A comparison of different indicators of chaos based on the deviation vectors. Application to symplectic mappings

The aim of this research work is to compare the reliability of several variational indicators of chaos on mappings. The Lyapunov Indicator (LI); the Mean Exponential Growth factor of Nearby Orbits (MEGNO); the Smaller Alignment Index (SALI); the Fast Lyapunov Indicator (FLI); the Dynamical Spectra of stretching numbers (SSN) and the corresponding Spectral Distance (D); and the Relative Lyapunov Indicator (RLI), which is based on the evolution of the difference between two close orbits, have been included. The experiments presented herein allow us to reliably suggest a group of chaos indicators to analyze a general mapping. We show that a package composed of the FLI and the RLI (to analyze the phase portrait globally) and the MEGNO and the SALI (to analyze orbits individually) is good enough to make a description of the systems' dynamics.Comment: 25 pages, 40 figures. Celestial Mechanics and Dynamical Astronomy, in pres

Synergistic effects of zinc borate and aluminiumtrihydroxide on flammability behaviour of aerospaceepoxy system

The flame retardancy of mono-component epoxy resin (RTM6), widely used for aerospace composites, treated with zinc borate (ZB), aluminium trihydroxide (ATH) and their mixtures at different concentrations have been investigated by morphological and thermal characterization. Cone calorimeter data reveal that combustion behaviour, heat release rate peak (PHRR) and heat release rate average (HRR Average) of RTM6 resin decrease substantially when synergistic effects of zinc borate and aluminium trihydroxide intervene. Thermogravimetric (TGA) results and analysis of the residue show that addition higher than 20% w/w of ZB, ATH, and their mixture greatly promotes RTM6 char formation acting as a barrier layer for the fire development. Depending upon the different used flame additives, SEM micrographs indicate that the morphology of residual char could vary from a compact amalgam-like structure, for the RTM6+ZB system, to a granular structure, characterized by very small particles of degraded resin and additive for the AT

Ku & C Band solid state switch matrix for satellite payloads using LTCC multilayer substrate

This paper describes the design and development of Ku and C band solid state switch matrix for multimedia satellite payloads. The design, through the use of advanced packaging techniques, allows significant savings on mass and volume with respect to traditional electromechanical switches while guaranteeing a comparable reliability

The regaining of public spaces to enhance the historic urban landscape

Open spaces in the urban landscapes suffer from deterioration caused by man that leads to two major outcomes: on one side they are abandoned because of newer contemporary needs, on the other hand they tend to be “cannibalized” in the attempt to satisfy our society. This has caused a progressive retraction of urban open spaces that have become residual spaces with no shape and no name. This course of crisis has damaged the identity of places and this is more acute in historic urban landscapes that are recognised as cultural heritage and world heritage. The historic urban landscape approach suggested by UNESCO recognises public spaces’ importance for society and promotes the acknowledgement of public spaces and their dynamism aiming to the integration of preservation, social development and economic targets. To understand how “historic urban landscapes” are taking care of their public spaces, a few Management Plans of UNESCO’s World Heritage cities have been compared. Only Italian UNESCO sites with an “urban complex” characterisation have been considered, this means a limited part of a city with homogenous characteristics from a spatial, historic and cultural point of view. We have focused our attention on the specific interventions for the management of open spaces, in order to identify the major targets and their executive tools, projects and actions. In the light of the above-mentioned analyses, we propose some strategies to fight the decline of public spaces (streets, squares, gardens, etc.) and to enhance these spaces with great attention, trying to improve their fruition and comfort according to their historic and cultural values. The need to identify design strategies to enhance public spaces within the historic urban landscape is included in the research and test activities carried out in the UNESCO site of Mantova and Sabbioneta. This site is an excellent area of applicability because of its urban shape, molded in years by the Gonzaga family. Together with the UNESCO Mantova e Sabbioneta office, we have involved citizens in the requalification design to activate regaining process and test the applicability of our analyses in the city of Mantova, a very articulated and complex reality, starting from the fruition of its places and according to its morphological, environmental, cultural and perceptive aspects

A Method for the Measurement of Digitizers’ Absolute Phase Error

A lot of engineering applications, from telecommunications to power systems, require accurate measurement of phase angles. Some of them, like synchrophasor measurement and calibration of instrument transformers with digital output, in order to reach high phase measurement accuracy, require the knowledge of phase error of digitizers. Therefore, in this paper a method for the measurement of digitizers’ absolute phase errors is proposed. It adopts a sinewave and two square waves, that are the digitizer sample clock and a phase reference signal. Combining the measurements of the relative phase differences between the adopted signals it is possible to accurately evaluate the absolute phase error of a digitize

Reduction in insulin sensitivity and inadequate \u3b2-cell capacity to counteract the increase in insulin resistance in children with idiopathic growth hormone deficiency during 12 months of growth hormone treatment

Purpose: To evaluate the performance of various indexes of insulin sensitivity and secretion and to identify the most useful indicator of deterioration of glucose metabolism in a cohort of children with growth hormone (GH) deficiency (GHD) during GH treatment. Methods: In 73 GHD children (55 M, 18 F; mean age 10.5 years) at baseline and after 12 months of treatment, we evaluated a number of surrogate indexes of insulin secretion and sensitivity. In a subgroup of 11 children we also performed an euglycemic hyperinsulinemic clamp. Results: After 12 months, a significant increase in fasting glucose (p < 0.001) and HbA1c levels (p < 0.001) was documented, despite all children remained with a normal glucose tolerance. With regard the insulin secretion, Homa-\u3b2 did not show any significant change (p = 0.073), while oral disposition index (DIo) showed a significant decrease (p = 0.031). With regard the insulin sensitivity, Homa-IR significantly increased (p < 0.001) with a concomitant decrease in QUICKI (p < 0.001). ISI Matsuda showed a decrease, although not statistically significant (p = 0.069). In the subgroup of 11 children, the M value derived from clamp showed a significant decrease (p = 0.011) and a significant positive correlation was found between M value and ISI Matsuda both at baseline (\u3c1 0.950; p = 0.001) and after 12 months (\u3c1 0.980; p = 0.001) but not with Homa-IR and QUICKI. Conclusions: 12 months of GH treatment lead to a decrease in insulin sensitivity and impairment in insulin secretion relative to insulin sensitivity even without evident changes in glucose tolerance. DIo has proven to be the most useful indicator of deterioration of glucose metabolism even in cases in which the overt glucose abnormalities have not yet appeared