2,541 research outputs found
The gamma-ray and neutrino sky: A consistent picture of Fermi-LAT, Milagro, and IceCube results
We compute the gamma-ray and neutrino diffuse emission of the Galaxy on the
basis of a recently proposed phenomenological model characterized by radially
dependent cosmic-ray (CR) transport properties. We show how this model,
designed to reproduce both Fermi-LAT gamma-ray data and local CR observables,
naturally reproduces the anomalous TeV diffuse emission observed by Milagro in
the inner Galactic plane. Above 100 TeV our picture predicts a neutrino flux
that is about five (two) times larger than the neutrino flux computed with
conventional models in the Galactic Center region (full-sky). Explaining in
that way up to of the flux measured by IceCube, we reproduce the
full-sky IceCube spectrum adding an extra-Galactic component derived from the
muonic neutrino flux in the northern hemisphere. We also present precise
predictions for the Galactic plane region where the flux is dominated by the
Galactic emission.Comment: 5 pages, 3 figure
Gamma-ray and neutrino diffuse emissions of the Galaxy above the TeV
As recently shown, Fermi-LAT measurements of the diffuse gamma-ray emission
from the Galaxy favor the presence of a smooth softening in the primary
cosmic-ray spectrum with increasing Galactocentric distance. This result can be
interpreted in terms of a spatial-dependent rigidity scaling of the diffusion
coefficient. The DRAGON code was used to build a model based on such feature.
That scenario correctly reproduces the latest Fermi-LAT results as well as
local cosmic-ray measurements from PAMELA, AMS-02 and CREAM. Here we show that
the model, if extrapolated at larger energies, grasps both the gamma-ray flux
measured by MILAGRO at 15 TeV and the H.E.S.S. data from the Galactic ridge,
assuming that the cosmic-ray spectral hardening found by those experiments at
about 250 GeV/n is present in the whole inner Galactic plane region. Moreover,
we show as that model also predicts a neutrino emission which may account for a
significant fraction, as well as for the correct spectral shape, of the
astrophysical flux measured by IceCube above 25 TeV.Comment: Oral contribution to the 34th International Cosmic Ray Conference,
July 30 to August 6, The Hague, Netherland
A Hadronic Scenario for the Galactic Ridge
Several observations from Fermi-LAT, up to few hundred GeV, and from
H.E.S.S., up to 10 TeV, reported an intense -ray emission from
the inner part of the Galactic plane. After the subtraction of point-like
contributions, the remaining -ray spectrum can provide important hints
about the cosmic-ray (CR) population in that region. In particular, the diffuse
spectrum measured by both Fermi-LAT and H.E.S.S. in the Galactic Ridge is
significantly harder with respect to the rest of the Galaxy. These results were
recently interpreted in terms of a comprehensive CR transport model which,
adopting a spatial dependent diffusion coefficient and convective velocity,
reproduces Fermi-LAT results on the whole sky as well as local CR spectra. We
showed as that model predicts a significantly harder neutrino diffuse emission
compared to conventional scenarios: The predicted signal is able to account for
a significant fraction of the astrophysical flux measured by IceCube. In this
contribution, we use the same setup to calculate the expected neutrino flux
from several windows in the inner Galactic plane and compare the results with
IceCube observations and the sensitivities of Mediterranean neutrino
telescopes. In particular, for the ANTARES experiment, we compare the model
expectations with the upper limits obtained from a recent unblinded
data-analysis focused on the galactic ridge region. Moreover, we also show the
expectations from the galactic ridge for the future KM3NeT observatory, whose
position is optimal to observe this portion of the sky.Comment: Oral contribution to the 34th International Cosmic Ray Conference,
July 30 to August 6, The Hague, Netherland
Interpretation of astrophysical neutrinos observed by IceCube experiment by setting Galactic and extra-Galactic spectral components
The last IceCube catalog of High Energy Starting Events (HESE) obtained with
a livetime of 1347 days comprises 54 neutrino events equally-distributed
between the three families with energies between 25 TeV and few PeVs.
