Contributions to the performance analysis of continuum parallel robots

Continuum parallel robots (CPRs) are manipulators employing multiple flexible beams arranged in parallel and connected to a rigid end-effector. CPRs promise higher payload and accuracy than serial CRs while keeping great flexibility. As the risk of injury during accidental contacts between a human and a CPR should be reduced, CPRs may be used in large-scale collaborative tasks or assisted robotic surgery. There exist various CPR designs, but the prototype conception is rarely based on performance considerations, and the CPRs realization in mainly based on intuitions or rigid-link parallel manipulators architectures. This thesis focuses on the performance analysis of CPRs, and the tools needed for such evaluation, such as workspace computation algorithms. In particular, workspace computation strategies for CPRs are essential for the performance assessment, since the CPRs workspace may be used as a performance index or it can serve for optimal-design tools. Two new workspace computation algorithms are proposed in this manuscript, the former focusing on the workspace volume computation and the certification of its numerical results, while the latter aims at computing the workspace boundary only. Due to the elastic nature of CPRs, a key performance indicator for these robots is the stability of their equilibrium configurations. This thesis proposes the experimental validation of the equilibrium stability assessment on a real prototype, demonstrating limitations of some commonly used assumptions. Additionally, a performance index measuring the distance to instability is originally proposed in this manuscript. Differently from the majority of the existing approaches, the clear advantage of the proposed index is a sound physical meaning; accordingly, the index can be used for a more straightforward performance quantification, and to derive robot specifications.

A multi-instrumental approach to the study of equatorial ionosphere over South America

An extensive study of the morphology and the dynamics of the equatorial ionosphere over South America is presented here. A multi parametric approach is used to describe the physical characteristics of the ionosphere in the regions where the combination of the thermospheric electric field and the horizontal geomagnetic field creates the so-called Equatorial Ionization Anomalies. Ground based measurements from GNSS receivers are used to link the Total Electron Content (TEC), its spatial gradients and the phenomenon known as scintillation that can lead to a GNSS signal degradation or even to a GNSS signal ‘loss of lock’. A new algorithm to highlight the features characterizing the TEC distribution is developed in the framework of this thesis and the results obtained are validated and used to improve the performance of a GNSS positioning technique (long baseline RTK). In addition, the correlation between scintillation and dynamics of the ionospheric irregularities is investigated. By means of a software, here implemented, the velocity of the ionospheric irregularities is evaluated using high sampling rate GNSS measurements. The results highlight the parallel behaviour of the amplitude scintillation index (S4) occurrence and the zonal velocity of the ionospheric irregularities at least during severe scintillations conditions (post-sunset hours). This suggests that scintillations are driven by TEC gradients as well as by the dynamics of the ionospheric plasma. Finally, given the importance of such studies for technological applications (e.g. GNSS high-precision applications), a validation of the NeQuick model (i.e. the model used in the new GALILEO satellites for TEC modelling) is performed. The NeQuick performance dramatically improves when data from HF radar sounding (ionograms) are ingested. A custom designed algorithm, based on the image recognition technique, is developed to properly select the ingested data, leading to further improvement of the NeQuick performance.

Experimental Project on the Safety and the Optimization of the Use of Glyphosate-Based Herbicides in the Grain Sector.

INTRODUCTION: Glyphosate is the most widely applied pesticide worldwide and it is an active ingredient of all glyphosate-based herbicides (GBHs), including in the formulation “Roundup” . It is unclear if the glyphosate present in ground water can be absorbed and translocated in different parts of the pants, particularly wheat plants. This indeed represents an important aspect for productivity (being this a powerful herbicide) and organic certification of the products (the use of glyphosate is not admitted in organic farming and the ubiquitous contamination of glyphosate in water might in theory affect the level of glyphosate in the plants). Overall, epidemiological, in vivo and in vitro studies available in literature present conflicting findings on the safety of glyphosate. METHODS: The work performed for this PhD thesis aimed to experimentally test the root absorption and the eventual translocation of the glyphosate herbicide in the different parts of the wheat plant (Triticum durum) starting from ground water. Furthermore we aimed to experimentally test the effects of the exposure to GBHs at doses of glyphosate considered to be “safe”, the US ADI of 1.75 mg/kg bw/day, defined as the chronic Reference Dose (cRfD) determined by the US EPA, in in vivo models (Sprague-Dawley rats) and in vitro models (Caco2 and L929). RESULTS: All the experimental absorption studies on wheat plants performed have given negative results in terms of the presence of glyphosate or AMPA in the grain of durum wheat. On the other hand the experimental safety studies on in vitro and in vivo models highlighted different effects at doses currently considered safe for humans and with no effects in animals. CONCLUSION: Overall the integration of the findings from absorption in plants and safety studies will serve as solid evidence-base for risk assessment and productive strategies for agriculture.

