Statistical Properties of Transition Amplitudes in Generic Systems

I review some recent results on the statistical properties of matrix elements of typical observables (transition amplitudes) in an eigenbasis of generic quantum Hamiltonian systems. The classical limit of an underlying system can be either integrable, or fully chaotic, or mixed with regular and irregular regions coexisting in phase space. In any case, the variance of transition amplitudes (the local average transition probability) as a function of energy and transition frequency can be calculated in terms of classical power spectra. The probability distribution of transition amplitudes in high energy (semiclassical) regime is derived by means of random matrix theory, whereas in low and intermediate energy (nonsemiclassical) regime the probability distribution of transition amplitudes exhibits universal exponential tails which still call for theoretical explanation.     

Transport of electrons in a GaAs quantum well in high electric fields

The rates of intrasubband and intersubband scattering of electrons by polar optical and intervalley phonons are determined in relation to the electron energy and width of a deep rectangular quantum well in GaAs. The Monte Carlo method was used to calculate the field dependences of the electron’s drift velocity in quantum wells with the width of 10, 20, and 30 nm. It is shown that the drift velocity in high electric fields in a quantum well vastly exceeds the maximum drift’s saturation velocity in the bulk material.     

Ultrasonic air-coupled testing of square-shape CFRP composite rods by means of guided waves

In aerospace industry, one of the most important parts of gliders and motor-gliders is a lightweight longeron reinforcement made of carbon fibre reinforced plastics (CFRP) rods, known as Graphlite SM315 composite. During manufacturing, the rods as constructional elements are glued together in epoxy-filled matrix in order to build the arbitrary spar profile. The defects present in single rods such as breakage of fibres, multiple delaminations due to the lack of bonding between fibres and reduction in density affect essentially the strength and the fail-safety of the overall construction.The aim of the present work is to investigate the effects (transmission, reflection, scattering and mode conversion) of guided waves propagation along a square-shape CFRP rod in the case of contactless excitation/reception and interaction with region of multiple delaminations applying the numerical model and performing experiments.The square-shape CFRP composite rods possessing internal artificial delamination type defects have been investigated by numerical modelling and experiments employing the developed air-coupled technique (pitch-catch set-up) for cases of conventional transmission and advanced back-scattering configurations. Numerical predictions of guided wave interaction with a multiple delamination type defect in a CFRP composite rod have been made and the interaction mechanism explained. It is possible to conclude, that the actual sizes of the internal defects have been clearly detected using reception of the back-scattered waves over the edges of the defective regions only.     

Phase Transitions in Liquid Crystal Doped with Magnetic Particles of Different Shapes

In this study, observations of structural transitions in ferronematics based on the thermotropic nematic 4-trans-4′-n-hexyl-cyclohexyl-isothiocyanato-benzene (6CHBT) are described. Droplets of the nematic phase in the isotropic phase were observed in solutions of nematogenic 6CHBT dissolved in phenyl isocyanate and 6CHBT dissolved in phenyl isocyanate and doped with magnetic particles of different shapes (nanorods and chain-like particles). Magneto-dielectric measurements of structural transitions in these new systems enable to estimate of the type of anchoring of the nematic molecules on the magnetic particles surface.     

Influence of Whey Protein Addition and Feed Moisture Content on Chosen Physicochemical Properties of Directly Expanded Corn Extrudates

Production of extrudates from cereals is an often-used technological process in today’s world food industry. Extrudates from corn flour produced using the twin-screw extrusion process and enriched with whey protein concentrate represent high-quality source of proteins and fats. Whey protein concentrate (WPC) as a valuable source of proteins and minerals is one of the highest-quality components for possible extrudate enrichment. In this paper, the influence of various WPC addition and some extrusion process parameters such as feed moisture content ( Q_{textHtext2 textO} Q_{{{text{H}}_{text{2}} {text{O}}}} ) on physicochemical properties of directly expanded corn flour extrudates manufactured in twin-screw co-rotating extruder was investigated. Whey protein concentrate was added in the following ratios 7.5%, 15% and 22.5% and water in 10.08, 12.18 and 14.28 L/h. Final composition of products is determined with measuring of protein, fat and water shares, water absorption index (WAI) and water solubility index (WSI). With added WPC and with increase of water volume flow, there was a significant rise in total protein, fat and water content in final products, as well as lowering of WSI and rising of WAI indexes. The statistical analysis of the obtained data shows that the lowest WSI and the highest WAI had samples with the largest share of WPC (22.5%) and water volume flow of 14.28 L/h. Colour is measured for each sample, and results were represented with hue angle (H), chroma (C) and lightness (L) values. Process parameters, WPC and Q_{textHtext2 textO} Q_{{{text{H}}_{text{2}} {text{O}}}} influence the increase of saturation of C and lightness of L colour value, while H value stays unchanged. Mean value of H was 90.14 ± 1.06, which corresponds to dominance of yellow colour of samples.     

