Ballistic aggregation: a solvable model of irreversible many particles dynamics

The adhesive dynamics of a one-dimensional aggregating gas of point particles is rigorously described. The infinite hierarchy of kinetic equations for the distributions of clusters of nearest neighbours is shown to be equivalent to a system of two coupled equations for a large class of initial conditions. The solution to these nonlinear equations is found by a direct construction of the relevant probability distributions in the limit of a continuous initial mass distribution. We show that those limiting distributions are identical to those of the statistics of shocks in the Burgers turbulence. The analysis relies on a mapping on a Brownian motion problem with parabolic constraints.Comment: 23 pages, 6 figures include

Convergence Rates in L^2 for Elliptic Homogenization Problems

We study rates of convergence of solutions in L^2 and H^{1/2} for a family of elliptic systems {L_\epsilon} with rapidly oscillating oscillating coefficients in Lipschitz domains with Dirichlet or Neumann boundary conditions. As a consequence, we obtain convergence rates for Dirichlet, Neumann, and Steklov eigenvalues of {L_\epsilon}. Most of our results, which rely on the recently established uniform estimates for the L^2 Dirichlet and Neumann problems in \cite{12,13}, are new even for smooth domains.Comment: 25 page

Reactive Turbulent Flow in Low-Dimensional, Disordered Media

We analyze the reactions $A+A \to \emptyset$ and $A + B \to \emptyset$ occurring in a model of turbulent flow in two dimensions. We find the reactant concentrations at long times, using a field-theoretic renormalization group analysis. We find a variety of interesting behavior, including, in the presence of potential disorder, decay rates faster than that for well-mixed reactions.Comment: 6 pages, 4 figures. To appear in Phys. Rev.

Exact solution of the one-dimensional ballistic aggregation

An exact expression for the mass distribution $\rho(M,t)$ of the ballistic aggregation model in one dimension is derived in the long time regime. It is shown that it obeys scaling $\rho(M,t)=t^{-4/3}F(M/t^{2/3})$ with a scaling function $F(z)\sim z^{-1/2}$ for $z\ll 1$ and $F(z)\sim \exp(-z^3/12)$ for $z\gg 1$. Relevance of these results to Burgers turbulence is discussed.Comment: 11 pages, 2 Postscript figure

Interior comfort regulation with gypsum plasters

In this work, the performance of a manually applied thin layer of a multilayer gypsum plaster system, for interior lining of walls and ceilings, incorporating phase change materials (PCM), is investigated. The study aims the development of a passive solar storage system that can be combined with both active heating and cooling storage systems and equipments. Mechanical and thermal tests were carried in laboratory, in two test cells and in residential buildings. Results so far showed that the gypsum plaster with 20%-wt. PCM reduces up to 45-50% flexural and compressive strengths, but the specifications of the European standard for these materials are fulfil. On what concerns thermal properties, the use of gypsum-PCM plaster reduces the maximum room temperature up to 5 ºC with a time delay of 3 hours and increases the minimum room temperature up to 1.5 ºC with a time delay of 2 hours. Besides, it also reduces room relative humidity up to 10%. Power savings of 0.44 W/m2wall.m2floor were estimated, with higher potential for lower temperatures, according to tests carried in a Passy’s test cell during the cooling season.Agência de Inovação (ADI

The Pursuit of External Knowledge in Eco-Innovation. Analysis of the Agri-Food Sector in Spain

The research about the search for opportunities through open cooperation strategies points to an exchange of knowledge among a certain number of sources, aimed at sustaining competitive advantage. From this new vision emerges the paradigm of open innovation, which has prompted a change in the organization of resources, information filtering, and rapid absorptive capacity. Awareness of climate problems and external societal pressures can motivate companies to create new technologies and new forms of cooperation to avoid environmental problems. Based on a survey of Spanish agri-food firms, we find that the depth of external sources of innovation increases environmental improvement in a U-shaped relationship

Spectrum of the Fokker-Planck operator representing diffusion in a random velocity field

We study spectral properties of the Fokker-Planck operator that represents particles moving via a combination of diffusion and advection in a time-independent random velocity field, presenting in detail work outlined elsewhere [J. T. Chalker and Z. J. Wang, Phys. Rev. Lett. {\bf 79}, 1797 (1997)]. We calculate analytically the ensemble-averaged one-particle Green function and the eigenvalue density for this Fokker-Planck operator, using a diagrammatic expansion developed for resolvents of non-Hermitian random operators, together with a mean-field approximation (the self-consistent Born approximation) which is well-controlled in the weak-disorder regime for dimension d>2. The eigenvalue density in the complex plane is non-zero within a wedge that encloses the negative real axis. Particle motion is diffusive at long times, but for short times we find a novel time-dependence of the mean-square displacement, $\sim t^{2/d}$ in dimension d>2, associated with the imaginary parts of eigenvalues.Comment: 8 pages, submitted to Phys Rev

La sostenibilidad en la arquitectura industrializada: cerrando el ciclo de los materiales

