An alternative method of analysis for base accelerated dynamic response in NASTRAN

An alternative method of analysis to determine the dynamic response of structures subjected to base accelerations is presented. The method is exact as opposed to the approximate technique of using unusually large masses and loads to enforce desired base accelerations. This paper presents the relevant equations to motion, ALTERs for direct and modal frequency-, random- and transient-response rigid formats, and illustrative examples

Probing the geometry and motion of AGN coronae through accretion disc emissivity profiles

To gain a better understanding of the inner disc region that comprises active galactic nuclei it is necessary to understand the pattern in which the disc is illuminated (the emissivity profile) by X-rays emitted from the continuum source above the black hole (corona). The differences in the emissivity profiles produced by various corona geometries are explored via general relativistic ray tracing simulations. Through the analysis of various parameters of the geometries simulated it is found that emissivity profiles produced by point source and extended geometries such as cylindrical slabs and spheroidal coronae placed on the accretion disc are distinguishable. Profiles produced by point source and conical geometries are not significantly different, requiring an analysis of reflection fraction to differentiate the two geometries. Beamed point and beamed conical sources are also simulated in an effort to model jet-like coronae, though the differences here are most evident in the reflection fraction. For a point source we determine an approximation for the measured reflection fraction with the source height and velocity. Simulating spectra from the emissivity profiles produced by the various geometries produce distinguishable differences. Overall spectral differences between the geometries do not exceed 15 per cent in the most extreme cases. It is found that emissivity profiles can be useful in distinguishing point source and extended geometries given high quality spectral data of extreme, bright sources over long exposure times. In combination with reflection fraction, timing, and spectral analysis we may use emissivity profiles to discern the geometry of the X-ray source.Comment: 15 pages, 12 figures. Accepted for publication in MNRA

Acoustical modes of arbitrary volumes using NASTRAN transient heat transfer RF9

An equivalence between temperature and pressure, heat conduction and stiffness and heat capacity and mass is defined, enabling acoustical modal analysis of arbitrary three dimensional volumes. The transient heat transfer analysis rigid format in NASTRAN, RF9, has been altered providing the acoustical analysis capability. Examples and ALTERs are included

NASTRAN forced vibration analysis of rotating cyclic structures

Theoretical aspects of a new capability developed and implemented in NASTRAN level 17.7 to analyze forced vibration of a cyclic structure rotating about its axis of symmetry are presented. Fans, propellers, and bladed shrouded discs of turbomachines are some examples of such structures. The capability includes the effects of Coriolis and centripetal accelerations on the rotating structure which can be loaded with: (1) directly applied loads moving with the structure and (2) inertial loas due to the translational acceleration of the axis of rotation (''base' acceleration). Steady-state sinusoidal or general periodic loads are specified to represent: (1) the physical loads on various segments of the complete structure, or (2) the circumferential harmonic components of the loads in (1). The cyclic symmetry feature of the rotating structure is used in deriving and solving the equations of forced motion. Consequently, only one of the cyclic sectors is modelled and analyzed using finite elements, yielding substantial savings in the analysis cost. Results, however, are obtained for the entire structure. A tuned twelve bladed disc example is used to demonstrate the various features of the capability

How Pandemic Shock Affects Claim for Minimum Income Measures

Social transfers, and minimum income schemes in particular, are key tools to support people’s income and protect their living standards, especially in times of crisis. This paper aims to understand how the claiming of social benefits changed in response to the biggest crisis of recent years, i.e. the pandemic shock. In particular, we test whether the pandemic has reduced the transaction costs associated with claiming social transfers, increasing their spread across the population even controlling for recent recessive trends. We focus on Italy as an interesting case study, because it was the first Western country to be strongly affected by the Covid-19 pandemic and the latest EU country introducing a national minimum income scheme (the Reddito di Cittadinanza or RDC). Based on a rich dataset of statistics at NUTS-3 regional level, results show a significant and positive correlation between the spread of RDC recipients and the one of Covid-19 contagions, especially during the first stage of pandemic. This evidence confirms that lockdown measures strongly affected the economic wellbeing of households and, in turn, transaction costs associated with the RDC claim. Main results hold when relevant demographic and socioeconomic variables directly influencing the RDC claim are considered

Could financial education be a universal social policy? A simulation of potential influences on inequality levels

This paper aims to identify the potential influence of financial literacy’s marginal change on households’ income (wealth) inequality levels both at the mean value and along with the distribution. Using data from the Bank of Italy Survey of Households Income and Wealth (SHIW)’s 2016 wave – which includes the Big Three questions, a widely used measure of financial literacy - we show that replacing 10% of respondents reporting no correct answers with respondents reporting two correct answers out of three would increase the mean value of the household equivalized disposable income by 0.8% (160€ per year). Additionally, it would increase by +1.5% (285€ per year) if we replace 10% of respondents reporting no correct answers with those reporting three correct answers. These results are not trivial. A lump sum leading to the same household income increase would cost on average EUR 4.1 to 7.3 billion per year in Italy. Finally, heterogeneous analysis reveals that an increase in financial literacy levels often engenders a greater reduction of inequality levels among the most vulnerable groups. Our preliminary cost analysis supports mandatory financial education in schools

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

Double dynamical regime of confined water

The Van Hove self correlation function of water confined in a silica pore is calculated from Molecular Dynamics trajectories upon supercooling. At long time in the $\alpha$ relaxation region we found that the behaviour of the real space time dependent correlators can be decomposed in a very slow, almost frozen, dynamics due to the bound water close to the substrate and a faster dynamics of the free water which resides far from the confining surface. For free water we confirm the evidences of an approach to a crossover mode coupling transition, previously found in Q space. In the short time region we found that the two dynamical regimes are overimposed and cannot be distinguished. This shows that the interplay between the slower and the faster dynamics emerges in going from early times to the $\alpha$ relaxation region, where a layer analysis of the dynamical properties can be performed.Comment: 6 pages with 9 figures. RevTeX. Accepted for pulbication in J. Phys. Cond. Mat