Testing for equivalence: an intersection-union permutation solution

The notion of testing for equivalence of two treatments is widely used in clinical trials, pharmaceutical experiments,bioequivalence and quality control. It is essentially approached within the intersection-union (IU) principle. According to this principle the null hypothesis is stated as the set of effects lying outside a suitably established interval and the alternative as the set of effects lying inside that interval. The solutions provided in the literature are mostly based on likelihood techniques, which in turn are rather difficult to handle, except for cases lying within the regular exponential family and the invariance principle. The main goal of present paper is to go beyond most of the limitations of likelihood based methods, i.e. to work in a nonparametric setting within the permutation frame. To obtain practical solutions, a new IU permutation test is presented and discussed. A simple simulation study for evaluating its main properties, and three application examples are also presented.Comment: 21 pages, 2 figure

American women, Italian souls: identity in contemporary italian american women writers

ope

Conjunction analysis and collision avoidance maneuvers for electrodynamic tether missions

openQuesta Tesi Magistrale presenta uno studio di astrodinamica sulle Conjunction Analysis, ossia le Analisi delle Congiunzioni tra satelliti e altri oggetti nello spazio, e sulle manovre di correzione orbitale (Collision Avoidance Maneuvers) per sistemi spaziali a filo elettrodinamico. Lo scopo principale della tesi è quello di analizzare i rischi d’impatto fra satelliti e detriti spaziali e studiare in modo dettagliato i processi che riducono al minimo la possibilità che i veicoli spaziali si scontrino con altri oggetti orbitanti. Il lavoro di tesi si inserisce nell’ambito della sostenibilità spaziale e della Space Situational Awareness (SSA), che riguarda la comprensione dello Spazio attraverso il tracciamento dei resident space objects (RSO), ovvero di tutti quegli oggetti che orbitano attorno alla Terra, con l’obiettivo di prevenire eventuali collisioni per proteggere l’ambiente spaziale e l’uso delle risorse extra-atmosferiche da parte dell’uomo. Quando si vuole valutare il livello di rischio d’impatto, ossia stimare la probabilità che un approccio ravvicinato diventi una collisione, bisogna considerare alcuni dati fondamentali relativi ai due oggetti identificati: la dimensione, i parametri orbitali e la covarianza. Tuttavia, la conoscenza della posizione orbitale di un corpo in orbita e della sua futura evoluzione è influenzata dall’effetto degli errori sulle misure e dalla presenza di diversi termini perturbativi, come il drag atmosferico e la pressione di radiazione solare. La presente tesi si propone di realizzare un modello tramite il software MATLAB per determinare le incertezze su questo tipo di analisi, la probabilità di collisione, l’accuratezza e la tolleranza temporale necessaria per lo svolgimento delle manovre di correzione. In particolare, sono considerati satelliti in orbite LEO (orbite terrestri basse) dotati di dispositivi per il deorbiting di tipo tethered. Questi sistemi a filo elettrodinamico vengono qualificati come tecnologie green, in quanto non prevedono il consumo di propellente per eseguire le manovre, ma basano il loro funzionamento sullo spegnimento o sulla modulazione della corrente all’interno del tether, attraverso cui possono cambiare il rateo di discesa. Il modello e i risultati delle simulazioni, svolte a diverse altitudini e inclinazioni orbitali, costituiscono uno strumento per garantire la sicurezza delle missioni con sistemi elettrodinamici a filo che può essere integrato nelle strategie di soluzione per il problema dei detriti spaziali.This Master's thesis presents an astrodynamics study on Conjunction Analysis and Collision Avoidance Maneuvers for electrodynamic tether systems. The main purpose of the thesis is to analyze the risks of impact between satellites and space debris, and study in detail the processes which minimize the possibility that spacecraft collide with other orbiting objects. The research work is related to space sustainability and Space Situational Awareness (SSA), which concerns the understanding of Space through the tracking of resident space objects (RSO), in other words all those objects that orbit the Earth, with the goal of preventing collisions to protect the space environment and the use of extra-atmospheric resources. When evaluating the level of impact risk, i.e. estimating the probability that a close approach becomes a collision, some fundamental data related to the two identified objects are considered: size, orbital parameters and position covariance. However, the knowledge of a body’s orbital position and its future evolution is influenced by the effect of errors on measurements and by the presence of different perturbative terms, such as atmospheric drag and solar radiation pressure. This thesis aims to create a model using MATLAB to investigate the uncertainties on this type of analysis, the probability of collision, the accuracy and the time tolerance necessary for carrying out the orbital correction maneuvers. In particular, satellites in LEO orbits (Low Earth orbits) equipped with tethered deorbiting devices are considered for the analysis. These electrodynamic tether systems are qualified as green technologies, because they do not require the consumption of propellant to perform the maneuvers, but base their functioning on switching on and off the current inside the tether, through which they can change the rate of descent. The model and the results of the simulations, carried out at different altitudes and orbital inclinations, represent a tool to ensure the safety of electrodynamic tether missions that can be integrated into solution strategies for the space debris problem

