382 research outputs found
A knowledge based tool-kit for collaborative tradespace exploration: A front-end support to concurrent decisionmaking
No full textConcurrent engineering has reached a huge popularity among companies and agencies, especially when compared with classic design approaches in early design phases. This trend is caused by all the benefits observable in early design performances. Examples are given by reduced design time, reduced costs and improvement of design quality. These qualities are also proven by the space agencies' experiences. Indeed, agencies are currently adopting the concurrent approach as their state of the art approach for conceptual and preliminary design of their future space missions. Despite all the benefits obtained by the concurrent approach, designers currently don't have a clear view of all the alternatives that can be evaluated when designing a space system. The manuscript presents a Microsoft Excel® add-on, which can be integrated with a concurrent engineering open source software, such as the European Space Agency's Open Concurrent Design Tool. The aim is to assist the designers via a graphical user interface which integrates two main tools: autonomous generation and exploration of the concurrent tradespace and domain knowledge exploration. The generated tradespace is constrained to the choices of the other designers. In fact, the generation is obtained by the analysis of the data shared within the design team and by the applicable knowledge when components database and mission information are addressed. The proposed tool is also flexible with the environment of application, from the academic one to industrial mission design and optimization. Indeed, it could be used in either academic or industrial environment, aiming to both assisting during the design phase and assisting the training activities. The users can explore the sensitivity of their choices and learn how an actual decision on their domain influences all the other technical domains involved with the design. The tool offers also the capability of learning and exploring new concepts thanks to the assistance provided by the expert's knowledge that can be applied when a specific context is under analysis. Furthermore, in an industrial environment, the tool demonstrates its benefits. Examples are given by stored and updatable knowledge and guided tradespace optimization which entails reduced design time and costs. These benefits are obtained thanks to a clear and complete visualization of the design alternatives with a quantitative measure of their outcomes. Finally, the paper presents the decision-making tool within a university concurrent design facility exploring in details the peculiar characteristic and benefits given to the design sessions
Deep learning for event detection: Autonomous operations for interplanetary missions
No full textThe history of Artificial Intelligence covers more than five decades, alternating periods of great enthusiasm and prosperity with periods of scepticism. In recent years, Artificial Intelligence has entered a new period of scientific relevance, with countless applications being developed in several scientific fields: medicine, security, speech recognition, image classification and more. The reason behind this progress is clear: Artificial Intelligence allows the implementation of algorithms that origin directly from human knowledge, emulating human behaviours and improving them. Despite the diffusion of these algorithms in several fields, Artificial Intelligence in space engineering has yet to find a defined sphere where it emerges from the competition of other algorithms. Nonetheless, several key directions where Artificial Intelligence has been applied have shown incredible progress in the last decade: mission replanning, fault detection, payload data selection and prioritization can be cited. The paper presents the key advancements and applications developed at Politecnico di Torino in the field of Artificial Intelligence for Space Mission Autonomy, focusing in particular on autonomous event detection during interplanetary missions. The key technology that lies behind the presented research falls in the category of Machine Learning, and in particular in the field of Deep Learning. This technology is used to perform event detection for missions around asteroid and comet objects, performing autonomous detection of key events such as plumes, impacts and changes in brightness. The algorithm, developed in Matlab, is presented and described into details, covering aspects of the design of the network, considerations on its performances, training dataset construction and training strategies. Finally, the algorithm is ported on an embedded board representing the spacecraft Command and Data Handling subsystem. The resulting Hardware-in-the-Loop simulation is described, where a CMOS Image Sensor is used as a sensor to perform the event detection in situ during the mission. The research demonstrates the feasibility of the presented training approach thanks to the embedded implementation described
Tri-Bimaximal Neutrino Mixing and Discrete Flavour Symmetries
