A note on the combustion of blends of diesel and soya, sunflower and rapeseed vegetable oils in a light boiler

Producción CientíficaThis paper deals with the study of the vegetable oils (VO) used as fuel for heating. The properties of sunflower, rape and soya oils are studied and these are compared with the properties of C-diesel fuel (used for heating domestic purposes in Spain). The mixtures of VO and diesel are studied and characterized and, finally, the results of a series of combustion trials of the mixtures in a conventional heating installation with a mechanical pulverization burner are presented. The results show that viscosity of VO limits the use of blends up to 40% of them, and the oxygen present in their structures contributes to an efficiency gai

PVT-Robust CMOS Programmable Chaotic Oscillator: Synchronization of Two 7-Scroll Attractors

Designing chaotic oscillators using complementary metal-oxide-semiconductor (CMOS) integrated circuit technology for generating multi-scroll attractors has been a challenge. That way, we introduce a current-mode piecewise-linear (PWL) function based on CMOS cells that allow programmable generation of 2–7-scroll chaotic attractors. The mathematical model of the chaotic oscillator designed herein has four coefficients and a PWL function, which can be varied to provide a high value of the maximum Lyapunov exponent. The coefficients are implemented electronically by designing operational transconductance amplifiers that allow programmability of their transconductances. Design simulations of the chaotic oscillator are provided for the 0.35μ m CMOS technology. Post-layout and process–voltage–temperature (PVT) variation simulations demonstrate robustness of the multi-scroll chaotic attractors. Finally, we highlight the synchronization of two seven-scroll attractors in a master–slave topology by generalized Hamiltonian forms and observer approach. Simulation results show that the synchronized CMOS chaotic oscillators are robust to PVT variations and are suitable for chaotic secure communication applications.Universidad Autónoma de Tlaxcala CACyPI-UATx-2017Program to Strengthen Quality in Educational Institutions C/PFCE-2016-29MSU0013Y-07-23National Council for Science and Technology 237991 22284

Combustion of Soya Oil and Diesel Oil Mixtures for Use in Thermal Energy Production

Producción CientíficaIn August 2005, Spain approved the Plan for Renewable Energy Sources for the period 2005-2010 (P.E.R.), including co-combustion installations. Co-combustion in the P.E.R. aims to increase power output by 12,185.3 GWh in five years and shows great interest in studies of the combustion of mixtures of fossil and bio-combustible fuels. This paper presents studies of the co-combustion of soya oil and diesel for thermal heating. The paper begins with a characterization of soya oil as well as mixtures of this oil, with diesel, as fuels. The combustion of the soya oil mixtures and diesel is made in an installation, where the pressure of injection as well as the air volume of the burner can be changed. The obtained results inside to be the environmental average legislation and a greater efficiency of combustion is found. The conclusions show that the use of mixtures of soya oil and Diesel for producing thermal energy in conventional equipment is feasible

Pathological element-based active device models and their application to symbolic analysis

This paper proposes new pathological element-based active device models which can be used in analysis tasks of linear(ized) analog circuits. Nullators and norators along with the voltage mirror-current mirror (VM-CM) pair (collectively known as pathological elements) are used to model the behavior of active devices in voltage-, current-, and mixed-mode, also considering parasitic elements. Since analog circuits are transformed to nullor-based equivalent circuits or VM-CM pairs or as a combination of both, standard nodal analysis can be used to formulate the admittance matrix. We present a formulation method in order to build the nodal admittance (NA) matrix of nullor-equivalent circuits, where the order of the matrix is given by the number of nodes minus the number of nullors. Since pathological elements are used to model the behavior of active devices, we introduce a more efficient formulation method in order to compute small-signal characteristics of pathological element-based equivalent circuits, where the order of the NA matrix is given by the number of nodes minus the number of pathological elements. Examples are discussed in order to illustrate the potential of the proposed pathological element-based active device models and the new formulation method in performing symbolic analysis of analog circuits. The improved formulation method is compared with traditional formulation methods, showing that the NA matrix is more compact and the generation of nonzero coefficients is reduced. As a consequence, the proposed formulation method is the most efficient one reported so far, since the CPU time and memory consumption is reduced when recursive determinant-expansion techniques are used to solve the NA matrix.Promep-Mexico UATLX-PTC-088Junta de Andalucía TIC-2532Ministerio de Educación y Ciencia TEC2007-67247, TEC2010-14825UC-MEXUS-CONACyT CN-09-31