Definition of hydrologic regimes in regulated rivers for aquatic biodiversity conservation.

Negative ecological effects of water withdrawal activities from lotic systems have led to the need for the restoration of naturally shaped flow schemes. As a first step in this direction, individuation of sustainable minimum flow volumes can limit extreme alteration of ecosystem structure and functionality. The definition of such minimum flow values, to be released downstream each water diversion structure, must follow the understanding and the quantification of ecological alteration related to flow reduction. This thesis focuses on the study of instream ecological effects of water withdrawal from lowland rivers (Ticino and Adda rivers), with the purpose to define adequate indicators for the identification of ecological effects of hydrological alteration. The application of such indicators should be useful for the definition of environmentally sustainable minimum flow schemes. For this purpose, national protocols for the study of biological communities were applied and critically analyzed. These monitoring criteria and tools appeared inadequate for addressing the hydrological assessment as postulated in this work and for the studied geographical context. Alternative sampling and analysing methods are proposed, following two different directions: (1) a different approach in the use of a common and well known structural indicator (macroinvertebrate fauna) and (2) the integration of such structural descriptors with a functional approach that considers the river quality through ecosystem methabolism measures. Although their widespread use, connected to simple field and laboratory application, macroinvertebrates appeared to be an inadequate tool for hydrological alteration monitoring. However, interesting considerations about relationship between community density and richness and environmental disturbance could be made. Presented data about physico-chemical parameters, collected through the open-channel method, show an influence of flow on ecosystem functional processes, mainly related to influence on aquatic vegetation. Collected data were useful to define an easy method to assess general response of the ecosystem to hydrological modifications, which future application could lead to interesting results and to an alternative approach for the application of WFD (Dir. 2000/60/EC) requirements

STATCOM-BASED CONTROL TECHNIQUES TO REBALANCE DISTRIBUTION GRIDS

openGiven the recent trends that wants to bring our world to be more and more electrified( or simply dependent on electricity as energy source), the "power quality" topic is becoming more interesting and "valuable" as the time passes. In this thesis I'll talk about different control techniques as well as 3 main methods to balance an unbalanced grid using an inverter(statcom).Given the recent trends that wants to bring our world to be more and more electrified( or simply dependent on electricity as energy source), the "power quality" topic is becoming more interesting and "valuable" as the time passes. In this thesis I'll talk about different control techniques as well as 3 main methods to balance an unbalanced grid using an inverter(statcom)

Multivariate small sample tests for two-way designs with applications to industrial statistics

