict a texture evolution in agreement with published experimental data, and other modeling approaches as well.

Flood Damage Reduction Program (FDRP) in Québec: Case Study of the Chaudiére River

This study presents the evolution of agreements between the governments of Canadaand Quebec on flood damage reduction. In Quebec, the implementation of a regulation about building in floodplains came about in 1983–1984. Today, this regulation takes the form of a policy called ``Policy of shores, littoral and floodplain protection''. Municipalities must adopt rules that concur with the principles of this policy.

Magnetohydrodynamic transfer function applied to ultramicroelectrode systems

The magnetohydrodynamic (MHD) transfer function (∂ I/∂ B), which has been successfully used in the investigation of various electrochemical systems, has also proved useful for the elucidation of reaction mechanisms involved in electrodeposition of metals. Yet, its use had been so far restricted to macroscopic electrodes. We propose here its application for ultramicroelectrodes (UMEs). In a recent work carried out in our laboratory with classical EIS techniques, we have demonstrated the reliability of the UMEs for the characterisation of the magneto-induced convective effect. We confirm this behaviour through the measurement of (∂ I/∂ B): at the limiting current, (∂ I/∂ B) shows an evolution in agreement with the previous stationary studies and the EIS investigations. In particular, the variation of the low frequency modulus confirms the relationship between the limiting current and the product B 1/3× C 4/3 insofar as the non-MHD convection has been taken into account.

Molecular evolution modeled as a fractal renewal point process in agreement with the dispersion of substitutions in mammalian genes.

A fractal renewal point process (FRPP) is used to model molecular evolution in agreement with the relationship between the variance and the mean numbers of nonsynonymous and synonymous substitutions in mammals. Like other episodic models such as the doubly stochastic Poisson process, this model accounts for the large variances observed in amino acid substitution rates, but unlike certain other episodic models, it also accounts for the increase in the index of dispersion with the mean number of substitutions in Ohta's (1995) data. We find that this correlation is significant for nonsynonymous substitutions at the 1% level and for synonymous substitutions at the 10% level, even after removing lineage effects and when using Bulmer's (1989) unbiased estimator of the index of dispersion. This model is simpler than most other overdispersed models of evolution in the sense that it is fully specified by a single interevent probability distribution. Interpretations in terms of chaotic dynamics and in terms of chance and selection are discussed.

Coupling mechanisms for damped vortex motion in superfluids

We investigate different dissipative dynamics for a vortex line immersed into a superfluid where density fluctuations have been excited. For this sake, we consider various linear coupling models where the vortex interacts with the quasiparticles of the normal fluid through its coordinate or momentum. We can unambiguously show that one and only one combination of these variables leads to damped evolution in agreement with the phenomenological descriptions. {copyright} {ital 1997} {ital The American Physical Society}

Filamentation in long scale length plasmas: Experimental evidence and effects of laser spatial incoherence

Signatures of filamentation have been observed in preformed plasmas using complementary diagnostics: time-resolved images of the transmitted laser light, dark field imaging, and time-resolved spectra of Raman light. This last diagnostic clearly shows the presence of small channels inside the plasma with temporal evolution in agreement with the formation of filaments. The filamentary structures disappeared when random phase plates were used in the laser beam. This result is in agreement with a theoretical analysis showing that filamentation does not grow when the speckle size is smaller than the perturbation wavelength which maximizes, in the coherent case, the filamentation growth.

Excited levels 1s n, n−1 of the two-electron atom

Closed formulas for the Coulomb and exchange integrals in the excited states 1snl, l=n−1, of the two-electron atom are applied to the computation of the ionization energy of the singlet and tripet 1s2p states from He i up to O vii and to singlet and triplet 1s3d and 1s4f states of He i and Li ii. Two methods are compared: (a) the use of first-order perturbation theory considering the mutual electrrostatic repulsion e2/r12 as a small perturbation and (b) imposing as solution of the Schrödinger equation a symmetrized product of a Z and a screened Z−1 hydrogenic wave functions. Computed and experimental values of the ionization energy and of the singlet-triplet interval are compared and the evolution of agreement with increasing Z and n is discussed.