Piezoelectric transducer design optimization

To respond to the design of a torsion sensor into mechanical ultrasonic tissue applications, it is necessary to use FEM Finite Element Models. Through a simplified analytical model of torsion transducer, we determine the resonant frequency for a torque transducer ultrasonic waves. It is computationally validated. More specifically the idea is to refine and optimize the design to be applied to the detection of preterm birth identifying changes in the consistency of the cervical tissue through the shear modulus measurements. Therefore, a model with a disk transmitter and a ring receiver for easy accessibility was performed and sensitivity analysis to find the range of optimal design values with this application was calculated. Therefore, it is neces- sary to optimize the piezoelectric transducer model design regarding two types of parameters. On one hand the design parameters, and on the other hand the model parameters that characterize the specimen. The forward problem is obtained by performing a three-dimensional finite element simulation. The experimental measurements are simulated by adding a gaussian noise as a percentage of the RMS of the numerically predicted signals. In addition, a semi-analytical estimate of the probability of detection (POD) is developed to provide a rational criterion to optimize the experimental design.Para responder al diseño de un sensor de torsión con aplicaciones a la mecánica tisular ultrasónica, es necesario el uso de modelos de elementos finitos FEM como procedimiento directo. A través de un modelo simplificado de análisis de transductor de torsión, se determina la frecuencia de resonancia que se valida computacionalmente. Más específicamente, la idea es refinar y optimizar el diseño que debe aplicarse a la detección de parto prematuro identificar los cambios en la consistencia del tejido del cuello uterino a través de medidas del módulo G . Por lo tanto, se elige un modelo con un disco transmisor y un anillo receptor para facilitar la accesibilidad en el diseño y se realizó un análisis de sensibilidad para encontrar el rango de valores óptimos con esta aplicación. Para optimizar el diseño del modelo del transductor piezoeléctrico con respecto a dos tipos de parámetros. Por un lado los parámetros de diseño, y por otra parte los parámetros del modelo que caracterizan la muestra. Las medi- ciones experimentales se simulan mediante la adición de un ruido gaussiano como un porcentaje de la RMS de las señales predichas numéricamente. Además, una estimación semi-analítica de la probabilidad de detección (POD) se ha desarrollado para proporcionar un criterio racional para optimizar el diseño experimental.Universidad de Granada. Departamento de Mecánica de Estructuras e Ingeniería Hidráulica. Máster Universitario en Estructuras, curso 2011-2012Este trabajo a sido financiado por el Ministerio de Educación a través de Dpi2010-1706

Nonlinear Classical Elasticity Model for Materials with Fluid and Matrix Phases

Materials with fluid and matrix phases present different acoustic responses in each phase. While longitudinal waves propagate in both phases, shear waves do it only through the solid matrix. Longitudinal waves are mainly described by volumetric propagation and shear waves by deviatoric processes. In the case of nonlinear propagation cross effects occur between both components. This paper presents a new classical nonlinear model proposing a constitutive equation that separates volumetric and deviatoric effects. Four nonlinear constants of third order are defined. The formulation is compared to constitutive equations with Landau constants for weakly elasticity and both types of nonlinear constants related. Some reinterpretation of the Landau's constants arises in terms of parallel or cross nonlinear effects between volumetric and deviatoric components.Ministry of Education [Grant nos. DPI2014-51870-R, DPI2017-85359-R, and UNGR15-CE-3664]Ministry of Health [DTS15/00093 and PI16/00339]Junta de Andalucía [PIN-0030-2017 and PI0107-2017 projects]University of Granada [PP2017- PIP2019

Service quality perceptions in higher education institutions: the case of a colombian university

Recognizing that higher education institutions (HEI) are currently competing aggressively through competitive advantages and high service quality, the assessment of the service quality is essential to provide information on the effectiveness of educational plans and improvement programs. This article presents a study which tests the 5Q’s model proposed by Zineldin (2007), and examines the service quality factors that most impact on student satisfaction. Factor analysis and regression analysis showed significant variables in explaining student satisfaction as: trust developed toward the university and the academic program, and the perception they have of assessment techniques as a challenge to improve intellectual growt

