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Search Results: 1 - 10 of 26608 matches for " Diego Alexander; "
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Scalar field instability in de Sitter space-time
Alexander Dolgov,Diego N. Pelliccia
Physics , 2005, DOI: 10.1016/j.nuclphysb.2005.12.002
Abstract: Starting from the equation of motion of the quantum operator of a real scalar field phi in de Sitter space-time, a simple differential equation is derived which describes the evolution of quantum fluctuations of this field. Full de Sitter invariance is assumed and no ad hoc infrared cutoff is introduced. This equation is solved explicitly and in massive case our result agrees with the standard one. In massless case the large time behavior of our solution differs by sign from the expression found in earlier papers. A possible cause of discrepancy may be a spontaneous breaking of de Sitter invariance.
Metodología de los gráficos de unión (bond graphs) en aplicaciones biomédicas Bond graph methodology in biomedical applications
Diego Edgardo Fuentes Herrera,Diego Alexander Garzón-Alvarado
Revista Cubana de Investigaciones Biom??dicas , 2012,
Abstract: Se presentan las aplicaciones realizadas en el campo de la medicina y la biología usando la técnica gráfica de modelado conocida como gráficos de unión (bond graphs), con el objetivo de mostrar las diferentes formas en las que se han usado los gráficos de unión como herramienta para la obtención de modelos y simulaciones de sistemas biológicos. Para el análisis de los trabajos realizados por los investigadores se hace una clasificación de los campos de aplicación con el fin de tener una visión más clara de lo diversa que ha sido la adaptación de esta metodología. Asimismo se discuten las posibilidades aún no exploradas, es decir, se habla de la aplicabilidad de los gráficos de unión en campos adicionales a los tratados en las referencias. The paper presents applications carried out in the field of medicine and biology using the graphical modeling technique known as bond graphs, with the purpose of showing the different ways in which bond graphs have been used to obtain models and simulations of biological systems. To approach the work done by researchers, a classification is made of the fields of application, so as to obtain a clearer view of the variety of adaptations undergone by the methodology. Possibilities not yet explored are also discussed, i.e. comments are included on the applicability of bond graphs to fields other than those mentioned in the references.
A Model of Layered Architectures
Diego Marmsoler,Alexander Malkis,Jonas Eckhardt
Computer Science , 2015, DOI: 10.4204/EPTCS.178.5
Abstract: Architectural styles and patterns play an important role in software engineering. One of the most known ones is the layered architecture style. However, this style is usually only stated informally, which may cause problems such as ambiguity, wrong conclusions, and difficulty when checking the conformance of a system to the style. We address these problems by providing a formal, denotational semantics of the layered architecture style. Mainly, we present a sufficiently abstract and rigorous description of layered architectures. Loosely speaking, a layered architecture consists of a hierarchy of layers, in which services communicate via ports. A layer is modeled as a relation between used and provided services, and layer composition is defined by means of relational composition. Furthermore, we provide a formal definition for the notions of syntactic and semantic dependency between the layers. We show that these dependencies are not comparable in general. Moreover, we identify sufficient conditions under which, in an intuitive sense which we make precise in our treatment, the semantic dependency implies, is implied by, or even coincides with the reflexive-transitive closure of the syntactic dependency. Our results provide a technology-independent characterization of the layered architecture style, which may be used by software architects to ensure that a system is indeed built according to that style.
Behavioral Analysis of a Lithium Ion Battery (Li-Ion), a Nickel Metal Hydride Battery (Ni-MH) and a Supercapacitor in an Isolated Photovoltaic Solar System  [PDF]
Laura Milena Cruz Moreno, Diego Fabián Martín Rincón, Johann Alexander Hernández
Energy and Power Engineering (EPE) , 2017, DOI: 10.4236/epe.2017.94020
Abstract: This paper presents experimental research about the behavior of different storage devices such as Li-ion, Ni-MH batteries and supercapacitors when charged by a solar photovoltaic system. Photovoltaic systems work as a variable current source, depending on the solar irradiance. These devices present a different profile charge compared to a constant and controlled charge generated by a traditional charger. For this work, several charging and discharging cycles of batteries and supercapacitors under the same environmental conditions were carried out in order to observe the different characteristics of each technology, and some harmful effects on the storage devices operation such as the memory effect and partial discharges involved in the proper functioning of the solar photovoltaic system.
Desulfurization of Dibenzothiophene and Oxidized Dibenzothiophene Ring Systems
Diego P. Morales,Alexander S. Taylor,Steven C. Farmer
Molecules , 2010, DOI: 10.3390/molecules15031265
Abstract: Lithium, used in conjunction with sodium metal, produces a high yield of biphenyl when reacted with dibenzothiophene, dibenzothiophene sulfoxide or dibenzothiophene sulfone.
