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REGULUS is an Iodine-based electric propulsion system. It has been designed and manufactured at the Italian company Technology for Propulsion and Innovation SpA (T4i). REGULUS integrates the Magnetically Enhanced Plasma Thruster (MEPT) and its subsystems, namely electronics, fluidic, and thermo-structural in a volume of 1.5 U. The mass envelope is 2.5 kg, including propellant. REGULUS targets CubeSat platforms larger than 6 U and CubeSat carriers. A thrust T = 0.60 mN and a specific impulse Isp = 600 s are achieved with an input power of P = 50 W; the nominal total impulse is Itot = 3000 Ns. REGULUS has been integrated on-board of the UniSat-7 satellite and its In-orbit Demonstration (IoD) is currently ongoing. The principal topics addressed in this work are: (i) design of REGULUS, (ii) comparison of the propulsive performance obtained operating the MEPT with different propellants, namely Xenon and Iodine, (iii) qualification and acceptance tests, (iv) plume analysis, (v) the IoD.

Passive sensing is a branch of structural health monitoring which aims at detecting positions and intensities of impacts occurring on aeronautical structures. Impacts are one of the main causes of damage in composite panels, limiting the application of these modern components on aircraft. In particular, impacts can cause the so called barely visible impact damage which, if not detected rapidly, can grow and lead to catastrophic failure. The determination of the impact location and the reconstruction of impact force is necessary to evaluate the health of the structure. These data may be measured indirectly from the measurements of responses of sensors located on the system subjected to the impact. The impact force reconstruction is a complex inverse problem, where the cause is to be inferred from its consequences. Inverse problems are in general ill-posed and ill-conditioned. Therefore, several techniques have been employed in the last four decades and have proven to be effective within certain limitations. Among these methods, transfer function based methods have been mainly validated for low-energy impact where the linear assumption should be valid. Nonlinearities may affect the accuracy in the reconstruction process and thus in the evaluation of damage other techniques have been adopted, such as artificial neural networks (ANN) or genetic algorithms (GA). In this study, a stiffened panel model developed in Abaqus/CAE is first validated, then numerical simulations are used to obtain data for several impacts, characterized by different impact locations and different energy (by changing the impactor mass and/or velocity). Geometrical nonlinearities of the dynamic system are considered in order to represent accurately the mechanics of the composite panel. Then the complex nonlinear behavior will be modeled through a nonlinear system identification approach, such as ANN, and an intelligent algorithm with global search capabilities, such as GA, will be used in sequence to accurately recovery the impact force peak and, therefore, properly evaluate the health status of the structure.

In this work we have analyzed the colony and cellular morphologies of natural populations of Saccharomyces cerevisiae strains in response to different environmental stimuli. Among one thousand strains grown on YPD medium, 2.5% exhibited a rough (R) colony phenotype versus a smooth (S) phenotype. When grown on the ammonium-deficient medium SLAD, 56% of the strains showed a filamentous phenotype, often associated (43.8%) with an invasive phenotype, while 4.7% of the strains exhibited only an invasive phenotype. The rough phenotype on YPD was always associated with the filamentous phenotype on SLAD. A subset of 52 strains was further characterized for the growth phenotype under different stimuli (nitrogen deprivation, addition of alcohols, growth on proline as sole nitrogen source). On 27 strains, genetic analysis of the spore products was also performed. The entire set of data showed a wide distribution of dimorphism in the yeast population and great variability with respect to the dimorphic switch capability. Some strains grew with peculiar colony morphologies under different environmental stimuli and some showed colony morphology variations. Ecological implications of the wide spreading of dimorphic behavior and the occurrence of peculiar colony morphologies in natural yeasts are discussed.