Comparison between Hemiarthroplasty in the First Proximal Phalanx and Keller's Arthroplasty. A Finite Element Study

Hallux valgus and hallux rigidus are the most common pathologies in the first ray of the foot. Arthroplasty can restore the mobility of the joint but is a destructive procedure. This paper presents three finite element analysis of the foot studying two different kinds of arthroplasty

Droplet charging by high voltage discharges and its influence on precipitation enhancement

Laboratory experiments were performed to determine the effect of electrical charges transferred on droplets by electrical discharges on their growth by collision and coalescence. A twin cloud chamber was built inside a large cold room and was filled with cloudy air. One chamber was used as the control chamber and, therefore, was left unperturbed. On the other hand, in an experimental chamber, electrical discharges were produced. Droplets grow during a free fall of 1. m, and the droplet spectrum was sampled by microscope slides covered in Formvar. The experimental arrangement could also measure charge on individual drops between 325 and 415 μm in diameter by using small induction rings.After comparing the spectra from both chambers, a shift towards larger sizes was observed in the cloud that sustained electrical discharge. Also, by measuring the charge on the droplets, it could be observed that the electrical discharge transferred charges of both signs. Discussions about the relevance for cloud seeding and fog elimination are carried out. © 2012 Elsevier B.V.Fil: Pérez Hortal, Andrés Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: García, Sebastián Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Caranti, Giorgio Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentin

A methodology for the calculation of typical gas concentration values and sampling intervals in the power transformers of a distribution system operator†

Predictive maintenance strategies in power transformers aim to assess the risk through the calculation and monitoring of the health index of the power transformers. The parameter most used in predictive maintenance and to calculate the health index of power transformers is the dissolved gas analysis (DGA). The current tendency is the use of online DGA monitoring equipment while continuing to perform analyses in the laboratory. Although the DGA is well known, there is a lack of published experimental data beyond that in the guides. This study used the nearest-rank method for obtaining the typical gas concentration values and the typical rates of gas increase from a transformer population to establish the optimal sampling interval and alarm thresholds of the continuous monitoring devices for each power transformer. The percentiles calculated by the nearest-rank method were within the ranges of the percentiles obtained using the R software, so this simple method was validated for this study. The results obtained show that the calculated concentration limits are within the range of or very close to those proposed in IEEE C57.104-2019 and IEC 60599:2015. The sampling intervals calculated for each transformer were not correct in all cases since the trend of the historical DGA samples modified the severity of the calculated intervals.This work was partially financed by the EU Regional Development Fund (FEDER) and the Spanish Government under RETOS-COLABORACIÓN RTC-2017-6782-3 and by the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 864579 (FLEXIGRID)

Relationship between self-efficacy and anxiety towards science in high school studentes

El aprendizaje de las ciencias está determinado por factores personales, como la autoeficacia, que se manifiestan durante el estudio de materias de Física, Química, Biología y Ciencias de la Tierra y del Ambiente. En este trabajo se describe el tipo de relación entre la autoeficacia y la ansiedad ante las ciencias, para lo que se dispuso de una muestra aleatoria de alumnos del bachillerato (N = 215, con edades de 15 a 21 años) a los que, mediante encuesta tipo Likert, se les aplicó el instrumento de Autoeficacia General de Baessler y Schwarzer y el de Ansiedad ante las Ciencias de Britner y Pajares. Los resultados mostraron correlación en dirección negativa (d de Somers = -.305), con buen nivel de significancia (Sig. = .000) para las variables señaladas. La población analizada muestra índices positivos de autoficacia general, lo que explica los bajos niveles de ansiedad.Science learning is influenced by such personal factors as self-efficacy that are manifested during the study of subjects like Physics, Chemistry, Biology, and Earth and Environmental Sciences. This study explores the relationship between self-efficacy and anxiety towards science in a random sample of high-school students (N = 215, ages from 15 to 21) to which the Baessler’s and Schwarcer’s Self-Efficacy Scale and the Britner’s and Pajares’ Scale of Anxiety towards Science were administered. Results show a negative correlation (Somers’ d = -0.305) with a good level of significance (Sig. = .000) between the variables examined. Students show positive indexes of general self-efficacy, which explain the low levels on anxiety

A comparison of mechanical and ultrasonic anemometers for ampacity thermal rating in overhead lines

CIGRE TB601 guide for thermal rating calculations recommends the use of ultrasonic anemometers over mechanical devices [1]. This paper aims to compare the mechanical and ultrasonic wind speed measurement technologies for the purpose of dynamic ampacity rating. The comparison consists of applying the measurements of both anemometers (placed in the same spot) to the computation of ampacity in the same overhead line, and evaluating the diferences at different speed ranges.This work was supported by the Spanish Government under the R+D initiative INNPACTO with reference IPT- 2011-1447-920000 and Spanish R+D initiative with reference ENE2013-42720-R. The authors of this article would also like to acknowledge Viesgo for its continuous support to the dynamic ampacity rating line of investigation

Determination of transformer oil contamination from the OLTC gases in the power transformers of a distribution system operator