Clinorotation Effect on Response of Cress Leaves to Red and Far-Red Light

Responses of cress (Lepidium sativum L.) seedling leaves to separate and simultaneous illumination with red (660 nm) and far-red (735 nm) light were studied under fast clinorotation (50 rpm) and usual gravity (1g) conditions. The monochromatic light emitting diodes (LEDs) have been used for illumination of seedlings from above. The growth and spatial orientation of leaves and the location of presumable gravisensors in petioles were analysed. Clinorotation in the dark promoted the radial expansion of leaf lamina and unfolding of leaves. It was shown that clinorotation in red light inhibited significantly the elongation of petioles as compared with that under the action of gravity force. Simultaneous red and far-red illumination promoted the growth of petioles under clinorotation, but did not affect the orientation of laminas, which remained the same as of the 1-g control ones. Red light, applied separately and simultaneously with far-red light, guided the bending of laminas as well as the unfolding of leaf petioles in both usual and clinorotation conditions. Histological and cytological analyses of petioles revealed the presence of movable amyloplasts in endodermic cells in proximal region of petioles. Comparison of intracellular positioning of amyloplasts in petioles of leaves grown under clinorotation and the action of gravity allows a presumption that these plastids may be identified as gravisensors of garden cress leaves. The obtained data imply that clinorotation and exposition to monochromatic red light or simultaneous illumination by red and far-red light affect the elongation of petioles of cress seedling leaves. Spectral components guide the unfolding of laminas in a gravity-independent manner.     

Fines characterization through the methylene blue and sand equivalent test: comparison with other experimental techniques and application of criteria to the aggregate quality assessment

In road construction the general term fines is used to describe particles passing the 0.063, 0.074 or 0.08 mm sieve. Some types of fines are considered to be relatively inert and have almost no effect on pavement performance, whilst the presence of even small amounts of others can significantly affect the stiffness and freezing–thawing behaviour of unbound and hydraulically bound layers. This paper presents the results of research on 12 Slovenian aggregates produced from limestone and dolomite bedrock, and naturally occurring river alluvium gravel. At each production site three different materials were sampled and tested: the actual aggregate for unbound base layers, the clayey soils, which presented the most potentially harmful component at the specific location, and the stony dust, which presented the finest size of crushed aggregate and is typically found as coatings on the crushed grains. Six different methods were used to identify the nature of the fines: X-ray diffractometry, carbonate content determination, methylene blue, sand equivalent, Enslin–Neff water absorption, Atterberg limits test, soil suction measurements and soil water characteristic curves. Based on the results, the relationship between the properties of the different fines was determined and included in draft Slovenian national criteria for sand equivalent and methylene blue values currently being trialed.     

Closed-loop control of hydraulic telescopic handler

Automatization is supposed to improve working conditions and safety in the construction industry, as it already did in manufacturing industries. This paper presents the development of a robotic control system for a commercially available hydraulic telescopic handler. The target application for the telescopic handler is semi-automated assembly of facade panels. The base handler was upgraded with two additional hydraulic axes, position sensors and closed-loop control system, while the original handler safety assurance mechanisms were preserved. The control approach is based on a PI controller with velocity feedforward and valve overlap compensation. The direct and inverse kinematic models of handler mechanism were developed to enable control of end-effector motion along a straight line in the Cartesian coordinate system. The motion performances were evaluated following the ISO 9283 standard with payload of 2000 kg. Results show the repeatability of positioning bellow 7.0 mm and the straight line tracking error smaller than 63 mm.     

Poly(l-lactic acid)/alkali lignin composites: properties,biocompatibility, cytotoxicity and antimicrobial behavior

In this study, poly(L-lactic acid) (PLA)/low molar mass alkali lignin (aL) (1%, 5% and 10% w/w) composites were prepared primarily for a comprehensive understanding of the effect of aL on their antimicrobial properties, biocompatibility and cytotoxic behavior. The properties were evaluated by Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, thermogravimetry and X-ray diffraction. The mechanical, water vapor barrier properties and photodegradability were analyzed as well. The results showed a significant inhibiting effect of aL on the crystallization behavior of PLA, increased water barrier properties (up to 73%) and photodegradability. PLA/aL composites showed a tenfold reduction in Gram-positive bacteria viability, very good cellular response and very low cytotoxicity levels, thus validating these materials as non-cytotoxic and with high potential to be used as food packaging.

Graphical abstract