Novel piecewise trajectory shaping in Hill's canonical variables

Shape-based methods have been proven to be computationally efficient techniques to quickly estimate the cost of low-thrust interplanetary trajectories. However, in some cases the solution is far from optimal, like in the case of the exponential sinusoid, or requires a special treatment when the motion is not completely planar. More recent developments allows for a full three-dimensional representation of the trajectory but either constraints need to be imposed on the thrust direction or approximations need to be introduced on the trajectory time-evolution, causing the domain of representable trajectories to shrink. As a consequence, trajectories transferring to highly inclined or highly eccentric orbits can lead to infeasible control laws. This paper presents a new analytical framework for the quick estimation of the $\Delta v$ and peak thrust of two-point boundary value low-thrust transfers. The novelty of this method is that it solves an inverse optimal control problem in Hill's canonical variables. The parameterisation in Hill's variables was selected so that the shaping of the in-plane and out-of-plane motions can be treated separately and the boundary conditions can be analytically satisfied. This choice leads to a computationally efficient extraction of the control profile and allows for the integration of known analytical solutions for the in-plane motion. The computation of the value of the objective function (usually the total $\Delta v$ or the spacecraft final mass) and path constraints is reduced to computationally inexpensive quadratures. The shaping proposed in this paper is piecewise continuous and allows for a flexible full three-dimensional representation of the trajectory. In particular, the out-of-plane motion is represented by piecewise continuous functions so that one can independently maximise both the change of inclination and the variation of the longitude of the ascending node. The method is applied to some well-known test cases, a rendezvous with Mars, asteroid 1989ML and comet Tempel-1, and the results compared to the solutions obtained with exponential sinusoid, pseudoequinoctial elements and spherical shaping

Novel piecewise trajectory shaping in Hill's canonical variables

Shape-based methods have been proven to be computationally efficient techniques to quickly estimate the cost of low-thrust interplanetary trajectories. However, in some cases the solution is far from optimal, like in the case of the exponential sinusoid, or requires a special treatment when the motion is not completely planar. More recent developments allows for a full three-dimensional representation of the trajectory but either constraints need to be imposed on the thrust direction or approximations need to be introduced on the trajectory time-evolution, causing the domain of representable trajectories to shrink. As a consequence, trajectories transferring to highly inclined or highly eccentric orbits can lead to infeasible control laws. This paper presents a new analytical framework for the quick estimation of the $\Delta v$ and peak thrust of two-point boundary value low-thrust transfers. The novelty of this method is that it solves an inverse optimal control problem in Hill's canonical variables. The parameterisation in Hill's variables was selected so that the shaping of the in-plane and out-of-plane motions can be treated separately and the boundary conditions can be analytically satisfied. This choice leads to a computationally efficient extraction of the control profile and allows for the integration of known analytical solutions for the in-plane motion. The computation of the value of the objective function (usually the total $\Delta v$ or the spacecraft final mass) and path constraints is reduced to computationally inexpensive quadratures. The shaping proposed in this paper is piecewise continuous and allows for a flexible full three-dimensional representation of the trajectory. In particular, the out-of-plane motion is represented by piecewise continuous functions so that one can independently maximise both the change of inclination and the variation of the longitude of the ascending node. The method is applied to some well-known test cases, a rendezvous with Mars, asteroid 1989ML and comet Tempel-1, and the results compared to the solutions obtained with exponential sinusoid, pseudoequinoctial elements and spherical shaping

Closing the loop between mission design and navigation analysis

This research presents a contribution to the field of optimisation under uncertainty by proposing a nonlinear navigation analysis approach under both aleatoric and epistemic uncertainty. The navigation analysis is framed as a sequential filtering problem with an alternation of uncertainty propagation arcs and orbit determination instances. The state distribution is modelled as a mixture of kernels where the mixture weights are interval-valued to model the epistemic component. Specific techniques are discussed for Gaussian mixtures in particular. The uncertainty propagation step is solved by using Gaussian Hermite quadrature rules to compute the propagated means and covariances. The observation update is efficiently solved with a combination of variational inference and importance sampling, and a routine is developed to compute the posterior interval-valued weights. Given the distribution representation, lower and upper expectations of a generic quantity of interest are the solutions of linear programming problems and, therefore, are inexpensive to compute. The developed navigation analysis is finally applied to the robust quantification of the probability of impact of Europa Clipper with Jupiter’s moon Europa during one of its close flybys

