1,721,062 research outputs found
Improving the QoS of IEEE 802.11e networks through imprecise computation
Full text linkIEEE 802.11e HCCA reference scheduler is based on fixed value parameters that do not adapt to traffic changes, thus quality of service (QoS) for multimedia applications is a challenge, especially in the case of variable bit rate (VBR) streams, that requires dynamic resource assignment. This paper is focused on immediate dynamic TXOP HCCA (IDTH) scheduling algorithm and its new evolution immediate dynamic TXOP HCCA plus (IDTH+). Their reclaiming mechanisms, refined by the monitoring of transmission duration, aim at overcoming the limits of fixed preallocation of resources by varying the stations transmission time and avoiding waste of resources. Simulations and theoretical analysis based on the imprecise computation model show that the integration of IDTH and IDTH+ can achieve improved network performance in terms of transmission queues length, mean access delay and packets drop rate, and to efficiently manage bursty traffic. Moreover, the performance improvements of IDTH+ with respect to IDTH are highlighted
The biomonitoring approach as a tool of trace metal assessment in an uncontaminated marine ecosystem: The island of Ustica (Sicily, Italy)
No full textMarine organisms were tested as possible biomonitors of heavy metal
contamination in a reference marine ecosystem, in Ustica (an island of the
Southern Tyrrhenian Sea). The goal of this preliminary work is to evaluate the
concentrations of Cu, Zn and Pb, using two gastropod molluscs, Monodonta
turbinata Born and Patella caerulea L.
Samples were collected in the tidal zone, at five coastal stations, according to
their availability. Namely, the stations included the Marine Reserve (a “Marine
Park” area), which is an uncontaminated site, and the Harbour station, where the
contamination level was expected to be higher than the other sites. In order to
gain additional information on both the environmental conditions of the area and
possible bioaccumulation patterns, seawater samples were also collected in each
site to assess soluble metal concentrations.
Statistical analyses (one way ANOVA and multiple comparison tests) were
applied to test the differences between metal concentrations in different sites and
species. Results show high concentration factors (CFs) with respect to the
concentrations in marine waters (soluble fraction). This confirms the suitability
of these species for biomonitoring purposes.
The metal concentrations recorded at the stations generally fall in the range of
the lowest values available in the literature and may be considered as useful
background levels to which to refer for intraspecific comparison within the
Mediterranean area
Indagine sperimentale sulla dispersione di fibre di vetro da pannelli usati per la coibentazione
No full text2nd International Workshop on Smart Agriculture for the environmental emergency (SmartAgr) Welcome message from Workshop Chairs
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A Smart Sensor-Based Watering Automation System for Nursery Plants
No full textWater scarcity and resource (water, soil, energy) efficient management are critical challenges in modern agriculture. This paper proposes a novel sensor-based smart irrigation system for nurseries, describing its design and experimentation. The system utilizes real-time data from soil moisture sensors and environmental sensors to optimize irrigation based on plant needs and available green energy, activating irrigation only when necessary, minimizing water waste and energy consumption. A software program analyzes sensor data alongside user-defined parameters and factors such as weather and renewable energy availability. The paper demonstrates how this approach can improve plant health, production yield, and product quality, while also achieving significant cost savings for nursery operators. This research contributes to sustainable agricultural practices by promoting efficient water and energy use
Elastic QoS Scheduling with Step-by-Step Propagation in IEEE 802.11e Networks with Multimedia Traffic
No full textThe spreading diffusion of wireless devices and the crowded coexistence of multimedia applications greedy of bandwidth and with strict requirements stress the service provisioning offered by wireless technologies. WiFi is a reference for wireless connectivity and it requires a continuous evolution of its mechanism in order to follow increasingly demanding service needs. In particular, despite the evolution of physical layer, some critical contexts, such as industrial networks, telemedicine, telerehabilitation, and virtual training, require further refined improvements in order to ensure the respect of strict real-time service requirements. In this paper an in-depth analysis of Dynamic TXOP HCCA (DTH) MAC enhanced centralized scheduler is illustrated and it is further refined introducing a new improvement, DTH with threshold. DTH and DTH with threshold can be integrated with preexisting centralized schedulers in order to improve their performances, without any overprovisioning that can negatively impact on the admission control feasibility test. Indeed, without modifying the centralized scheduler policy, they combine together the concepts of reclaiming transmission time and statistical estimation of the traffic profile in order to provide, at each polling, an instantaneous transmission time tailored to the variable traffic requirements, increasing, when necessary, the service data rate. These mechanisms can coexist with advanced physical layer-based solutions, providing the required service differentiation. Experimental results and theoretical analysis, based on elastic scheduler theory, show that they are effective especially in the case of Variable Bit Rate traffic streams in terms of transmission queues length, packets loss, delay, and throughput
Cloud Networks for ERTMS Railways Systems (Short Paper)
No full textEuropean Rail Traffic Management System(ERTMS) efficiently manages and schedules the trainsguaranteeing passengers safety and service constraints andmaximizing railways capacity. The management system isresponsible of the elaboration needed to control the trainscirculation and to derive the necessary commands for trainsand trackside actuators such as railroad switches. Theseoperations need heavy computational resources and require anexchange of information between trains, trackside equipmentsand elaboration components. Currently the managementsystem is hosted in the Central Control Rooms that centrallymanage and supervise trains traffic of different geographicalareas. This paper proposes a new paradigm about the executionof the ERTMS management activities taking advantage fromcloud networks. It suggests to distribute among cloud resourcesthe computational load due to the elaboration of the collecteddata and the derivation of required commands for trains andactuators. This can make possible a proactive approach tothe trains management, suitable not only to consider the datasent by the trackside equipments, but also the informationdirectly collected onboard of the train. Despite trackside dataare considered by the management system, actually they arenot integrated with onboard real-Time data that are sent tothe ground system for diagnosis purposes. These two sourcesof information can be jointly used to simulate in advance thetrain transit, deduce possible delays and anomalies and moreefficiently manage the trains circulation
Energy harvesting for on-board railway systems
No full textGreenhouse effect due to CO2 emission is a global emergency issue affecting all human activities, including transportation systems. With the aim of reducing greenhouse gas emissions of the transport systems, the evolution of railway systems is toward environmental sustainability and energy efficiency. In this paper, a study about the use of energy harvesting to integrate the powering system of trains is presented. Currently available technologies are analyzed and photovoltaic systems are selected being technologically mature, since until now only big solar plants are considered as energy source for railways, and few studies have investigated solutions local to the trains. However, these studies date back to the early 2000s when photovoltaic technology was not sufficiently mature for this field of application. Taking advantage from the technology evolution the presented evaluation show by simulation that the electricity production can be increased until 400% with respect to the early 2000s. Furthermore, simulation results show that new power optimization solutions based on micro-inverters and on decoupling the PV modules of a string allow overcoming the limitation due to not optimal panel orientation on the train roof, train movement and shadows, increasing the production from 2 to 25%. The proposed approach can make the railway system more attractive for users sensitive to environmental issues and can promote intermodal connections with other green solutions for urban and local transport
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