1,505 research outputs found
Sparsity promoting hybrid solvers for hierarchical bayesian inverse problems
No full textThe recovery of sparse generative models from few noisy measurements is an important and challenging problem. Many deterministic algorithms rely on some form of l1-l2 minimization to combine the computational convenience of the l2 penalty and the sparsity promotion of the l1. It was recently shown within the Bayesian framework that sparsity promotion and computational efficiency can be attained with hierarchical models with conditionally Gaussian priors and gamma hyperpriors. The related Gibbs energy function is a convex functional, and its minimizer, which is the maximum a posteriori (MAP) estimate of the posterior, can be computed efficiently with the globally convergent Iterated Alternating Sequential (IAS) algorithm [D. Calvetti, E. Somersalo, and A. Strang, Inverse Problems, 35 (2019), 035003]. Generalization of the hyperpriors for these sparsity promoting hierarchical models to a generalized gamma family either yield globally convex Gibbs energy functionals or can exhibit local convexity for some choices for the hyperparameters [D. Calvetti et al., Inverse Problems, 36 (2020), 025010]. The main problem in computing the MAP solution for greedy hyperpriors that strongly promote sparsity is the presence of local minima. To overcome the premature stopping at a spurious local minimizer, we propose two hybrid algorithms that first exploit the global convergence associated with gamma hyperpriors to arrive in a neighborhood of the unique minimizer and then adopt a generalized gamma hyperprior that promotes sparsity more strongly. The performance of the two algorithms is illustrated with computed examples
Strategies for new measurements in the VH, H → bb channel in ATLAS
No full textThe analysis of the data collected by the ATLAS detector for the search of the associate production of a Higgs boson decaying in bb and a W or Z boson decaying leptonically is briefly described. This analysis led in 2017 to the first evidence of the Higgs boson decaying in b b. The same analysis channel can be used in the so-called Simplified Template Cross-Section Framework to extract information on the Higgs couplings and eventually on their variations due to Beyond the Standard Model physics effects
Note sul concetto di ‘stato’ e ‘nazione’ nel Giappone alla fine dell’Ottocento”, in Patrie. Territori mentali
No full textL'articolo ripercorre la formazione del lessico giapponese relativo ai campi semantici di "stato" e "nazione" intesi in senso moderno, nella seconda metà dell'800, quando tali termini ancora non esistevano. Anche il contatto con l'Occidente contribuì alla formazione dei lessici politici, filosofici, sociali, dopo l'apertura dei porti successiva alla Restaurazione Meiji (1868)
Regional Integration in East Asia: Can Japan Be a Leading Player?
No full textSince the end of the Cold War, East Asia has been experiencing a growing commitment
on the part of national governments towards regional cooperation in such key areas as
trade, finance and security. The institutionalisation of intra-regional relations is investigated with
a focus on the role of Japan, in order to assess the country’s past achievements, and potential for
further contributions. The first section outlines in general terms what the incentives are to pursue
multilateralism at regional level, then points at the problems that may arise from the formation
of overlapping frameworks. The second section discusses more specifically the position of Japan
with respect to the competing ‘Asian’ and ‘Asia-Pacific’ schemes, commenting on game theory
as applied to the relation between these two regional models. On this basis, the latter part of the
paper explores in detail the development of diplomatic frameworks in East Asia, seeking to explain
the reasons for the centrality of ASEAN in the resulting regional architecture. The final paragraphs
further elaborate on the Japanese perspective on the idea of an ‘East Asian community’,
as expressed by successive cabinets in the last decade. The conclusion, while reaffirming that the
open character of regionalism in East Asia allows Japan to take initiative as a major player, also
addresses the political obstacles in the way of closer integration
Numerical simulation of dry granular flows: from the reproduction of small-scale experiments to the prediction of rock avalanches
No full textNumerical Modelling of Permafrost Degradation Effects on Rock Slopes
