Improving fault handling in marine vehicle course-keeping systems

Proposes a FDI algorithm that is tested by simulation of the rudder servosystem in the closed-loop course-keeping system for a Mariner Class vessel. A properly adjusted recursive extended least-squares (RELS) identification algorithm is utilized for fault-detection purposes, since hardly detectable faults (also called multiplicative faults) are handled. The rudder subsystem model, as a part of the overall closed-loop course-keeping system, is presented, and the three main parts of the proposed FDI module, which are configured on the basis of a RELS algorithm, are described. We show simulation results and provide comments for both linear and nonlinear (complete 3 degree-of-freedom model) Mariner Class vessel dynamics. We also discuss the connection to some other approaches and provide possible improvements for the suggested algorithm     

Interactions and Chemical Transformations of Coronene Inside and Outside Carbon Nanotubes

By exposing flat and curved carbon surfaces to coronene, a variety of van der Waals hybrid heterostructures are prepared, including coronene encapsulated in carbon nanotubes, and coronene and dicoronylene adsorbed on nanotubes or graphite via π–π interactions. The structure of the final product is determined by the temperature of the experiment and the curvature of the carbon surface. While at temperatures below and close to the sublimation point of coronene, nanotubes with suitable diameters are filled with single coronene molecules, at higher temperatures additional dimerization and oligomerization of coronene occurs on the surface of carbon nanotubes. The fact that dicoronylene and possible higher oligomers are formed at lower temperatures than expected for vapor‐phase polymerization indicates the active role of the carbon surface used primarily as template. Removal of adsorbed species from the nanotube surface is of utmost importance for reliable characterization of encapsulated molecules: it is demonstrated that the green fluorescence attributed previously to encapsulated coronene is instead caused by dicoronylene adsorbed on the surface which can be solubilized and removed using surfactants. After removing most of the adsorbed layer, a combination of Raman spectroscopy and transmission electron microscopy was employed to follow the transformation dynamics of coronene molecules inside nanotubes.     

The comparison of structure and properties in DC magnetron sputtered and HiPIMS W-C:H coatings with different hydrogen content

The comparison of the structure, composition, hardness and friction behavior of DCMS and HiPIMS W-C:H coatings made by hybrid reactive deposition in the presence of C₂H₂ and H₂ in Ar atmosphere revealed a transition from textured to columnar-like structures with the increased addition of acetylene in DCMS coatings whereas only amorphous-like structures were produced by HiPIMS. The hybrid sputtering involves acetylene and hydrogen dissociation and recombination reactions in the plasma resulting in the generation of carbon as well as –CH₃ and =CH₂ radicals which are chemisorbed at the growing coating surface. The concentration of hydrogen in carbon matrix seems to be controlled by –CH₃ and =CH₂ radicals and not by the amount of molecular hydrogen. The main advantage of HiPIMS compared to DCMS technology includes coefficients of dry friction below 0.1 attributed to the formation of lubricious transfer layer at moderate level of hardness (around 20?GPa) over the studied acetylene additions range. Hybrid HiPIMS technology seems to offer possibilities for substantial COF decrease without hardness degradation which results in widening of the potential of W-C:H coatings for practical engineering applications.     

Preparation and Compaction Behaviour of Poly(methyl methacrylate) Coated Iron Microparticles

The poly(methyl methacrylate)(PMMA) coatings onto surface of iron particles were electrochemically prepared and the effect on both surface structure and internal structure of the resulted material after compaction was carried out.The electrochemical polymerization treatment was performed in a fluidized bed electrolyzer using sulphuric acid solution containing potassium persulphate and methyl methacrylate(MMA).The surface topography and the microstructure of the samples were observed by scanning electron mic...     

Bioactives Screening in Overripe Fruits and Vegetables by Liquid Chromatography Coupled to Photodiode Array and Mass Spectrometry Detection

Food waste production generated by large distribution represents an emerging issue due to the large polluting impact and, at the same time, due to the enormous increase of nutrients’ need worldwide. Overripe fruits are considered as “food wastes” despite they could be yet rich sources of food ingredients and bioactives, such as carotenoids and polyphenols. In this work, a phytochemical screening of 20 selected overripe vegetables and fruits was accomplished by liquid chromatography coupled to photodiode array and mass spectrometry detection. The obtained results showed that the low-sugar-content fruits and vegetables had a higher bioactive content compared to the high-sugar fruits; in particular, tomato, wild swiss chard, green bell pepper, and lettuce leaves were the richest in bioactive phytochemicals. Green bell peppers showed the highest pigment content (875.3 mg/kg), whereas tomato, wild swiss chard, and lettuce leaves showed the highest polyphenol contents, 4541.9, 1692.4, and 712.9 mg/kg, respectively. This is the first work where a large-scale monitoring of bioactives in overripe fruits was carried out and two mixtures of fresh and dry material for animal feed are presented.     

A review of failure of sintered steels: fractography of static and dynamic crack nucleation,coalescence, growth and propagation

The failure of sintered steels differs from the behaviour of wrought steels because of factors such as porosity, remnants of previous particle surfaces and generally more complex microstructures. All these factors influence initiation, growth and propagation of microcracks when the sintered microstructure is mechanically loaded. Fracture paths and fracture resistance are shown to be related to details of the microstructures comprising ferrite, austenite, bainite, martensite, pores and weak interfaces. All these have characteristic fracture resistance properties resulting in, frequently combinations of, dimple rupture, cleavage, intergranular and interparticle failure micromechanisms. Results are presented of systematic studies, enabling identification of relevant stresses, in static and dynamic three-point loading, as the cracking process progresses. In static loading, microcracking has been detected in some steels below the macroscopic yield stress and in the first 100 cycles in fatigue. Microcracks nucleate, grow and coalesce, in a step-wise manner, before achieving a catastrophic size – for which conventional fracture mechanics holds. Thus, application of Paris-type analysis to Stage II fatigue is therefore inappropriate. The review focuses on failure micromechanisms and interpretation of fracture surface composition of sintered steels, particularly of those based on Distaloy AE and Astaloy CrL powders. The relationships between microstructure and mechanical properties are discussed.     

Comparison of intelligent systems in detecting a child’s mathematical gift

This paper compares the efficiency of two intelligent methods: expert systems and neural networks, in detecting children’s mathematical gift at the fourth grade of elementary school. The input space for the expert system and the neural network model consisted of 60 variables describing five basic components of a child’s mathematical gift identified in previous research. The expert system estimated a child’s gift based on heuristically defined logic rules, while the scientifically confirmed psychological evaluation of gift based on Raven’s standard progressive matrices was used at the output of neural network models. Three neural network algorithms were tested on a Croatian dataset. The results show that both the expert system and the neural network recognize more pupils as mathematically gifted than teachers do. The expert system produces the highest average hit rate, although the highest accuracy in classifying gifted children is obtained by the radial basis neural network algorithm, which also yields lower type II error. Due to the ability of expert systems to explain the result, it can be suggested that both the expert system and the neural network model have potential to serve as effective intelligent decision support tools in detecting mathematical gift in early stage, therefore enabling its further development.