Secondary school students’ strategies in solving arrangement problems

Project PID2019-105601GB-I00 / AEI / 10.13039/50110001103

Numerical investigation on the influence of tightening in bolted joints

In a bolted joint, the preload level resulting from the tightening torque represents a very important parameter governing the stresses distributions involving the joint under the real loading conditions. This paper deals with the development of a Finite Element (FE) model for the investigation of the effects of some selected preload levels on the stress-strain states affecting both bolt and plate in a single lap joint. The aim of this FE model is to support the design phase of strain gauges instrumented bolt to evaluate experimentally the rate of tensile load applied to the joint that the bolt absorbs with different preloads. The test article consists of two steel plates, a steel bolt and an aluminum nut. The results herein presented showed firstly that, without bolt preload, the tensile load applied to the joint is completely transferred to the bolt and that the load transferred to the bolt almost linearly decreases as the preload increases. Moreover, at a selected preload level, the transversal and longitudinal stresses (with respect to the load direction) increase as the tensile load increases, while the stress along the plate thickness direction decreases, reaching negative values. On the other hand, at a selected tensile load level, the transversal and longitudinal stresses as well as the stress along the thickness direction decrease as the preload level increases. Predicting the mechanical behaviour of the only bolted joint, if the same bolt model will be used to simulate the mechanical behaviour in a hybrid single-lap joint, possible imperfections of the model will have to certainly be linked to the modelling of the adhesive

Do Secondary School Students’ Strategies in Solving Permutation and Combination Problems Change with Instruction?

This work is part of an investigation conducted in Italy, which aims to explore the effects of instruction on secondary school students’ combinatorial reasoning. We gave a questionnaire adapted from Navarro-Pelayo’s research to two groups of students with and without instruction on combinatorics in order to analyse the students’ performances and the strategies used in their solutions, as well as the effect of instruction on the same. We present the results obtained in two permutation and two combination problems (each in the distribution and selection models). Permutation problems were found easier than combination problems, selection problems were found easier after instruction, and the instruction group obtained better results. We found differences in the main strategies used in both groups: enumeration and dividing a problem in parts was more common in the no-instruction group. The instruction group frequently relied on the use of a formula and the product rule.Ce travail s’inscrit dans le cadre d’une enquête faite en Italie dont le but consiste à explorer les effets d’une formation portant sur le raisonnement combinatoire donnée aux élèves du secondaire. Afin d’analyser les performances et les stratégies de résolution des élèves ainsi que l’impact de l’administration d’une formation sur ces aspects, nous avons soumis un questionnaire inspiré du travail de recherche effectué par Navarro-Pelayo à deux groupes d’élèves, l’un à qui on a donné une formation en combinatoire et l’autre à qui aucune formation n’a été fournie. Nous présentons les résultats obtenus à deux problèmes de combinaison ainsi qu’à deux problèmes de permutation (chacun s’inscrivant dans des modèles de distribution et de sélection). Les problèmes de permutation se sont avérés plus faciles que ceux relevant de la combinatoire, ce fut de même pour les problèmes de sélection après la formation et le groupe qui a bénéficié de celle-ci a obtenu de meilleurs résultats. Nous avons constaté des différences dans les stratégies principales utilisées dans les deux groupes: le groupe sans formation a eu davantage recours à l’énumération et à la division du problème en parties que l’autre groupe alors que ce dernier a souvent utilisé une formule et la règle du produit.AEI/Spanish Research Agency and Research Group PID2019-105601GB-I00 FQM126 Junta de AndaluciaEuropean Commissio

Parametric simulation of LVI test onto CFRP plates

The paper deals with the study of the structural behaviour of laminated composite plates under low velocity impacts. Three test cases, respectively with 6J, 10J and 13J impact energies have been experimentally carried out under ASTM D7136 (American Standard Test Method for Measuring the Damage Resistance of a Fiber –Reinforced Polymer Matrix Composite to a Drop-Weight Impact) requirements. Within this work, virtual simulations of such impact tests have been developed by using the finite element code Abaqus®. The numerical model, based on explicit finite element theory, allows predicting the onset and evolution of both inter-laminar and intra-laminar damages. The former have been considered by using special-purpose elements (cohesive elements); the latter thanks to Hashin criteria. For validation purpose, numerical results have been compared with the experimental ones. After the validation phase, a parametric analysis has been numerically performed; the size of the panel support fixture has been considered as main parameter

NaNet:a low-latency NIC enabling GPU-based, real-time low level trigger systems

We implemented the NaNet FPGA-based PCI2 Gen2 GbE/APElink NIC, featuring GPUDirect RDMA capabilities and UDP protocol management offloading. NaNet is able to receive a UDP input data stream from its GbE interface and redirect it, without any intermediate buffering or CPU intervention, to the memory of a Fermi/Kepler GPU hosted on the same PCIe bus, provided that the two devices share the same upstream root complex. Synthetic benchmarks for latency and bandwidth are presented. We describe how NaNet can be employed in the prototype of the GPU-based RICH low-level trigger processor of the NA62 CERN experiment, to implement the data link between the TEL62 readout boards and the low level trigger processor. Results for the throughput and latency of the integrated system are presented and discussed.Comment: Proceedings for the 20th International Conference on Computing in High Energy and Nuclear Physics (CHEP

Drop test simulation and validation of a full composite fuselage section of a regional aircraft