The condition of sustainability, from a physical point of view, can be defined as the closure of the material cycle. This is reached in determined systems, in the absence of residual flows, and in which resources are constantly recycled. Such systems can encounter serious obstacles in the productive model that characterises the majority of contemporary industry. The productive model, born during the Industrial Revolution, can be summarised by the following lineal sequence: extraction > manufacture > use > residue. In contrast, this research focuses on a productive model from the ecological industry, based on the example of the biosphere as a recycling machine. Requiring the elimination of the concept of residues, the system can be summarised by the following continuous cycle: recycling-manufacturing-use-recycling. The hypothesis posed is as follows: using technology presently available, represented by the lightweight modular construction that is commercialised by renting (making it possible to return the modules to the factory once their useful life is over, therefore recuperating resources), a management system capable to close the material cycle at least to 90% can be developed. (conventional building construction currently manages a recycling value of 10% of used resources).La condición de sostenibilidad, desde el punto de vista físico, puede ser definida como el cierre de los ciclos materiales, alcanzándose éste en un sistema determinado cuando no existen flujos de residuos sino que los recursos se reciclan constantemente. Tal condición encuentra un fuerte obstáculo en el modelo productivo que caracteriza a la mayor parte de la industria contemporánea, nacido en la revolución industrial, que puede sintetizarse en la secuencia lineal extracción > fabricación > uso > residuo. En oposición a ello, el modelo productivo en el que se centra la investigación que aquí se presenta es la ecología industrial y se basa en el ejemplo de la biosfera como máquina de reciclar. Supone la eliminación del concepto de residuo y puede resumirse en el ciclo continuo de reciclaje-fabricación-uso-reciclaje. La hipótesis planteada consiste en que, a partir de los sistemas de construcción modular ligera que se comercializan bajo el sistema de alquiler (que hace posible que los módulos regresen a la fábrica una vez cumplida su vida útil, recuperándose sus componentes) se puede desarrollar un sistema de gestión de los recursos empleados en el ciclo de vida de los edificios capaz de cerrar los ciclos materiales hasta en un 90% (en la construcción convencional se alcanza un 10%)

Thin film solar cells based on the ternary compound Cu2SnS3

Alongside with Cu2ZnSnS4 and SnS, the p-type semiconductor Cu2SnS3 also consists of only Earth abundant and low-cost elements and shows comparable opto-electronic properties, with respect to Cu2ZnSnS4 and SnS, making it a promising candidate for photovoltaic applications of the future. In this work, the ternary compound has been produced via the annealing of an electrodeposited precursor in a sulfur and tin sulfide environment. The obtained absorber layer has been structurally investigated by X-ray diffraction and results indicate the crystal structure to be monoclinic. Its optical properties have been measured via photoluminescence, where an asymmetric peak at 0.95 eV has been found. The evaluation of the photoluminescence spectrum indicates a band gap of 0.93 eV which agrees well with the results from the external quantum efficiency. Furthermore, this semiconductor layer has been processed into a photovoltaic device with a power conversion efficiency of 0.54%, a short circuit current of 17.1 mA/cm2, an open circuit voltage of 104 mV hampered by a small shunt resistance, a fill factor of 30.4%, and a maximal external quantum efficiency of just less than 60%. In addition, the potential of this Cu2SnS3 absorber layer for photovoltaic applications is discussed

Factores que afectan la calidad del ensilaje de pasto Kikuyo (Cenchrus clandestinus)

Introducción. La oferta de ensilaje de pasto Kikuyo permite reducir la estacionalidad de la producción láctea, pero es necesario evaluar los factores que afectan el proceso de ensilado para mantener una calidad similar a la del forraje fresco. Objetivo. Evaluar el efecto de la edad de rebrote, el tamaño del picado, el tiempo de oreo con el uso de aditivos sobre la calidad del ensilaje de pasto Kikuyo. Materiales y métodos. El estudio se realizó en Mosquera, Colombia, durante el 2020. Se evaluó el efecto de la edad de rebrote (28, 42 y 70 días), el tamaño de picado (1,5 cm, 3,0 cm y planta completa), tiempo de oreo (0 y 6 h) y uso de aditivos (glicerina cruda y bacterias ácido lácticas (BAL)) sobre la composición química, digestibilidad in situ de la materia seca (DISMS), dinámica del pH, perfil de ácidos grasos volátiles (AGV’s), pérdidas de materia seca y calidad organoléptica. La información se analizó como un diseño completamente al azar con arreglo factorial. Resultados. El uso de pasto Kikuyo de 70 días de rebrote redujo (p<0,05) la proteína cruda, la digestibilidad y la energía, y aumentó la pared celular y la materia seca (MS) del ensilaje. La utilización de aditivos redujo (p<0,05) el pH final del pasto maduro. El picado pequeño o la inclusión de glicerina cruda en la planta completa incrementaron (p<0,05) la DISMS. El uso de aditivos redujo (p<0,05) el pH final del ensilaje elaborado con la planta completa. El oreo previo al empaque incrementó (p<0,05) la MS, pero redujo (p<0,05) la proteína cruda (PC) y ácido láctico e incrementó (p<0,05) el pH final. Conclusión. El uso de forrajes tiernos, el picado pequeño y el embolsado en fresco mejoraron la calidad del ensilaje de pasto Kikuyo. El uso de forrajes maduros requiere la aplicación de aditivos.