Functional approach to quantum friction: effective action and dissipative force

We study the Casimir friction due to the relative, uniform, lateral motion of two parallel semitransparent mirrors coupled to a vacuum real scalar field, $\phi$. We follow a functional approach, whereby nonlocal terms in the action for $\phi$, concentrated on the mirrors' locii, appear after functional integration of the microscopic degrees of freedom. This action for $\phi$, which incorporates the relevant properties of the mirrors, is then used as the starting point for two complementary evaluations: Firstly, we calculate the { in-out} effective action for the system, which develops an imaginary part, hence a non-vanishing probability for the decay (because of friction) of the initial vacuum state. Secondly, we evaluate another observable: the vacuum expectation value of the frictional force, using the { in-in} or Closed Time Path formalism. Explicit results are presented for zero-width mirrors and half-spaces, in a model where the microscopic degrees of freedom at the mirrors are a set of identical quantum harmonic oscillators, linearly coupled to $\phi

Solving Integral Equations by Means of Fixed Point Theory

The authors thank their respective universities. A.F. Roldan Lopez de Hierro is grateful to Ministerio de Ciencia e Innovacion by Project PID2020-119478GB-I00 and to Program FEDER Andalucia 2014-2020 by Project A-FQM-170-UGR20.One of the most interesting tasks in mathematics is, undoubtedly, to solve any kind of equations. Naturally, this problem has occupied the minds of mathematicians since the dawn of algebra. There are hundreds of techniques for solving many classes of equations, facing the problem of finding solutions and studying whether such solutions are unique or multiple. One of the recent methodologies that is having great success in this field of study is the fixed point theory. Its iterative procedures are applicable to a great variety of contexts in which other algorithms fail. In this paper, we study a very general class of integral equations by means of a novel family of contractions in the setting of metric spaces. The main advantage of this family is the fact that its general contractivity condition can be particularized in a wide range of ways, depending on many parameters. Furthermore, such a contractivity condition involves many distinct terms that can be either adding or multiplying between them. In addition to this, the main contractivity condition makes use of the self-composition of the operator, whose associated theorems used to be more general than the corresponding ones by only using such mapping. In this setting, we demonstrate some fixed point theorems that guarantee the existence and, in some cases, the uniqueness, of fixed points that can be interpreted as solutions of the mentioned integral equations.Instituto de Salud Carlos III Spanish Government European Commission PID2020-119478GB-I00Program FEDER Andalucia 2014-2020 A-FQM-170-UGR2

Identification of the water stress level in olive trees during pit hardening using the trunk growth rate indicator.

Water scarcity is generating an increasing interest in deficit irrigation scheduling. The trunk diameter fluctuations are daily cycles that have been suggested as tools for irrigation scheduling. The trunk growth rate (TGR) was suggested as the best indicator for olive trees during pit hardening. The aim of this work is to clarify how the TGR could be used to identify water stress levels. The experiment was performed during the 2017 season, in a commercial, super-high-density orchard in Carmona (Seville, Spain). Four different irrigation treatments were performed according to midday stem water potential values and TGR. The data obtained were very variable and both indicators presented a wide range of water status throughout the season. The maximum trunk diameter data clearly showed the pattern of the trees water status but the comparison between treatments and the identification of the water stress level was not possible. The average TGR was linked to the midday stem water potential, but with a minimum amount of data. Irrigation scheduling based on the average TGR was difficult because of the great increases in some daily TGR values. For clarity, the pool of data was grouped by midday stem water potential. These water stress levels were characterized using the weekly frequency of TGR values. The increase of water stress reduced the frequency of values between -0.1 and 0.3mm day-1 from 60% to less than 25%. Moderate water stress levels increased the percentage of values lower than -0.3mm day-1 from 7% to 37%. The most severe water stress conditions increased the TGR values between -0.3 and -0.1mm day-1 from 16% up to 22%.IRNASINSTITUTO DE LA GRASACSI

