Hypersonic blunt body computations including real gas effects

The recently developed second-order explicit and implicit total variation diminishing (TVD) shock-capturing methods of the Harten and Yee, Yee, and van Leer types in conjunction with a generalized Roe's approximate Riemann solver of Vinokur and the generalized flux-vector splittings of Vinokur and Montagne for two-dimensional hypersonic real gas flows are studied. A previous study on one-dimensional unsteady problems indicated that these schemes produce good shock-capturing capability and that the state equation does not have a large effect on the general behavior of these methods for a wide range of flow conditions for equilibrium air. The objective of this paper is to investigate the applicability and shock resolution of these schemes for two-dimensional steady-state hypersonic blunt body flows. The main contribution of this paper is to identify some of the elements and parameters which can affect the convergence rate for high Mach numbers or real gases but have negligible effect for low Mach number cases for steady-state inviscid blunt body flows

High- Resolution Shock-Capturing Schemes for Inviscid and Viscous Hypersonic Flows

A class of high-resolution implicit total variation diminishing (TVD) type algorithms suitable for transonic multidimensional Euler and Navier-Stokes equations has been extended to hypersonic computations. The improved conservative shock-capturing schemes are spatially second- and third-order and are fully implicit. They can be first- or second-order accurate in time and are suitable for either steady or unsteady calculations. Enhancement of stability and convergence rate for hypersonic flows is discussed. With the proper choice of the temporal discretization and implicit linearization, these schemes are fairly efficient and accurate for very complex two-dimensional hypersonic in viscid and viscous shock interactions. This study is complemented by a variety of steady and unsteady viscous and inviscid hypersonic blunt body flow computations. Due to the inherent stiffness of viscous flow problems, numerical experiments indicated that the convergence rate is in general slower for viscous flows than for inviscid steady flows

Resistant starch reduces large intestinal pH and promotes fecal lactobacilli and bifidobacteria in pigs

Research Areas: Agriculture. Veterinary SciencesABSTRACT - Dietary resistant starch (RS) may have prebiotic properties but its effects on fermentation and the microbial population are inconsistent. This meta-analysis aimed to quantify the relationship between RS type 2 (RS2) and intestinal short-chain fatty acids (SCFA) and pH as well as certain key bacterial taxa for intestinal health in pigs. From the 24 included articles with sufficient information about the animal, and dietary and physiological measurements published between 2000 and 2017, individual sub-data sets for fermentation metabolites, pH, bacterial abundances and apparent total tract digestibility were built and used to parameterize prediction models on the effect of RS2, accounting for inter- and intra-study variability. In addition, the effect of pig's BW at the start of the experiment and duration of the experimental period on response variables were also evaluated using backward elimination analysis. Dietary RS levels ranged from 0% to 78.0% RS, with median and mean RS levels of 28.8% and 210%, respectively. Negative relationships could be established between dietary RS and pH in the large intestine (P < 0.05), with a stronger effect in the mid and distal colon, and feces (R = 0.64 to 0.81; P < 0.001). A dietary level of 15% RS would lower the pH in the proximal, mid-, distal colon and feces by 0.2, 0.6, 0.4 and 0.6 units, respectively. Increasing RS levels, however, did not affect SCFA concentrations in the hindgut, but enhanced the molar proportion of propionate in mid-colon and reduced those of acetate in mid-colon and of butyrate in mid- and distal colon (R-2 = 0.46 to 0.52; P < 0.05). Backward elimination indicated an age-related decrease in mid-colonic propionate proportion and increase in mid- and distal colonic butyrate proportion (P < 0.05), thereby modulating RS2 effects. In feces, increasing RS levels promoted fecal lactobacilli (R-2 = 0.46; P < 0.01) and bifidobacteria (R-2 = 0.57; P < 0.01), whereby the slope showed the need for a minimal RS level of 10% for a 0.5 log unit-increase in their abundance. Best-fit equations further supported that a longer experimental period increased fecal lactobacilli but decreased fecal bifidobacteria (P < 0.05). In conclusion, dietary RS2 seems to effectively decrease digesta pH throughout the large intestine and increase lactic acid-producing bacteria in feces of pigs which may limit the growth of opportunistic pathogens in the hindgut. To achieve these physiologically relevant changes, dietary RS should surpass 10% to 15%.info:eu-repo/semantics/publishedVersio

Phase-Locked Spatial Domains and Bloch Domain Walls in Type-II Optical Parametric Oscillators

We study the role of transverse spatial degrees of freedom in the dynamics of signal-idler phase locked states in type-II Optical Parametric Oscillators. Phase locking stems from signal-idler polarization coupling which arises if the cavity birefringence and/or dichroism is not matched to the nonlinear crystal birefringence. Spontaneous Bloch domain wall formation is theoretically predicted and numerically studied. Bloch walls connect, by means of a polarization transformation, homogeneous regions of self-phase locked solutions. The parameter range for their existence is analytically found. The polarization properties and the dynamics of walls in one- and two transverse spatial dimensions is explained. Transition from Bloch to Ising walls is characterized, the control parameter being the linear coupling strength. Wall dynamics governs spatiotemporal dynamical states of the system, which include transient curvature driven domain growth, persistent dynamics dominated by spiraling defects for Bloch walls, and labyrinthine pattern formation for Ising walls.Comment: 27 pages, 16 figure