Considering the homogeneous flavors distribution (1:1:1) and the spectral
features of these neutrinos the IceCube collaboration claims the astrophysical
origin of these events with more than . The spatial distribution of
cited events does not show a clear correlation with known astrophysical
accelerators leaving opened both the Galactic and the extra-Galactic origin
interpretations. Here, we compute the neutrino diffuse emission of our Galaxy
on the basis of a recently proposed phenomenological model characterized by
radially-dependent cosmic-ray (CR) transport properties. We show that the
astrophysical spectrum measured by IceCube experiment can be well explained
adding to the diffuse Galactic neutrino flux (obtained with this new model) a
extra-Galactic component derived from the astrophysical muonic neutrinos
reconstructed in the Northern hemisphere. A good agreement between the expected
astrophysical neutrino flux and the IceCube data is found for the full sky as
well as for the Galactic plane region.Comment: 4 pages, 2 figures, accepted for the VLVnT-2015 Conference
proceeding
Towards Design Strategies for Requalifying the Rural: A Comparative Study of Hollow Settlements in China and Italy
Smallsettlementsincountrysideareascallforagrowingnumberofchallengesagainst the backdrop of global rural-urban transition. In this paper, we focus on the processes of depopulation and building abandonment in rural areas of China and Italy. We consider two similar experiences taking place in different contexts, and suggest useful design tools for strategies of architectural requalification. In China, we study a small village in Fujian Province as a paradigmatic example of the well-known phenomenon of “hollow villages.” The word hollow refers to the emptying of dwellings in the central parts of rural settlements, while, paradoxically, their fringe areas are the object of residential land expansion. This notion was coined in the early 1990s to describe the spatial, social and economic consequences of the combination of a rural exodus and a rampant urbanisation. In Italy, we consider a case study in the Province of Trento, where the evacuation of village central cores follow the sprawling towards the village’s outskirts. Even though the recent trends show that the demographic haemorrhage away from the village is declining, the abandonment of old houses in favour of the construction of new ones seems relentless. Such issues gather a growing interest by cultural, political and academic institutions. Never the less, little attention has been paid to the similarities of architectural experiences across national boundaries. Aiming to bridge this gap, we compare the results of our studies on the architectural requalification of rural settlements in both China and Italy. Our methodology embodies a graphic representation of our fieldwork, examines the relationships between the built form and its natural framework and analytically assesses the physical condition and use level of the existing buildings. Despite local specificities, there are significant overlaps from which these and other cases can gain insight. We observe that similar transnational issues can be stimulated by global transition processes driven by local forces and context-related patterns of spatial transformation. More specifically, the intensity and the extent of hollowing of Chinese villages stimulates the broad testing of a spectrum of methodologies and knowledges. These can be both inherited from other contexts or experimented with as innovative approaches. From this perspective, the Italian experience, where the abandonment dates backwards in time, is a fruitful source of comparison
A novel Dynamic programming approach for Two-Echelon Capacitated Vehicle Routing Problem in City Logistics with Environmental considerations
Abstract The paper proposes a Two-Echelon Capacitated Vehicle Routing Problem with Environmental consideration, intended for managing urban freight distribution in City Logistics. It presents a novel Dynamic programming approach that divides the main problem into several ones and uses an exact algorithm to obtain optimal route paths. The approach applies Fuzzy C-Means Clustering for assigning a group of customers to a satellite. The initial solution is improved with roulette selection, 2-opt, and Or-opt exchange heuristics. The approach was tested on benchmark instances, and obtained results are satisfactory. Moreover, the proposed method highlights the environmental improvement we can obtain in managing urban freight transportation
The emergent city. Interactive relational systems between public administration and citizen to foster sustainable processes of urban development