Testing the effectiveness of phytoscreening to monitor shallow groundwater contamination by chlorinated ethenes

The research presented herein aims to investigate the strengths and weaknesses of a relatively new technique called phytoscreening. Parallel to the well-known phytoremediation, it consists of exploiting the absorbing potential of trees to delineate groundwater contamination plumes, especially for chlorinated ethenes (i.e., PCE, TCE, 1,2-cis DCE, and VC). The latter are prevalent contaminants in groundwater but their fate and transport in surface ecosystems, such as trees, are still poorly understood and subjected to high variability. Moreover, the analytical validity of tree-coring is still limited in many countries due to a lack of knowledge of its application opportunities. Tree-cores are extracted from trunks and generally analyzed by gas chromatography/mass spectrometry. A systematic review of former literature on phytoscreening for chlorinated ethenes is presented in this PhD thesis to evaluate the factors influencing the effectiveness of the technique. Besides, we tested the technique by probing eight sites contaminated by chlorinated ethenes in Italy (Emilia-Romagna) in different hydrogeological and seasonal settings. We coupled the technique with the assessment of gaseous-phase concentrations directly on-site, inserting detector tubes or a photoionization detector in the tree-holes left by the coring tool. Finally, we applied rank order statistic analysis on field data along with literature data to assess under which conditions phytoscreening should be applied to either screen or monitor environmental contamination issues. A relatively high correlation exists between tree-core and groundwater concentrations (Spearman’s ρ > 0.6), being higher for compounds with higher sorption, for sites with shallower and thinner aquifers, and when sampling specific tree types with standardized sampling and extraction protocols. These results indicate the opportunities for assessing the occurrence, type, and concentration of solvents directly from the stem of trees. This can reduce the costs of characterization surveys, allowing rapid identification of hotspots and plume direction and thus optimizing the drilling of boreholes.

Identification of resistance factors to the main wheat diseases in the Mediterranean area

Several diseases challenge bread and durum wheat productions worldwide. The importance of these cereals requires adequate protection to pathogens that can cause strong yield and grain quality losses. The main work of this thesis was related to phenotype GDP (Global Durum Panel) in the Mediterranean region (Italy, Egypt, Lebanon, Morocco and Turkey) and Argentina across three years (2019-2021) for yellow rust resistance (infection type and severity). GWAS shows in particular, loci in chromosome 1B, 2B, 4B, 5A, 6A, 7B showed high significance across nurseries/years, with various patterns of GxE. The second chapter is about Zymoseptoria tritici, agent of STB (Septoria Tritici Blotch), a foliar pathogen that yearly causes high damages if not controlled. In recent years research in durum wheat breeding is focused on the identification of novel, underexploited resistance genes to be subsequently and conveniently moved into the pre-breeding and breeding stream. The plants were phenotyped for disease height characters, infection type at the flag leaf and infection type at the level of the canopy below the flag leaf. This experiment opens up a rich scenario of analysis and opportunities to investigate and discover new loci of resistance to STB. Third chapter is about Fusarium head blight (FHB) is a fungal disease caused by pathogens belonging to the genus Fusarium. In particular, Fusarium culmorum and Fusarium graminearum species cause severe grain yield losses and accumulation of mycotoxins in wheat that compromise food safety. Over 250 QTL/genes for FHB resistance have been identified in bread wheat, such as Fhb 1 and Fhb 5 but only a small number of FHB resistance loci have been mapped in durum wheat. The aim of this work is to find loci of partial resistance to FHB already present in durum and bread wheat germplasm and therefore easily cumulative.