Power transformers are considered to be the most important assets in power substations. Thus, their maintenance is important to ensure the reliability of the power transmission and distribution system. One of the most commonly used methods for managing the maintenance and establishing the health status of power transformers is dissolved gas analysis (DGA). The presence of acetylene in the DGA results may indicate arcing or high-temperature thermal faults in the transformer. In old transformers with an on-load tap-changer (OLTC), oil or gases can be filtered from the OLTC compartment to the transformer?s main tank. This paper presents a method for determining the transformer oil contamination from the OLTC gases in a group of power transformers for a distribution system operator (DSO) based on the application of the guides and the knowledge of experts. As a result, twenty-six out of the 175 transformers studied are defined as contaminated from the OLTC gases. In addition, this paper presents a methodology based on machine learning techniques that allows the system to determine the transformer oil contamination from the DGA results. The trained model achieves an accuracy of 99.76% in identifying oil contamination.This work was partially financed by the EU Regional Development Fund (FEDER) and the Spanish Government under RETOS-COLABORACIÓN RTC-2017-6782-3 and by the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 864579 (FLEXIGRID)

Biomechanical Evaluation of Three New Implants for the First Metatarsophalangean Joint of the Human Foot

Hallux valgus y hallux rigidus son las dos patologías más comunes en el primer radio del pie. Los tratamientos para estas patologías han tenido un avance considerable en los ultimos a~nos. Entre las tecnicas quirurgicas destructivas están la artrodesis, artroplastia y quilectomia mientras que entre las técnicas quirúrgicas no destructivas se incluyen varios tipos de osteotomías. La artroplastia de la primera articulación metatarsofalángica es un procedimiento que conserva la dorsiflexión de la articulación, además de aliviar el dolor causado por las patologías mencionadas. Por otro lado, realizar un análisis estructural del pie mediante métodos análiticos es sumamente difícil por lo que los métodos numéricos son una buena herramienta para comprender la biomecánica del pie, en particular los análisis de elementos finitos. El objetivo de esta investigación es realizar una evaluación biomecánica del pie tras de haberse desarrollado los diferentes tipos de artroplastia en la primera articulación metatarsofalángica. Cinco modelos de elementos finitos son comparados y tres diferentes implantes son investigados. Los resultados en los modelos de elementos finitos arrojan consecuencias en la biomecánica del pie tras haberse desarrollado los distintos procesos de artroplastia. Para los implantes investigados se realiza un estudio a fatiga partiendo de los resultados de las simulaciones computacionales, basándose enun enfoque de deformación y realizando aproximaciones con series de Taylor de primer orden, utilizando las expresiones de Ramberg-Osgood y Coffin-Basquin-Manson para la construcción de un modelo B de salto de unidad.Hallux valgus and hallux rigidus are the two most common pathologies in the first ray of the foot. The treatments against these pathologies have had considerable advances in recent years. The destructive surgical techniques include arthrodesis, arthroplasty, and cheilectomy, while the nondestructive surgical techniques include many kinds of osteotomies. Arthroplasty of the first metatarsophalangeal joint is a procedure that preserves the dorsiflexion of the joint, in addition to relieving pain caused by the aforementioned pathologies. On the other hand, performing a structural analysis of the foot using analytical methods is extremely difficult, so numerical methods are a good tool to understand the biomechanics of the foot, particularly finite element analysis. The objective of this research is to develop a biomechanical evaluation of the foot after having developed the different types of arthroplasty in the first metatarsophalangeal joint. Five finite element models are compared and three different implants are investigated. The results in the finite element models show consequences in the biomechanics of the foot after the different arthroplasty processes have been developed. For the implants investigated, a fatigue study is developed from the results of the computational simulations, based on a strain approach and making first-order Taylor series expansions, using the Ramberg-Osgood and Coffin-Basquin-Manson expressions for building a one-step B model.<br /

CO2 footprint reduction and efficiency increase using the dynamic rate in overhead power lines connected to wind farms

Since the first wind farms began operating in the early 1980s, several important factors have changed in the overall picture of energy politics worldwide. The total renewable wind energy capacity of Spain currently accounts for more than 20% of the total installed capacity, which makes integration into the grid challenging for wind farm owners as well as electricity transportation and distribution companies. The smart-grid concept, which focuses on real-time monitoring and dynamic rating operation of power lines, is an important component in the solution to these new challenges. This paper explains how a more efficient operation of energy-generating activities via dynamic rating of the electric grid due to a better knowledge of the main parameters contributes to more clean, renewable energy and decreases the CO2 footprint. The dynamic rating operation of a Spanish overhead power line is analysed, and different scenarios are studied. The dynamic rate achieved in 2015 has saved more than 1100 tonnes of CO2 and has generated over 240,000 € of extra income. This dynamic rating operation also increased the actual annual energy generated from 231.5 GW h to 834.7 GW h with only a 2% greater loss along the line due to Joule and magnetic effects.This work was supported by the Spanish Government under the R+D initiative INNPACTO with reference IPT-2011-1447-920000, the Spanish R+D initiative with reference ENE-2013-42720-R and RETOS RTC-2015-3795-3. The authors also acknowledge support from Viesgo