1,721,680 research outputs found
Algorithmic modeling and prototyping of a structural joint for freeform surfaces
No full textThis paper describes a parametric approach in architectural design through the elaboration of a process for generating non-standard structural joints particularly suitable for the arrangement of freeform surfaces in which maximum adaptability of the system is required to join a different number of members converging in a node from generic directions.
The algorithmic definitions, developed using the graphical editor Grasshopper integrated with Rhinoceros, allow the management of an integrated workflow from the conceptual design of freeform surface to the prototyping of a structural joint with 3D printing techniques
Dynamical Evolution and Galaxy Populations in the Cluster ABCG 209 at z=0.2
Full text link2002/2003Il lavoro di questa tesi è basato sull'analisi dell'ammasso di galassie ABCG 209, a zrv 0.2, che e' caratterizzato da una forte evoluzione dinamica. Lo studio si basa su dati ottici nuovi (EMMI-NTT: immagini nelle bande B, V e R, e spettri MOS) acquisiti in ottobre 2001 all'osservatorio europeo del sud (ESO) in Cile. Sono stati analizzati, inoltre, dati ottici di archivio (immagini a grande campo nelle bande B ed R del CFHR12k), dati X-ray (Chandra) e osservazioni (VLA). Lo scopo principale di questa analisi è lo studio della relazione tra la dinamica degli ammassi e la storia di formazione stellare delle galassie, al fine di capire i complessi meccanisn1i della formazione e dell'evoluzione degli ammassi. Sulla base di 112 spettri di galassie di ammasso è stata studiata la dinamica interna di ABCG 209. Questa analisi ha mostrato che l'ammasso è caratterizzato da un valore particolarmente alto della dispersione di velocità lungo la linea di vista: av = 1250-1400 km s- 1 , che implica un valore della massa viriale pari a M = 1.6-2.2 x 1015 h- 1 M0 all'interno di un raggio viriale, Rvir· Inoltre, l'ammasso presenta un'elongazione lungo la direzione SE-NW, come mostrato da: a) la presenza di un gradiente di velocità; b) l'elongaziòne della distribuzione spaziale delle galassie di ammasso selezionate in base alla sequenza della colore-magnitudine; c) l'elongazione dei contorni dell'emissione X; d) l'allungamento della galassia centrale dominante (cD). La presenza di sottostrutture è indicata sia dalla non-gaussianità della distribuzione delle velocità, che presenta due sottogruppi spazialmente segregati a z = 0.199 e z = 0.215, sia dal test di Dressler & Schectrnan in 3 dimensioni, che utilizza contemporaneamente l'informazione in ascensione retta e declinazione, e quella in velocità. Infine le galassie selezionate in base alla colore-magnitudine presentano una segregazione in luminosità, ovvero le galassie brillanti R 19.5 mostrano dei sottogruppi, dei quali quello più ad est coincide con il picco secondario dell'emissione X. Lo studio della funzione di luminosità (LF) nelle bande B, V ed R, ha mostrato che l'ammasso presenta caratteristiche intermedie tra un ammasso ricco rilassato ed un ammasso irregolare, dinamic; unente giovane. Questi risultati suggeriscono che ABCG 209 è un ammasso che si sta ancora evolvendo dinamicamente, in cui vi è stato un merging di due o più sottogruppi lungo la direzione SE-NW, in un piano non parallelo a quello del cielo. Il merging potrebbe essere in uno stadio avanzato in cui le galassie luminose tracciano la struttura del sottogruppo che ospitava la galassie centrale dominante prima del rnerging. L'elongazione e l'asimmetria della distribuzione di galassie e dell'emissione X, e la forma della funzione di luminosità indicano, infine, che l'ammasso non è ancora rilassato. L'effetto dell'ambiente (valutato in termini di densità superficiale locale delle galassie con magnitudini R 3.0 A implica che il burst deve essere avvenuto non più di 2 Gyrs fa. Le galassie HDSblue si trovano in regioni a densità intermedia, 1na lungo una direzione perpendicolare a quella di allungamento dell'ammasso, vicine al picco secondario dell'emissione X, ed in una regione in cui l'intracluster medium è particolarmente denso. Queste galassie sono caratterizzate da un'alta dispersione di velocità. Le galassie con righe di emissione si trovano principalmente nelle regioni a bassa densità e hanno alta dispersione di velocità. Sia la posizione spaziale, che la dispersione di velocità di queste ultime due classi di galassie indicano che queste potrebbero essere due popolazioni recentemente cadute nell'ammasso dal campo. Tutti questi risultati indicano uno scenario evolutivo in cui ABCG 209 è caratterizzato principalmente dalla sovrapposizione di due componenti: una