Periodic orbits of a perturbed 3-dimensional isotropic oscillator with axial symmetry

We study the periodic orbits of a generalized Yang-Mills Hamiltonian H depending on a parameter β. Playing with the parameter β we are considering extensions of the Contopoulos and of the Yang-Mills Hamiltonians in a 3-dimensional space. This Hamiltonian consists of a 3-dimensional isotropic harmonic oscillator plus a homogeneous potential of fourth degree having an axial symmetry, which implies that the third component N of the angular momentum is constant. We prove that in each invariant space H = h > 0 the Hamiltonian system has at least four periodic solutions if either β 6 and β != 5 sqrt(13). We also study the linear stability or instability of these periodic solutions

Size-Controlled Water-Soluble Ag Nanoparticles

Ag nanoparticles of two different sizes (1 and 4 nm) were prepared within an apoferritin cavity by using an Ag+-loaded apoferritin as a nanoconfined environment for their construction. The initial amount of Ag' ions injected in the apoferritin cavity dictates the size of the final Ag particles. The protein shell prevents bulk aggregation of the metal particles, which renders them water soluble and extremely stable

New families of periodic orbits for a galactic potential

Agraïments: Fundación Séneca de la Región de Murcia grant number 19219/PI/14.The Hamiltonian system associated to the Hamiltonian $$H=(P_1^2 P_2^2 P_3^2)/2 (Q_1^2 Q_2^2 Q_3^2)/2 (Q_1^4 Q_2^4 Q_3^4 a(Q_1^2Q_2^2 Q_1^2Q_3^2 Q_2^2Q_3^2)),$$ where and a are parameters and is small, describes the local motion in the central area of a galaxy. Its dynamics have been study by many authors. Here we find analytically new families of periodic orbits of this Hamiltonian system

Fundamentals of Electrochemistry with Application to Direct Alcohol Fuel Cell Modeling

Fuel cell modeling is an inherently multiphysics problem. As a result, scientists and engineers trained in different areas are required to work together in this field to address the complex physicochemical phenomena involved in the design and optimization of fuel cell systems. This multidisciplinary approach forces researchers to become accustomed to new concepts. Electrochemical processes, for example, constitute the heart of a fuel cell. Accurate modeling of electrochemical reactions is therefore essential to successfully predict the performance of these devices. However, becoming familiar with the complex concepts of electrochemistry can be an arduous task for those who approach the study of fuel cells from fields other than chemical engineering. This process can extend over time and requires careful reading of many textbooks and papers, the most illuminating ones being hidden to the newcomer in a plethora of recent publications on the subject. The authors, who engaged in the study of fuel cells coming from the field of mechanical engineering, had to travel this road once and, with this contribution, would like to make the journey easier for those who come behind. As an illustrative example, the thermodynamic and electrochemical principles reviewed in this chapter are applied to a complex electrochemical system, the direct ethanol fuel cell (DEFC), reviewing recent work on this problem and suggesting future research directions

Fundamentals of electrochemistry with application to direct alcohol fuel cell modeling

Fuel cell modeling is an inherently multiphysics problem. As a result, scientists and engineers trained in different areas are required to work together in this field to address the complex physicochemical phenomena involved in the design and optimization of fuel cell systems. This multidisciplinary approach forces researchers to become accustomed to new concepts. Electrochemical processes, for example, constitute the heart of a fuel cell. Accurate modeling of electrochemical reactions is therefore essential to successfully predict the performance of these devices. However, becoming familiar with the complex concepts of electrochemistry can be an arduous task for those who approach the study of fuel cells from fields other than chemical engineering. This process can extend over time and requires careful reading of many textbooks and papers, the most illuminating ones being hidden to the newcomer in a plethora of recent publications on the subject. The authors, who engaged in the study of fuel cells coming from the field of mechanical engineering, had to travel this road once and, with this contribution, would like to make the journey easier for those who come behind. As an illustrative example, the thermodynamic and electrochemical principles reviewed in this chapter are applied to a complex electrochemical system, the direct ethanol fuel cell (DEFC), reviewing recent work on this problem and suggesting future research directions

Sistemas caóticos y su aplicación a la encriptación de señales

La sincronización y control de señales caóticas es una activa área de investigación por sus posibles aplicaciones en telecomunicaciones y transmisión de señales [1, 2, 3, 4]. En el presente trabajo se estudia un sistema de comunicación basado en la sincronización de dos sistemas no lineales caóticos, cada uno modelado a partir de las ecuaciones de movimiento de un péndulo forzado amortiguado y que se encuentran en el mismo punto de operación del espacio de parámetros. Synchronization and control of chaotic signals is an active research area because of its applications in telecommunications and secure signal transmission [1,2,3,4]. In this work a communication system based in the synchronization of two chaotic nonlinear systems, each one being modeled by the motion equations of a driven damped pendulum and operated in the same parameter space region is shown. Two communication channels were used: the first one for the synchronizing signal and the second one for the sent message. By using two channels the initial conditions sensibility problem is solved. In the receiver system a feedback loop as a proportional controller is used in order to drive quickly the error between the decoder and encoder states to zero. The last two facts make the system to be robust to external pertubative signals such as noise in the communication channels

A genetically optimized kinetic model for ethanol electro-oxidation on Pt-based binary catalysts used in direct ethanol fuel cells

A one-dimensional model is proposed for the anode of a liquid-feed direct ethanol fuel cell. The complex kinetics of the ethanol electro-oxidation reaction is described using a multi-step reaction mechanism that considers free and adsorbed intermediate species on Pt-based binary catalysts. The adsorbed species are modeled using coverage factors to account for the blockage of the active reaction sites on the catalyst surface. The reaction rates are described by Butler-Volmer equations that are coupled to a onedimensional mass transport model, which incorporates the effect of ethanol and acetaldehyde crossover. The proposed kinetic model circumvents the acetaldehyde bottleneck effect observed in previous studies by incorporating CH3CHOHads among the adsorbed intermediates. A multi-objetive genetic algorithm is used to determine the reaction constants using anode polarization and product selectivity data obtained from the literature. By adjusting the reaction constants using the methodology developed here, different catalyst layers could be modeled and their selectivities could be successfully reproduced.This work has been partially supported by Projects ENE2011-24574 and ENE2015-68703-C2-1-R (MINECO/FEDER, UE). We would like to thank Dr. José J. Linares for his initial suggestion to work on this problem, and Dr. J. Gómez-Hernandez for helpful comments and discussions

El Instituto de Ciencias del Hombre y la Psicología española en la transición (1973-1984): una relación poco estudiada.

El presente trabajo está destinado a subrayar la importancia histórica del Instituto de Ciencias del Hombre, una institución privada que hizo de soporte a la psicología española en un periodo muy delicado de su historia. Según tratamos de argumentar en este artículo, a partir del análisis de fuentes primarias, el Instituto pudo participar activamente en la promoción del atractivo que la psicología estaba ya despertando en un número cada vez mayor de potenciales consumidores. En efecto, en el momento en que España vivía su transición política desde la dictadura hacia la democracia, en el momento en que la propia psicología transitaba hacia su consolidación académica, científica y profesional, el Instituto de Ciencias del Hombre organizó un variado conjunto de actividades que coadyuvaron a fomentar el interés por el conocimiento psicológico. Sin embargo, y este es el centro de interés del trabajo, su labor ha pasado incomprensiblemente desapercibida para la mayor parte de los historiadores que se han dedicado al análisis institucional de la historia de la psicología en España