75 research outputs found
Characterization of biologically effective UV radiation at mid-latitudes sites: innovative method for the calculation of the human vitamin D exposure
No full textThe Italian territory has the potential for receiving high solar ultraviolet (UV) doses during most of the year. This may represent a serious hazard for human health as UV radiation is responsible for skin cancer: Italy is in the third place, after Australia and USA, for melanoma occurrences. It ought to be remember that UV radiation has well-established beneficial effects on the skin, most notably the synthesis of vitamin D3. However a climatological characterization of biologically effective UV radiation in Italy is still missing.
Given the dual biological effect of UV radiation, we focused on the characterization of erythemal and vitamin D dose rates at two Italian sites with different environmental conditions: Rome (41.9°N,12.5°E, 70 m a.s.l) and Aosta (45.8°N, 7.4°E, 569m a.s.l.). For both sites multi-year series of high quality spectral UV measurements, provided by Brewer spectrophotometers are available, especially at the Rome station which has the longest available spectral measurements of UV irradiances in Italy (more than 15 years).
The climatological characterization of erythemal and vitamin D radiation has been carried out in relation to total ozone, solar zenith angle, and aerosol optical index. In addition, the results of the climatological analysis allowed to study the applicability of an innovative method to derive vitamin D doses based on pholysulphonedosimetry -- normally used to measure erythemal exposures -- and hence to expand the potential applications of the PS dosimetric technique
Direct numerical simulation of forced thermal convection in square ducts up to
No full textWe carry out direct numerical simulation (DNS) of flow in a turbulent square
duct by focusing on heat transfer effects, considering the case of unit Prandtl
number. Reynolds numbers up to are considered which are
much higher than in previous studies, and which yield clear scale separation
between inner- and outer-layer dynamics. Close similarity between the behavior
of the temperature and the streamwise velocity fields is confirmed as in
previous studies related to plane channels and pipes. Just like the mean
velocity, the mean temperature is found to exhibit logarithmic layers as a
function of the nearest wall, however with a different slope. The most
important practical implication is the validity of the traditional hydraulic
diameter as the correct reference length for reporting heat transfer data, as
we rigorously show here. Temperature and velocity fluctuations also have
similar behavior, but apparently logarithmic growth of their inner-scaled peak
variances is not observed here unlike in canonical wall-bounded flows. Analysis
of the split contributions to the heat transfer coefficient shows that mean
cross-stream convection associated with secondary motions is responsible for
about of the total. Finally, we use the DNS database to highlight
shortcomings of traditional linear closures for the turbulent heat flux, and
show that substantial modeling improvement may be in principle obtained by
retaining at least the three terms in the vector polynomial integrity basis
expansion
STREAmS-2.0: Supersonic turbulent accelerated Navier-Stokes solver version 2.0
No full textWe present STREAmS-2.0, an updated version of the flow solver STREAmS, first introduced in Bernardini et al. (2021) [1]. STREAmS-2.0 has an object-oriented design which separates the physics equations from the specific back-end, making the code more suitable for future expansions, such as porting to novel computing architectures or implementation of additional flow physics. Similarly to the previous version, STREAmS-2.0 supports NVIDIA-GPU and CPU back-ends. Additionally, this version features improvements of the input/output data management, new energy and entropy preserving schemes for the discretization of the convective fluxes, recycling/rescaling inflow boundary condition, and a model for thermally perfect gases with variable specific heats. New version program summary: Program Title: STREAmS CPC Library link to program files: https://doi.org/10.17632/hdcgjpzr3y.2 Developer's repository link: https://github.com/STREAmS-CFD/STREAmS-2 Licensing provisions: GPLv3 Programming language: Fortran, CUDA Journal reference of previous version: M. Bernardini, D. Modesti, F. Salvadore, and S. Pirozzoli. STREAmS: a high-fidelity accelerated solver for direct numerical simulation of compressible turbulent flows. Comput. Phys. Commun. 