On Provably Safe and Live Multirobot Coordination With Online Goal Posting

A standing challenge in multirobot systems is to realize safe and efficient motion planning and coordination methods that are capable of accounting for uncertainties and contingencies. The challenge is rendered harder by the fact that robots may be heterogeneous and that their plans may be posted asynchronously. Most existing approaches require constraints on the infrastructure or unrealistic assumptions on robot models. In this article, we propose a centralized, loosely-coupled supervisory controller that overcomes these limitations. The approach responds to newly posed constraints and uncertainties during trajectory execution, ensuring at all times that planned robot trajectories remain kinodynamically feasible, that the fleet is in a safe state, and that there are no deadlocks or livelocks. This is achieved without the need for hand-coded rules, fixed robot priorities, or environment modification. We formally state all relevant properties of robot behavior in the most general terms possible, without assuming particular robot models or environments, and provide both formal and empirical proof that the proposed fleet control algorithms guarantee safety and liveness

TULOU: THE RAMMED EARTH DWELLINGS OF FUJIAN (CHINA). FUNCTIONAL, TYPOLOGICAL AND CONSTRUCTIVE FEATURES

Abstract. This research is focused on different aspects concerning two types of Tulou: Minnan and Hakka Tulou. Through the analysis of eight case studies, we managed to highlight the relation between typological-functional features and constructive ones aiming to offer a more orderly analysis of distinct models, divided into two substantially different families. Future studies will further analyse the knowledge of these rammed earth buildings by studying the phases of the construction site, conducting architectural surveys on the most important details and investigating the mechanical behaviour of both types. The future goal is the creation of a "Manuale del recupero dei Tulou" (Manual on Tulou restoration) in order to provide a guide for restoration and spread the knowledge about original materials and techniques applied in the construction of these unique rammed earth architectures. The research, which is currently ongoing, has been carried out by the Architecture Department of Roma Tre University in cooperation with Fuzhou University

SN1987A: Revisiting the Data and the Correlation between Neutrino and Gravitational Detectors

We re-examine the data taken by the neutrino detectors during the supernova SN1987A. It is found that the Kamiokande data, in addition to the well known burst at 7:35 hours UT, show another one at 7:54 hours, with seven pulses in 6.2 seconds. This second burst supports the idea that the duration of the collapse was much longer than a few seconds, as already suggested by the LSD detection at 2:56 hours the same day, i.e. four and a half hours earlier. The correlations between the gravitational wave detectors (Rome and Maryland) and the neutrino detectors are also revisited. It is shown that the g.w. detectors exhibit significant correlations with both the LSD and the Kamiokande detectors over periods of one-two hours that are centered, in both cases, at the LSD time.Comment: Presented at the VULCANO WOKSHOP 2008, Frontier Objects in Astrophysics and Particle Physics, May 26-3

On uniform k-partition problems

AbstractWe study various uniform k-partition problems which consist in partitioning m sets, each of cardinality k, into k sets of cardinality m such that each of these sets contains exactly one element from every original set. The problems differ according to the particular measure of “set uniformity” to be optimized. Most problems are polynomial and corresponding solution algorithms are provided. A few of them are proved to be NP-hard. Examples of applications to scheduling and routing problems are also discussed

Indoor real-time localisation for multiple autonomous vehicles fusing vision, odometry and IMU data

Due to the increasing usage of service and industrial autonomous vehicles, a precise localisation is an essential component required in many applications, e.g. indoor robot navigation. In open outdoor environments, differential GPS systems can provide precise positioning information. However, there are many applications in which GPS cannot be used, such as indoor environments. In this work, we aim to increase robot autonomy providing a localisation system based on passive markers, that fuses three kinds of data through extended Kalman filters. With the use of low cost devices, the optical data are combined with other robots’ sensor signals, i.e. odometry and inertial measurement units (IMU) data, in order to obtain accurate localisation at higher tracking frequencies. The entire system has been developed fully integrated with the Robotic Operating System (ROS) and has been validated with real robots

Measurements and modelling of shelf sea productivity using oxygen-argon ratios and oxygen triple isotopes

This thesis provides net (N) and gross (G) oxygen production estimates for North Sea surface waters during late summer 2019. Net production rates (N(O2/Ar)) were based on the O2/Ar saturation anomaly Δ(O2/Ar), while triple oxygen isotopes were used as tracer for gross production (G(17O)). The research revealed that on average, surface waters were in metabolic balance (N(O2/Ar) = (–3±40) mmol m–2 d–1). Stations located closest to UK coasts were net heterotrophic (N(O2/Ar) = (–29±21) mmol m–2 d–1 < 0) despite high G(17O) values of (500±90) mmol m–2 d–1. This result suggests strong remineralisation occurring in the area. Using a modelling approach, this thesis also investigated the robustness of the steadystate assumption for net and gross production estimates in a shelf sea environment. Station L4 (Western English Channel), was used as case study. Results showed that the steady-state approach can be improved by using a repeat discrete sampling strategy to estimate as non-steady-state contributions to G(17O) and N(O2/Ar) and reduce the prediction error by 53 % and 75 %, respectively. We also used model simulations to investigate the impact of phytoplankton species-specific isotope effects in photosynthesis on diagnosed G(17O). We found that neglecting these isotope effects can cause a small systematic overestimate of G(17O), rising to up to +50 % during the spring bloom at Station L4. Taken together, these results can be used to design observational studies aimed at determining G(17O) and N(O2/Ar) in dynamic shelf-sea environments like Station L4. (Super- and subscript is not shown in this abstract due to textbox limitations for complex formatting)

The fast matched filter for gravitational-wave data analysis: Characteristics and applications

We report on the application of a matched filter to the data of two-mode resonant gravitational-wave antennas for the detection of burst signals, with reference to data obtained by direct acquisition, i.e. without going through lock-in amplifiers, sampled at relatively high speed. After a review of the basic model of resonant detectors, that includes a discussion of the signal and of the noise, we present a detailed mathematical derivation of the optimum filter matched to an input burst. We then analyze and discuss the performance of the matched filter as regards both the improvement of the signal-to-noise ratio and the observation bandwidth, also considering the adaptive realization of the filter, based on the actual spectrum of the noise as estimated from the data. The discussion that follows is centered on various aspects concerning the practical application of the matched filter as well as the loss of performance due both to uncertainties on the parameters used for building the filter and to various discretization effects, both in the time and frequency domains. Finally, we consider some experimental results obtained by applying the matched filter to the data of the Explorer detector, also providing a comparison with what we obtained by applying an optimum filter to data processed by lock-in amplifiers, sampled at lower speed