Electrocommunication for weakly electric fish

This paper addresses the problem of the electro-communication for weakly electric fish. In particular we aim at sheding light on how the fish circumvent the jamming issue for both electro-communication and active electro-sensing. A real-time tracking algorithm is presented

Task-related models for teaching and assessing iteration learning in high school

A number of studies report about students’ difficulties with basic flow-control constructs, and specifically with iteration. Although such issues are less explored in the context of pre-tertiary education, this seems to be especially the case for high-school programming learning, where the difficulties concern both the “mechanical” features of the notional machine as well as the logical aspects connected with the constructs, ranging from the implications of loop conditions to a more abstract grasp of the underlying algorithms. For these reasons, the aim of this work is to: i) identifying methodological tools to enhance a comprehensive understanding of the iteration constructs, ii) suggest strategies to teach iterations. We interviewed 20 experienced upper secondary teachers of introductory programming in different kinds of schools. The interviews were mainly aimed at ascertaining teachers’ beliefs about major sources of issues for basic programming concepts and their approach to the teaching and learning of iteration constructs. Once teachers’ perception of students’ difficulties have been identified, we have submitted, to a sample of 164 students, a survey which included both questions on their subjective perception of difficulty and simple tasks probing their understanding of iteration. Data collected from teachers and students confirm that iteration is a central programming concept and indicate that the treatment of conditions and nested constructs are major sources of students’ difficulties with iteration. The interviews allowed us to identify a list of problems that are typically presented by teachers to explain the iterations. Hence, a catalogue of significant program examples has been built to support students’ learning, tasks with characteristics different from those typically presented in class. Based on the outcome of previous steps, a survey to collect related information and good practices from a larger sample of teachers has been designed. Data collected have been analysed distinguishing an orientation towards more conceptual objectives, and one towards more practical objectives. Furthermore, regarding evaluation, a orientation focused on process-based assessment and another on product-based assessment. Finally, based on the outcome of previous students’ survey and drawing from the proposed examples catalogue, we have designed and submitted a new students’ survey, composed of a set of small tasks, or tasklets, to investigate in more depth on high-school students’ understanding of iteration in terms of code reading abilities. The chosen tasklets covered the different topics: technical program feature, correlation between tracing effort and abstraction, the role of flow-charts, students’ perception of self-confidence concerning high-level thinking skills.A number of studies report about students’ difficulties with basic flow-control constructs, and specifically with iteration. Although such issues are less explored in the context of pre-tertiary education, this seems to be especially the case for high-school programming learning, where the difficulties concern both the “mechanical” features of the notional machine as well as the logical aspects connected with the constructs, ranging from the implications of loop conditions to a more abstract grasp of the underlying algorithms. For these reasons, the aim of this work is to: i) identifying methodological tools to enhance a comprehensive understanding of the iteration constructs, ii) suggest strategies to teach iterations. We interviewed 20 experienced upper secondary teachers of introductory programming in different kinds of schools. The interviews were mainly aimed at ascertaining teachers’ beliefs about major sources of issues for basic programming concepts and their approach to the teaching and learning of iteration constructs. Once teachers’ perception of students’ difficulties have been identified, we have submitted, to a sample of 164 students, a survey which included both questions on their subjective perception of difficulty and simple tasks probing their understanding of iteration. Data collected from teachers and students confirm that iteration is a central programming concept and indicate that the treatment of conditions and nested constructs are major sources of students’ difficulties with iteration. The interviews allowed us to identify a list of problems that are typically presented by teachers to explain the iterations. Hence, a catalogue of significant program examples has been built to support students’ learning, tasks with characteristics different from those typically presented in class. Based on the outcome of previous steps, a survey to collect related information and good practices from a larger sample of teachers has been designed. Data collected have been analysed distinguishing an orientation towards more conceptual objectives, and one towards more practical objectives. Furthermore, regarding evaluation, a orientation focused on process-based assessment and another on product-based assessment. Finally, based on the outcome of previous students’ survey and drawing from the proposed examples catalogue, we have designed and submitted a new students’ survey, composed of a set of small tasks, or tasklets, to investigate in more depth on high-school students’ understanding of iteration in terms of code reading abilities. The chosen tasklets covered the different topics: technical program feature, correlation between tracing effort and abstraction, the role of flow-charts, students’ perception of self-confidence concerning high-level thinking skills

Mechanical characterization and modeling of the heavy tungsten alloy IT180

Pure tungsten or its alloys (WHA) find applications in several fields, especially due to the fact that these materials show a good combination of mechanical and thermal properties and they are commonly used in aerospace, automotive, metal working processes, military and nuclear technologies. Looking at the scientific literature, a lack in the mechanical characterization over wide ranges in temperature and strain-rates was found, especially for W-Ni-Cu alloys. In this work, the mechanical characterization and the consequent material modeling of the tungsten alloy INERMET® IT180 were performed. The material is actually used in the collimation system of the Large Hadron Collider at CERN and several studies are currently under development in order to be able to numerically predict the material damage in case of energy beam impact, but to do this, a confident strength model has to be obtained. This is the basis of this work, in which a test campaign in compression and tension at different strain-rates and temperatures was carried out. The dynamic tests were performed using Hopkinson Bar setups, and the heating of the specimen was reached using an induction coil system. The experimental data were, finally, used to extract the coefficient of three different material models via an analytical approach