La gestió de les instal·lacions aquàtiques cobertes

El següent article té com a objectiu caracteritzar el funcionament de les instal•lacions aquàtiques cobertes. A través d'una mostra de 14 gestors s'analitza la importància que tenen diferents decisions per a la posada en pràctica dels programes aquàtics. La recollida de dades es va produir mitjançant el qüestionari Q.A.G.I.A. (Qüestionari per a l'Anàlisi del Gestor d’Instal·lacions Aquàtiques) (Moreno, 1997). Una de les parts d'aquest instrument li demana al gestor que valori aspectes relacionats amb la gestió de la instal·lació i els programes aquàtics, entre els que ressalten elements de màrqueting i promoció, relació dels programes amb els òrgans de gestió, ofertar programes i explotació de la instal·lació aquàtica coberta i qüestions pròpies de la gestió de la instal·lació. Entre les conclusions a destacar, vam trobar que els programes de natació escolar són els que millor funcionen, seguits de la natació per a adults, natació competitiva i manteniment, adduint els seus motius a l'especialització del professorat. També ressalta que el director tècnic i la demanda pública són els òrgans que més influeixen sobre l'engegament dels programes i que confirmen les aportacions de Ramos i cols. (1996)

La gestión de las instalaciones acuáticas cubiertas

El siguiente artículo tiene como objetivo caracterizar el funcionamiento de las instalaciones acuáticas cubiertas. A través de una muestra de 14 gestores se analiza la importancia que tienen diferentes decisiones para la puesta en práctica de los programas acuáticos. La recogida de datos se produjo a través del cuestionario C.A.G.IA. (Cuestionario para el Análisis del Gestor de Instalaciones Acuáticas) (Moreno, 1997). Una de las partes de este instrumento le pide al gestor que valore aspectos relacionados con la gestión de la instalación y los programas acuáticos, entre los que resaltan elementos de marketing y promoción, relación de los programas con los órganos de gestión, oferta de programas y explotación de la instalación acuática cubierta y cuestiones propias de la gestión de la instalación. Entre las conclusiones a destacar, encontramos que los programas de natación escolar son los que mejor funcionan, seguidos de la natación para adultos, natación competitiva y mantenimiento, aduciendo sus motivos a la especialización del profesorado. También resalta que el director técnico y la demanda pública son los órganos que más influyen sobre la puesta en marcha de los programas y que confirman las aportaciones de Ramos y cols. (199

Video pulse rate variability analysis in stationary and motion conditions

Background: In the last few years, some studies have measured heart rate (HR) or heart rate variability (HRV) parameters using a video camera. This technique focuses on the measurement of the small changes in skin colour caused by blood perfusion. To date, most of these works have obtained HRV parameters in stationary conditions, and there are practically no studies that obtain these parameters in motion scenarios and by conducting an in-depth statistical analysis. Methods: In this study, a video pulse rate variability (PRV) analysis is conducted by measuring the pulse-to-pulse (PP) intervals in stationary and motion conditions. Firstly, given the importance of the sampling rate in a PRV analysis and the low frame rate of commercial cameras, we carried out an analysis of two models to evaluate their performance in the measurements. We propose a selective tracking method using the Viola–Jones and KLT algorithms, with the aim of carrying out a robust video PRV analysis in stationary and motion conditions. Data and results of the proposed method are contrasted with those reported in the state of the art. Results: The webcam achieved better results in the performance analysis of video cameras. In stationary conditions, high correlation values were obtained in PRV parameters with results above 0.9. The PP time series achieved an RMSE (mean ± standard deviation) of 19.45 ± 5.52 ms (1.70 ± 0.75 bpm). In the motion analysis, most of the PRV parameters also achieved good correlation results, but with lower values as regards stationary conditions. The PP time series presented an RMSE of 21.56 ± 6.41 ms (1.79 ± 0.63 bpm). Conclusions: The statistical analysis showed good agreement between the reference system and the proposed method. In stationary conditions, the results of PRV parameters were improved by our method in comparison with data reported in related works. An overall comparative analysis of PRV parameters in motion conditions was more limited due to the lack of studies or studies containing insufficient data analysis. Based on the results, the proposed method could provide a low-cost, contactless and reliable alternative for measuring HR or PRV parameters in non-clinical environments.Peer ReviewedPostprint (published version

Effectiveness of Chemical and Thermal Treatments on Control Rhizopus stolonifer Fruit Infection Comparing Tomato Cultivars with Different Sensitivities to Cracking

