Construction of the Lyapunov spectrum in a chaotic system displaying phase synchronization

We consider a three-dimensional chaotic system consisting of the suspension of Arnold's cat map coupled with a clock via a weak dissipative interaction. We show that the coupled system displays a synchronization phenomenon, in the sense that the relative phase between the suspension flow and the clock locks to a special value, thus making the motion fall onto a lower dimensional attractor. More specifically, we construct the attractive invariant manifold, of dimension smaller than three, using a convergent perturbative expansion. Moreover, we compute via convergent series the Lyapunov exponents, including notably the central one. The result generalizes a previous construction of the attractive invariant manifold in a similar but simpler model. The main novelty of the current construction relies in the computation of the Lyapunov spectrum, which consists of non-trivial analytic exponents. Some conjectures about a possible smoothening transition of the attractor as the coupling is increased are also discussed.Comment: 24 pages, 10 figure

Trade and Labor Outcomes in Latin America's Rural Areas: A Cross-Household Surveys Approach

This paper explores the potential link between trade and labor outcomes in rural areas in Latin America by estimating cross household-survey regression models with microdata from 60 Latin American household surveys and country aggregate data. We find a significant positive association between labor outcomes in rural areas and some measures of international trade, in particular exports, trade as a share of GDP, and the price of exports. International trade has been associated with higher wages and labor income in rural areas, in particular for those workers located in the bottom quantiles of the conditional wage distribution. Instead, our results suggest that all individuals in rural areas benefit about the same due to higher export prices. Results for urban areas are rarely statistically significant.trade, wages, labor, rural, Latin America

Spherical collapse in quintessence models with zero speed of sound

We study the spherical collapse model in the presence of quintessence with negligible speed of sound. This case is particularly motivated for w<-1 as it is required by stability. As pressure gradients are negligible, quintessence follows dark matter during the collapse. The spherical overdensity behaves as a separate closed FLRW universe, so that its evolution can be studied exactly. We derive the critical overdensity for collapse and we use the extended Press-Schechter theory to study how the clustering of quintessence affects the dark matter mass function. The effect is dominated by the modification of the linear dark matter growth function. A larger effect occurs on the total mass function, which includes the quintessence overdensities. Indeed, here quintessence constitutes a third component of virialized objects, together with baryons and dark matter, and contributes to the total halo mass by a fraction ~ (1+w) Omega_Q / Omega_m. This gives a distinctive modification of the total mass function at low redshift.Comment: 38 pages; small changes, including modification of the window function. JCAP published versio

Development of an eco-friendly composite based on geopolymer matrix produced with fired clay brick powder and reinforced with natural fibers

Current construction industry is responsible for a large amount of greenhouse gas emissions due to the widespread use of building materials with high-embodied energy such as ordinary Portland cement-based materials and steel. Therefore, this thesis presents the development of a new eco-friendly building material based on a geopolymer matrix produced with Fired Clay Brick Powder (FCBP) and reinforced with natural fibers as a low CO2 alternative for the traditional building materials. With this purpose, a review of recent advances in the application of geopolymer composites and geopolymers reinforced with natural fibers in the construction industry were first presented. This review covers two major eco-friendly materials for construction: first, geopolymers obtained from industrial by-products and waste materials, such as fly ash, ground granulated blast furnace slag, construction and demolition wastes and main tailings; and second, natural fibers used as reinforcement for geopolymer composite materials. Literature review allowed the definition of morphology, size, and the molar ratio of SiO2/Al2O3 in the raw material, together with the alkaline solution/solid ratio, NaOH concentration, SiO2/M2O molar ratio in the total alkaline solution and the curing conditions as key parameters in the formulation of geopolymers. It has been also found that the type, pre-treatment, amount and length of the natural fibers play an important role in the reinforcement of geopolymer matrices. Once key parameters of geopolymer composites production were identified, an attempt for the formalization of a methodology to improve the compressive strength of FCBP-based geopolymers is presented. The tests allowed the definition of optimum conditions of the FCBP-based geopolymers formulation and curing conditions, which resulted in a cementitious matrix with high compression strengths of up to 37 MPa. Nevertheless, high-strength geopolymers evidenced a fragile behavior and low ductility similar to Portland cement-based materials. Therefore, the last part of the work was focused on the evaluation of natural cellulose fibers (jute and sisal) as reinforcement of FCBP-based geopolymers. The results indicated that jute and sisal fiber addition at the optimum content significantly improved the compressive, splitting tensile and flexural strength with respect to the unreinforced geopolymer matrix and lead to a shifting of the failure mode from a brittle to a more ductile failure in all mechanical tests.Tesi

A parsec-scale flow associated with the IRAS 16547-4247 radio jet

IRAS 16547-4247 is the most luminous (6.2 x 10^4 Lsun) embedded young stellar object known to harbor a thermal radio jet. We report the discovery using VLT-ISAAC of a chain of H_2 2.12 um emission knots that trace a collimated flow extending over 1.5 pc. The alignment of the H_2 flow and the central location of the radio jet implies that these phenomena are intimately linked. We have also detected using TIMMI2 an isolated, unresolved 12 um infrared source towards the radio jet . Our findings affirm that IRAS 16547-4247 is excited by a single O-type star that is driving a collimated jet. We argue that the accretion mechanism which produces jets in low-mass star formation also operates in the higher mass regime.Comment: Accepted for publication in ApJL, 10 pages, 2 figure

Autonomous navigation with deadlock detection and avoidance

This paper studies alternatives to solve the problem of autonomous mobile robots navigation in unknown indoor environments. The navigation system uses fuzzy logic to combine the information obtained from range sensors and the navigational data to plan the robot’s movements. The strategy is built upon five modules: i) target following, ii) obstacle avoidance, iii) possible path, iv) deadlock detection and v) wall following. Given a possible path and obstacles near the environment of the robot, the controller will modulate the output velocity in order to go to the target and avoid collisions. In case of dead lock situations, a method that enables the robot to detect, escape and reach the target is proposed. The performance and behavior of the proposed navigational system was evaluated through simulations in different conditions, where the effectiveness of the proposed method is demonstrated and compared with previous results.Sociedad Argentina de Informática e Investigación Operativ

Autonomous navigation with deadlock detection and avoidance

This paper studies alternatives to solve the problem of autonomous mobile robots navigation in unknown indoor environments. The navigation system uses fuzzy logic to combine the information obtained from range sensors and the navigational data to plan the robot’s movements. The strategy is built upon five modules: i) target following, ii) obstacle avoidance, iii) possible path, iv) deadlock detection and v) wall following. Given a possible path and obstacles near the environment of the robot, the controller will modulate the output velocity in order to go to the target and avoid collisions. In case of dead lock situations, a method that enables the robot to detect, escape and reach the target is proposed. The performance and behavior of the proposed navigational system was evaluated through simulations in different conditions, where the effectiveness of the proposed method is demonstrated and compared with previous results.Sociedad Argentina de Informática e Investigación Operativ