Extremal Synthesis for Generic Planar Systems

For a generic single-input planar control system we analyze the structure of the set of extremals for the time-optimal problem. Generically all extremals are finite concatenations of regular arcs that are bang or correspond to a smooth feedback. Moreover, the support of extremals is a Whitney stratified set. We collect these information in the definition of extremal synthesis. In the cotangent bundle, we give a topological classification of the singularities of the extremal synthesis and study the projections of the support of extremals (regarded as a two-dimensional object, after normalization) from ² × S ¹ to the plane. With respect to the Whitney classical singularities here we deal with a stratified set with edges and corners, and along with cusps and folds, we find other stable singularities.     

Killers, fridges, and slaves: a legal journey in robotics

This paper adopts a legal perspective to counter some exaggerations of today’s debate on the social understanding of robotics. According to a long and well-established tradition, there is in fact a relative strong consensus among lawyers about some key notions as, say, agency and liability in the current use of robots. However, dealing with a field in rapid evolution, we need to rethink some basic tenets of the contemporary legal framework. In particular, time has come for lawyers to acknowledge that some acts of robots should be considered as a new source of legal responsibility for others’ behaviour.     

Shock absorption performance of a motorbike helmet with honeycomb reinforced liner

The enhancement of the energy absorption properties of motorbike helmets could significantly improve the safety of riders. This study reports a novel concept of helmet design, which consists in the use of aluminium honeycomb as reinforcement material of the helmet liner. A modified version of a commercial helmet is presented, in which aluminium honeycombs are used in the energy absorbing liner. The ECE 22.05 standard tests were performed on both the prototype helmets and their commercial counterparts (presenting same dimensions, geometry, material properties and weight), and the dynamic responses were compared. The results showed that the prototype helmets provided better protection to the head from impacts against the kerbstone anvil. More limited improvements were also observed in some of the impacts on flat anvil, although other results indicated to some extent the limitations of the strategy adopted in our research.     

Logical Equivalence for Subtyping Object and Recursive Types

Subtyping in first order object calculi is studied with respect to the logical semantics obtained by identifying terms that satisfy the same set of predicates, as formalised through an assignment system. It is shown that equality in the full first order ς-calculus is modelled by this notion, which in turn is included in a Morris-style contextual equivalence. U. de’Liguoro’s research was partially supported by project PRIN’05 prot. 2005015785_003.     

Ionic liquids as diathermic fluids for solar trough collectors’ technology: A corrosion study

The AISI 304 and AISI 1018 steels (frequently used in solar collectors’ plants) in contact with four different ionic liquids (ILs) suitable as diathermic fluids, were studied. Immersion tests were performed at 220 °C (the working temperature in such plants) for 10 days. The corrosion morphologies of the steels were investigated by scanning electron microscopy coupled with energy dispersive X-ray (EDX) microanalysis and the content of metals in the solution were detected via ICP-OES. The tests showed that the most performing IL is the ethyl-dimethyl-propyl-ammonium-bis(trifluoromethylsulphonyl)imide. The corrosion properties of the two alloys in contact with such IL were investigated by means of Tafel plots and resistance polarization at room temperature in open-to-air vessels.     

Imputation through finite Gaussian mixture models

Imputation is a widely used method for handling missing data. It consists in the replacement of missing values with plausible ones. Parametric and nonparametric techniques are generally adopted for modelling incomplete data. Both of them have advantages and drawbacks. Parametric techniques are parsimonious but depend on the model assumed, while nonparametric techniques are more flexible but require a high amount of observations. The use of finite mixture of multivariate Gaussian distributions for handling missing data is proposed. The main reason is that it allows to control the trade-off between parsimony and flexibility. An experimental comparison with the widely used imputation nearest neighbour donor is illustrated.     