In this paper, we present a novel nonparametric approach for multivariate analysis of two-way crossed factorial design based on NonParametric Combination applied to Synchronized Permutation tests. This nonparametric hypothesis testing procedure not only allows to overcome the shortcomings of MANOVA test like violation of assumptions such as multivariate normality or covariance homogeneity, but, in an extensive simulation study, reveals to be a powerful instrument both in case of small sample size and many response variables. We contextualize its application in the field of industrial experiments and we assume a linear additive model for the data set analysis. Indeed, the linear additive model interpretation well adapts to the industrial production environment because of the way control of production machineries is implemented. The case of small sample size reflects the frequent needs of practitioners in the industrial environment where there are constraints or limited resources for the experimental design. Furthermore, an increase in rejection rate can be observed under alternative hypothesis when the number of response variables increases with fixed number of observed units. This could lead to a strategical benefit considering that in many real problems it could be easier to collect more information on a single experimental unit than adding a new unit to the experimental design. An application to industrial thermoforming processes is useful to illustrate and highlight the benefits of the adoption of the herein presented nonparametric approach

Characterisation of a nuclear transient in NGC 6315

Iope

Angular resolution improvement of slumped thin glass optics for x-ray telescopes.

Current X-ray telescopes such as Chandra and XMM were designed and built to privilege the angular resolution or the collecting area respectively, but using two different manufacturing techniques, and these two key aspects could not be optimised at the same time. The result is that the high-redshift X-ray Universe is still too unresolved to provide us with the understanding of the time evolution of the universe as we see it nowadays. Now the ATHENA mission, approved for the L2 slot in the Cosmic Vision program, is required to have an effective area of 2 m2 at 1 keV and an angular resolution better than 5 arcsec Half-Energy Width (HEW). At this regard, in addition to the baseline solution based on Silicon Pore Optics (SPO), thin glass foils are considered a viable alternative. Slumped glass foils are also considered as substrates for X-ray optics being developed in other projects; for example, the X-ray Surveyor mission being developed at SAO/CfA in USA, and the AXYOM project being developed in Italy. They both foresee the use of piezo-electric actuators to correct the shape errors of the mirrors. The Brera Astronomical Observatory (INAF-OAB, Merate - Italy) has been working, from 2009 till 2013, under ESA contract aimed to develop in Europe a Slumped Glass Optics (SGO) technology, alternative to the one based on silicon pores, and based on the slumping of thin glass foils, in parallel to the work being carried out at NASA/GSFC and other institutes. The INAFOAB innovation is the use of pressure in the hot slumping process to replicate the mould figure. This technology is coupled with an integration process able to damp low frequency errors. My Ph.D. activity, carried out at the INAF-OAB, is devoted to the advancement in the hot slumping technology assisted by pressure, for the production of glass mirrors for future X-ray telescopes. As a preliminary work, I have developed a new method to precisely characterise the mid frequency errors of the glass foils. An existing model, developed by Jimenez-Garate in 2003 to account for the relaxation of ripples in the slumped glass foil when in contact with the slumping mould, was modified to include the application of pressure, and the model was compared to the experimental results. The pressure was found to be essential, also from the the theory viewpoint, to reduce mid-frequency errors in the profile of slumped glass foils, which crucially degrade the performances of the optics. As for the slumping process, I have introduced a new glass material (Corning Eagle XG) combined with the Schott Zerodur K20, already chosen at earlier times as slumping mould material for its anti-sticking properties. I have developed cleaning protocols, used different thermal cycles and different pressures conditions, and reconditioned the pressure control system. I have also optimised the mould height with experiments based on Finite Element Analysis, and reduced the thermal gradients inside the mould and the glass foils. The final result obtained in this research are slumped glass foils with angular resolution improved from the initial 7 arcsec to 2.2\ub10.3 arcsec in single reflection, as expected from metrology at 1 keV X-ray energy and 0.7 incidence angle, and computed by simulating a perfect integration. This result has to be compared with 2 arcsec defined as the error budget allocated for the slumped glass foils. About 1 arcsec is due to replication of the mid-frequency errors in the slumping mould which, owing to the improved result in the slumping, are now a limiting factor in the quality of the slumped glass foils. From the roughness point of view, the contribution to the HEW is guaranteed to be less then 1 arcsec at 1 keV, with an rms improvement from 21 to 11 \uc5 throughout my Ph.D. Moreover, the last tests carried out proved that the roughness of the slumped glass foils can be further reduced to _ 7 \uc5, making the technology attractive also for higher X-ray energies and higher incidence angles. The glass foils slumped during this Ph.D. have been used for the production of two SGO Proof Of Concept prototypes (POC) for the ATHENA mission: the POC#3, (with 2 glass foils assembled) is characterised by HEW value of 5.5 arcsec at 0.27 keV in the best portion of the module, as tested at the PANTER facility; the POC#4 (with 8 glass foils) has expected HEW of about 15 arcsec from metrological data, but the result in X-ray was much higher because of accidental problems during the integration. The next prototype, the POC#5 (with the best eight glass foils produced during my Ph.D. activity), will soon be integrated and tested in X-rays, to assess the improvement already proven by metrology and simulations. Some of the produced slumped glass foils have also been used for studies of active profile corrections with piezoelectric elements, both for the AXYOM project and X-ray Surveyor mission. Alternative materials and techniques have been used in this research to further improve the result. To reduce the surface micro-roughness of the slumped glass foils, I have proven that the slumping technique with pressure application can also be suited in the indirect slumping, in which the optical surface of the glass is not in contact with the mould, thus preserving its initial surface smoothness. Moreover, the dip coating technique was studied to fill the micro-pores present on the surface of the glass foils slumped with the direct technique. Alternative materials for the slumping mould were tested, defining Si3N4 as a very promising candidate, owing to its higher rigidity with respect to Zerodur K20 and therefore preferable to avoid mould deformations with the slumping, as experienced with K20. The Gorilla glass (normally used for smartphones and tablets), was proven to preserve the surface quality of the glass foils, once slumped and chemically tempered to increase the mirror endurance against the vibrations experienced at launch. Finally, I have also studied the scattering and the reflectivity properties of multilayer coatings for X-ray optics. I have upgraded an IDL code to simulate the roughness growth in the multilayer deposition process, extending the computations from periodic to the more general case of graded multilayers. I have also contributed to the X-ray measurements at the BEAR beamline of the Elettra synchrotron in Trieste, on multilayers deposited on glass, silicon and electroformed nickel, for the polarimetric LAMP projec

