Spatio-temporal patterns of the European wildcat in a Mediterranean coastal area

Like most small felids, the European wildcat Felis silvestris is a rather elusive species, poorly detectable in the wild, due to several aspects of its biology. Camera trapping can represent a suitable tool to understand temporal activity patterns and habitat preferences of such elusive species. We used intensive camera trapping over two full years to investigate spatio-temporal patterns of the wildcat in a Mediterranean coastal protected area (Maremma Regional Park, central Italy). At the seasonal scale, the wildcat showed a marked twilight activity in summer and winter (mating period), and nocturnal activity in autumn. Conversely, a peak of activity during the day, i.e., in broad daylight, was reported in spring. Reproductive females may limit their nocturnal movements in spring to increase protection from predators to their kittens at the den, although further data are required to support this conclusion. At seasonal, semestral, and yearly temporal scales, the frequency of wildcat detections increased along with availability of shrubwood. These results emphasise the importance for this small felid of areas with dense vegetation cover (Mediterranean maquis and shrubwood, in our study area). Areas densely covered with shrubby vegetation are expected to provide benefits to this elusive small cat in terms of reduced human disturbance (included tourists), availability of prey (e.g., small mammals), as well as shelter, essential to ensure protection towards potential larger predators

Designing Innovative Electronic Systems to Face the Challenges of Feasibility and Performance in Sensing and Control Applications

This thesis reports the results obtained during a three year research program on electronic systems design. Two advanced applications in the field of sensing and control electronics are analysed and discussed, with a particular emphasis on the design solutions which allowed to improve the performance provided by the state-of-the-art and, at the same time, to implement new functionalities previously considered unfeasible. The first application is focused on the design, implementation and test of a long--range optical fibre Distributed Temperature Sensor (DTS). A new architecture, aiming to address the main design issues related to the sensing range extension and to the measurement time reduction, is presented. A low-noise APD-based optoelectronic front-end allows to optimize the input signal-to-noise ratio (SNR) of the system. A high level of configurability is also obtained by allowing the user to control the gain and offset of the amplification chain, as well as to fine tune the APD bias voltage and operating temperature. This way, the optimum multiplication factor of the APD, which ensures the best available input SNR, can easily be selected. Signals are acquired through a flexible ADC/FPGA-based platform. Here, a set of decimation and interleaved sampling algorithms allows to efficiently exploit the available memory resources and reach long measurement ranges. Finally, a patented SNR enhancing technique based on laser pulse coding allows to efficiently apply, for the first time, Simplex codes to long-range DTS systems, and therefore to significantly reduce the measurement time. A prototype, which is able to cover distances up to 87.4 km with a spatial resolution of just 1.3 m, has been implemented. Preliminary tests on a 20 km range, carried out without coding, show a performance comparable with the state-of-the-art. The benefits of the coding technique have been instead evaluated on a 10 km range. It has been proved that an outstanding measurement time reduction up to 95 % with respect to conventional long-range uncoded systems is achievable. The second application is instead focused on the development of automotive embedded systems for Formula SAE vehicles. For the first time, linear Voice Coil Actuators (VCAs) have been used to implement a robotized shift-by-wire system, which has been applied to the gear and the clutch devices of the first student-build race car developed at the University of Pisa. A numerical model of the electromechanical system allows to properly size the actuators, so as to obtain a shifting performance better than any other known solution adopted for Formula SAE vehicles. A DSP-based Gear Control Unit (GCU), has been specifically designed to implement the upshift, downshift and car start procedures, and to direct drive the actuators. On-track tests show that the achieved upshift time is just 40 ms, i.e. less than half of the one provided by counterparts. Moreover, a data logging system and a telemetry system have been also implemented. Both are based on a 16 MHz, 8 b microcontroller and communicate with other on-board units through the CAN bus. The first is able to record on a removable SD card the information related to the speed of wheels, the suspensions stroke and the steering angle, as well as the data coming from a 3-axial accelerometer, a gyroscope and a GPS. Using a 2 GB card, signals can be logged for 97 h with a 40 Hz sampling frequency, which is a very good result if compared with commercially available products. Acquired data are also sent over the CAN bus and made available to other units. On the other hand, the telemetry system is composed by two twin units, one on-board and one connected to a PC via USB. The on-board unit listens to CAN activity and forwards messages to the PC unit over a 2.4 GHz wireless encrypted link. A custom developed LabVIEW application allows for the real-time monitoring of the vehicle status and for a rapid fault detection. The radio link is bidirectional, so that the PC is also able to send CAN messages back to on-board units, such as the GCU, and configure their parameters remotely. These capabilities, along with a maximum outdoor range of 2 km, make the system very interesting with respect to other Formula SAE products available on the market

Studio e progetto di un contatore multicanale configurabile ad alte prestazioni basato su piattaforma FPGA/DSP