No full textRockfalls and rockslides are being observed with increased frequency in high mountains during last decades. Permafrost degradation, driven by global warming, is considered to be the main triggering factor. This paper describes a series of Distinct Element simulations of a selected rock face, where the presence of ice in joints is taken into consideration. These simulations are part of a wider multi-scale approach to modelling of potentially rock slopes. Previous research at the material scale (ice and frozen soil) allowed defining an original failure criterion for continuous and discontinuous rock joints filled with ice. This criterion is now included in large scale DEM model of punta Gnifetti (4554 m asl - Monte Rosa massif) in order to reproducing the actual configuration through back-analysis based on geomechanical investigation, and assessing evolutionary scenarios driven by the increase of persistence and of temperature. Relevant numerical issues, regarding boundary conditions and model generation are preliminary discussed, as well
Hi-J: High-School Japanese Learning System
No full textProject of the Italian Association for Japanese Language teaching (AIDLG), funded by the Japan Foundation Sakura Network gran
Stochastic modelling of muscle recruitment during activity
No full textMuscle forces can be selected from a space of muscle recruitment strategies that produce stable motion and variable muscle and joint forces. However, current optimization methods provide only a single muscle recruitment strategy. We modelled the spectrum of muscle recruitment strategies while walking. The equilibrium equations at the joints, muscle constraints, static optimization solutions and 15-channel electromyography (EMG) recordings for seven walking cycles were taken from earlier studies. The spectrum of muscle forces was calculated using Bayesian statistics and Markov chain Monte Carlo (MCMC) methods, whereas EMG-driven muscle forces were calculated using EMG-driven modelling. We calculated the differences between the spectrum and EMG-driven muscle force for 1–15 input EMGs, and we identified the muscle strategy that best matched the recorded EMG pattern. The best-fit strategy, static optimization solution and EMG-driven force data were compared using correlation analysis. Possible and plausible muscle forces were defined as within physiological boundaries and within EMG boundaries. Possible muscle and joint forces were calculated by constraining the muscle forces between zero and the peak muscle force. Plausible muscle forces were constrained within six selected EMG boundaries. The spectrum to EMG-driven force difference increased from 40 to 108 N for 1–15 EMG inputs. The best-fit muscle strategy better described the EMG-driven pattern (R2 = 0.94; RMSE = 19 N) than the static optimization solution (R2 = 0.38; RMSE = 61 N). Possible forces for 27 of 34 muscles varied between zero and the peak muscle force, inducing a peak hip force of 11.3 body-weights. Plausible muscle forces closely matched the selected EMG patterns; no effect of the EMG constraint was observed on the remaining muscle force ranges. The model can be used to study alternative muscle recruitment strategies in both physiological and pathophysiological neuromotor conditions
ROCKFALL IMPACTS ON SHELTERING TUNNELS: REAL SCALE EXPERIMENTS
No full textIn this paper the results of a series of rockfall impact tests on a sheltering tunnel are discussed. A RC concrete sphere (mass 850 kg, diameter 0.9 m) was dropped (falling height ranging between 5 and 45 m) on a tunnel along a road in the Dolomites. This experimental campaign represents the extension of a previous one, performed at Politecnico di Milano (Campus Bovisa), when the same RC sphere was dropped on a circular pool filled with a loose sand stratum. Besides the mentioned differences, the new campaign is characterised by larger falling heights and the monitoring of the mechanical response of the shelter. A series of instruments have been employed to measure impact forces, stress propagation within the absorbing soil stratum on top of the shelter and its deflection.
The results, which are in good agreement with available literature data, are presented with the aim of highlighting the features of the complex impact event and discussing the engineering factors to be considered for conceiving a realistic and reliable design approach. As to this point, the main conclusion is that the impact force is unaffected by the presence of the plate, and that the stress increment on the structure is slightly reduced by the structure deflection, which can be neglected for design purposes without unreasonable levels of conservatism being introduced
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