4,957 research outputs found
Push & Pull: autonomous deployment of mobile sensors for a complete coverage
Mobile sensor networks are important for several strategic applications
devoted to monitoring critical areas. In such hostile scenarios, sensors cannot
be deployed manually and are either sent from a safe location or dropped from
an aircraft. Mobile devices permit a dynamic deployment reconfiguration that
improves the coverage in terms of completeness and uniformity.
In this paper we propose a distributed algorithm for the autonomous
deployment of mobile sensors called Push&Pull. According to our proposal,
movement decisions are made by each sensor on the basis of locally available
information and do not require any prior knowledge of the operating conditions
or any manual tuning of key parameters.
We formally prove that, when a sufficient number of sensors are available,
our approach guarantees a complete and uniform coverage. Furthermore, we
demonstrate that the algorithm execution always terminates preventing movement
oscillations.
Numerous simulations show that our algorithm reaches a complete coverage
within reasonable time with moderate energy consumption, even when the target
area has irregular shapes. Performance comparisons between Push&Pull and one of
the most acknowledged algorithms show how the former one can efficiently reach
a more uniform and complete coverage under a wide range of working scenarios.Comment: Technical Report. This paper has been published on Wireless Networks,
Springer. Animations and the complete code of the proposed algorithm are
available for download at the address:
http://www.dsi.uniroma1.it/~novella/mobile_sensors
Il Laboratorio per l’accreditamento di Ateneo. Prime valutazioni di un’esperienza di formazione personale e collettiva a UNIMORE
A Workshop for the accreditation of the University. Preliminary evaluations of an experience of individual and collective training at UNIMORE.
The paper presents the results of the Workshop for the accreditation of the University, organized by the University of Modena and Reggio Emilia (UNIMORE). The workshop is devoted to the students that are members of the Joint docents - students committees and consists of several educational activities ranging from lessons to practical exercises. The workshop is based on a principle established in the Document for QA of the education of UNIMORE, that is the commitment of the University «to act deliberately so that students are involved, individually and collectively, as partners in quality assurance and in strengthening their educational experience». The work considers some problematic aspects that gradually have emerged in the course of its implementation; it develops some critical reflections on the experience and concludes by outlining possible developments of this work, which seems to be unique on the national scene
K-Band Spectroscopy of (Pre-)Cataclysmic Variables: Are Some Donor Stars Really Carbon Poor?
We present a new sample of -band spectral observations for CVs:
non-magnetic and magnetic as well as present day and pre CVs. The purpose of
this diverse sample is to address the recent claim that the secondary stars in
dwarf novae are carbon deficient, having become so through a far more evolved
evolution than the current paradigm predicts. Our new observations, along with
previous literature results, span a wide range of orbital period and CV type.
In general, dwarf novae in which the secondary star is seen show weak to no CO
absorption while polar and pre-CV donor stars appear to have normal CO
absorption for their spectral type. However, this is not universal. The
presence of normal looking CO absorption in the dwarf nova SS Aur and the
hibernating CV QS Vir and a complete lack of CO absorption in the long period
polar V1309 Ori cloud the issue. A summary of the literature pointing to
non-solar abundances including enhanced NV/CIV ratios is presented. It appears
that some CVs have non-solar abundance material accreting onto the white dwarf
suggesting an evolved secondary star while for others CO emission in the
accretion disk may play a role. However, the exact mechanism or combination of
factors causing the CO absorption anomaly in CVs is not yet clear.Comment: Accepted in A
Simplified relationships for estimating seismic slope stability
Eurocode 8 addresses seismic slope stability analysis with reference to limit state design, specifying a 50% re-duction of the peak horizontal inertia force of a potentially sliding mass. Such a coefficient has been shown to depend on several factors, including soil deformability and the frequency content of the seismic action. In this paper the reduction coefficient is expressed with reference to the above factors and compared to EC8 provisions for all soil classes. A simplified design procedure is then suggested by referring to updated correla-tions based on the Newmark sliding block model, including the influence of amplitude, duration and mean pe-riod of the ground motion on the predicted displacement. The reduction coefficient is further generalised to account for the slope ductility, i.e. the capability of sustain prescribed threshold displacements. The whole procedure has been calibrated through analyses carried out using acceleration time histories, selected from a database of records of Italian seismic events, on typical subsoil layering pertaining to the EC8 classes, also adopted by the Italian seismic Code
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Migration and the challenges of Italian multiculturalism
The migration crisis is analysed here in the context of the fundamental challenges which Italy faces through becoming a country of immigration in a period of recession. It is argued that there has been no serious debate in Italy on multiculturalism, or on religious freedom, despite the growing socio-cultural and religious diversity arising from population movements and international conflict. The analysis begins with the Italian government’s attempts in 2015 to deal with migration and diversity, and the associated domestic conflicts at the levels of both party politics and society. This leads to a discussion of the meaning of the Christian/Catholic identity of the country in its changed conditions. The external dimension of Italian politics is examined in terms of both Rome’s impatient calls for EU help and the weak political position of Italy in relation to the root causes of migration, whether through intervention or diplomatic influence
Health-related quality of life in patients with Gilles de la Tourette syndrome at the transition between adolescence and adulthood
Gilles de la Tourette syndrome (GTS) is a neurodevelopmental
condition characterised by tics and comorbid
behavioural problems, affecting predominantly
male patients. Tic severity typically fluctuates over time,
with a consistent pattern showing improvement after adolescence
in a considerable proportion of patients. Both tics
and behavioural co-morbidities have been shown to have
the potential to affect patients’ health-related quality of life
(HR-QoL) in children and adults with persisting symptoms.