263 (2021) 107906. Does the new version supersede the previous version?: Yes. Reasons for the new version: New code structure and release of new features. Summary of revisions: • The original solver [1] has been rewritten following an object-oriented design implemented through Fortran derived types that include variables and type bound procedures. The new software architecture has been designed to increase modularity and extensibility of the code, allowing users to add new back-ends and physics equations while maintaining the same code structure. This allows users to reuse portions of the code that are independent of the physics equations, the back-end, or both. The layer of computing procedures maintains a lean structure that can be highly optimized with respect to the implemented back-end. • Input handling is now based on the classic.ini format improving both user readability and input data management. • A family of new kinetic energy and entropy preserving schemes (KEEP) are now available and can be selected for stable, non-dissipative and accurate spatial discretization of the convective terms of the Navier–Stokes equations in smooth flow regions [2]. Concerning the shock-capturing flux, the improved low-dissipative WENO-Z scheme proposed by [3] is now available. • New inflow boundary conditions based on the recycling/rescale approach [4] have been implemented for the simulation of spatially evolving compressible turbulent boundary layers. Moreover, a new inflow condition based on the solution of the compressible Blasius equation is available to take into account the case of laminar boundary layers. • The constitutive relations have been generalized to take into account thermally perfect gases with variable specific heats, approximated with polynomial functions of the temperature that can be specified by the user [5]. • A new stretching function has been implemented to improve the distribution of grid nodes for the computation of wall-bounded turbulent flows. The formulation blends uniform near-wall spacing with uniform resolution in terms of Kolmogorov units in the outer wall layer, guaranteeing accuracy with higher computational efficiency [6]. Nature of problem: The code solves the compressible Navier–Stokes equations in Cartesian coordinates for a thermally perfect gas. The solver is designed for direct numerical simulation (DNS) of compressible supersonic turbulent boundary layers and various canonical configurations are supported, including turbulent channel flow, laminar and turbulent boundary layer and shock-wave/boundary layer interaction. Solution method: The equations are discretized using high-order finite difference approximations with hybrid low-dissipative/shock-capturing capabilities and the time advancement is performed using a Runge–Kutta scheme. References: [1] M. Bernardini, D. Modesti, F. Salvadore, S. Pirozzoli, STREAmS: A high-fidelity accelerated solver for direct numerical simulation of compressible turbulent flows, Comput. Phys. Commun. 263 (2021) 107906. [2] Y. Tamaki, Y. Kuya, S. Kawai, Comprehensive analysis of entropy conservation property of non-dissipative schemes for compressible flows: KEEP scheme redefined, J. Comput. Phys. 468 (2022) 111494. [3] R. Borges, M. Carmona, B. Costa, W. Don, An improved weighted essentially non-oscillatory scheme for hyperbolic conservation laws, J. Comput. Phys. 227 (6) (2008) 3191–3211, https://doi.org/10.1016/j.jcp.2007.11.038 [4] S. Pirozzoli, M. Bernardini, F. Grasso, Direct numerical simulation of transonic shock/boundary layer interaction under conditions of incipient separation, J. Fluid Mech. 657 (2010) 361–393. [5] B. J. McBride, M. J. Zehe, S. Gordon, NASA Glenn coefficients for calculating thermodynamic properties of individual species, NASA/TP 211556, NASA, 2002. [6] S. Pirozzoli, P. Orlandi, Natural grid stretching for DNS of wall-bounded flows, J. Comput. Phys. 439 (2021) 110408.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Aerodynamic
Investigation on the capability of polysulphone for measuring biologically effective solar UV exposures
No full textPolysulphone (PS) dosimetry is a well-known technique broadly used to assess the erythemally effective solar UV dose received by anatomical sites (personal exposure). We investigate the capability of PS dosimetry to convert doses absorbed by PS badges into biologically effective solar UV exposures taking as examples two relevant effects for human skin: erythema induction and pre-vitamin D-3 production. PS calibration curves for erythemal and pre-vitamin D-3 were distinctly determined by using an empirical relationship between the biologically effective UV exposures and the PS absorbance change. This relationship is parameterized by a coefficient, distinct for each of the two considered biological effects, multiplying the same cubic polynomial function. It is shown how the multiplying coefficient is related to the ratio between the biologically effective and the PS weighted irradiances which is the prevailing factor affecting the accuracy of the calibration and, consequently, the capability of PS films for measuring biologically effective solar UV exposures. The points addressed in this paper can be extended to other biological effects of interest whose action spectra have some similarity with the PS film response