Artificial Intelligence in the Intensive Care Unit

AbstractThe diffusion of electronic health records collecting large amount of clinical, monitoring, and laboratory data produced by intensive care units (ICUs) is the natural terrain for the application of artificial intelligence (AI). AI has a broad definition, encompassing computer vision, natural language processing, and machine learning, with the latter being more commonly employed in the ICUs. Machine learning may be divided in supervised learning models (i.e., support vector machine [SVM] and random forest), unsupervised models (i.e., neural networks [NN]), and reinforcement learning. Supervised models require labeled data that is data mapped by human judgment against predefined categories. Unsupervised models, on the contrary, can be used to obtain reliable predictions even without labeled data. Machine learning models have been used in ICU to predict pathologies such as acute kidney injury, detect symptoms, including delirium, and propose therapeutic actions (vasopressors and fluids in sepsis). In the future, AI will be increasingly used in ICU, due to the increasing quality and quantity of available data. Accordingly, the ICU team will benefit from models with high accuracy that will be used for both research purposes and clinical practice. These models will be also the foundation of future decision support system (DSS), which will help the ICU team to visualize and analyze huge amounts of information. We plea for the creation of a standardization of a core group of data between different electronic health record systems, using a common dictionary for data labeling, which could greatly simplify sharing and merging of data from different centers

Additive Manufacturing using UV Polymerization of Complex Surfaces Generated by Two Main B-Splines

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L’evoluzione quanti-qualitativa dei flussi turistici: il movimento turistico in Campania

Questo testo è stato pubblicato anche in un Report "L’impatto territoriale e socioeconomico del turismo in Campania (marzo 2008)" a cura dell'Osservatorio Del Turismo della Regione Campania, scaricabile alla pagina: http://www.ontit.it/opencms/export/sites/default/ont/it/documenti/archivio/files/ONT_2008-03-01_00776.pd

Robust Bayesian particle filter for space object tracking under severe uncertainty

This paper introduces a robust Bayesian particle filter that can handle epistemic uncertainty in the measurements, dynamics, and initial conditions. The robust filter returns robust bounds on the output quantity of interest, rather than a crisp value. Particles are generated with an importance sampling technique and propagated only one time during the estimation process. The proposal distribution is constructed by running a parallel unscented Kalman filter to drive particles in regions of high expected likelihood and achieve a high effective sample size. The bounds are then computed by an inexpensive tuning of the importance weights via numerical optimization. A Branch & Bound algorithm over simplexes with a Lipschitz bounding function is employed to achieve guaranteed convergence to the lower and upper bounds in a finite number of steps. The filter is applied to the robust computation of the collision probability of SENTINEL 2B with a FENGYUN 1C debris in different operational instances, all characterized by a mix of aleatory and epistemic uncertainty on initial conditions and observation likelihoods

La catena di creazione del valore: il sistema di offerta turistico campano

Questo testo è stato pubblicato anche in un Report "L’impatto territoriale e socioeconomico del turismo in Campania (marzo 2008)" a cura dell'Osservatorio Del Turismo della Regione Campania, scaricabile alla pagina: http://www.ontit.it/opencms/export/sites/default/ont/it/documenti/archivio/files/ONT_2008-03-01_00776.pd

Il "Sistema Locale di Offerta Turistica" nella provincia di Benevento: un modello allo stato embrionale

Questo testo è stato pubblicato anche in un Report "L’impatto territoriale e socioeconomico del turismo in Campania (marzo 2008)" a cura dell'Osservatorio Del Turismo della Regione Campania, scaricabile alla pagina: http://www.ontit.it/opencms/export/sites/default/ont/it/documenti/archivio/files/ONT_2008-03-01_00776.pd

