Continuation methods for nonlinear equations

Feasibility of overcoming local convergent nature of continuation methods for nonlinear equation

Stability of nonuniform rotor blades in hover using a mixed formulation

A mixed formulation for calculating static equilibrium and stability eigenvalues of nonuniform rotor blades in hover is presented. The static equilibrium equations are nonlinear and are solved by an accurate and efficient collocation method. The linearized perturbation equations are solved by a one step, second order integration scheme. The numerical results correlate very well with published results from a nearly identical stability analysis based on a displacement formulation. Slight differences in the results are traced to terms in the equations that relate moments to derivatives of rotations. With the present ordering scheme, in which terms of the order of squares of rotations are neglected with respect to unity, it is not possible to achieve completely equivalent models based on mixed and displacement formulations. The one step methods reveal that a second order Taylor expansion is necessary to achieve good convergence for nonuniform rotating blades. Numerical results for a hypothetical nonuniform blade, including the nonlinear static equilibrium solution, were obtained with no more effort or computer time than that required for a uniform blade

Isolated elliptical galaxies in the local Universe

We have studied a sample of 89 very isolated, elliptical galaxies at z < 0.08 and compared their properties with elliptical galaxies located in a high-density environment such as the Coma supercluster. Our aim is to probe the role of environment on the morphological transformation and quenching of elliptical galaxies as a function of mass. In addition, we elucidate the nature of a particular set of blue and star-forming isolated ellipticals identified here. We study physical properties of ellipticals such as color, specific star formation rate, galaxy size, and stellar age, as a function of stellar mass and environment based on SDSS data. We analyze the blue star-forming isolated ellipticals in more detail, through photometric characterization using GALFIT, and infer their star formation history using STARLIGHT. Among the isolated ellipticals ~ 20% are blue, 8% are star forming, and ~ 10% are recently quenched, while among the Coma ellipticals ~ 8% are blue and just <= 1% are star forming or recently quenched. There are four isolated galaxies (~ 4.5%) that are blue and star forming at the same time. These galaxies, with masses between 7 x 10^9 and 2 x 10^10 h-2 M_sun, are also the youngest galaxies with light-weighted stellar ages <= 1 Gyr and exhibit bluer colors toward the galaxy center. Around 30-60% of their present-day luminosity, but only < 5% of their present-day mass, is due to star formation in the last 1 Gyr. The processes of morphological transformation and quenching seem to be in general independent of environment since most of elliptical galaxies are 'red and dead', although the transition to the red sequence should be faster for isolated ellipticals. In some cases, the isolated environment seems to propitiate the rejuvenation of ellipticals by recent (< 1 Gyr) cold gas accretion.Comment: 23 pages, 15 figures (16 pages and 9 figures without appendices). A&A, in pres

On the Structure of Dark Matter Halos at the Damping Scale of the Power Spectrum with and without Relict Velocities

We report a series of high-resolution cosmological N-body simulations designed to explore the formation and properties of dark matter halos with masses close to the damping scale of the primordial power spectrum of density fluctuations. We further investigate the effect that the addition of a random component, v_rms, into the particle velocity field has on the structure of halos. We adopted as a fiducial model the Lambda Warm Dark Matter cosmology with a non-thermal sterile neutrino mass of 0.5 keV. The filtering mass corresponds then to M_f = 2.6x10^12 M_sun/h. Halos of masses close to M_f were simulated with several million of particles. The results show that, on one hand, the inner density slope of these halos (at radii <~0.02 the virial radius Rvir) is systematically steeper than the one corresponding to the NFW fit or to the CDM counterpart. On the other hand, the overall density profile (radii larger than 0.02Rvir) is less curved and less concentrated than the NFW fit, with an outer slope shallower than -3. For simulations with v_rms, the inner halo density profiles flatten significantly at radii smaller than 2-3 kpc/h (<~0.010-0.015Rvir). A constant density core is not detected in our simulations, with the exception of one halo for which the flat core radius is ~1 kpc/h. Nevertheless, if ``cored'' density profiles are used to fit the halo profiles, the inferred core radii are ~0.1-0.8 kpc/h, in rough agreement with theoretical predictions based on phase-space constrains, and on dynamical models of warm gravitational collapse. A reduction of v_rms by a factor of 3 produces a modest decrease in core radii, less than a factor of 1.5. We discuss the extension of our results into several contexts, for example, to the structure of the cold DM micro-halos at the damping scale of this model.Comment: 13 pages, 6 figures, accepted for publication in The Astrophysical Journa

BVRI Surface Photometry of Isolated Spiral Galaxies

A release of multicolor broad band (BVRI) photometry for a subsample of 44 isolated spirals drawn from the Catalogue of Isolated Galaxies (CIG) is presented. Total magnitudes and colors at various circular apertures, as well as some global structural/morphological parameters are estimated. Morphology is reevaluated through optical and sharp/filtered R band images, (B-I) color index maps, and archive near-IR JHK images from the Two-Micron Survey. The CAS structural parameters (Concentration, Asymmetry, and Clumpiness) were calculated from the images in each one of the bands. The fraction of galaxies with well identified optical/near-IR bars (SB) is 63%, while a 17% more shows evidence of weak or suspected bars (SAB). The sample average value of the maximum bar ellipticity is 0.4. Half of the galaxies in the sample shows rings. We identify two candidates for isolated galaxies with disturbed morphology. The structural CAS parameters change with the observed band, and the tendencies they follow with the morphological type and global color are more evident in the redder bands. In any band, the major difference between our isolated spirals and a sample of interacting spirals is revealed in the A-S plane. A deep and uniformly observed sample of isolated galaxies is intended for various purposes including (i) comparative studies of environmental effects, (ii) confronting model predictions of galaxy evolution and (iii) evaluating the change of galaxy properties with redshift.Comment: 44 pages, 9 figures and 7 tables included. To appear in The Astronomical Journal. For the 43 appendix figures 4.1-4.43 see http://www.astroscu.unam.mx/~avila/Figs4.1_4.43.tar.gz (7.2 Mb tar.gz file

Avaliação da relação entre soja e produção de biodiesel.