Digital campaigning: day of reckoning

With the rise of the Tea Party and the decline in President Obama’s ratings, the upcoming US mid-term elections are going to be crucial. So two years after the triumph of Obama’s Internet-fuelled campaign it is a good time to debate the role of digital politics. Polis brought together ePolitics founder Colin Delany, a veteran of 15 years in the digital politics space, and UK political analyst, Anthony Painter, who has written a book about the US 2008 campaign, too

Can the effects of anthropogenic pressures and environmental variability on nekton fauna be detected in fishery data? Insights from the monitoring of the artisanal fishery within the Venice lagoon

Nekton communities in transitional ecosystems are naturally adapted to stressful conditions associated with high environmental variability. Human activities in these systems are likely to determine additional stress with a possible effect on fish fauna, hence on fisheries. In order to test the relative importance of natural and anthropogenic factors in determining changes in nekton community, catches (incl. bycatch) from artisanal fisheries (fyke nets) were monitored seasonally in different areas of the Venice lagoon (Italy) between 2001 and 2013. Changes in nekton community composition and in the biomass of target and non-target species/groups were analysed, and the results were related to temporal factors, environmental characteristics and to the variability in anthropogenic pressures. Statistical tests were carried out using a model-based analysis of both univariate and multivariate data. Results highlighted that temporal factors and environmental conditions (i.e. the main chemico-physical descriptors) are more relevant than anthropogenic pressures in explaining spatial and temporal changes in the lagoon nekton assemblage, but that several characteristics of the assemblage, in particular the biomass of some particular categories and of the whole assemblage, are sensitive to human impacts. A particularly negligible effect seemed to be associated with fishing effort, thus suggesting that the monitoring of the local artisanal fishery is suitable also to provide useful information on the evaluation of the status of nekton assemblage

Reconstruction of a small acoustic inclusion via Time-dependent Polarization Tensors

This paper aims at introducing the concept of time-dependent polarization tensors (TDPTs) for the wave equation associated to a diametrically small acoustic inclusion, with constitutive parameters different from those of the background and size smaller than the operating wavelength. Firstly, the solution to the Helmholtz equation is considered, and a rigorous systematic derivation of a complete asymptotic expansion of the scattered field due to the presence of the inclusion is presented. Then, by applying the Fourier transform, the corresponding time-domain expansion is readily obtained after truncating the high frequencies. The new concept of TDPTs is shown to be promising for performing imaging. Numerical simulations are driven, showing that the TDPTs reconstructed from noisy measurements allow to image fine shape details of the inclusion

An Exploration of High School Students' Self-Confidence while Analysing Iterative Code

A number of studies on novice programming report that loops and conditionals can be potential sources of errors and misconceptions. We then felt the need to engage in a more systematic and in-depth investigation about the teaching and learning of iteration in some representative high schools of our regional area. As a medium-term outcome of this endeavour we expect to get fine-grained insights about the nature of students' difficulties, on the one hand, as well as to identify possible pedagogical approaches to be adopted by teachers, on the other. As a step of this project, we designed and administered a survey composed of a set of small tasks, addressing students’ understanding of iteration in terms of code reading abilities. After summarising the motivations underlying the choice of the tasklets and the overall structure of the instrument, in this paper we will focus on a particular aspect which has not yet received extensive attention in the computer science education literature. Specifically, we will consider students' perception of self-confidence, in connection with their actual performance in each task, the specific program features, the cognitive demands (procedural vs. higher-level thinking skills), and the use of code vs. flow-charts. A noteworthy result of this analysis is that students’ perception of self-confidence is poorly correlated to actual performance in the task at hand. The main implications of our study are twofold, pertaining our understanding of less conspicuous facets of the learning of iteration as well as possible pedagogical strategies to strengthen metacognitive skills

Plastic behavior of laser‐deposited inconel 718 superalloy at high strain rate and temperature

2noNickel‐based superalloys have several applications for components exposed to high temperatures and high strain rate loading conditions during services. The objective of this study was to investigate the tensile properties of Inconel 718 produced using the laser metal deposition technique. Specimens with different heat treatments were investigated. Experimental tests were performed at the DYNLab at Politecnico di Torino (Italy). The temperature sensitivity was investigated between 20 °C and 1000 °C on a Hopkinson bar setup at a nominal strain rate of 1500 s−1. The specimens heating was obtained by means of an induction heating system, and the temperature control was performed by thermocouples, an infrared pyrometer, and a high‐speed infrared camera. The thermal images were analyzed to check the uniformity of the heating and to investigate the presence of adiabatic self‐heating. The results showed that the materials strength exhibited a significant drop starting from 800 °C. The strain rate influence was investigated at room temperature, and limited sensitivity was found covering six orders of magnitude in the strain rate. A preliminary analysis of the fracture mode was performed. Finally, different solutions for the strength material modeling were proposed and discussed with the aim of identifying models to be used in finite element simulations.openopenPeroni L.; Scapin M.Peroni, L.; Scapin, M