Dynamics of localized structures in vector waves

Dynamical properties of topological defects in a twodimensional complex vector field are considered. These objects naturally arise in the study of polarized transverse light waves. Dynamics is modeled by a Vector Complex Ginzburg-Landau Equation with parameter values appropriate for linearly polarized laser emission. Creation and annihilation processes, and selforganization of defects in lattice structures, are described. We find "glassy" configurations dominated by vectorial defects and a melting process associated to topological-charge unbinding.Comment: 4 pages, 5 figures included in the text. To appear in Phys. Rev. Lett. (2000). Related material at http://www.imedea.uib.es/Nonlinear and http://www.imedea.uib.es/Photonics . In this new version, Fig. 3 has been replaced by a better on

Управління загрозами фінансовій безпеці підприємства

Розроблено блок-схему алгоритму управління загрозами фінансовій безпеці підприємства; виділено основні етапи здійснення цього процесу: оцінювання, аналіз та управління. Визначено сутність, зміст, переваги та недоліки застосування методів оцінювання загроз фінансовій безпеці в системі фінансового менеджменту підприємства. Ключові слова: підприємство, фінансова безпека, загрози, оцінювання, аналіз, управління.Составлена блок-схема алгоритма управления угрозами финансовой безопасности предприятия. Выделены основные этапы осуществления данного процесса: оценивание, анализ и управление. Определены сущность, содержание, преимущества и недостатки методов оценивания угроз финансовой безопасности в системе финансового менеджмента предприятия. Ключевые слова: предприятие, финансовая безопасность, угрозы, оценивание, анализ, управление.Enterprise financial security threats management main terms essence and contents were defined on the basis of financial and economic literature analysis and generalization: enterprise financial security threats management is a multistage process, which includes evaluation, management and analysis of enterprise financial security threats management; evaluation of enterprise financial security threats is a process of identification of threats influence on enterprise financial security; analysis of enterprise financial security threats is a process of threats identification, which influence on enterprise financial security. It is established that the majority of modern domestic and foreign scientists consider two groups of enterprise financial security threats estimation: qualitative or subjective (expert, probabilistic (concerning loss, favorable possibilities), consequences analysis) and quantitative or objective (statistical, analytical, rating, expense expediency, analogues, decision tree, normative). Comparative analysis of qualitative and quantitative enterprise financial security threats estimation enables to detect that use either of them has its own advantages and disadvantages. Some methods require using the considerable mass data and at the same time leave out of the account the time factor; others are insufficiently developed for using in the domestic economic conditions. Therefore the choice of the method is made only owing to the purpose of the enterprise financial security threats estimation. It is proved that the methods of the enterprise financial security threats management could be divided into three groups: reduction, maintenance and transmission. Reduction of enterprise financial security threats level provides preventive management and logistical measures implementation as to unfavorable events in financial and economic activities prevention or negative consequences liquidation. As measures, implemented for enterprise financial security threats level maintaining, could be referred the following: getting loans on compensation for losses, which enterprise got as a result of unforeseen, unfavorable events in its financial and economic activities, resumption of output production (goods, works, services) with the help of finance and credit establishments activities, government grants etc. Keywords: enterprise, financial security, threats, evaluation, analysis, management

Winding number instability in the phase-turbulence regime of the Complex Ginzburg-Landau Equation

We give a statistical characterization of states with nonzero winding number in the Phase Turbulence (PT) regime of the one-dimensional Complex Ginzburg-Landau equation. We find that states with winding number larger than a critical one are unstable, in the sense that they decay to states with smaller winding number. The transition from Phase to Defect Turbulence is interpreted as an ergodicity breaking transition which occurs when the range of stable winding numbers vanishes. Asymptotically stable states which are not spatio-temporally chaotic are described within the PT regime of nonzero winding number.Comment: 4 pages,REVTeX, including 4 Figures. Latex (or postscript) version with figures available at http://formentor.uib.es/~montagne/textos/nupt

Wound-up phase turbulence in the Complex Ginzburg-Landau equation

We consider phase turbulent regimes with nonzero winding number in the one-dimensional Complex Ginzburg-Landau equation. We find that phase turbulent states with winding number larger than a critical one are only transients and decay to states within a range of allowed winding numbers. The analogy with the Eckhaus instability for non-turbulent waves is stressed. The transition from phase to defect turbulence is interpreted as an ergodicity breaking transition which occurs when the range of allowed winding numbers vanishes. We explain the states reached at long times in terms of three basic states, namely quasiperiodic states, frozen turbulence states, and riding turbulence states. Justification and some insight into them is obtained from an analysis of a phase equation for nonzero winding number: rigidly moving solutions of this equation, which correspond to quasiperiodic and frozen turbulence states, are understood in terms of periodic and chaotic solutions of an associated system of ordinary differential equations. A short report of some of our results has been published in [Montagne et al., Phys. Rev. Lett. 77, 267 (1996)].Comment: 22 pages, 15 figures included. Uses subfigure.sty (included) and epsf.tex (not included). Related research in http://www.imedea.uib.es/Nonlinea