Molecular dynamics of ferroelectric polymeric systems as studied by incoherent quasielastic neutron scattering

11 págs.; 15 figs.We have studied by incoherent quasielastic neutron scattering the molecular dynamics of the ferroelectric copolymers of vinylidene fluoride and trifluoroethylene with two different molar ratios. Thermal hysteresis effects accompanying the structural changes observed in these materials are found. In the temperature range investigated three motions were identified: (i) a vibrational motion of Debye-Waller type which shows increasing amplitude until the vicinity of the Curie temperature and then it follows a Q4 law, (ii) a slow jump diffusive motion of each chain in the restricted volume defined by other chains, thermally activated with an activation barrier of 8 kcal/mol, and (iii) a fast local diffusive motion with only some fraction of the chains concerned. © 1994 The American Physical Society.Grateful acknowledgments is due to DGICYT (Grant No. PB91-0355), to CICYT (Grant No. MAT92-148), to CICYT (Grant No. MAT94-0740E), to the Consejeria de Educacion de la Comunidad de Madrid (Grant No. 284/92) and to Fundacion Domingo Martinez (Grant No. 1992/93) for the generous support of this investigation.Peer Reviewe

Effects of threat and motivation on classical musicians’ professional performance practice during the Covid-19 pandemic

In the past 2 years our world has experienced huge disruptions because of COVID-19. The performing arts has not been insulated from these tumultuous events with the entire music industry being thrown into a state of instability due to the paralyzing effects of the COVID-19 pandemic. In this study, we examined how classical professional musicians’ ability to cope with uncertainty, economic struggles, and work-life interplay during COVID-19 was influenced by various factors that affect a crucial part of the development and sustainment of music careers: musicians’ practice. We analyzed responses to an online survey of 309 classical performing musicians from 41 countries in Europe and Latin America across three pandemic stages: immediately before the pandemic, during the pandemic, and when vaccines were being made available and lockdowns were being reduced or lifted. Structural equation modeling indicates relationships between perceptions of threat at the peak of the pandemic and the musicians Self- or External-Based Motivation for the three periods in which respondents were asked to reflect. Findings suggest that musicians who are more internally self-motivated seemed to be more resilient to the pandemic threats and more capable of managing their practicing routines, whereas more externally motivated musicians experienced a reduction in their dedicated time to practice during lockdown. We suggest pedagogical and policy implications, as well as future lines of research that are oriented toward supporting professional musicians in assessing and understanding their motivational drives so that they can cope with situations that disrupt their professional lives

El evento científico, un medio para acercar la academia con el sector privado

Los eventos científicos brindan un espacio para la interacción entre los distintos actores que desarrollan las diferentes áreas del conocimiento y a la vez es un punto importante de convergencia entre el sector privado y la academia.  Gracias a esta interacción, los representantes del sector privado encuentran posibles soluciones a sus problemáticas y los investigadores hallamos focos de interés que pueden definir las rutas futuras de trabajo.Los eventos científicos brindan un espacio para la interacción entre los distintos actores que desarrollan las diferentes áreas del conocimiento y a la vez es un punto importante de convergencia entre el sector privado y la academia.  Gracias a esta interacción, los representantes del sector privado encuentran posibles soluciones a sus problemáticas y los investigadores hallamos focos de interés que pueden definir las rutas futuras de trabajo