No full textWe review the application of non-Abelian discrete groups to Tri-Bimaximal (TB) neutrino mixing, which is supported by experiment as a possible good first approximation to the data. After summarizing the motivation and the formalism, we discuss specific models, mainly those based on A4 but also on other finite groups, and their phenomenological implications, including the extension to quarks. The recent measurements of \theta_13 favour versions of these models where a suitable mechanism leads to corrections to \theta_13 that can naturally be larger than those to \theta_12 and \theta_23. The virtues and the problems of TB mixing models are discussed, also in connection with lepton flavour violating processes, and the different approaches are compared.We review the application of non-Abelian discrete groups to Tri-Bimaximal (TB) neutrino mixing, which is supported by experiment as a possible good first approximation to the data. After summarizing the motivation and the formalism, we discuss specific models, mainly those based on A_4 but also on other finite groups, and their phenomenological implications, including the extension to quarks. The recent measurements of theta_13 favour versions of these models where a suitable mechanism leads to corrections to theta_13 that can naturally be larger than those to theta_12 and theta_23. The virtues and the problems of TB mixing models are discussed, also in connection with lepton flavour violating processes, and the different approaches are compared.We review the application of non-Abelian discrete groups to Tri-Bimaximal (TB) neutrino mixing, which is supported by experiment as a possible good first approximation to the data. After summarizing the motivation and the formalism, we discuss specific models, mainly those based on A4 but also on other finite groups, and their phenomenological implications, including the extension to quarks. The recent measurements of \theta_13 favour versions of these models where a suitable mechanism leads to corrections to \theta_13 that can naturally be larger than those to \theta_12 and \theta_23. The virtues and the problems of TB mixing models are discussed, also in connection with lepton flavour violating processes, and the different approaches are compared
Revisiting bimaximal neutrino mixing in a model with S-4 discretesymmetry
No full textIn view of the fact that the data on neutrino mixing are stillcompatible with a situation where Bimaximal mixing is valid in firstapproximation and it is then corrected by terms of O(lambda(C)) (withlambda(C) being the Cabibbo angle), arising from the diagonalization ofthe charged lepton masses, such that delta sin(2)theta(12) similar tosin theta(13) similar to O(lambda(C)) while delta sin(2)theta(23)similar to O(lambda(2)(C)), we construct a model based on the discretegroup S 4 where those properties are naturally realized. The model issupersymmetric in 4-dimensions and the complete flavour group is S-4 xZ(4) x U(1)(FN), which also allows to reproduce the hierarchy of thecharged lepton spectrum. The only fine tuning needed in the model is toreproduce the small observed value of r = Delta m(sun)(2)/Deltam(atm)(2). Once the relevant parameters are set to accommodate r thenthe spectrum of light neutrinos shows a moderate normal hierarchy andis compatible, within large ambiguities, with the constraints fromleptogenesis as an explanation of the baryon asymmetry in the Universe.Citazioni 36 (Source: SPIRES, Date 7.7.2010
Repressing Anarchy in Neutrino Mass Textures
No full textThe recent results that is relatively large, of the order of the previous upper bound, and the indications of a sizable deviation of from the maximal value are in agreement with the predictions of Anarchy in the lepton sector. The quark and charged lepton hierarchies can then be reproduced in a SU(5) GUT context by attributing non-vanishing charges, different for each family, only to the SU(5) tenplet states. The fact that the observed mass hierarchies are stronger for up quarks than for down quarks and charged leptons supports this idea. As discussed in the past, in the flexible context of , different patterns of charges can be adopted going from Anarchy to various types of hierarchy. We revisit this approach by also considering new models and we compare all versions to the present data. As a result we confirm that, by relaxing the extreme ansatz of equal charges for all SU(5) pentaplets and singlets, better agreement with the data than for Anarchy is obtained without increasing the model complexity. We also present the distributions obtained in the different models for the Dirac CP-violating phase. Finally we discuss the relative merits of these simple models.The recent results that is relatively large, of the order of the previous upper bound, and the indications of a sizable deviation of from the maximal value are in agreement with the predictions of Anarchy in the lepton sector. The quark and charged lepton hierarchies can then be reproduced in a SU(5) GUT context by attributing non-vanishing charges, different for each family, only to the SU(5) tenplet states. The fact that the observed mass hierarchies are stronger for up quarks than for down quarks and charged leptons supports this idea. As discussed in the past, in the flexible context of , different patterns of charges can be adopted going from Anarchy to various types of hierarchy. We revisit this approach by also considering new models and we compare all versions to the present data. As a result we confirm that, by relaxing the extreme ansatz of equal charges for all SU(5) pentaplets and singlets, better agreement with the data than for Anarchy is obtained without increasing the model complexity. We also present the distributions obtained in the different models for the Dirac CP-violating phase. Finally we discuss the relative merits of these simple models
