A Flexible Transport Service for Passengers

AbstractThe realization of innovative passengers transport services requires more and more often a greater flexibility and inexpensiveness of the service. To answer this request in many cases the physical solution is to realize a demand responsive transportation system (DRTS). A DRTS require the planning of travel paths (routing) and customers pick-up and drop-off times (scheduling) according to received requests, respecting the limited capacity of the fleet and time constraints (hard time windows) for each network's node, and the service time of the system. By the modelling point of view a DRTS can be effectively represented with a Dial-a-ride problem (DaRP). A DaRP derives from the Pick-up and Delivery Problem with Time Windows (PDPTW) and may operate according to a static or to a dynamic mode. In the static setting, all customers’ requests are known beforehand and the DaRP returns the vehicles routing and the passengers pick up and drop off time scheduling. The static setting may be representative of a phase of reservation occurred the day before the execution of the service. But, if the reservation requests must be processed on-line, even during the booking process there may be a certain level ad dynamism. In fact, if the algorithm works online, it manages each and every incoming request separately, and accepts or refuses it immediately, without knowing anything about the following. The operative program is constantly updated after each received request without refusal to carry out previous accepted services. In the dynamic mode, customers’ requests arrive when the service is already running and, consequently, the solution may change whilst the vehicle is already travelling. In this mode it is necessary that the schedule is updated when each new request arrives and that this is done in a short time to ensure that the potential customer will not leave the system before a possible answer. In this work, we describe a flexible people transport system capable of managing incoming transport demand in dynamic mode, using a solution architecture based on a two-stage algorithm to solve Dial-a-Ride Problem instances. In the first stage, a constructive heuristic algorithm quickly provides a feasible solution to accept the incoming demand. The algorithm in the second stage try to improve the solution evaluated at the first stage by using the time between two consecutive transportation events. The algorithm, unlike most of the works in the literature, use an objective function that optimizes the service punctuality

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

Finding the ℓ-core of a tree

AbstractAn ℓ-core of a tree T=(V,E) with |V|=n, is a path P with length at most ℓ that is central with respect to the property of minimizing the sum of the distances from the vertices in P to all the vertices of T not in P. The distance between two vertices is the length of the shortest path joining them. In this paper we present efficient algorithms for finding the ℓ-core of a tree. For unweighted trees we present an O(nℓ) time algorithm, while for weighted trees we give a procedure with time complexity of O(nlog2n). The algorithms use two different types of recursive principle in their operation

Spitzer-IRS high resolution spectroscopic survey of the 12 micron Seyfert galaxies: II. Results for the Complete Dataset

We present the Spitzer 10-37um IRS high resolution (R~600) spectroscopic survey of the Seyfert galaxies of the 12 micron Galaxy Sample. The new spectra of 61 galaxies, with those already published, gives us a total of 91 12micron Seyfert galaxies observed, out of 112. We use an improved AGN classification for Seyfert galaxies: instead of the type 1 and 2 classes, we use the spectropolarimetric data to divide them into "AGN 1" and "AGN 2", where AGN 1's include all broad-line objects, including the Seyfert 2's showing hidden broad lines in polarized light, while AGN 2's contains only Seyferts with no detectable broad lines at all. We present various mid-IR observables and we find that these properties characterize the AGN 1's objects as a single family, with strongly AGN-dominated spectra. In contrast, the AGN 2's can be divided in two groups, the first one with properties similar to the AGN 1's and the second similar to the non-Seyfert galaxies, such as LINERs or starburst galaxies. We computed a semianalytical model to estimate the AGN and the starburst contributions to the mid-IR galaxy emission at 19um. We find that AGN 1 have an AGN contribution >73% and AGN 2 >45% of their total emission at 19um. The detection of [NeV] lines is an almost perfect signature of energy production by an AGN. We present mean spectra of the various AGN categories. We derive the first local luminosity functions for the mid-infrared lines and the PAH feature. No statistical difference is found in the space densities for Seyfert 1's and 2's, nor for the new classes of AGN 1's and 2's. The global output of accretion-powered galactic nuclei in the local universe is derived from the correlation between [NeV] line and the nonstellar IR continuum luminosity.Comment: Accepted in The Astrophysical Journal Part 1 on November 15, 2009. 58 page

SDSS IV MaNGA : metallicity and ionisation parameter in local star-forming galaxies from Bayesian fitting to photoionisation models

We measured gas-phase metallicity, ionisation parameter, and dust extinction for a representative sample of 1795 local star-forming galaxies using integral field spectroscopy from the SDSS-IV MaNGA survey. We self-consistently derive these quantities by compar ing observed line fluxes with photoionisation models using a Bayesian framework. We also present the first comprehensive study of the [S iii]λλ9069,9532 nebular lines, which have long been predicted to be ideal tracers of the ionisation parameter. However, we find that current photoionisation model predictions substantially over-predict the intensity of the [S iii] lines, while broadly reproducing other observed optical line ratios. We discuss how to nonetheless make use of the information provided by the [S iii] lines by setting a prior on the ionisation parameter. Following this approach, we derive spatially resolved maps and radial profiles of metallicity and ionisation parameter. The metallicity radial profiles derived are comparable with previous works, with metallicity declining toward the outer parts and showing a flattening in the central regions. This is in agreement with infall models of galaxy formation, which predict that spiral discs build up through accretion of material, leading to an inside-out growth. On the other hand, ionisation parameter radial profiles are flat for low-mass galaxies, while their slope becomes positive as galaxy mass increases. However, the ionisation parameter maps we obtain are clumpy, especially for low-mass galaxies. The ionisation parameter is tightly correlated with the equivalent width of Hα [EW(Hα)], following a nearly universal relation, which we attribute to the change of the spectral shape of ionising sources due to ageing of Hii regions. We derive a positive correlation between ionisation parameter and metallicity at fixed EW(Hα), in disagreement with previous theoretical work that predict an anti-correlation