El trabajo juvenil y la calidad de vida en la ciudad de Palermo

Objetivo: El objetivo de la presente investigación es indagar sobre la relación entre condición laboral y calidad de vida, es decir cómo la calidad del trabajo influye directamente en el acercamiento psico-físico a la propia vida personal, midiendo, en particular, en el ámbito de una más amplia distinción entre trabajo autónomo y trabajo asalariado o dependiente, y comprender cómo el trabajo afecta a los principales aspectos socio-relacionales, por ejemplo la actitud hacia la actividad laboral, la gestión del tiempo, la utilizacion del tiempo libre, la relación con el dinero, las actitudes y los valores transmitidos por la familia en el trabajo. “Ad adiuvandum” queremos tambien comprender cómo el contexto social puede influir sobre el proceso productivo. La siguiente investigación se orienta, por primera vez en Italia, a enmarcar estos aspectos del trabajo en el panorama socio-económico de una grande metrópoli de Italia Meridional, la ciudad de Palermo y su provincia. Método: Los participantes en la investigación son 200 jóvenes de edad comprendida entre los 20 y los 35 años residentes en la ciudad de Palermo y en su provincia a los que han sido suministrados cuestionarios estructurados con preguntas abiertas y cerradas y después la escala del “Empowerment”. Los sujetos a los que se suministraron los cuestionarios y la escala del empowerment han sido divididos en dos macrogrupos: los trabajadores autónomos y los trabajadores dependientes. Para analizar los datos se utilizó: el análisis del contenido, el cálculo de las frecuencias, el test del Chi-cuadrado y el análisis de la varianza. Resultados: De los daros que surgen del cuestionario se evidencian, contra lo esperado, resultados homogéneos con las mismas orientaciones en los participantes que pertenecen a los dos grupos en relación a algunas hipótesis formuladas, mientras que en algunas hipotesis formuladas se confirman los diferentes resultados entre los dos grupos de trabajadore. Conclusiones: Esta investigación, única hoy en su género, en el territorio palermitano, por cuanto hemos podido averiguar, confirma en parte las hipótesis formuladas en principio: los datos demuestran, de hecho, cómo el trabajo desarrollado por los participantes en la investigación influye de manera determinante sobre algunos aspectos fundamentales y contenidos en las áreas de investigación A, B, E mientras no resultan confirmadas las hipótesis contenidas en las áreas C y D. Sirndo la actitud hacia la actividad laboral (área A); la gesión del tiempo (área B) La utilizacion del tiempo libre (área C), la gestión del dinero (área D) y las actitudes y valores transmitidos por la familia de origen hacia el trabajo (área E). A la luz de estos resultados es posible demostrar varias de las hipótesis fundamentales de la investigación que, como se decía, pretende demostrar la conexión directa entre trabajo, expectativas y calidad devida personal de los trabajadores.Objective: The aim of this research is to investigate the relationship between working condition and quality of life, in other word show the working quality affects the psyco-physic approach directly on our own personal life. Making a distinction between independent and dipendent work, we want to evaluate how the work influences the main socio relational aspects, like for example the behavior towards working activity, time organization, free time using, relationship with money, the attitudes and values passed down by the family about the work. Ad adiuvandum, to understand how the social context can influence this constructive process, we choose for the first time to focus this research in the socio-economic scenery of a large city of the South of Italy, the city of Palermo and its province. Method: The research participants are people between 20 and 35 years old, living in Palermo and its province, to whom have been given 200 questionnaires with open and closed questions as wellas the empowerment scale. The subjects who have answered to the questionnaire and empowerment scale have been divided in two macro groups: independent and dependent workers. To analyse these data we have used the following criteria: content analysis, frequency calculation, Chi-square test andvariance analysis. Results: According to the questionnaires results, we are surprised by homogeneous data related to some formulated hipotesis, while different results are confirmed in the two groups concerning other hipotesis. Conclusions: This research, partially confirms the ipotesis stated at the beginning: the data show how the research participants jobs affect some principal aspects contained in the investigation areas A, B, E, while the hipotesis of Investigation area C and D are not fully confirmed. In the light of these considerations, It is possible to underline one of the essential hipotesis of this research: the direct connection between work, expectations and quality of life