Nell'ambito del progetto di ricerca COFIN-PRIN "Development of Monolithic Photon-Counter Arrays for Transient High-Energy Phenomena and Adaptive Optics in Astrophysics" avviato nel 2003, il Dipartimento di Ingegneria dell'Informazione dell'Università di Pisa ha sviluppato un contatore multicanale a 60 canali, capace di raggiungere una finestra minima di integrazione di 20 µs con una profondità di conteggio di 16 b, di 10 µs con una profondità di 8 b, e in grado di elaborare i risultati di conteggio in tempo reale. Inoltre, per contenere i costi e i tempi di implementazione, il sistema è stato realizzato utilizzando una scheda di sviluppo commerciale, basata su piattaforma FPGA/DSP. Lo scopo di questa tesi è stato quello di sfruttare al meglio le risorse disponibili su tale scheda per migliorare quanto possibile le prestazioni del sistema, cercando di raggiungere quelle dei migliori contatori multicanale presenti attualmente sul mercato. A tal fine, è stato sviluppato un modello teorico che consente l'analisi delle prestazioni in funzione della profondità di conteggio; sono state determinate le ipotesi da verificare per ottenere un generale miglioramento delle prestazioni rendendo variabile tale profondità; è stata completamente riprogettata l'FPGA ed è stato ottimizzato il firmware del DSP in modo non solo da consentire una profondità variabile e verificare le ipotesi determinate precedentemente, ma anche da massimizzare il numero dei canali. Si è ottenuto di conseguenza un nuovo contatore a 64 canali, capace di raggiungere una finestra minima di integrazione di 14 µs con una profondità di conteggio di 16 b, di 8 µs con una profondità di 8 b e, ovviamente, ancora in grado di elaborare i risultati in tempo reale. Inoltre, l'utente può scegliere anche una nuova profondità di 23 b, con cui è possibile raggiungere una finestra minima di 24 µs

ON THE EFFECTS OF THE INTERPHASE ON THE DAMPING OF CFRP STRUCTURES: AN EXPERIMENTAL INVESTIGATION

The increased adoption of composite laminates in modern engineering requires advancement in the prediction of their dynamic behavior. Damping is a major design constraint in aerospace structures subjected to cyclic loads. While the effects caused by damping are well known, the mechanisms that cause it at the microscopic level are still unclear on a quantitative basis. Testing of these phenomena requires some difficulties to be overcome, like the contribution of spurious sources. The study focuses on the effects that the interphase has on the damping properties of carbon fiber-reinforced polymer (CFRP) composite structures. Three-phase models are employed to investigate the dependence of damping on the interphase mechanical properties, with a focus on the fiber-matrix interfacial shear strength. The experimental campaign confirms the attended results: in particular, a stronger interphase determines a lower damping of the structure

Synergistic effects of nucleating agents and plasticizers on the crystallization behavior of Poly(lactic acid)

The synergistic effect of nucleating agents and plasticizers on the thermal and mechanical performance of PLA nanocomposites was investigated with the objective of increasing the crystallinity and balancing the stiffness and toughness of PLA mechanical properties. Calcium carbonate, halloysite nanotubes, talc and LAK (sulfates) were compared with each other as heterogeneous nucleating agents. Both the DSC isothermal and non-isothermal studies indicated that talc and LAK were the more effective nucleating agents among the selected fillers. Poly(D-lactic acid) (PDLA) acted also as a nucleating agent due to the formation of the PLA stereocomplex. The half crystallization time was reduced by the addition of talc to about 2 min from 37.5 min of pure PLA by the isothermal crystallization study. The dynamic mechanical thermal study (DMTA) indicated that nanofillers acted as both reinforcement fillers and nucleating agents in relation to the higher storage modulus. The plasticized PLA studied by DMTA indicated a decreasing glass transition temperature with the increasing of the PEG content. The addition of nanofiller increased the Young's modulus. PEG had the plasticization effect of increasing the break deformation, while sharply decreasing the stiffness and strength of PLA. The synergistic effect of nanofillers and plasticizer achieved the balance between stiffness and toughness with well-controlled crystallization

Thermoplastic Blends Based on Poly(Butylene Succinate- co -Adipate) and Different Collagen Hydrolysates from Tanning Industry: I—Processing and Thermo-mechanical Properties

AbstractIn this study, blends of a biodegradable thermoplastic polyester, poly (butylene succinate-co-adipate) (PBSA) with two different raw hydrolyzed collagens (HCs), derived from the tannery industry, were investigated in terms of processability, rheological, thermal and mechanical properties. HCs, obtained by alkaline (HCa) and enzymatic (HCe) hydrolysis of the solid wastes generated during the shaving of the tanned leather, were used in PBSA/HC blends, up to 20 wt% of HC, produced by melting extrusion and processed by injection molding. All the blends up to 20 wt% HCs resulted suitable for the injection molding obtaining flexible molded specimens with good tensile properties. The different secondary structure of the two HCs influenced the rheology, morphology and mechanical properties of the produced blends. In particular, HCa, due its higher content of oligopeptides and free amino-acids, showed a good compatibility with the polymeric matrix acting as a plasticizer with consequent reduction of melt viscosity with increasing its loading. The molded dog-bones specimens containing 20 wt% HCa showed a value of elongation at break of 810%. While, HCe, due its higher presence of b-sheet structures, behaved as organic filler, showing a poor interfacial interaction with PBSA with consequent decrease of the tensile properties with increasing its loading. The good processability and satisfactory mechanical properties obtained encourage the use of both investigated collagen hydrolysates in the production of thermoplastic blends and relative molded products for applications in agriculture and plant nurseries, such as pots or small containers with fertilizing properties, due the presence of HCs

