256 research outputs found
The influence of resistant force equations and coupling system on long train dynamics simulations
In the simulation of the longitudinal dynamics of long trains, the modeling of the resistant forces and of the coupling system are two essential aspects. The modeling of the resistant forces directly affects the speed reached by each vehicle as well as the in-train forces. A literature review witnesses different laws for the calculation of both ordinary and accidental resistances. One of the objectives of this paper is to evaluate from the numerical point of view the influence of the resistant forces modeling strategy on the simulation outputs, i.e., on the speeds and in-train forces, by comparing different laws for propulsion and curving resistances. For what concerns the connection between the vehicles of the train, it is well known that the connection system is of utmost importance for the safety and running stability of the train. In this paper, the two existing coupling systems, i.e., the European buffer-hook system and the coupler used outside the European continent are first described, both in terms of operation and modelling techniques, and then they are compared on the same simulation scenario. All the simulations are performed on the first scenario of the International benchmark of the longitudinal train dynamic simulators, using the LTDPoliTO code developed by the railway research team from Politecnico di Torino
The Management of Type 2 Diabetic Patients with Hypoglycemic Agents
Aims and Scope. Aims of the paper are to suggest the best treatment to improve the glycemic control in patients with Type 2 diabetes using hypoglycemic agents, in particularly, we think that every patient is different from another one in terms of BMI, family history, duration of the disease and so on. We propose for every clinical aspect the best hypoglycemic agents to use, considering the scientific evidence and physiopathology
Ecosistemi di acque interne e di transizione
In questo contributo la vulnerabilità degli ecosistemi acquatici ai cambiamenti climatici è analizzata in relazione ai meccanismi di organizzazione e mantenimento della biodiversità e dei processi ecosistemici. Dai processi degli ecosistemi derivano funzioni che forniscono una serie di benefici o servizi per il genere umano (Daily et al., 2009). Tali servizi sono in larga misura
dipendenti dalle componenti biologiche degli ecosistemi86. Negli ecosistemi acquatici i processi biogeochimici (ad es. denitrificazione batterica e assimilazione da parte della vegetazione acquatica), garantiscono l’abbattimento dei nutrienti, una funzione ecosistemica che produce il servizio di depurazione dell’acqua. Altri servizi sono la laminazione delle piene, la ricarica degli acquiferi, la regolazione del microclima locale, la produzione di risorse alimentari quali pesci, crostacei, ecc. (Jones, 2013). Le alterazioni degli ecosistemi, in particolare la perdita di specie e la diminuzione della biodiversità danneggiano questi servizi, con ricadute anche di tipo economico(si pensi, ad esempio, ai costi della depurazione dell’acqua destinata al consumo umano)
High Altitude test of RPCs for the ARGO-YBJ experiment
A 50 m**2 RPC carpet was operated at the YangBaJing Cosmic Ray Laboratory
(Tibet) located 4300 m a.s.l. The performance of RPCs in detecting Extensive
Air Showers was studied. Efficiency and time resolution measurements at the
pressure and temperature conditions typical of high mountain laboratories, are
reported.Comment: 16 pages, 10 figures, submitted to Nucl. Instr. Met
Gamma ray flares from Mrk421 in 2008 observed with the ARGO-YBJ detector
In 2008 the blazar Markarian 421 entered a very active phase and was one of
the brightest sources in the sky at TeV energies, showing frequent flaring
episodes. Using the data of ARGO-YBJ, a full coverage air shower detector
located at Yangbajing (4300 m a.s.l., Tibet, China), we monitored the source at
gamma ray energies E > 0.3 TeV during the whole year. The observed flux was
variable, with the strongest flares in March and June, in correlation with
X-ray enhanced activity. While during specific episodes the TeV flux could be
several times larger than the Crab Nebula one, the average emission from day 41
to 180 was almost twice the Crab level, with an integral flux of (3.6 +-0.6)
10^-11 photons cm^-2 s^-1 for energies E > 1 TeV, and decreased afterwards.