23Na and 35/37Cl as NMR probes of growth and shape of sodium taurodeoxycholate micellar aggregates in the presence of NaCl
No full textThe growth of the aggregates of the dihydroxylated bile salt sodium taurodeoxycholate (NaTDC) upon NaCl addition and the involvement of the counterion were investigated by NMR spectroscopy of monoatomic ionic species. 23Na T1 values from 0.015, 0.100, and 0.200 mol kg1 NaTDC solutions in D2O, at variable NaCl content, proved to be sensitive to the transition from primary to secondary aggregates, which occurs in the former sample, and to intermicellar interaction. Some 79Br NMR measurements were performed on a 0.100 mol kg1 NaTDC sample added by NaBr in place of NaCl for comparison purposes. The 23Na, 35Cl, and 37Cl double quantum filtered (DQF) patterns, from the 0.100 mol kg1 NaTDC sample, and 23Na ones also from the 0.200 mol kg1 NaTDC one, in the presence of 0.750 mol kg1 NaCl, are a clear manifestation of motional anisotropy. Moreover, the DQF spectra of 23Na and 37Cl, which possess close quadrupole moments, display a striking similarity. The DQF lineshapes were simulated exploiting the Scilab environment to obtain an estimate of the residual quadrupole splitting magnitude. These results support the description of NaTDC micelles as cylindrical aggregates, strongly interacting at high ionic strengths, and capable of association with added electrolytes
STARSIM: a stand-alone tool for "in-the-loop" verification
No full textIn the last decades, systems have strongly increased their complexity remarking the importance of defining methods and tools that improve the design, verification and validation of the system process: effectiveness and costs reduction without loss of confidence in the final product are the objectives that have to be pursued. Within the System Engineering context, the modern Model and Simulation based approach is a promising strategy because it reduces the wasted resources with respect to the traditional methods. Considering a wild range of simulations architectures and methods, crucial stages are defined by algorithm in the loop (AIL), software in the loop (SIL), hardware in the loop (HIL). This paper presents an in-house tool, developed at Politecnico di Torino, able to perform different simulation sessions in any phase of the space product life-cycle using a unique and self-contained platform, called StarSim: modularity, flexibility, real time operation, fidelity with real world, ease of data management, effectiveness and congruence of the outputs with respect to the inputs are StarSim sought-after features. The main issue is to guarantee the possibility to verify the behavior of the system under test thanks to virtual models, that substitute all those elements not yet available and all the non-reproducible dynamics and environmental conditions. Progressively, pieces of the on board software and hardware can be introduced without stopping the process of design and verification, avoiding delays and loss of resources. StarSim has been applied for the first time on the e-st@r-II Cubesat, developed the "CubeSat Team Polito" within the ESA Education Office initiative called "Fly Your Satellite". StarSim has been mainly used for the payload development, an Active Attitude Determination and Control System, but StarSim's capabilities have also been updated to evaluate functionalities, operations and performances of the entire satellite. AIL, SIL, HIL simulations have been constantly performed, successfully verifying a great number of functional and operational requirements. In particular, attitude determination algorithms, control laws, modes of operation have been selected and verified; software has been developed step by step and the bugs-free executable files have been loaded on the micro- controller. Actuators, logic and electrical circuits have been designed, built and tested and sensors calibrated. Problems such as real time and synchronization have been solved, allowing, at the end of the process, a complete hardware in the loop simulation test for the entire satellite. The case study has allowed the successfully validation of the first release of StarSim
Baryon and lepton nonconservation in supersymmetric models
No full textThe possible baryon- and lepton-nonconserving effective interactions among ordinary particles are analysed in the frame of SU 3×SU2×U1supersymmetric models. Operators of lower dimensionalities than in ordinary GUTs are generally allowed in the supersymmetric schemes of Dimopoulos and Georgi type, in which a discrete symmetry is imposed to guarantee B and L conservation in renormalizable terms. Operators of the same dimensionalities as in GUTs are obtained, instead, in the schemes of the type considered by Weinberg and by Sakai and Yanagida, where either R-invariance or an extra U 1 gauge factor is assumed. However, the different terms lead in most cases, with the exception of the ΔB=ΔL proton decay, to unobservable rates for physical processes, unless Higgs supermultiplets are introduced at an intermediate mass scale. © 1982 Società Italiana di Fisica
Considerazioni cliniche sull’asportazione di un corpo estraneo dal canale vertebrale di un cane
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