Tomatoes are among the most important horticultural crops; however, it is estimated that 30% of tomato yield is lost due to postharvest rot due to Rhizopus stolonifer, a fungus which requires lesions to initiate the infectious process. Tomato fruit cracking is a physiopathy which causes significant economic losses, since cracking is the door used by the fungus. In this experiment, 14 cultivars of tomato of different types were used. Fruit sampling was carried out in the middle of the crop cycle, coinciding with the peak of yield; then, the fruits were divided into two groups: one group was inoculated with Rhizopus in order to assess the effectiveness of washing, whilst the other was treated with sterile water. The fruits of each group were divided into lots to be treated with six washing treatments: dipping in hot water at 20, 40 and 60 °C for 20 s; the fruits were then sprayed with the following solutions: 0.6% of Hydrogen Peroxide 23% + Peracetic acid 15%; commercial bleach at 0.5% and 2% of Hydrogen Peroxide 50%. The control sample was not washed. The results show that there was an influence of cultivar on fruit cracking, which was strongly related with Rhizopus infection. Three cultivars were not susceptible to cracking, and therefore, were not sensitive to Rhizopus infection. The effectiveness of different washing treatments of tomato fruits depends on several factors; nonetheless, hot water treatment has been shown to be more effective than the use of chemical products such as commercial bleach or hydrogen peroxide. Another factor, the susceptibility of cultivars to cracking, determines the effectiveness of the washing treatment. The results provide an important basis for making decisions about the washing management of tomato fruits in packaging houses

The Impact of Direct Subsidies in Spain before and after the CAP'92 Reform

This paper focuses on the changes in farm e±ciency as a tool for policy analysis. The methodology is applied to the introduction of direct payments (DP) and the price sup- port reduction a®ecting large samples of individual farms with joint animal and vegetal production (comparing before and after CAP'92). The case study is justi¯ed for their relevance for Mediterranean forest and grazing land preservation in Spain. Using a non parametric method (DEA) we do not specify the production function of the farms, and can explain the impact of the direct payments on environmental adaptation and e±ciency for animal orientated farms before and after the (DP) introduction in 1992 (CAP'92 reform). Even though the direct payments increased sharply after the CAP'92 reform, in general, the new direct payment system turns out to be insu±cient to o®- set the fact that less environmentally friendly farms remain much more \e±cient," i.e. pro¯table for the farmer. The paper also studies the relationship of e±ciency with other policy relevant factors such as economic size. The results show that after the CAP'92 reform, the subsidy schedule was even more correlated with farm size than before, which we ¯nd to be counterproductive

Optimally tuned secondary system with viscous damping for vibration supression in torsional systems

Dynamic vibration absorbers and dampers are used to reduce the vibration responses of mechanical systems. A dynamic vibration absorber reduces vibrations of a primary system over a desired frequency range by absorbing the energy through responding with opposite phase to that of the force acting on the primary system. A damper, on the other hand, is a device used for reducing the magnitude of a shock or vibration by energy dissipation methods. The latter is extensively used in automotive engines to reduce torsional oscillations and in aircraft landing gears to damp out shimmy oscillations. This thesis aims to study and understand an optimally tuned viscous torsional vibration damper which is a combination of a dynamic vibration absorber and damper. The primary system whose vibration is to be suppressed, along with the optimally tuned viscous torsional vibration damper, will form a two-degree-of-freedom system which will be studied for its dynamic behaviour. The analytical model includes parameters such as primary inertia, damping and stiffness and secondary inertia, damping and stiffness. Numerical determination of optimum damping and stiffness for a secondary system is carried out and simulated results are presented and discussed. Validation of some aspects of the analytical studies is carried out with experimental investigation for the optimally tuned viscous torsional vibration damper and viscous damper. The test results of the two damping devices and the analytical investigations are compared. In addition, the study is extended, applying the optimally tuned viscous torsional vibration damper to a seven-degree-of-freedom torsional system namely to a four-stroke six-in-line cylinder internal combustion engine. This numerical study compares the engine response with and without damping. For both cases same excitation torque per cylinder was applied. The optimally tuned viscous damper reduces the vibrations

Elaboración y pronóstico de la estructura del costo de limpieza pública: (recolección/transporte/disposición final)

Evalúa el pronóstico presupuestal de la estructura de costos del servicio de limpieza pública para cada periodo(mensual), para ello utilizaremos el modelo ARIMA-AI, que es un método de análisis univariado de series temporales, quienes describen mejor el comportamiento dinámico de las variables y así también en la parte estocástica, estudiar las tendencias, las variaciones estacionales, las oscilaciones cíclicas, el grado de impredictibilidad, etc., y mediante la parte del análisis de intervención se pueden fijar hipótesis para ciertos acontecimientos económicos que se contrastan por medio de los modelos para validar o rechazar las hipótesis establecidas.Tesi