Influence of Reynolds number on theoretical models for trailing vortices

We conduct direct numerical simulations for a NACA0012 airfoil at Reynolds numbers (Re) ranging from 300 to 7000 to determine the wake behavior behind this wing profile. We characterize the structure of the wing-tip vortex, finding a reasonable agreement with experimental results at Re=7000. In addition, we model the trailing vortex theoretically, thus obtaining the parameters for Batchelor’s and Moore and Saffman’s models. We compare the results of the best fitting for the axial vorticity and the azimuthal velocity, finding only small discrepancies. The main contribution of this research work is to study the evolution of these theoretical parameters as function of the Reynolds number. We observe that the wake becomes unstable at Re ≈1200, in agreement with previous results. These instabilities in the wake behind the wing produce a change in the trend of theoretical parameters (keywords: vortex dynamics, trailing vortices, theoretical models).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Parabolic trough collectors. Fundamentals of heat transfer applied to solar thermal energy.

Solar thermal energy has undergone major development in recent years. The most widely used technologies are central receiver solar towers and parabolic trough collectors (PTC)[1]. The latter technology has great advantages due to its higher optical and thermal efficiency, but, despite being a well-proven technique, it presents certain problems inherent to the manufacturing and durability of some critical elements in the system. They are generally composed of an absorber tube surrounded by a glass cover and in the intermediate space, a vacuum is created to minimize thermal losses by convection[2]. The absorber tube is located at the focal line of a parabolic mirror that concentrates sun’s rays. To predict the thermal behavior of this type of system, ray-tracing techniques are used to determine the thermal load and accurate correlations are also needed to calculate the convective heat transfer. Also, the original design shows some problems such as the selective coating applied on the absorber surface, whose thermal performance decays with time. Besides, the metal-glass welding are also a significant weak spot, which due to the thermal expansion can cause the partial or total loss of the vacuum in the aforementioned annulus. In this work we present the results of the modeling of this type of systems in different working configurations, as well as a new design proposal to improve the thermal transfer in this type of systems.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Memristor variability and stochastic physical properties modeling from a multivariate time series approach

A powerful time series analysis modeling technique is presented to describe cycle-to-cycle variability in memristors. These devices show variability linked to the inherent stochasticity of device operation and it needs to be accurately modeled to build compact models for circuit simulation and design purposes. A new multivariate approach is proposed for the reset and set voltages that accurately describes the statistical data structure of a resistive switching series. Experimental data were measured from advanced hafnium oxide based devices. The models reproduce the experiments correctly and a comparison of the multivariate and univariate approaches is shown for comparison

Video-based assistance system for training in minimally invasive surgery

In this paper, the development of an assisting system for laparoscopic surgical training is presented. With this system, we expect to facilitate the training process at the first stages of training in laparoscopic surgery and to contribute to an objective evaluation of surgical skills. To achieve this, we propose the insertion of multimedia contents and outlines of work adapted to the level of experience of trainees and the detection of the movements of the laparoscopic instrument into the monitored image. A module to track the instrument is implemented focusing on the tip of the laparoscopic tool. This tracking method does not need the presence of artificial marks or special colours to distinguish the instruments. Similarly, the system has another method based on visual tracking to localize support multimedia content in a stable position of the field of vision. Therefore, this position of the support content is adapted to the movements of the camera or the working area. Experimental results are presented to show the feasibility of the proposed system for assisting in laparoscopic surgical training

EVALUACIÓN DE LA SUSTENTABILIDAD POSTERIOR A UNA INTERVENCIÓN AGROECOLÓGICA EN EL SUBTRÓPICO DEL ALTIPLANO CENTRAL DE MÉXICO

La sustentabilidad del rancho universitario de Temascaltepec, perteneciente a la Universidad Autónoma del Estado de México se evaluó por medio de indicadores. A partir de la caracterización y diagnóstico se diseñó una propuesta de manejo sustentable de recursos naturales. Para la instalación, operación y evaluación de algunos componentes de dicha propuesta se realizaron experimentos durante tres años. Así se incluyeron la evaluación comparativa de parcelas para producción de forrajes en monocultivo y asociación, lotes de árboles multipropósito y lotes de contención de erosión con técnicas vegetativas. Los rendimientos de forrajes mejoraron gradualmente durante el periodo de evaluación y mostraron mayor calidad para los forrajes asociados. Las diferentes especies arbóreas mostraron grados divergentes de adaptación y desarrollo debido a las condiciones adversas del suelo y clima. Las técnicas vegetativas fueron eficaces para contener los procesos erosivos acelerados. La comparación del estado final del sistema con el estado inicial permitió observar mejoras notables para la mayoría de los indicadores ambientales y sociales, aunque la rentabilidad fue negativa debido al alto costo de la instalación de los componentes. Se comprobó la relevancia de esta metodología, tanto para el diseño y operación de la propuesta, como para la evaluación de sustentabilidad