New eco-composites based on polyhydroxyalkanoates (PHA) for marine applications

Bio-based polymers have attracted increasing attention over the last two decades, predominantly due to their environmental friendly nature and no dependence on petroleum resources. This type of polymers has got a growing consideration which has been so far focused specifically on starch based products, PLA (Polylactic acid), PHA (Polyhydroxylalkanoates) in particular PHB (Polyhydroxyl butyrate), cellulose derived plastics, etc. The production of these materials is based on renewable agricultural and biomass feedstocks. The degradability of bio-based materials not just in compost but also in different natural environments is an important property for sustainability and reduction of plastic pollution. In this work, blends of PHA and PHB with Posidonia Oceanica fibres were investigated to assess the feasibility of producing materials biodegradable in marine environment, varying the fiber percentage from 10 to 30 wt%. The chemical composition of the Posidonia O. fiber is similar to that of other lignocellulosic materials. It consists mainly of cellulose, hemicellulose, and lignin. Thermal, rheological, mechanical and morphological characterization of the developed PHA/PHB-fibre blends has been conducted in order to investigate the effect of the fibres on their processability and tensile properties. Biodegradability of the produced composites has been investigated in sea water in view of their use in marine environment

Modeling the overalternating bias with an asymmetric entropy measure

Psychological research has found that human perception of randomness is biased. In particular, people consistently show the overalternating bias: they rate binary sequences of symbols (such as Heads and Tails in coin flipping) with an excess of alternation as more random than prescribed by the normative criteria of Shannon's entropy. Within data mining for medical applications, Marcellin proposed an asymmetric measure of entropy that can be ideal to account for such bias and to quantify subjective randomness. We fitted Marcellin's entropy and Renyi's entropy (a generalized form of uncertainty measure comprising many different kinds of entropies) to experimental data found in the literature with the Differential Evolution algorithm. We observed a better fit for Marcellin's entropy compared to Renyi's entropy. The fitted asymmetric entropy measure also showed good predictive properties when applied to different datasets of randomness-related tasks. We concluded that Marcellin's entropy can be a parsimonious and effective measure of subjective randomness that can be useful in psychological research about randomness perception

Complete exploitation of Arundo Donax L. in a biorefinery approach: Production of furfural, levulinic acid and polyurethane foams

A novel process for the complete and efficient acid-catalyzed exploitation of giant reed (Arundo donax L.) was developed. Acid-catalyzed conversion of the hemicellulose and cellulose fractions allows to obtain furfural and levulinic acid, two very interesting platform chemicals. The solid residue recovered at the end of the process, that is mainly composed of lignin and degradation products of sugars (humins), can be easily separated by filtration at the end of the reaction. This fraction has been employed for the formulation of polyurethane foams, without any preliminary purification step, thus making the overall process economically advantageous

Thermal, Mechanical and Micromechanical Analysis of PLA/PBAT/POE-g-GMA Extruded Ternary Blends

In order to toughen Poly(lactic) acid and binary blends with low PBAT content while maintaining a high biodegradability of the final material, poly(lactic) acid (PLA)/poly(butylene-adipate-co-terephthalate) (PBAT)/ polyolefin elastomer grafted with glycidyl methacrylate (POE-g-GMA) extruded ternary blends have been investigated in this work from a thermal, mechanical, and rheological point of view. The two elastomers have been added in different amounts as dispersed phases into the PLA matrix, paying attention to the final objective: the design of a 90% biodegradable formulation according to EN 13432. These ternary blends exhibited improved impact properties but still low elongation at break. Consequently, to the ternary composition with the best compromise of PLA quantity, biodegradability and thermo-mechanical properties (81 wt.% PLA, 9 wt.% PBAT, and 10 wt.% POE-g-GMA) a small quantity (10 wt.%) of a biobased plasticizer was added in order to further increase the impact properties in parallel with the tensile flexibility. Two types of plasticizers were investigated, one not reactive [Acetyl Tributyl Citrate (ATBC)], and one reactive [Glycidyl ether (EJ-400)]. A micromechanical study, in order to investigate the toughening mechanism of these systems, was carried out on the final formulations. They were also examined by dilatometric tests and elasto-plastic fracture mechanics correlating the data obtained to the morphology and to the rheological properties. In conclusion, the best compromise between impact, tensile properties and biodegradability content was achieved using the reactive plasticizer (EJ-400) whose interaction with the matrix is confirmed by the FT-IR analysis