In this study, we present the results of the first investigation
of HR-QoL in patients with Gilles de la Tourette syndrome
at the transition between adolescence and adulthood using
a disease-specific HR-QoL measure, the Gilles de la
Tourette Syndrome-Quality of Life-Children and Adolescents
scale. Our results showed that patients with GTS and
more severe co-morbid anxiety symptoms reported lower
HR-QoL across all domains, highlighting the impact of
anxiety on patient’s well-being at a critical stage of
development. Routine screening for anxiety symptoms is
recommended in all patients with GTS seen at transition
clinics from paediatric to adult care, to implement effective
behavioural and pharmacological interventions as
appropriate
Comment on "Soil salinity assessment by using near-infrared channel and Vegetation Soil Salinity Index derived from Landsat 8 OLI data: a case study in the Tra Vinh Province, Mekong Delta, Vietnam" by Kim-Anh Nguyen, Yuei-An Liou, Ha-Phuong Tran, Phi-Phung Hoang and Thanh-Hung Nguyen
Nguyen et al. (Prog Earth Planet Sci 7:1, 2020. ) suggest that Landsat 8 OLI can be used to map and monitor soil salinity in the coastal zone of the Mekong River Delta. The authors use empirical correlations between the near-infrared (NIR) band, or vegetation indexes containing the NIR band, and soil salinity. We show that within the coastal portion of the Mekong Delta, extensively ponded due to widespread shrimp farming, about 90% of Landsat 8 pixels are fully or partially covered by water. We then find that, due to strong NIR radiation absorption, NIR reflectance from ponded pixels decreases linearly with increasing water percentage cover, while no significant correlation is found between reflectance and soil salinity. Through detailed new analyses, we conclude that NIR reflectance attenuation cannot be ascribed to vegetation stress caused by soil salinity, but rather to the presence of water ponds. We also show that a similar behavior exists in ponded freshwater inland areas, confirming that the NIR absorption exerted by water is independent of salinity
Influence of Beams Distribution on the Dynamic and Seismic Linear Response of RC Frame Buildings
The present study compares the dynamic properties and seismic performances offered by reinforced concrete frame structures characterized by different beams distribution. The understanding of the influence of beams distribution on spatial frames is not only useful when dealing with the seismic vulnerability assessment of existing buildings that may show unusual layouts of beams, such as alternating beams at each storey, but also when facing the design of new buildings with fluid viscous dampers for which some structural flexibility is required. A systematic study is described in this paper. Four (2-, 3-, 6-, and 10-storey) regular frame buildings with rectangular plan are considered as reference structures. Different models are developed according to various layouts of the primary beams, exploring alternatives to the full three-dimensional organisation of beams and frames. For instance: beams placed along the longitudinal direction at the odd storeys and placed along the transversal direction at the even storeys, and vice versa; alternating beams every one and two storeys; beams just placed along one direction. Modal analysis has been conducted to evaluate the influence of beams distribution on the dynamic properties (periods of vibration and modal participating mass ratios). Response spectrum analysis and linear time-history dynamic analysis have been carried out to assess the effects of beams distribution on the fundamental seismic response parameters (shear forces, bending moments, top-storey displacements, interstorey drifts, and floor accelerations). On the contrary of what could be expected, the results indicate that structures with beams alternating every storey may show interesting advantages in terms of reduced total base shear, almost comparable bending moments and accelerations, within a still balanced overall behaviour along the two directions, with respect to the complete three-dimensional frame. Two effects are recognized: the period effect and the static scheme effect. The former acting basically on the storey shear forces; the latter acting mainly on the bending moments
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