Understanding slope behavior through microseismic monitoring

It is well known that microseismic activity originates as an elastic stress wave at locations where the material is mechanically unstable. Monitoring techniques focusing on this phenomenon have been studied for over seventy years and are now employed in a wide range of applications. As far as the study of unstable slope is concerned, microseismic monitoring can provide real-time information about fracture formation, propagation and coalescence and may be an appropriate solution to reduce the risk for human settlements when structural mitigation interventions (e.g., rock fall nets and ditches) cannot cope with large rock volumes and high kinetic energies. In this work we present the datasets collected in a 4-year period with a microseismic monitoring network deployed on an unstable rock face in Northern Italy. We mainly focus on the classification and the interpretation of collected signals with the final aim of identifying microseismic events related to the kinematic and dynamic behavior of the slope. We have analyzed signal parameters both in time and frequency domains, spectrograms, polarization of 3-component recordings supported by principal component analysis. Clustering methodologies have been tested in order to develop an automatic classification routine capable to isolate a cluster with most of the events related to slope behavior and to discard all disturbances. The network features both geophones and meteorological sensors so that we could also explore the correlation between microseismic events and meteorological datasets, although no significant relationships emerged. On the contrary, it was found that the majority of the events collected by the network are short-time high-frequency signals generated by electromagnetic activity caused by near and far thunderstorms. Finally, we attempted a preliminary localization of the most promising events according to an oversimplified homogeneous velocity model to get a rough indication about the regions of the monitored area that could be prone to collapse

Analysis of microseismic signals collected on an unstable rock face in the Italian Prealps

In this work we present the analysis of more than 9000 signals collected from February 2013 to January 2016 by a microseismic monitoring network installed on a 300 m high limestone cliff in the Italian Prealps. The investigated area was affected by a major rockfall in 1969 and several other minor events up to nowadays. The network features five three-component geophones and a weather station and can be remotely accessed thanks to a dedicated radio link. We first manually classified all the recorded signals and found out that 95 per cent of them are impulsive broad-band disturbances, while about 2 per cent may be related to rockfalls or fracture propagation. Signal parameters in the time and frequency domains were computed during the classification procedure with the aim of developing an automatic classification routine based on linear discriminant analysis. The algorithm proved to have a hit rate higher than 95 per cent and a tolerable false alarm rate and it is now running on the field PC of the acquisition board to autonomously discard useless events. Analysis of lightning data sets provided by the Italian Lightning Detection Network revealed that the large majority of broad-band signals are caused by electromagnetic activity during thunderstorms. Cross-correlation between microseismic signals and meteorological parameters suggests that rainfalls influence the hydrodynamic conditions of the rock mass and can trigger rockfalls and fracture propagation very quickly since the start of a rainfall event. On the other hand, temperature seems to have no influence on the stability conditions of the monitored cliff. The only sensor deployed on the rock pillar next to the 1969 rockfall scarp typically recorded events with higher amplitude as well as energy. We deem that this is due to seismic amplification phenomena and we performed ambient noise recording sessions to validate this hypothesis. Results confirm that seismic amplification occurs, although we were not able to identify any spectral peak with confidence because the sensors used are not suitable for this task. In addition, we found out that there is a preferential polarization of the wave field along the EW direction and this is in agreement with the geological analysis according to which the pillar is overhanging towards the 1969 rockfall scarp and may preferentially evolve in a wedge failure. Event location was not possible because of the lack of a velocity model of the rock mass. We tried to distinguish between near and far events by analysing the covariance matrix of the three-component recordings. Although the parameters and the outcomes of this analysis should be evaluated very carefully, it seems that about 90 per cent of the considered microseismic signals are related to the stability conditions of the monitored area

Producir geometría con GeoGebra. Una experiencia colaborativa en el nivel universitario

Este trabajo pretende comunicar una experiencia colaborativa realizada por un grupo de docentes que tenemos la doble intención de modificar prácticas de enseñanza incluyendo las TIC en un aula de nivel universitario e iniciar un camino de estudio colaborativo en temas de enseñanza de la geometría en este nivel. El grupo colaborativo está conformado por siete profesores de matemática que desarrollamos actividades docentes en escuelas secundarias de la ciudad de Tandil y en los primeros años de las carreras que se dictan en la Facultad de Ciencias Exactas de la UNICEN. Dos de nosotros tenemos un recorrido de investigación en matemática y didáctica de la matemática respectivamente. Concretamente realizamos colaborativamente el diseño, estudio y puesta en el aula de una secuencia de dos problemas de geometría para trabajar con GeoGebra. También hicimos registros de esas escenas del aula y de nuestras propias discusiones grupales. En estos momentos iniciamos un análisis de la experiencia. En los apartados que siguen, explicitamos algunos puntos de partida respecto de cómo concebimos esta experiencia de trabajo colaborativo. Luego caracterizamos los problemas de la secuencia y su puesta en el aula de la materia “Geometría con regla y compás” de la carrera de Profesorado de Matemática a partir de las producciones de un alumno para resolverla y sus discusiones con el resto del grupo.Facultad de Humanidades y Ciencias de la Educació

Producir geometría con GeoGebra. Una experiencia colaborativa en el nivel universitario

