Residual Stresses in Machining of AISI 52100 Steel under Dry and Cryogenic Conditions: A Brief Summary

17th Conference on Material Forming (ESAFORM) - FinlandResidual stress is one of the most important surface integrity parameter that can significantly affect the service performance of a mechanical component, such as: contact fatigue, corrosion resistance and part distortion. For this reason the mechanical state of both the machined surface and subsurface needs to be investigated. Residual stress induced by dry and cryogenic machining of hardened AISI 52100 steel was determined by using the X-ray diffraction technique. The objective was to evaluate the influence of the tool cutting edge geometry, workpiece hardness, cutting speed, microstructural changes and cooling conditions on the distribution of the residual stresses in the machined surface layers. The results are analysed in function of the thermal and mechanical phenomena generated during machining and their consequences on the white layer formation

Izhikevich neural model and STDP learning algorithm mapping on spiking neural network hardware emulator

From the 20th century, biological mechanisms of the brain behaviour have become more and more interesting for the research communities in information fields due to the computational power of the systems they inspire. In fact, despite the lack of consensus about the information processing actually involved in brain, biological processes have served as reference for recent computational models. The first Artificial Neural Networks (ANNs) were developed as simplified versions of biological neural net- works in terms of structure and function. Today, the third generation of artificial network is that of the Spiking Neural Networks (SNNs), which reach a more realistic modelling by utilizing true biological features, like spikes, to transmit information between neurons. The proposal of this thesis is to embed the Izhikevich neuron model and a full custom "Spike timing dependent plasticity" (STDP) learning algorithm in an architecture called HEENS (Hardware Emulator of Evolved Neural System). HEENS is a multi-chip structure developed at the "Universitat Politecnica de Catalunya" (UPC) based on a ring link topology connecting several SIMD processors reproducing each one a group of neuron of a Spiking neural network. The Izhikevich neuron model is a worldwide adopted mathematical model for reproducing the neural membrane potential evolution, observed in some mammalian cortex, a long time and according to external stimuli. STDP is a biological learning algorithm which shapes the strength of a synaptic connection according to the timing with which that connection takes part to the overall spiking activity of the post or pre-synaptic neurons. This master thesis project, in particular, acts at algorithm level and at instruction level as well at architectural level. It takes place analysing the mathematical models for the right data parallelism, writing the assembly program describing the routine common to all the neurons of the implemented SNN, modifying the instruction set and the existing hardware of the HEENS architecture, in order to fullfil the biological model needs from a computational and performance point of view. HEENS architecture is described in VHDL code, its set-up operations (assembler for code translation, generation of memories, Network configuration) are performed by Python scripts, the comparison between the actual behaviour of HEENS to that of the mathematical models is instead performed via MatLAB scripts. The latter allow: to imitate the performances of a special purpose hardware; to generate source files in order to synchronize and align the model and the architecture even with the randomization of several neural parameters; to make some design choices; to verify and to show the results

Chapter Profiling visitors of a national park in Italy through unsupervised classification of mixed data

Cluster analysis has for long been an effective tool for analysing data. Thus, several disciplines, such as marketing, psychology and computer sciences, just to mention a few, did take advantage from its contribution over time. Traditionally, this kind of algorithm concentrates only on numerical or categorical data at a time. In this work, instead, we analyse a dataset composed of mixed data, namely both numerical than categorical ones. More precisely, we focus on profiling visitors of the National Park of Majella in the Abruzzo region of Italy, which observations are characterized by variables such as gender, age, profession, expectations and satisfaction rate on park services. Applying a standard clustering procedure would be wholly inappropriate in this case. Therefore, we hereby propose an unsupervised classification of mixed data, a specific procedure capable of processing both numerical than categorical variables simultaneously, releasing truly precious information. In conclusion, our application therefore emphasizes how cluster analysis for mixed data can lead to discover particularly informative patterns, allowing to lay the groundwork for an accurate customers profiling, starting point for a detailed marketing analysis

Interspecific somatic hybrids between Solanum bulbocastanum and S. tuberosum and their haploidization for potato breeding.

Protoplast fusion between incongruent Solanum bulbocastanum and S. tuberosum haploids was accomplished to produce hybrids combining elite traits from both parents. We identified 11 somatic hybrids out of 42 regenerants analyzed through ISSR markers. Some hybrids had loss or gain of fragments compared to the parents, likely due to rearrangements and deletions of chromosome segments after fusion, and/or to somaclonal variation during hybrid regeneration. Increased heterotic vigor for some traits as well as high diversity was observed as the effect of both ploidy and fusion combination. Microsporogenesis analysis indicated the occurrence of multivalent configurations and several meiotic abnormalities, such as chromosomes bridges and various spindle orientations. Since all hybrids were sterile, in vitro anther culture was employed for haploidization as a possible strategy to overcome barriers to hybridizations. Haploids were obtained from all the tetraploid S. bulbocastanum (+) S. tuberosum somatic hybrids tested, although with differences in both the number of embryos per 100 anthers cultured and the number of differentiated green plantlets. This is the first report on the successful production of haploid plants from S. bulbocastanum (+) S. tuberosum hybrids

Dolphin Morbillivirus in Eurasian Otters, Italy

We report biomolecular evidence of dolphin morbillivirus in 4 wild Eurasian otters (Lutra lutra) from southern Italy; 2 animals showed simultaneous immunohistochemical reactivity against morbilliviral antigen. These cases add further concern and support to the progressively expanding host range of dolphin morbillivirus in the western Mediterranean Sea