Biologically Effective Surface UV Climatology at Rome and Aosta, Italy
No full textGiven the beneficial and harmful effects of UV radiation on human health, our study aims to provide a characterization of erythemal and vitamin D dose rates at two Italian sites, Rome and Aosta, subject to quite different environmental conditions. Based on the respective UV climatologies, exposure times needed to induce erythema or vitamin D photoproduction are provided as a function of the UV index
Permeability and Turbulence Over Perforated Plates
No full textWe perform direct numerical simulations of turbulent flow at friction Reynolds number Reτ≈ 500 - 2000 grazing over perforates plates with moderate viscous-scaled orifice diameter d+≈ 40 - 160 and analyse the relation between permeability and added drag. Unlike previous studies of turbulent flows over permeable surfaces, we find that the flow inside the orifices is dominated by inertial effects, and that the relevant permeability is the Forchheimer and not the Darcy one. We find evidence of a fully rough regime where the relevant length scale is the inverse of the Forchheimer coefficient, which can be regarded as the resistance experienced by the wall-normal flow. Moreover, we show that, for low porosities, the Forchheimer coefficient can be estimated with good accuracy using a simple analytical relation.In this article the author name Stefan Hickel was incorrectly written as Hickel Stefan. The original article has been corrected.Aerodynamic
Lo sviluppo della coscienza morale nella prima infanzia: il contributo di Grazyna Kochanska
No full textPremesse teoriche: La psicologia del ‘900 ha descritto i processi di base dello sviluppo morale. La psicoanalisi, la psicologia cognitiva e quella evoluzionista hanno descritto traiettorie diverse dello sviluppo morale, sottolineando il ruolo delle interazioni e rappresentazioni precoci, della cognizione e del bisogno di connessione interindividuale. Obiettivo: È stata condotta una rassegna sul lavoro di Grazyna Kochanska relativo alle determinanti precoci della Coscienza Morale. Definendo la Coscienza Morale come un sistema autonomo di guida del bambino che si compone di tre sistemi interrelati – emotivo, comportamentale e cognitivo –, le ricerche dell’autrice inseriscono in una cornice sovraordinata i diversi aspetti della moralità infantile descritti dalle principali correnti teoriche del secolo scorso. Metodologia: Abbiamo passato in rassegna alcuni dei contributi più significativi dell’autrice, riportando i dati di maggior rilievo e illustrando quei processi che secondo l’autrice definiscono in modo integrato fasi e peculiarità dello sviluppo precoce di una Coscienza Morale. Discussione critica e conclusioni: Muovendosi all’interno di una cornice integrata, l’autrice descrive l’emergere della Coscienza Morale attraverso l’interdipendenza di emozioni, condotte e cognizione morali sia in relazione al temperamento che alla matrice di accudimento del bambino. In questo modo, la Coscienza Morale in Kochanska diviene un sistema sofisticato ad esordio precoce, che evolve progressivamente durante l’infanzia al fine di guidare il bambino nell’adattare il proprio comportamento in maniera appropriata al suo contesto.Theoretical background: 19th century psychology shed light on child morality and its main processes. Psychoanalysis, cognitive and evolutionary psychology described different moral developmental trajectories during childhood, underlining the part played by early relational interactions and representational processes, the crucial role of cognition, and the need for interindividual connectedness. Objective: Our review focuses on Grazyna Kochanska’s work on the early determinants of Moral Conscience. By describing Moral Conscience as an autonomous inner guiding system which encompasses three interrelated systems – emotional, behavioral and cognitive - Kochanska’s body of research makes it possible to consider within a coherent framework the different aspects peculiar to child’s morality described by the main psychological fields during last century. Method: We reviewed some of Kochanska’s most representative articles, summarizing relevant data and illustrating the processes that in the author’s view tie together phases and peculiarities of an early development of Moral Conscience. Critical discussion and conclusions: Within an integrated framework, the author describes the emergence of a Moral Conscience through the interplay of moral emotions, behaviors and cognitions both in relation to child’s temperament and as shaped by his early caregiving matrix. By so doing, Kochanska see Moral Conscience as a sophisticated system with early onset and evolving through infancy in order to guide the child in adjusting his behavior in a context-appropriate way
