Design of A Test-Rig for Gerotor Pump

Gerotor pumps are a kind of fluid power machines widely used in the automotive field, especially for fuel injection as well as lubrication. To improve the performance of these units, virtual prototyping is necessary to decrease time and cost related to trial and error. Within this research a simulation model for Gerotor units has been developed with the aim of predicting accurately the performance of a generic unit. The model can accurately predict the system behavior regarding mechanical and volumetric losses by considering real machining tolerances and their interactions. Ultimately, this model should help to design new generations of Gerotor units and to improve existing ones by improving their efficiency. To justify and refine the model, a test-rig which can enable measurements of rotor micro-motions of the gears of Gerotors is needed. This paper proposes an innovative approach for measuring micro-motions together with the design of a test-rig specifically conceived to allow such measurements. Reference Gerotor units will be put in a specially designed pump housing. The measurements will be performed using capacitive sensors capable of measuring the lubricant film thickness in the lubricated gaps. In this way, the micro-motions of the reference Gerotor unit can be detected. A data acquisition system will be created to collect the experimental data. Results will be analyzed to understand the correctness of the prediction given by the model. With these results, the lumped parameter model is expected to be validated or refined allowing more precise predictions in the future

Transnationalism and Belonging: The Case of Moroccan Entrepreneurs in Amsterdam and Milan

Research on migrant transnationalism has mostly focused on particular transnational activities, their salience in various contexts and populations, and their relationship with migrant incorporation. Less attention has been paid to the interplay between the different domains of transnationalism (economic, political, and socio-relational) and to the way in which they affect migrants’ identity. This study investigates whether and how one domain of migrant transnationalism—transnational entrepreneurship—influences migrants’ (1) transnational involvement in other domains and (2) sense of belonging to different social groups and places. Focusing on the case of Moroccan entrepreneurs in Amsterdam, the Netherlands, and Milan, Italy, we compare transnational migrant entrepreneurs, whose business is based on cross-border relationships and exchanges, with domestic migrant entrepreneurs, who are active exclusively in the destination country. Combining quantitative and qualitative data, we find that transnational entrepreneurs differ from domestic entrepreneurs mostly in terms of socio-relational transnational involvement. On the other hand, transnational entrepreneurship does not substantially change transnational practices in other domains or sense of belonging among Moroccan migrants

The Vehicle Routing Problem with Discrete Split Delivery and Time Windows

The Discrete Split Delivery Vehicle Routing Problem with Time Windows (DSDVRPTW) consists of designing the optimal set of routes to serve, at least cost, a given set of customers while respecting constraints on vehicles capacity and customer time windows. The delivery request of a customer consists of several discrete items which cannot be split further. The problem belongs to the class of split delivery problems since each customers demand can be split in orders, i.e. feasible combinations of items, and each customer can be visited by more than one vehicle. In this work, we model the DSDVRPTW as a mixed integer linear program, assuming that all feasible orders are known in advance and that each vehicle can serve at most one order per customer. Remarkably, service time at customers location depends on the serviced combination of items, which is a modeling feature rarely found in literature. We present a branch-and-price algorithm, analyzing the implications of the classical Dantzig-Wolfe reformulation. Preliminary computational results on instances based on Solomons data set are discussed

Two-stage column generation: a novel framework

Column generation has been intensively used in the last decades to compute good quality lower bounds for combinatorial problems reformulated through Dantzig-Wolfe decomposition. In this work we propose a novel framework to cope with problems in which the structure of the original formulation, namely the presence of a combinatorial number of decision variables, does not allow for straightforward reformulation. The basic idea is to start from a meaningful subset of original variables, apply the DW reformulation to the subset, solve the reformulation with column generation and perform the explicit pricing on original variables retracing back the reformulation and using complementary-slackness conditions. The Discrete Split Delivery Vehicle Routing Problem with Time Windows (DSDVRPTW) is used as an illustration for the method, which provides a new exact approach to the problem. Preliminary computational experiments are reported. This is joint work with Matteo Salani

An exact algorithm for the discrete split delivery vehicle routing problem with time windows

The Split Delivery Vehicle Routing Problem (SDVRP) is a variant version of the classical VRP in which each customer can be visited by more than one vehicle which serves a fraction of its demand. The Discrete SDVRP is another variant in which the delivery request of a customer consists of several items which cannot be split further. In this work we consider the DSDVRP with time windows where the service of items' combinations imply a corresponding service time. We present a branch-and-price algorithm and discuss preliminary computational results

Mega-parsec scale magnetic fields in low density regions in the SKA era: filaments connecting galaxy clusters and groups