The widespread of Information and Communication Technologies and the consequently redefinition of roles in the usage and management of the city brought along new systems of relationships and interactions that produce an auto-organisation of territories or communities, showed also through temporary transformation of the environment. In effect, cities are continuously redefined by emergent properties that may, both be originated and then impact on social, political, cultural, and economical people practices. On the other hand, through the arrangement of its patterns the city shapes the social and connective relations occurring among people. So, the city can be regarded as a complex system, that in the last years has been expanded by the widespread of communication devices and sensors connected to the Internet. In this context, the design of new patterns of interactions that focuses on the new relationship opportunities, in part offered by the Information and Communication Technologies, but not limited to them, may significantly affect sustainable processes of urban development. This paper focuses on the civic aspect of the so-called smart cities, and, in details, on the relation between citizens and Public Administration. Some existing interaction patterns are illustrated in order to support the visualisation of the dynamic relationships between citizens and Public Administration, while new possible relations derived by the interaction with the urban space are supposed
Improving the Performance of the Bilevel Solution for the Continuous Network Design Problem
For a long time, many researchers have investigated the continuous network design problem (CNDP) to distribute equitably additional capacity between selected links in a road network, to overcome traffic congestion in urban roads. In addition, CNDP plays a critical role for local authorities in tackling traffic congestion with a limited budget. Due to the mutual interaction between road users and local authorities, CNDP is usually solved using the bilevel modeling technique. The upper level seeks to find the optimal capacity enhancements of selected links, while the lower level is used to solve the traffic assignment problem. In this study, we introduced the enhanced differential evolution algorithm based on multiple improvement strategies (EDEMIS) for solving CNDP. We applied EDEMIS first to a hypothetical network to show its ability in finding the global optimum solution, at least in a small network. Then, we used a 16-link network to reveal the capability of EDEMIS especially in the case of high demand. Finally, we used the Sioux Falls city network to evaluate the performance of EDEMIS according to other solution methods on a medium-sized road network. The results showed that EDEMIS produces better solutions than other considered algorithms, encouraging transportation planners to use it in large-scale road networks.</p
Fusion of Two Metaheuristic Approaches to Solve the Flight Gate Assignment Problem
AbstractOne of the most important activity in airport operations is the gate scheduling. It is concerned with finding an assignment of flights to terminal and ramp positions (gates), and an assignment of the start and completion times of the processing of a flight at its position. The objectives related to the flight gate assignment problem (FGAP) include the minimization of the number of flights assigned to remote terminals and the minimization of the total walking distance. The main aim of this research is to find a methodology to solve the FGAP. In this paper, we propose a hybrid approach called Biogeography-based Bee Colony Optimization (B-BCO). This approach is obtained fusing two metaheuristics: biogeography-based (BBO) and bee colony optimization (BCO) algorithms. The proposed B-BCO model integrates the BBO migration operator into to bee's search behaviour. Results highlight better performances of the proposed approach in solving FGAP when compared to BCO
A Fuzzy set-based method to identify the car position in a road lane at intersections by smartphone GPS data
Abstract Intelligent transportation systems (ITS) work by collections of data in real time. Average speed, travel time and delay at intersections are some of the most important measures, often used for monitoring the performance of transportation systems, and useful for system management and planning. In urban transportation planning, intersections are usually considered critical points, acting as bottlenecks and clog points for urban traffic. Thus, detecting the travel time at intersections in different turning directions is an activity useful to improve the urban transport efficiency. Smartphones represent a low-cost technology, with which is possible to obtain information about traffic state. However, smartphone GPS data suffer for low precision, mainly in urban areas. In this paper, we present a fuzzy set-based method for car positioning identification within road lanes near intersections using GPS data coming from smartphones. We have introduced the fuzzy sets to take into account uncertainty embedded in GPS data when trying to identify the position of cars within the road lanes. Moreover, we introduced a Genetic Algorithm to calibrate the fuzzy parameters in order to obtain a novel supervised clustering technique. We applied the proposed method to one intersection in the urban road network of Bari (Italy). First results reveal the effectiveness of the proposed methodology when comparing the outcomes of the proposed method with two well-known clustering techniques (Fuzzy C-means, K-means)
- …