Direct numerical simulation of forced thermal convection in square ducts
No full textWe carry out direct numerical simulation (DNS) of flow in a turbulent square duct by focusing on heat transfer effects, considering the case of unit Prandtl number. Reynolds numbers up to Reτ ≈ 2000 are considered which are much higher than in previous studies, and which yield clear scale separation between inner- and outer-layer dynamics. Close similarity between the behavior of the temperature and the streamwise velocity fields is confirmed as in previous studies related to plane channels and pipes. We find good agreement between the Nusselt number of square duct and circular pipe flow when the Reynolds number based on the hydraulic diameter is used, thus corroborating the common engineering practice. Popular engineering correlations for the heat transfer reveal deviations up to 5% with respect to DNS data, which are nicely fitted by a power law.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Aerodynamic
Rediscovered presences: women as builders in the building sites of Rome and Latium between 16th and 18th century
No full textThe presence of women in Roman and Latium building sites in the modern age was not episodic. Yet, for a long time, gender identity prevailed over labour identity, and activities related to the construction of architecture were long considered the exclusive prerogative of men. On the contrary, construction sites have welcomed many female workers, employed in different, even heavy, roles. They deserve redemption from a persistent prejudice, which has erased their memory. An important contribution has come from the research conducted by the author in collaboration with the Archives of the Fabbrica of St. Peter’s in the Vatican, where one would never have imagined finding women permanently employed in the roles of the building site. As documented in notarial deeds relating to the production and trade of bricks and other similar activities in the Papal States, female employment also affected the entrepreneurial sphere of construction. The building trade in the Modern Age is therefore configured as a multiform reality, in which custom and necessity concurred to emancipate the female condition, overcoming the historical prejudice of the preclusion of certain jobs to women. The distinction was much less defined than is commonly believed, despite the persistent exclusion of women from trade guilds. Between the 16th and 18th centuries, a large sector of women's employment in the Papal States consisted of the building industry and related activities.
The various roles assigned to women are documented both in the Fabbrica of St. Peter’s and in numerous private construction sites in Rome and the provincial fiefdoms. The tasks performed by women carters, transporters, and bricklayers are surprising not only for the substantial equality of pay compared to men, but also for the strength and determination shown by these exceptional women. The same equality is found in the relations between the Fabbrica of St. Peter’s and the suppliers of building materials, among whom the 'carter women' stood out for their entrepreneurial skills. If evidence of the presence of women bricklayers in St. Peter's building site is rare, it is instead widely documented in other building sites of the 17th century, from Abruzzo to the noble fiefdoms of Lazio. Here, the work of several female bricklayers is documented until the 18th century. An example are the building sites in Palestrina, a fief of the Barberini family, where several 'masonry women', 'spicconatrici' (breakers with a pickaxe) and 'garzone' (apprentices) worked. For instance, several women were active in the building sites of the monastery of Sant'Andrea (18th cent.) and the church of Santa Rosalia (17th cent.). This essay reconstructs the activities and roles of these strong-willed women in order to bring to light their history, memory and professional dignity, now forgotte
Acoustic liners and their induced drag
No full textIn order to reduce the noise emitted by aircraft engines, the nacelle is coated with acoustic liners. An undesirable effect of these surfaces is that they increase the aerodynamic drag. In the present work, we characterize this type of surface roughness by performing Direct Numerical Simulations of fully resolved acoustic liner geometries. We find evidence of a fully rough regime, whose onset is determined by the value of the viscous-scaled Forchheimer coefficient. Moreover, the intensity of the wall-normal velocity fluctuations at the wall also scales with the viscous-scaled wall-normal permeability, leading to a relation between fluctuations and added drag.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Aerodynamic
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