popolazione di galassie vecchie che si sono forrr1ate molto presto (zJ ;G 3), ed una popolazione più giovane di galassie che sono state accresciute dal campo. Inoltre, l'ammasso potrebbe aver sperimentato un merging con un gruppo l o 2 Gyrs fa, come indicato anche precedentemente dall'analisi dinamica. Questo studio dettagliato ha mostrato chiaramente l'importanza di avere dati multi-banda e di un approccio multi-direzionale nello studio di questi sistemi così complessi. E', a questo punto, fondamentale estendere questo tipo di analisi ad altri ammassi a redshifts maggiori, e con differenti proprietà dinamiche. Per rispondere definitivamente alla domanda se gli ammassi sono generalmente giovani o vecchi è necessario avere informazioni sulle proprietà di un gran numero di ammassi e contemporaneamente studiare in dettaglio le componenti appartenenti a diverse strutture ed ambienti in un singolo ammasso.The thesis work is focused on the analysis of the galaxy clusters ABCG 209, at zrv 0.2, which is characterized by a strong dynamical evolution. The data sample used is based mainly on new optical data (EMMI-NTT: B, V and R band images and MOS spectra), acquired in October 2001 at the European Southern Observatory in Chile. Archive optical data ( CFHR12k: B and R images), and X-ray (Chandra) and radio (VLA) observations are also analysed. The n1ain goal of this analysis is the investigation of the connection between internal cluster clynamics and star formation history, aimed at understanding the complex mechanisms of cluster formation and evolution. The internal dynamics of the cluster was studied through a spectroscopic survey of 112 cluster Inembers. The dynamical analysis has pointed out that ABCG 209 is characterized by a very high value of the line of sight velocity dispersion: av = 1250-1400 km s- 1that results in a virial mass of M = 1.6-2.2 x 1015 h-1 M0 within Rvir· A preferential SE-NW direction is indicated by: a) the presence of a velocity gradient in the velocity field; b) the elongation in the spatial distribution of colour-selected cluster members; c) the elongation of the X-ray contour levels in the Chandra image; d) the elongation of the cD galaxy. T h ere is evidence of substructure, as shown by i) significant cleviation of the velocity distribution from a Gaussian, with evidence for two secondary clumps at z = 0.199 and z = 0.215, which appear spatially segregated from the main cluster, ii) the Dressler & Schectman test and iii) the two-dimensional distribution of the colour-selected members shows a strong luminosity segregation: bright galaxies R 19.5 show some clumps. The main one, Eastern with respect to the cD galaxy, is well coincident with the secondary X -ray peak. ' The study of the galaxy luminosity function (LF) in B, V and R bands has pointed out that ABCG 209 is a cluster with intermediate characteristic between a dynamically-evolved, rich clusters and clusters with central dominant galaxies having bright characteristic luminosities and shallow faint-end slopes and less evolved clusters, characterized by steep faint-end slopes, thus reconciling the asynnnetric properties of X-ray emission with the non flat-LF shape of irregular systen1s. This observational scenario suggests that ABCG 209 is undergoing a strong dynan1ical evolution with the Inerging of two or more subclumps along the SE-NW direction in a plane which is not parallel to the plane of sky. The merging might be in a more advanced status, where luminous galaxies trace the remnant of the core-halo structure of a pre-merging clump hosting the cD galaxy. The elongation and asymmetry of the galaxy distribution (of the X-ray emission) and the shape of the LFs show that ABCG 209 is not yet a fully relaxed system. The effect of cluster environment (as measured in terms of the local surface density of R 3a significance level from high- to low-density environments. The red sequence is found to be 0.022 ± 0.014 mag redder in the high-density region than for the intermediate-density region by fixing the slope. In contrast no correlation between the slope of the red sequence and environment was observed. Studying the effect of the cluster environment on galaxy star-formation, we find that the blue galaxy fraction decreases monotonically with density, in agreement with other studies. The observed trends of steepening of the faint-end slope, faintening of the characteristic luminosity, and increasing blue galaxy fraction, from high- to low-density environments, are manifestations of the morphology-density relation, where the fraction of early-type galaxies decreases smoothly and monotonically from the cluster core to the periphery, while