The impact of chest CT body composition parameters on clinical outcomes in COVID-19 patients

We assessed the impact of chest CT body composition parameters on outcomes and disease severity at hospital presentation of COVID-19 patients, focusing also on the possible mediation of body composition in the relationship between age and death in these patients. Chest CT scans performed at hospital presentation by consecutive COVID-19 patients (02/27/2020-03/13/2020) were retrospectively reviewed to obtain pectoralis muscle density and total, visceral, and intermuscular adipose tissue areas (TAT, VAT, IMAT) at the level of T7-T8 vertebrae. Primary outcomes were: hospitalization, mechanical ventilation (MV) and/or death, death alone. Secondary outcomes were: C-reactive protein (CRP), oxygen saturation (SO2), CT disease extension at hospital presentation. The mediation of body composition in the effect of age on death was explored. Of the 318 patients included in the study (median age 65.7 years, females 37.7%), 205 (64.5%) were hospitalized, 68 (21.4%) needed MV, and 58 (18.2%) died. Increased muscle density was a protective factor while increased TAT, VAT, and IMAT were risk factors for hospitalization and MV/death. All these parameters except TAT had borderline effects on death alone. All parameters were associated with SO2 and extension of lung parenchymal involvement at CT; VAT was associated with CRP. Approximately 3% of the effect of age on death was mediated by decreased muscle density. In conclusion, low muscle quality and ectopic fat accumulation were associated with COVID-19 outcomes, VAT was associated with baseline inflammation. Low muscle quality partly mediated the effect of age on mortality.We assessed the impact of chest CT body composition parameters on outcomes and disease severity at hospital presentation of COVID-19 patients, focusing also on the possible mediation of body composition in the relationship between age and death in these patients. Chest CT scans performed at hospital presentation by consecutive COVID-19 patients (02/ 27/2020-03/13/2020) were retrospectively reviewed to obtain pectoralis muscle density and total, visceral, and intermuscular adipose tissue areas (TAT, VAT, IMAT) at the level of T7-T8 vertebrae. Primary outcomes were: hospitalization, mechanical ventilation (MV) and/or death, death alone. Secondary outcomes were: C-reactive protein (CRP), oxygen saturation (SO2), CT disease extension at hospital presentation. The mediation of body composition in the effect of age on death was explored. Of the 318 patients included in the study (median age 65.7 years, females 37.7%), 205 (64.5%) were hospitalized, 68 (21.4%) needed MV, and 58 (18.2%) died. Increased muscle density was a protective factor while increased TAT, VAT, and IMAT were risk factors for hospitalization and MV/death. All these parameters except TAT had borderline effects on death alone. All parameters were associated with SO2 and extension of lung parenchymal involvement at CT; VAT was associated with CRP. Approximately 3% of the effect of age on death was mediated by decreased muscle density. In conclusion, low muscle quality and ectopic fat accumulation were associated with COVID-19 outcomes, VAT was associated with baseline inflammation. Low muscle quality partly mediated the effect of age on mortality

A Woman’s Loss of Imagination: Paola Masino’s Magical Realism in Nascita e morte della Massaia

Criticism on Paola Masino has flourished since the early 2000s. This increased attention has contributed towards reclaiming an author often overshadowed by the attention received by her partner, Massimo Bontempelli, the father of realismo magico. Masino experimented with a variety of styles—realismo magico was one of them—as she rejected strictly naturalistic forms of representation, preferring to co-opt myths and the supernatural. Nascita e morte della Massaia (1945) is Masino’s most renowned literary effort, both for its critique of Fascist Italy and for its sophisticated stylistic effects. Nascita, while indebted to Bontempelli’s theorizations, features all the chief characteristics listed in Faris’s analysis of magical realism as an international phenomenon, and illustrates how magical realism offers strategies for evading censorship to those writing against totalitarianism regimes. At the same time, it is an example of how magical realism can be used to denounce socially imposed gender roles. My analysis shows how this narrative mode emerges on multiple levels within Masino’s text

On Uniform K-Partition Problems

In this work we study various uniform k-partition problems which consist in partitioning a collection of m sets, each of them of cardinality k, into k sets of cardinality m such that each of these sets contains exactly one element coming from every original set. The problems dier according to the particular measure of \set uniformity" to be optimized. Most of the studied problems are polynomial and the 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. Key words: Partition, matrix permutation, algorithms, complexity.

Shortest viable path algorithm in multimodal networks

We consider an approach using label correcting techniques to find the shortest viable path from an origin to a destination, in a multimodal transportation network. A path is called viable if its sequence of modes is feasible with respect to a set of constraints. We present an ad hoc modification of the Chronological Algorithm to solve the multimodal shortest viable path problem. We show the resulting paths of an application on a network, for different number of modal transfers. Since the results are a solution set, the choice of a path depends on the user's preferences with respect to cost and number of modal transfers.