Wavelet Based Fractal Analysis of Airborne Pollen

The most abundant biological particles in the atmosphere are pollen grains and spores. Self protection of pollen allergy is possible through the information of future pollen contents in the air. In spite of the importance of airborne pol len concentration forecasting, it has not been possible to predict the pollen concentrations with great accuracy, and about 25% of the daily pollen forecasts have resulted in failures. Previous analysis of the dynamic characteristics of atmospheric pollen time series indicate that the system can be described by a low dimensional chaotic map. We apply the wavelet transform to study the multifractal characteristics of an a irborne pollen time series. We find the persistence behaviour associated to low pollen concentration values and to the most rare events of highest pollen co ncentration values. The information and the correlation dimensions correspond to a chaotic system showing loss of information with time evolution.Comment: 11 pages, 7 figure

Trapping mechanism in overdamped ratchets with quenched noise

A trapping mechanism is observed and proposed as the origin of the anomalous behavior recently discovered in transport properties of overdamped ratchets subject to external oscillatory drive in the presence of quenched noise. In particular, this mechanism is shown to appear whenever the quenched disorder strength is greater than a threshold value. The minimum disorder strength required for the existence of traps is determined by studying the trap structure in a disorder configuration space. An approximation to the trapping probability density function in a disordered region of finite length included in an otherwise perfect ratchet lattice is obtained. The mean velocity of the particles and the diffusion coefficient are found to have a non-monotonic dependence on the quenched noise strength due to the presence of the traps.Comment: 21 pages, 6 figures, to appear in PR

Experimental Study of Tapping Wear Mechanisms on Nodular Cast Iron

AbstractTapping by cutting is one of the most common operations in manufacturing. This multi-teeth tool, known as a tap, cuts the thread in a hole when the piece has a high added value. The thread quality is ensured when the tap is new or slightly worn, yet when tap wear is high; the quality of profiles exceeds tolerance limits and therefore a defect occurs in the manufacturing line.The aim of this paper is to study the tap wear of titanium nitride coated taps measured on nodular cast iron. The level of tap wear is determined by optical images and the wear mechanics are classified by scanning images and energy dispersion spectroscopy analysis. The results highlight that the critical part in measured taps is between the last chamfer and the first cylinder teeth and, consequently, the thread profile is under-sized. Beside adhesive wear, coating removal and chipping are the main wear aspects during tapping operations

Second Order Cumulants: second order even elements and R-diagonal elements

We introduce $R$-diagonal and even operators of second order. We give a formula for the second order free cumulants of the square $x^2$ of a second order even element in terms of the second order free cumulants of $x$. Similar formulas are proved for the second order free cumulants of $aa^*$, when $a$ is a second order $R$-diagonal operator. We also show that if $r$ is second order $R$-diagonal and $b$ is second order free from $r$, then $rb$ is also second order $R$-diagonal.Comment: 49 p

Pyroelectric Trapping and Arrangement of Nanoparticles in Lithium Niobate Opposite Domain Structures

The particular ferroelectric domain structure of periodic opposite domain lithium niobate (ODLN) crystals has been used for the first time for structured nanoparticle trapping. The surface charge density produced by a temperature change in this pyroelectric material is the origin of the trapping forces: dielectrophoretic on neutral particles and electrophoretic on charged ones. Metallic and dielectric particles are trapped and structured. The results show that ODLN structures are efficient substrates for pyroelectric trapping. The different trapping behaviors are presentedThis work has been supported by the Spanish Ministerio de Economía y Competitividad under grant ref.: MAT2014-57704-C3-1-

Luminescence study of thermal treated and laser irradiated Bi_12GeO_20 and Bi_12SiO_20 crystals

Changes on the defect structure of Bi12GeO20 (BGO) and Bi12SiO20 (BSO) crystals induced by thermal treatments and laser irradiation have been studied by means of cathodoluminescence in the scanning electron microscope. The results have been compared to those previously reported for untreated and electron irradiated samples and recombination mechanisms responsible for some of the observed luminescence bands are discussed. Annealing of EGO samples causes the appearance of a new luminescence band at about 390 nm. The centers responsible for this band decorate the deformation slip bands in quenched EGO as observed in the cathodoluminescence images. The emission observed in BSO in the same spectral range is quenched during the annealing treatment. The annealing induced reduction of Bi ions to metallic Bi appears to be related to the quenching of a band at 640 nm observed in untreated samples