A theoretical basis for the Harmonic Balance Method

The Harmonic Balance method provides a heuristic approach for finding truncated Fourier series as an approximation to the periodic solutions of ordinary differential equations. Another natural way for obtaining these type of approximations consists in applying numerical methods. In this paper we recover the pioneering results of Stokes and Urabe that provide a theoretical basis for proving that near these truncated series, whatever is the way they have been obtained, there are actual periodic solutions of the equation. We will restrict our attention to one-dimensional non-autonomous ordinary differential equations and we apply the results obtained to a couple of concrete examples coming from planar autonomous systems

Bifurcation diagram and stability for a one-parameter family of planar vector fields

We consider the 1-parameter family of planar quintic systems, $\dot x= y^3-x^3$, $\dot y= -x+my^5$, introduced by A. Bacciotti in 1985. It is known that it has at most one limit cycle and that it can exist only when the parameter $m$ is in $(0.36,0.6)$. In this paper, using the Bendixon-Dulac theorem, we give a new unified proof of all the previous results, we shrink this to $(0.547,0.6)$, and we prove the hyperbolicity of the limit cycle. We also consider the question of the existence of polycycles. The main interest and difficulty for studying this family is that it is not a semi-complete family of rotated vector fields. When the system has a limit cycle, we also determine explicit lower bounds of the basin of attraction of the origin. Finally we answer an open question about the change of stability of the origin for an extension of the above systems.Comment: 27 pages, 11 figure

Phase portraits of Abel quadratic differential systems of second kind with symmetries

Altres ajuts: Universitat Jaume I grant P1-1B2015-16We provide normal forms and the global phase portraits on the Poincaré disk of the Abel quadratic differential equations of the second kind having a symmetry with respect to an axis or to the origin. Moreover, we also provide the bifurcation diagrams for these global phase portraits

advances and perspectives of supercritical fluid technology

1 Dipartimento di Ingegneria Industriale, Universita di Salerno, Salerno, 84084 Fisciano, Italy 2 Departamento de Ingenieŕia Quimica, Universidad de Castilla-La Mancha, 13004 Ciudad Real, Spain 3 Department of Agricultural, Food & Nutritional Sciences, University of Alberta, Edmonton, AB, Canada T6G 2P5 4Dipartimento di Ingegneria Chimica, Gestionale, Informatica, Meccanica, Universita di Palermo, 90128 Palermo, Ital

Influencia de los incentivos laborales en el desempeño de los colaboradores en la empresa Cordsol Group SAC, Cajamarca 2017

El autor no autorizó la publicación de la tesi

On the locus formed by the maximum heights of projectile motion with air resistance

We present an analysis on the geometrical place formed by the set of maxima of the trajectories of a projectile launched in a media with linear drag. Such a place, the locus of apexes, is written in term of the Lambert $W$ function in polar coordinates, confirming the special role played by this function in the problem. In order to characterize the locus, a study of its curvature is presented in two parameterizations, in terms of the launch angle and in the polar one. The angles of maximum curvature are compared with other important angles in the projectile problem. As an addendum, we find that the synchronous curve in this problem is a circle as in the drag-free case.Comment: 7 pages, 6 color eps figures. Synchronous curve added. Typos and style corrected

Bioethanol Production from Coffee Mucilage

AbstractChiapas is one of the largest coffee-producing states in Mexico. In this industry, there are large quantities of waste, which are toxic and harmful to the environment. During the extraction process of coffee bean the waste generated are: pulp, mucilage and parchment. Recently, investigations have been done to utilize these residues for bioenergy generation. This paper provides an overview of coffee and one of its major industrial wastes. The objective of this research was the production of bioethanol from coffee mucilage at laboratory scale and extract and characterize the substrate used as raw material and establish a fermentation process for the production of bioethanol. Our results show the kinetics of fermentation of coffee mucilage as a substrate to yeast Saccharomyces cerevisiae. The cell density, concentration of ethanol, reducing sugar consumption, physico-chemical variables such as pH and temperature were analyzed. The Fermentation parameters such as growth rate, saturation constant and yields were estimated

Análisis de la eficacia de las medidas de protección como mecanismo para cesar la violencia contra las mujeres

Las mujeres son víctimas sistemáticas de violencia en Perú. Se puede encontrar estas manifestaciones en diversos aspectos; sobre todo en la presencia del machismo impregnado en nuestra sociedad. Debido a este panorama, se han buscado implementar mecanismos que permitan cesar la violencia. A propósito de esto, surge la Ley N° 30364 con el propósito de otorgar medidas de protección a las víctimas de violencia. Estas medidas de protección deberían apuntar a la búsqueda de una solución concreta que atienda el caso en particular en el que se encuentra una víctima. Sin embargo, esto no sucede en la realidad. Los jueces otorgan estas medidas sin aterrizar su análisis en cada caso concreto. Por lo tanto, las medidas de no serán cumplidas por las partes, puesto que no se logra analizar y erradicar el problema en verdad. En el presente trabajo de investigación, se analizaron nueve resoluciones judiciales que nos permitieron demostrar que no existe una verdadera intención de erradicar la violencia, sino que sólo se cumple con la formalidad de otorgar estas medidas de protección. Esto trae como consecuencia que la violencia continúe propagándose en nuestra sociedad y muchas mujeres seguirán siendo víctima de la misma.Women are systematic victims of violence in Peru. These manifestations can be found in various aspects. Due to this scenario, efforts have been made to implement mechanisms to stop the violence. In this regard, Law No. 30364 arises to grant protection measures to victims of violence. These protection measures should aim at finding a specific solution that addresses the particular case in which a victim is found. However, this does not happen in reality. The judges grant these measures without landing their analysis in each specific case. Therefore, the measures will not be complied with by the parties, since it is not possible to truly analyze and eradicate the problem. In this research work, nine judicial resolutions were analyzed, which allowed us to demonstrate that there is no real intention to eradicate violence, but that only the formality of granting these protection measures is complied with. As a consequence, violence continues to spread in our society and many women will continue to be victims of it