Abstract In the aircraft industry, the use of fiber reinforced materials for primary structural components over metallic parts has increased up to more than 50% in the recent years, because of their high strength and high modulus to weight ratios, high fatigue and corrosion resistance. Currently, the need of lowering weight and fuel consumption is pushing the world's largest aircraft manufacturers in the design and building of structures entirely made of composites. Fuselage structure plays an important role in absorbing the kinetic energy during a crash. Through the deformation, crushing and damage of fuselage sub-floor structure, a survivable space inside the cabin area should be preserved during and after a crash impact in order to minimize the risk of passengers' injuries. In this work, a Finite Element (FE) model of a full-scale 95% composites made fuselage section of a regional aircraft under vertical drop test is presented. The experiment, conducted by the Italian Aerospace Research Centre (CIRA) with an actual impact velocity of 9.14 m/s in according to the FAR/CS 25, has been numerically simulated. Two ATDs (Anthropomorphic Test Dummies), both 50th percentile, seats and belts have been modelled to reproduce the experimental setup. The results of the simulation, performed by using LS-DYNA® explicit FE code, have been validated by correlation with the experimental ones. Such comparisons highlight that a good agreement has been achieved. The presented FE model allows verifying the structural behavior under a dynamic load condition and also estimating the passive safety capabilities of the designed structure. Since the experiment is expensive and non-repeatable, a FE model can be used for Certification by Analysis purposes since, if established, it is able to virtually demonstrate the compliance to the airworthiness rules

Do methadone and buprenorphine have the same impact on psychopathological symptoms of heroin addicts?

<p>Abstract</p> <p>Background</p> <p>The idea that the impact of opioid agonist treatment is influenced by the psychopathological profile of heroin addicts has not yet been investigated, and is based on the concept of a specific therapeutic action displayed by opioid agents on psychopathological symptoms. In the present report we compared the effects of buprenorphine and methadone on the psychopathological symptoms of 213 patients (106 on buprenorphine and 107 on methadone) in a follow-up study lasting 12 months.</p> <p>Methods</p> <p>Drug addiction history was collected by means of the Drug Addiction History Rating Scale (DAH-RS) and psychopathological features were collected by means of the Symptom Checklist-90 (SCL-90), using a special five-factor solution. Toxicological urinalyses were carried out for each patient during the treatment period.</p> <p>Results</p> <p>No statistically significant differences were detected in psychopathological symptoms, including 'worthlessness-being trapped', 'somatization', and 'panic-anxiety'. Methadone proved to be more effective on patients characterized by 'sensitivity-psychoticism', whereas buprenorphine was more effective on patients displaying a 'violence-suicide' symptomatology.</p> <p>Conclusions</p> <p>Heroin-dependent patients with psychiatric comorbidities may benefit from opioid agonist treatment not only because it targets their addictive problem, but also, precisely due to this, because it is effective against their mental disorder too.</p

Chitosan gated organic transistors printed on ethyl cellulose as a versatile platform for edible electronics and bioelectronics

Edible electronics is an emerging research field targeting electronic devices that can be safely ingested and directly digested or metabolized by the human body. As such, it paves the way to a whole new family of applications, ranging from ingestible medical devices and biosensors, to smart labelling for food quality monitoring and anti-counterfeiting. Being a newborn research field, many challenges need to be addressed to realize fully edible electronic components. In particular, an extended library of edible electronic materials is required, with suitable electronic properties depending on the target device and compatible with large-area printing processes, to allow scalable and cost-effective manufacturing. In this work, we propose a platform for future low-voltage edible transistors and circuits that comprises an edible chitosan gating medium and inkjet printed inert gold electrodes, compatible with low thermal budget edible substrates, such as ethylcellulose. We report the compatibility of the platform, characterized by critical channel features as low as 10 µm, with different inkjet printed carbon-based semiconductors, including biocompatible polymers present in the picograms range per device. A complementary organic inverter is also demonstrated with the same platform as a proof-of-principle logic gate. The presented results offer a promising approach to future low-voltage edible active circuitry, as well as a testbed for non-toxic printable semiconductors

A multi-port 10GbE PCIe NIC featuring UDP offload and GPUDirect capabilities

NaNet-10 is a four-ports 10GbE PCIe Network Interface Card designed for low-latency real-time operations with GPU systems. To this purpose the design includes an UDP offload module, for fast and clock-cycle deterministic handling of the transport layer protocol, plus a GPUDirect P2P/RDMA engine for low-latency communication with NVIDIA Tesla GPU devices. A dedicated module (Multi-Stream) can optionally process input UDP streams before data is delivered through PCIe DMA to their destination devices, re-organizing data from different streams guaranteeing computational optimization. NaNet-10 is going to be integrated in the NA62 CERN experiment in order to assess the suitability of GPGPU systems as real-time triggers; results and lessons learned while performing this activity will be reported herein

Sex-related morbidity and mortality in non-adult individuals from the Early Medieval site of Valdaro (Italy): the contribution of dental enamel peptide analysis

In this work, osteological and paleopathological analyses are combined with liquid-chromatography mass spectrometry to study life and death of 30 non-adult individuals from an Early Medieval Italian funerary context (Valdaro, 7th-8th cent. AD). We estimated individual sex by exploiting sexual differences in enamel-bounded peptides. Enamel proteins were extracted through an acid etching of the whole tooth crowns for 4 samples\ud and through a partial digestion of small enamel chunks for the remaining 26 samples. Both protocols were informative on the sex of the individuals through the identification of amelogenin isoforms (AMELX and AMELY). In addition, low-mineralized tooth germs were analysed and they provided reliable information on the infants’ sex. We observed the presence of 13 males and 17 females among the non-adults of Valdaro, not significantly different from a random sample with an equal frequency of males and females. Cribra cranii and endocranial lesion occurrence showed an association with sex, with higher frequencies in male individuals