Este trabajo pretende comunicar una experiencia colaborativa realizada por un grupo de docentes que tenemos la doble intención de modificar prácticas de enseñanza incluyendo las TIC en un aula de nivel universitario e iniciar un camino de estudio colaborativo en temas de enseñanza de la geometría en este nivel. El grupo colaborativo está conformado por siete profesores de matemática que desarrollamos actividades docentes en escuelas secundarias de la ciudad de Tandil y en los primeros años de las carreras que se dictan en la Facultad de Ciencias Exactas de la UNICEN. Dos de nosotros tenemos un recorrido de investigación en matemática y didáctica de la matemática respectivamente. Concretamente realizamos colaborativamente el diseño, estudio y puesta en el aula de una secuencia de dos problemas de geometría para trabajar con GeoGebra. También hicimos registros de esas escenas del aula y de nuestras propias discusiones grupales. En estos momentos iniciamos un análisis de la experiencia. En los apartados que siguen, explicitamos algunos puntos de partida respecto de cómo concebimos esta experiencia de trabajo colaborativo. Luego caracterizamos los problemas de la secuencia y su puesta en el aula de la materia “Geometría con regla y compás” de la carrera de Profesorado de Matemática a partir de las producciones de un alumno para resolverla y sus discusiones con el resto del grupo.Facultad de Humanidades y Ciencias de la Educació

Producir geometría con GeoGebra. Una experiencia colaborativa en el nivel universitario

Este trabajo pretende comunicar una experiencia colaborativa realizada por un grupo de docentes que tenemos la doble intención de modificar prácticas de enseñanza incluyendo las TIC en un aula de nivel universitario e iniciar un camino de estudio colaborativo en temas de enseñanza de la geometría en este nivel. El grupo colaborativo está conformado por siete profesores de matemática que desarrollamos actividades docentes en escuelas secundarias de la ciudad de Tandil y en los primeros años de las carreras que se dictan en la Facultad de Ciencias Exactas de la UNICEN. Dos de nosotros tenemos un recorrido de investigación en matemática y didáctica de la matemática respectivamente. Concretamente realizamos colaborativamente el diseño, estudio y puesta en el aula de una secuencia de dos problemas de geometría para trabajar con GeoGebra. También hicimos registros de esas escenas del aula y de nuestras propias discusiones grupales. En estos momentos iniciamos un análisis de la experiencia. En los apartados que siguen, explicitamos algunos puntos de partida respecto de cómo concebimos esta experiencia de trabajo colaborativo. Luego caracterizamos los problemas de la secuencia y su puesta en el aula de la materia “Geometría con regla y compás” de la carrera de Profesorado de Matemática a partir de las producciones de un alumno para resolverla y sus discusiones con el resto del grupo.Facultad de Humanidades y Ciencias de la Educació

Effects of the feeding solution composition on a reductive/oxidative sequential bioelectrochemical process for perchloroethylene removal

Chlorinated aliphatic hydrocarbons (CAHs) are common groundwater contaminants due to their improper use in several industrial activities. Specialized microorganisms are able to perform the reductive dechlorination (RD) of high-chlorinated CAHs such as perchloroethylene (PCE), while the low-chlorinated ethenes such as vinyl chloride (VC) are more susceptible to oxidative mechanisms performed by aerobic dechlorinating microorganisms. Bioelectrochemical systems can be used as an effective strategy for the stimulation of both anaerobic and aerobic microbial dechlorination, i.e., a biocathode can be used as an electron donor to perform the RD, while a bioanode can provide the oxygen necessary for the aerobic dechlorination reaction. In this study, a sequential bioelectrochemical process constituted by two membrane-less microbial electrolysis cells connected in series has been, for the first time, operated with synthetic groundwater, also containing sulphate and nitrate, to simulate more realistic process conditions due to the possible establishment of competitive processes for the reducing power, with respect to previous research made with a PCE-contaminated mineral medium (with neither sulphate nor nitrate). The shift from mineral medium to synthetic groundwater showed the establishment of sulphate and nitrate reduction and caused the temporary decrease of the PCE removal efficiency from 100% to 85%. The analysis of the RD biomarkers (i.e., Dehalococcoides mccartyi 16S rRNA and tceA, bvcA, vcrA genes) confirmed the decrement of reductive dechlorination performances after the introduction of the synthetic groundwater, also characterized by a lower ionic strength and nutrients content. On the other hand, the system self-adapted the flowing current to the increased demand for the sulphate and nitrate reduction, so that reducing power was not in defect for the RD, although RD coulombic efficiency was less

Rotation period determination for 3157 Novikov and 7485 Changchun

Collaborative photometric observations of two main-belt asteroids were conducted from five observatories in order to determine their synodic rotation periods. For 3157 Novikov we found a period of 9.952 ± 0.001 h with an amplitude of 0.31 ± 0.04 mag, for 7485 Changchun we found a period of 10.234 ± 0.001 h with an amplitude of 0.39 ± 0.02 mag.peer-reviewe

High speed drives review: machines, converters and applications

The development of new power electronic device and high performance magnetic materials are the main technological factors that have led both industries and research community to focus their attention on high speed electrical drives. Several papers have already outlined the electrical machine and/or converter topology choice for certain high speed application. This choice depends on the applications under study. This paper aims to identify the most important high speed applications. For each of them, the main design challenges are highlighted and an overview of available market product is presented