Diffusion regimes at nanoelectrode ensembles in different ionic liquids

The electrochemical and diffusion behaviour of different redox probes in different ionic liquids is studied at gold nanoelectrode ensembles (NEEs) in comparison with millimetre sized gold (Au-macro) and glassy carbon (GC) disk electrodes. The redox probes are neutral ferrocene (Fc), the ferrocenylmethyltrimetylammonium cation (FA⁺) and the ferrocenylmonocarboxylate anion (FcCOO⁻). The ILs are the dicyanamide, [N(CN)₂] or bis(trifluoromethylsulfonyl)amide), [N(Tf)₂] salts of the following cations: 1-butyl-3-methylimidazolium, [BMIm], 1-butyl-3-methylpyrrolidonium, [BMPy], or tris(n-hexyl)tetradecylphosphonium [P_14,666]. These ILs are characterized by different viscosities, ranging from 32 to 277 cP. The cyclic voltammetric behaviour of the redox probes is reversible and diffusion controlled at GC electrodes. Diffusion coefficients (D) calculated by the Randles-Sevcik equation scales inversely with the IL viscosity, ranging from 2 × 10⁻⁸ to 3 × 10⁻⁷ cm² s⁻¹. Ionic solutes, namely FA⁺ and FcCOO⁻, present slightly lower D values than neutral Fc. At the Au-macro the electrochemical behaviour of the redox probes is diffusion controlled in the ILs containing the [N(Tf)₂] anion, while it involves relevant adsorption processes in the [N(CN)₂] containing electrolyte. For this reason the diffusion at gold NEEs is studied only in the former ILs.The CVs of the redox probes at the NEEs are peak shaped at low scan rate (v), while they are sigmoidally shaped at high v, but with some shift between forward and backward patterns. This is indicative of the occurrence of a total overlap (TO) diffusion condition when v is low which becomes a mixed diffusion layers (MDL) regime, with only a partial overlapping of individual diffusion layers, at high v values. In the most viscous IL, namely [P_14,666] [N(Tf)₂], at v higher than 0.8 V s⁻¹, a plateau current independent on the scan rate is achieved, indicating the tendency to reach the pure radial regime in this IL. The v values at which the transition between TO and MDL is observed scales directly with D and inversely with the IL viscosity. This behaviour is interpreted on the basis of the dependence of individual diffusion layers at each nanoelectrode on redox probe/IL interaction which fits with existing theoretical models very recently developed for nanoelectrode arrays.     

A simple model for the photocurrent density of a graded band gap CIGS thin film solar cell

A simple model for the photocurrent density of a linearly graded band gap Cu(In,Ga)Se₂ solar cell is presented. Both generation and recombination mechanisms in the space charge region and absorber region of the cell are considered. The carrier collection function and effective absorption coefficient are introduced in the calculations to obtain a more realistic model. The results show that photocurrent density of the graded band-gap solar cell is higher than that with a constant averaged band gap. There is an optimum for grading strength or band gap widening of the absorber region. Recombination current reduces the photocurrent density with a lower reduction in the absorber material than in the depletion region. For longer diffusion lengths (or greater values of carrier collection factor), a higher photocurrent density is obtained except where collection probability is already unity everywhere in the absorber.     

Rapid and Simultaneous Analysis of Xanthines and Polyphenols as Bitter Taste Markers in Bakery Products by FT-NIR Spectroscopy

The food industry has a direct interest into bitter-tasting substances either for the identification of negative off-flavors or for the monitoring of a desired organoleptic quality. A rapid technique, based on Fourier transform-near infrared (FT-NIR) spectroscopy and able to detect taste molecular markers in bakery commodities, was developed, focusing the attention on biscuits category. Xanthines (caffeine, theobromine, and theophylline) and polyphenols (catechins and epicathechins), considered as mainly responsible for the bitter-taste of coffee\cocoa\chocolate based products, were firstly checked using a confirmatory liquid chromatography (LC)-ESI\mass spectrometry (MS)-MS procedure after hot methanol–water extraction. Correspondent data were used for the calibration of the FT-NIR through PLS regression. Values of the standard errors of prediction (lower than 10 %) were comparable to the values of the standard errors of cross-validation. Coefficients of determination indicated a good predictive power in the calibration model (R ² xanthines?=?0.97, R ² polyphenols?=?0.96) and a satisfying discriminating power among different contents in the validation models (R ² xanthines?=?0.96, R ² polyphenols?=?0.96). A testing phase on the generated model was executed by a comparison of LC-MS and sensory panel data with FT-NIR responses recorded on unknown biscuits: differences between found and predicted levels were generally below 5 % and the best predictability was achievable in chocolate-based biscuits. This methodology is able to work directly on solid products, has the potential to be expanded on other categories of gustative molecular markers (like sugars) and can be conceived as applicable for a routine control of a standardized bitter taste quality in a real industrial production.