The presence of magnetic fields in galaxy clusters has been well established in recent years, and their importance for the understanding of the physical processes at work in the Intra Cluster Medium has been recognized. Halo and relic sources have been detected in several tens clusters. A strong correlation is present between the halo and relic radio power and the X-ray luminosity. Since cluster X-Ray luminosity and mass are related, the correlation between the radio power and X-ray luminosity could derive from a physical dependence of the radio power on the cluster mass, therefore the cluster mass could be a crucial parameter in the formation of these sources. The goal of this project is to investigate the existence of non-thermal structures beyond the Mpc scale, and associated with lower density regions with respect to clusters of galaxies: galaxy filaments connecting rich clusters. We present a piece of evidence of diffuse radio emission in intergalactic filaments. Moreover, we present and discuss the detection of radio emission in galaxy groups and in faint X-Ray clusters, to analyze non-thermal properties in low density regions with physical conditions similar to galaxy filaments. We discuss how SKA1 observations will allow the investigation of this topic and the study of the presence of diffuse radio sources in low density regions. This will be a fundamental step to understand the origin and properties of cosmological magnetic fields.Comment: 9 pages, 5 figures - to appear as part of 'Cosmic Magnetism' in Proceedings 'Advancing Astrophysics with the SKA (AASKA14)', PoS(AASKA14)10

Branch and Price for the Vehicle Routing Problem with Discrete Split Deliveries and Time Windows

The Discrete Split Delivery Vehicle Routing Problem with Time Windows (DSDVRPTW) consists of designing the optimal set of routes to serve, at least cost, a given set of customers while respecting constraints on vehicles capacity and customer time windows. The delivery request of a customer is discrete since it consists of several items that cannot be split further. The problem belongs to the class of split delivery problems since each customers demand can be split in orders, i.e. feasible combinations of items, and each customer can be visited by more than one vehicle. In this work, we model the DSDVRPTW assuming that all feasible orders are known in advance and that each vehicle can serve at most one order per customer. Remarkably, service time at customers location depends on the serviced combination of items, which is a modeling feature rarely found in literature. We present a mixed integer program for the DSDVRPTW based on arc-flow formulation, we reformulate it via Dantzig-Wolfe and we apply column generation. We propose a branch-and-price algorithm, implemented using state-of-the-art techniques for the pricing and the master problem. Computational results on instances based on Solomons data set are presented and discussed

Prognostic impact of coronary microcirculation abnormalities in systemic sclerosis: a prospective study to evaluate the role of non-invasive tests

INTRODUCTION: Microcirculation dysfunction is a typical feature of systemic sclerosis (SSc) and represents the earliest abnormality of primary myocardial involvement. We assessed coronary microcirculation status by combining two functional tests in SSc patients and estimating its impact on disease outcome. METHODS: Forty-one SSc patients, asymptomatic for coronary artery disease, were tested for coronary flow velocity reserve (CFR) by transthoracic-echo-Doppler with adenosine infusion (A-TTE) and for left ventricular wall motion abnormalities (WMA) by dobutamine stress echocardiography (DSE). Myocardial multi-detector computed tomography (MDCT) enabled the presence of epicardial stenosis, which could interfere with the accuracy of the tests, to be excluded. Patient survival rate was assessed over a 6.7- ± 3.5-year follow-up. RESULTS: Nineteen out of 41 (46%) SSc patients had a reduced CFR (≤2.5) and in 16/41 (39%) a WMA was observed during DSE. Furthermore, 13/41 (32%) patients showed pathological CFR and WMA. An inverse correlation between wall motion score index (WMSI) during DSE and CFR value (r = -0.57, P <0.0001) was observed; in addition, CFR was significantly reduced (2.21 ± 0.38) in patients with WMA as compared to those without (2.94 ± 0.60) (P <0.0001). In 12 patients with abnormal DSE, MDCT was used to exclude macrovasculopathy. During a 6.7- ± 3.5-year follow-up seven patients with abnormal coronary functional tests died of disease-related causes, compared to only one patient with normal tests. CONCLUSIONS: A-TTE and DSE tests are useful tools to detect non-invasively pre-clinical microcirculation abnormalities in SSc patients; moreover, abnormal CFR and WMA might be related to a worse disease outcome suggesting a prognostic value of these tests, similar to other myocardial diseases

A multi-wavelength pipeline for pulsar searches

Pulsar studies in the recent years have shown, more than others, to have benefited from a multi-wavelength approach. The INAF - Astronomical Observatory in Cagliari (INAF-OAC) is a growing facility with a young group devoted to pulsar and fast transients studies across the electromagnetic spectrum. Taking advantage of this expertise we have worked to provide a suite of multi-wavelength software and databases for the observations of pulsars and compact Galactic objects at the Sardinia Radio Telescope (SRT). In turn, radio pulsar observations at SRT will be made available, in a processed format, to gamma-ray searches using AGILE and Fermi gamma-ray satellite and, in a near future, they will be complementary to polarimetric X-ray observations with IXPE.Comment: Accepted for publications in Rendiconti Lincei as Proceedings of "A Decade of AGILE: Results, Challenges and Prospects of Gamma-Ray Astrophysics