This paper concentrates on the flares occurred in the first half of June.
This period has been deeply studied from optical to 100 MeV gamma rays, and
partially up to TeV energies, since the moonlight hampered the Cherenkov
telescope observations during the most intense part of the emission. Our data
complete these observations, with the detection of a signal with a statistical
significance of 3.8 standard deviations on June 11-13, corresponding to a gamma
ray flux about 6 times larger than the Crab one above 1 TeV. The reconstructed
differential spectrum, corrected for the intergalactic absorption, can be
represented by a power law with an index alpha = -2.1 extending up to several
TeV. The spectrum slope is fully consistent with previous observations
reporting a correlation between the flux and the spectral index, suggesting
that this property is maintained in different epochs and characterizes the
source emission processes.Comment: Accepted for publication on ApJ
The ARGO-YBJ Experiment Progresses and Future Extension
Gamma ray source detection above 30TeV is an encouraging approach for finding
galactic cosmic ray origins. All sky survey for gamma ray sources using wide
field of view detector is essential for population accumulation for various
types of sources above 100GeV. To target the goals, the ARGO-YBJ experiment has
been established. Significant progresses have been made in the experiment. A
large air shower detector array in an area of 1km2 is proposed to boost the
sensitivity. Hybrid detection with multi-techniques will allow a good
discrimination between different types of primary particles, including photons
and protons, thus enable an energy spectrum measurement for individual specie.
Fluorescence light detector array will extend the spectrum measurement above
100PeV where the second knee is located. An energy scale determined by balloon
experiments at 10TeV will be propagated to ultra high energy cosmic ray
experiments
Mean Interplanetary Magnetic Field Measurement Using the ARGO-YBJ Experiment
The sun blocks cosmic ray particles from outside the solar system, forming a
detectable shadow in the sky map of cosmic rays detected by the ARGO-YBJ
experiment in Tibet. Because the cosmic ray particles are positive charged, the
magnetic field between the sun and the earth deflects them from straight
trajectories and results in a shift of the shadow from the true location of the
sun. Here we show that the shift measures the intensity of the field which is
transported by the solar wind from the sun to the earth.Comment: 6 papges,3 figure
Search for Gamma Ray Bursts with the Argo-YBJ Detector in Scaler Mode
We report on the search for Gamma Ray Bursts (GRBs) in the energy range 1-100
GeV in coincidence with the prompt emission detected by satellites using the
Astrophysical Radiation with Ground-based Observatory at YangBaJing (ARGO-YBJ)
air shower detector. Thanks to its mountain location (Yangbajing, Tibet, P.R.
China, 4300 m a.s.l.), active surface (about 6700 m**2 of Resistive Plate
Chambers), and large field of view (about 2 sr, limited only by the atmospheric
absorption), the ARGO-YBJ air shower detector is particularly suitable for the
detection of unpredictable and short duration events such as GRBs. The search
is carried out using the "single particle technique", i.e. counting all the
particles hitting the detector without measurement of the energy and arrival
direction of the primary gamma rays.
Between 2004 December 17 and 2009 April 7, 81 GRBs detected by satellites
occurred within the field of view of ARGO-YBJ (zenith angle < 45 deg). It was
possible to examine 62 of these for >1 GeV counterpart in the ARGO-YBJ data
finding no statistically significant emission. With a lack of detected spectra
in this energy range fluence upper limits are profitable, especially when the
redshift is known and the correction for the extragalactic absorption can be
considered. The obtained fluence upper limits reach values as low as 10**{-5}
erg cm**{-2} in the 1-100 GeV energy region.
Besides this individual search for a higher energy counterpart, a statistical
study of the stack of all the GRBs both in time and in phase was made, looking
for a common feature in the GRB high energy emission. No significant signal has
been detected.Comment: accepted for publication in Ap
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