the fraction of late-type galaxies increases in the same manner. The observed trends in the composite LF reflect this morphology-density relation: the galaxy population in the cluster core is dominateci by early-type galaxies and so the cornposite LF resembles that of this type of galaxy, with a shallow faint-end slope and a bright characteristic lun1inosity; whereas in lower density regions the fraction ~f late-type galaxies increases, and so the composite LF increasingly resembles that of the late-type, with a steep faint-end slope and a fainter characteristic magnitude. The analysis of the mean colour of luminous (R 3.0 A implies that the burst has occurred no more than 2 Gyr ago. HDSblue galaxies are found in intermediate density regions in a direction perpendicular to the cluster elongation, dose to the secondary peak of the X-ray flux andina region where the intracluster Inedium (ICM) is dense. Moreover galaxies belonging to this class seem to be aligned Thus the burst in the star formation seen in these galaxies could be due to the interaction with the hot dense ICM. They have high velocity dispersion. ELGs lie in low density regions and have high line-of-sight velocity dispersion. Both the spatial position and the velocity dispersion suggest that these two populations of galaxies have recently fallen into the cluster from the field. All these results support an evolutionary scenario in which ABCG 209 is characterized by a sum of two components: an old galaxy population, formed very earlier (zJ ;:G 3), and a younger population of infalling galaxies. Moreover this cluster may have experimented l or 2 Gyrs ago a merging with an infalling galaxy group, as indicated also by the previous dynamical analysis. This detailed study has showed clearly the importance to have multi-band data and to perform a n1ulti-directional analysis, in order to precisely characterize the different cluster components. It is now fundamental to extend this kind of analysis to other clusters at higher redshift and with different dynamical properties. To address the issue if clusters are generally young or old one needs to have measurements of subclustering properties of a large sample of clusters and at the same time it is fundamental to precisely characterize cluster components belonging to different structures and environments inside a single cluster.XVI Ciclo1976Versione digitalizzata della tesi di dottorato cartacea
Perceived Social Support and Well-Being of International Students at an Italian University
No full textThe present study aims at exploring international students’ well-being in relation to their perception of social support and dispersion of dependency on various resources. The participants were 139 international students at an Italian university who completed the WHO-5 Well-being Index, Symptom Checklist 90-R, Multidimensional Scale of Perceived Social Support, and Dependency Grids. The results show that higher well-being is correlated with higher support and lower distress and that higher dispersion of dependency was associated with higher perceived support. International students who seek professional psychological help also report lower well-being, higher distress, and fewer resources compared with those who do not seek psychological support. Further, coming from collectivist cultures (rather than individualist ones) as well as being a long-term (rather than short-term) student was mostly associated with higher distress and less perceived support. These results suggest that counseling services for international students should help them find new sources of social support
Novel approach to generation Portfolio Optimization by using genetic algorithms and stochastic methods
No full textIn this paper we present the Portfolio Optimization Problem in the electricity generation framework. We consider traditional and fully controllable energy sources together with wind source, strongly supported by economical benefits but exposed to intermittent generation volatility. Due to the statistical uncertainty about parameters, we formalize the optimization problem in a probabilistic sense and solve it by using Genetic Algorithms
La corrispondenza epistolare Niccolò De Martino - Girolamo Settimo. Con un saggio sull’inedito Trattato delle Unghiette Cilindriche di Settimo
No full textSanguinamento uterino anomalo: etiopatogenesi, forme cliniche, flow-chart diagnostico-terapeutica.
No full text
Per la costruzione dell’Unità d’Italia. Le corrispondenze epistolari Brioschi - Cremona e Betti - Genocchi, Firenze
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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