ASTRONOMICAL CALIBRATION OF THE SERRAVALLIAN/TORTONIANCASE PELACANI SECTION (SICILY, ITALY)

We performed a cyclostratigraphic study of a sedimentary sequence (Case Pelacani section) outcropping in the south-eastern margin of Sicily (Italy) and covering the Upper Serravallian/Lower Tortonian stratigraphic interval. Calcareous plankton biostratigraphic data reported in another paper proved that all the sequence of bio-events generally reported from just below and above the S/T boundary is present in the section. They allowed a detailed correlation with the Gibliscemi section.  Preliminary paleomagnetic data suggest that a secondary remagnetization  component prevents the recognition of the correct sequence of paleomagnetic chrons along the studied interval. The sedimentary record has been compared, on the basis of an integrated calcareous plankton biostratigraphy, with that of the Gibliscemi section. Cyclostratigraphic analysis of the lithological patterns recognized throughout the succession and the application of spectral methodologies to the abundance fluctuations of the planktonic foraminifer Globigerinoides quadrilobatus highlighted the presence in the signal of the classic Milankovitch frequencies (precession, obliquity and eccentricity). Correlation of the lithological patterns and of the different frequency bands extracted by numerical filtering from the faunal record with the same components modulating the insolation curve provided an astronomic calibration of the sedimentary record and, consequently, a precise age for all the calcareous plankton bioevents recognized throughout the studied interval.&nbsp

PALEOCEANOGRAPHIC CONDITIONS AT THE BASE OF THE PLIOCENE IN THE SOUTHERN MEDITERRANEAN BASIN

Detailed quantitative analyses of the benthic foraminiferal assemblage from the base of the Pliocene sections (M Pl 1 biozone) at Eraclea Minoa and the Capo Rossello area (southern Sicily) documented fluctuating paleoecological conditions indicative of a dysaerobic bottom water environment. In particular, we identify the Uvigerina pygmaea-peregrina Event, which in the area studied covers the upper part of the M Pl 1 biozone. According to the integrated calcareous plankton biostratigraphy and to cyclostratigraphy based on fluctuations in the relative abundance of fauna in the planktonic foraminiferal assemblage, the base of the Uvigerina pygmaea-peregrina Event coincides with cycle 6a and its top coincides with cycle 10 in the Sicilian sections.A similar temporal correlation is seen in the Tyrrhenian basin (ODP Site 652). On the contrary, the Uvigerina pygmaea-peregrina Event covers a longer time interval in the Jonian basin, where it is recognizable from cycle 4 to cycle 12. The Uvigerina pygmaea-peregrina Event is time equivalent with an interval characterized by cyclically repeated sapropels in the eastern Mediterranean basin. As a matter of fact, 10 sapropels are present in the deep-sea sediments (ODP Site 969) and 10 Uvigerina pygmaea-peregrina peaks are present in the Roccella Ionica - Capo Spartivento composite section in the M Pl 1- lowest M Pl 2 biozones. The diachronous termination of the Uvigerina pygmaea-peregrina Event may indicate that well-oxygenated bottom conditions were established earlier in the western than in the eastern Mediterranean basin. Both the sapropels interval in the eastern Mediterranean and low-oxygen bottom conditions in the Jonian basin occurred during a time interval which straddles a minimum of eccentricity in the astronomical record.  &nbsp

A 70-year long lessepsian colonization: the conquest of Malta by Amphistegina lobifera

The highly invasive Amphistegina lobifera (Larsen, 1976), a non-indigenous benthic foraminifera coming from the Red Sea through the Suez Canal, has colonized the Eastern Mediterranean during the last decades and in 2006 it was recorded for the first time from the Maltese Islands (Central Mediterranean). Here, we report new data from a sediment core collected in May 2018 near the northern coast of Malta. Results show that A. lobifera reached Malta between 1950 and 1955; then it progressively increased in abundance with time, probably favoured by the rising of Mediterranean SST during the last 40 years.peer-reviewe

Thermal-hydraulic analysis of an innovative decay heat removal system for lead-cooled fast reactors

Improvement of safety requirements in GEN IV reactors needs more reliable safety systems, among which the decay heat removal system (DHR) is one of the most important. Complying with the diversification criteria and based on pure passive and very reliable components, an additional DHR for the ALFRED reactor (Advanced Lead Fast Reactor European Demonstrator) has been proposed and its thermal-hydraulic performances are analyzed. It consists in a coupling of two innovative subsystems: the radiative-based direct heat exchanger (DHX), and the pool heat exchanger (PHX). Preliminary thermal-hydraulic analyses, by using RELAP5 and RELAP5-3D© computer programs, have been carried out showing that the whole system can safely operate, in natural circulation, for a long term. Sensitivity analyses for: the emissivity of the DHX surfaces, the PHX water heat transfer coefficient (HTC) and the lead HTC have been carried out. In addition, the effects of the density variation uncertainty on the results has been analyzed and compared. It allowed to assess the feasibility of the system and to evaluate the acceptable range of the studied parameters. A comparison of the results obtained with RELAP5 and RELAP5-3D© has been carried out and the analysis of the differences of the two codes for lead is presented. The features of the innovative DHR allow to match the decay heat removal performance with the trend of the reactor decay heat power after shutdown, minimizing at the same time the risk of lead freezing. This system, proposed for the diversification of the DHR in the LFRs, could be applicable in the other pool-type liquid metal fast reactors