DESARROLLO DE UNA FUENTE SíSMICA PORTáTIL PARA ADQUISICIóN SíSMICA DE ALTA RESOLUCIóN
Pinto,Omar; Rivera,Diego; Ojeda,Germán; Martínez,Alexander;
Boletin de Geología , 2012,
Abstract: one of the seismic energy sources most frequently used for shallow seismic data acquisition is the sledgehammer. however, the seismic pulse generated by the sledgehammer is not repeatable, it depends on the operating style of the person to use the sledgehammer. for a relative improvement in terms of increased penetration of waves elastic in the ground, to increase the signal - noise ratio, higher resolution vertical, the more impact energy, higher frequency content, and fewer of shots per site, the study reported here shows the design, building and testing of a device named gis (generador de impacto sísmico). device testing was conducted by comparing the results obtained on the same seismic line with the gis and the sledgehammer. it was concluded that seismic data obtained with the gis provide higher resolution and research depth than that obtained with the sledgehammer, as the signal amplitude, signal - noise, penetration of acoustic waves in the subsoil and number of reflectors displayed was greater.
Modelos unifactoriales de tipos de interés: aplicación al mercado Colombiano
Restrepo Tobón,Diego Alexander; Botero Ramírez,Juan Carlos;
Cuadernos de Administración , 2008,
Abstract: this article is a first approach to implementing in the colombian market the unifactorial interest rate models developed by hull and white (1990) and by black and karasinski (1991) with constant volatility and reversion velocity parameters. the main findings from this research are 1) implementing both models using trinomial trees enables accurately replicating the forward structure of market interest rates; 2) the parallel movements of the installment structure of interest rates in colombia explains most of their variability, thus, using unifactorial models such as the ones proponed herein is appropriate; 3) the volatility and reversion velocity mean parameters on the mean short-term interest rate must be estimated using time series econometric models; 4) future articles must broach the problems related to coverage using such types of models, to estimating volatility structures and surfaces, and to multifactorial model calibration.
Los informes de responsabilidad social empresarial: su evolución y tendencias en el contexto internacional y colombiano: Evolution and Trends in the International and Colombian Conte
Gómez-Villegas,Mauricio; Quintanill,Diego Alexander;
Cuadernos de Contabilidad , 2012,
Abstract: this document is framed by interdisciplinary studies on corporate social responsibility. the research aimed to build an analytical framework to identify, characterize and assess the evolution of social responsibility reports. the present paper is the third one that presents the progress of such research. the central question is about the evolution of the production of csr reports in colombia and at the international level. here we revisit the conclusions and the analytical framework central arguments that were developed in previous work and focus on the presentation and interpretation of the developments and trends in corporate social responsibility reports since the advent of the global reporting initiative, gri, in 1997, up to the reports presented in 2010. these developments and trends show that social and environmental information under the gri approach has been largely captured by financial logic, apparently playing a role that is more about legitimation than transformation (o'dwyer, 2003; o'dwyer owen & unerman, 2011).
Análisis de sensibilidad por la colocación de los electrodos en la electromiografía de superficie (semg)
Ramírez,Angélica; Garzón,Diego Alexander;
Revista Facultad de Ingeniería Universidad de Antioquia , 2008,
Abstract: the surface electromyography is widely used in laboratories of movement analysis due to its easy manipulation and its noninvasive character. however, this extended use generates a variation in the protocols and produces difficult to compare results [1]. in the present study, an analysis of sensitivity for the positioning of bipolar electrodes is made on three muscles of the quadriceps: vastus lateralis (vl), vastus medialis (vm) and rectus femoris (rf). the three main factors of the study are: a. the longitudinal position of electrode, b. the orientation of electrode and c. the angle of extension of the knee. additionally, the response factors are the maxima force and the rms of the emg signal. the tests were made for maxima voluntary contraction (mvc) during an isometric force. we conclude that there are differences in the emg signal when the electrodes are in different position and orientation. the best distance for the electrodes is 22.59 ± 2.84% for the vl, 29.44 ± 1.88% for the vm and 66.28 ± 0.38% for the rf from the apex of the patella. the best orientation of the electrodes is 0ofor the vl, 70ofor the vm and -20ofor the rf.
Formación de patrones de turing para sistemas de reacción-convección-difusión en dominios fijos sometidos a campos de velocidad toroidal
Galeano,Carlos Humberto; Garzón,Diego Alexander; Mantilla,Juan Miguel;
Revista Facultad de Ingeniería Universidad de Antioquia , 2010,
Abstract: this article studies the effect of the inclusion of the transport term in the reaction-diffusion equations, through toroidal velocity fields. the formation of turing patterns in diffusion-advection-reaction problems is studied specifically, considering the schnackenberg reaction kinetics and glycolysis models. three cases are analyzed and solved numerically using finite elements. it is found that, for the glycolysis models, the advective effect totally modifies the form of the obtained turing patterns with diffusion-reaction; whereas for the problems of schnackenberg, the original patterns distort themselves slightly, making them to rotate in the direction of the velocity field. also, this work was able to determine that for high values of velocity the advective effect surpasses the diffusive one and the instability by diffusion is eliminated. on the other hand, for very low values in the velocity field, the advective effect is not considerable and there is no modification of the original turing pattern.
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