Modeling the variability of Au/ Ti/h BN/Au memris t ive devices

The variability of memristive devices using multilayer hexagonal boron nitride (h-BN) coupled with Ti and Au electrodes (i.e., Au/Ti/h-BN/Au) is analyzed in depth using different numerical techniques. We extract the reset voltage using three different methods, quantified its cycle-to-cycle variability, calculated the charge and flux that allows to minimize the effects of electric noise and the inherent stochasticity of resistive switching, described the device variability using time series analyses to assess the “memory” effect, and employed a circuit breaker simulator to understand the formation and rupture of the percolation paths that produce the switching. We conclude that the cycle-to-cycle variability of the Au/Ti/h-BN/Au devices presented here is higher than that previously observed in Au/h-BN/Au devices, and hence they may be useful for data encryption.Ministry of Science and Technology of China (2019YFE0124200, 2018YFE0100800)National Natural Science Foundation of China (61874075)Consejería de Conocimiento, Investigación y Universidad, Junta de Andalucía (Spain) and European Regional Development Fund (ERDF) under projects A-TIC-117-UGR18, A-FQM-66-UGR20, A-FQM-345- UGR18, B-TIC-624-UGR20 and IE2017-5414Grant PGC2018-098860-B-I00 supported by MCIU/AEI/FEDERMaria de Maeztu” Excellence Unit IMAG, reference CEX2020-001105-M, funded by MCIN/AEI/10.13039/501100011033King Abdullah University of Science and Technolog

EVALUACIÓN PRELIMINAR DE LA SUSTENTABILIDAD DE UNA PROPUESTA AGROECOLOGICA, EN EL SUBTRÓPICO DEL ALTIPLANO CENTRAL DE MÉXICO

La evaluación de sustentabilidad mediante enfoques sistémicos, ha recibido atención recientemente dado su potencial como herramienta de toma de decisiones. Por otra parte, las fincas experimentales universitarias requieren cumplir con funciones de investigación, docencia y extensión, además de ser ambiental y económicamente sustentables. Se realizó la evaluación de una finca universitaria ubicada en el subtrópico del Altiplano Central de México. En la primera fase del estudio (2004) se realizaron la caracterización, el diagnóstico y la evaluación inicial. Se identificaron y priorizaron los principales problemas, para los cuales se derivaron propuestas de solución bajo un enfoque agroecológico. Posteriormente se seleccionaron y midieron 14 indicadores de carácter ambiental, económico y social. Los resultados muestran valores bajos en la mayoría de los indicadores, como resultado de una baja integración entre subsistemas y la ausencia de prácticas de conservación de recursos. La metodología utilizada fue útil para ampliar el entendimiento sobre los procesos ecosistémicos y plantear técnicas y alternativas de solución

Sevoflurano como coadyuvante en la sedación durante ventilación mecánica en pacientes médicos de unidad de cuidados intensivos: resultados preliminares en una serie de casos

ResumenObjetivoExplicar nuestra experiencia preliminar en la utilización de sedación inhalatoria de manera estandarizada con sevoflurano mediante el dispositivo Anaesthetic Conserving Device en pacientes críticos intubados en nuestra unidad de cuidados intensivos (UCI).PacientesSe ha utilizado en 9 casos, en pacientes adultos (6 hombres y 3 mujeres), durante un periodo de 24meses.ResultadosSe ha conseguido una adecuada implantación del protocolo por parte de médicos y personal de enfermería, logrando los objetivos de sedación fijados en un primer momento (RASS 0, −2) y sin obtener resultados adversos ni efectos secundarios a nivel hepático y/o renal.ConclusionesEn nuestra limitada experiencia, la sedación inhalatoria con sevoflurano coadyuvante en UCI es una técnica segura y complementaria al uso de fármacos intravenosos, como propofol, remifentanilo y midazolam, utilizados habitualmente para lograr una sedación guiada por objetivos.AbstractObjectiveTo disclose our preliminary experience in inhalation sedation with sevoflorane in a standardized manner using the Anaesthetic Conserving Device in intubated, critically ill patients in our ICU.PatientsIt has been used in 9 cases of adult patients (6 men and 3 women) over 24 months.ResultsA proper implementation of the protocol by physicians and the nursing staff has been achieved, meeting the goals established for sedation (RASS 0, −2) free of hepatic or renal adverse outcomes or side effects.ConclusionsIn our limited experience, adjuvant inhalation sedation with sevoflorane in the ICU is safe and complementary to the use of intravenous drugs such as propofol, remifentanil and midazolam, which are currently commonly used to achieve goal-directed sedation

Methods and Tools for Objective Assessment of Psychomotor Skills in Laparoscopic Surgery

Training and assessment paradigms for laparoscopic surgical skills are evolving from traditional mentor–trainee tutorship towards structured, more objective and safer programs. Accreditation of surgeons requires reaching a consensus on metrics and tasks used to assess surgeons’ psychomotor skills. Ongoing development of tracking systems and software solutions has allowed for the expansion of novel training and assessment means in laparoscopy. The current challenge is to adapt and include these systems within training programs, and to exploit their possibilities for evaluation purposes. This paper describes the state of the art in research on measuring and assessing psychomotor laparoscopic skills. It gives an overview on tracking systems as well as on metrics and advanced statistical and machine learning techniques employed for evaluation purposes. The later ones have a potential to be used as an aid in deciding on the surgical competence level, which is an important aspect when accreditation of the surgeons in particular, and patient safety in general, are considered. The prospective of these methods and tools make them complementary means for surgical assessment of motor skills, especially in the early stages of training. Successful examples such as the Fundamentals of Laparoscopic Surgery should help drive a paradigm change to structured curricula based on objective parameters. These may improve the accreditation of new surgeons, as well as optimize their already overloaded training schedules