O objetivo deste estudo foi avaliar a importância da producão de soja para o desenvolvimento do biodiesel no Brasil e o que representa o biocombustível para o mercado da oleaginosa. A análise de oferta e demanda por biodiesel revelou que as empresas apresentam capacidade produtiva para atender ao B5 e que as usinas da região sul são as mais eficientes, em relação às vendas. O estudo da expansão da produção de soja revelou que o seu cultivo está imerso em um contexto cercado por grandes movimentos e pressões por sustentabilidade ambiental. Embora o Brasil seja um grande exportador de soja ?in natura?, a tendência aponta para a evolução do volume produzido de óleo, o que, em grande parte, se deve ao aumento na produção do grão. Verificou-se que a dispersão do cultivo da soja em diferentes regiões do país, com escala de produção suficiente para atender à produção de volumes significativos de biodiesel, possibilitou combater os crônicos problemas logísticos existentes no agronegócio nacional. Por fim, a análise do Programa Nacional de Produção e Uso do Biodiesel confirmou que o óleo de soja é a matéria-prima que supre quase 80% da produção de biodiesel no Brasil. O desenvolvimento de outras fontes para a diversificação de matéria-prima para a produção de biodiesel, tais como sebo bovino, gordura de frango, algodão e mamona, possibilitará diminuir a pressão sobre a soja e tornar o negócio mais competitivo. Evaluation of the relationship between soybean and biodiesel production. Abstract. The objective of this study was to evaluate the importance of soybean production for the biodiesel development in Brazil and what the biofuel represents to the oilseed market. The analysis of biodiesel?s supply and demand has shown that companies have production capacity to attend B5 and that the plants of the south region are the most efficient in terms of sales. The study about soybean production revealed that its cultivation is immersed in an environment surrounded by great changes and pressures for environmental sustainability. Although Brazil is a great soybean exporter, the trend points to the evolution of the volume of oil producing, what, in the most, occurs due to the increase in the production of grain. It was found that the spread of soybean cultivation in different regions of the country, with sufficient production scale to attend the significant volumes of biodiesel production, became possible to combat the chronic problems in national agribusiness logistics. Finally, the analysis of the National Production and Use of Biodiesel showed that soybean oil is the raw material that supplies almost 80% of biodiesel production in Brazil. The development of other sources for diversification of feedstock for biodiesel production, such as beef tallow, chicken fat, cotton and castor beans, will allow to reduce the pressure on soybeans and to make the business more competitive

Meson Structure Functions in Valon Model

Parton distributions in a {\it{valon}} in the next-to-leading order is used to determine the patron distributions in pion and kaon. The validity of the valon model is tested and shown that the partonic content of the valon is universal and independent of the valon type. We have evaluated the valon distribution in pion and kaon, and in particular it is shown that the results are in good agreement with the experimental data on pion structure in a wide range of $x=[10^{-4},1]$Comment: 13 pages with 7 figures included, The manuscript is revised, figures are added and some errors are corrected. Accepted for publication in Physical Review

Business and Information Technology Alignment Measurement -- a recent Literature Review

Since technology has been involved in the business context, Business and Information Technology Alignment (BITA) has been one of the main concerns of IT and Business executives and directors due to its importance to overall company performance, especially today in the age of digital transformation. Several models and frameworks have been developed for BITA implementation and for measuring their level of success, each one with a different approach to this desired state. The BITA measurement is one of the main decision-making tools in the strategic domain of companies. In general, the classical-internal alignment is the most measured domain and the external environment evolution alignment is the least measured. This literature review aims to characterize and analyze current research on BITA measurement with a comprehensive view of the works published over the last 15 years to identify potential gaps and future areas of research in the field.Comment: 12 pages, Preprint version, BIS 2018 International Workshops, Berlin, Germany, July 18 to 20, 2018, Revised Paper

Anomalous infrared spectra of hybridized phonons in type-I clathrate Ba8_8Ga16_{16}Ge30_{30}

The optical conductivity spectra of the rattling phonons in the clathrate Ba$_8$Ga$_{16}$Ge$_{30}$ are investigated in detail by use of the terahertz time-domain spectroscopy. The experiment has revealed that the lowest-lying vibrational mode of a Ba(2)$^{2+}$ ion consists of a sharp Lorentzian peak at 1.2 THz superimposed on a broad tail weighted in the lower frequency regime around 1.0 THz. With decreasing temperature, an unexpected linewidth broadening of the phonon peak is observed, together with monotonic softening of the phonon peak and the enhancement of the tail structure. These observed anomalies are discussed in terms of impurity scattering effects on the hybridized phonon system of rattling and acoustic phonons.Comment: Submitted to JPS