Definition of hydrologic regimes in regulated rivers for aquatic biodiversity conservation.

Negative ecological effects of water withdrawal activities from lotic systems have led to the need for the restoration of naturally shaped flow schemes. As a first step in this direction, individuation of sustainable minimum flow volumes can limit extreme alteration of ecosystem structure and functionality. The definition of such minimum flow values, to be released downstream each water diversion structure, must follow the understanding and the quantification of ecological alteration related to flow reduction. This thesis focuses on the study of instream ecological effects of water withdrawal from lowland rivers (Ticino and Adda rivers), with the purpose to define adequate indicators for the identification of ecological effects of hydrological alteration. The application of such indicators should be useful for the definition of environmentally sustainable minimum flow schemes. For this purpose, national protocols for the study of biological communities were applied and critically analyzed. These monitoring criteria and tools appeared inadequate for addressing the hydrological assessment as postulated in this work and for the studied geographical context. Alternative sampling and analysing methods are proposed, following two different directions: (1) a different approach in the use of a common and well known structural indicator (macroinvertebrate fauna) and (2) the integration of such structural descriptors with a functional approach that considers the river quality through ecosystem methabolism measures. Although their widespread use, connected to simple field and laboratory application, macroinvertebrates appeared to be an inadequate tool for hydrological alteration monitoring. However, interesting considerations about relationship between community density and richness and environmental disturbance could be made. Presented data about physico-chemical parameters, collected through the open-channel method, show an influence of flow on ecosystem functional processes, mainly related to influence on aquatic vegetation. Collected data were useful to define an easy method to assess general response of the ecosystem to hydrological modifications, which future application could lead to interesting results and to an alternative approach for the application of WFD (Dir. 2000/60/EC) requirements