667 research outputs found
Simulation analysis of IEEE 802.15.4 for wireless networked control systems
The deployment of wireless networks in industrial
environments can bring several advantages over their wired
counterparts; however, the characteristics of the wireless channels
pose challenges to the provisioning of quality of service (QoS) that
are not seen in wired networks. This paper provides an analysis of
how important QoS parameters, such as message delivery ratio,
delay and energy consumption, vary as a function of the number
of sensor nodes injecting traffic in IEEE 802.15.4 networks
operating in unbeaconed mode. Results show that the peer-to-peer
topology enables better performance than the star topology, under
the same conditions, indicating that the former is a better option if
centralized control is not required. The use of retransmissions
increases significantly the reliability of the network; however, even
a high number of retransmissions are not enough to provide full
reliability when the channel is highly affected by errors. Results
also show that presence of hidden nodes can severely degrade the
performance of the network, while the reduction of the turnaround
time can improve the performance.Fundação para a CiĂȘncia e a Tecnologia (FCT
A personalized rehabilitation system based on wireless motion capture sensors
We live in an aging society, an issue that will be exacerbated in the coming decades, due to low birth rates
and increasing life expectancy. With the decline in physical and cognitive functions with age, it is of the
utmost importance to maintain regular physical activity,in order to preserve an individualâs mobility, motor
capabilities and coordination. Within this context, thispaper describes the development of a wireless sensor
network and its application in a human motion capturesystem based on wearable inertial and magnetic
sensors. The goal is to enable, through continuous real-time monitoring, the creation of a personalized
home-based rehabilitation system for the elderly population and/or injured people. Within this system, the
user can benefit from an assisted mode, in which their movements can be compared to a reference motion
model of the same movements, resulting in visual feedback alerts given by the application. This motion
model can be created previously, in a âlearning phaseâ, under supervision of a caregiver.Fundação para a CiĂȘncia e a Tecnologia (FCT
A telerehabilitation system based on wireless motion capture sensors
The constant growth of the elderly population in the world creates new challenges and opportunities in health care systems. New technological solutions have to be found in order to meet the needs and demands of our aging society. The welfare and quality of life of the elderly population must be a priority. Continuous physical activity will play an important role, due to the increase of the retirement age. However, physiotherapy can be expensive, even when the desire movements are autonomous and simple, also requires people to move to rehabilitation centres. Within this context, this paper describes the development and preliminary tests of a wireless sensor network, based on wearable inertial and magnetic sensors, applied to the capture of human motion. This will enable a personalized home-based rehabilitation system for the elderly or people in remote physical locations.Project âAAL4ALLâ, co-financed by the European Community Fund FEDER through COMPETE â Programa Operacional Factores de Competitividade (POFC).FCT â Foundation for Science and Technology â Lisbon, Portugal, through project PEst-C/CTM/LA0025/2013
Design and implementation of a wireless sensor network applied to motion capture
This paper describes the development of a wireless sensor network prototype and its application in a motion capture system based on inertial and magnetic sensors. The system presents a portable and modular architecture and allows the monitoring of several users at the same time using a single wireless network. The target application requires the wireless sensor network to operate efficiently under high loads, since it generates data intensive traffic and needs to support a high number of sensor modules. Other requirements imposed by the application are real-time operation and reliable data delivery. In order to provide the quality of service required by the application, an enhanced version of the LPRT medium access control protocol was developed and implemented in devices compliant with the IEEE 802.15.4 standard at the physical layer. Simulation results show that the proposed modifications improve the performance of the protocol. The implementation of the protocol is validated through the experimental results presented.Fundação para a CiĂȘncia e a Tecnologia (FCT) - projeto
PTDC/EEA-TEL/68625/2006
Cover Crops Alternatives for Sustainable Agriculture Systems in Uruguay
In Uruguay, the increase of cropland area during the last decade was based on rotation systems intensification and soybean expansion, achieving 1.321.000 ha (Souto, 2014). Diaz (2007) demonstrated the value of the ley-farming systems where the integration of livestock and crop production achieved benefits on sustainability. Despite the advantages of crop-pasture rotation systems (GarcĂa Prechac et al., 2004), grain market prices and food demand resulted in pasture phase losses in rotation with crops. Recently, Livestock Agriculture and Fisheries Ministry implemented a national soil conservation plan, that regulates cropping rotation systems based on soil erosion estimations and other key soil quality indicators. Although, no-till was full adopted, climatic and soil conditions determine that soil must be cover by residues or vegetation all year to reduce erosion and degradation (Thorup-Kristensen et al., 2003). Cover crops contribute to protect soils during fallow periods. The 17% of total soybean area cultivated is in Eastern Uruguay, being soils with erosion risk , fertility, structure and drainage limitations. This paper evaluates cover crops adaptation, subsequent effects on soybean productivity, and estimations of nitrogen supply and extraction from cover crops and soybean, respectively
A wireless posture monitoring system for personalized home-based rehabilitation
We live in an aging society, an issue that will be exacerbated in the coming decades, due to low birth
rates and increasing life expectancy. With the decline in physical and cognitive functions with age, it is of the
utmost importance to maintain regular physical activity, in order to preserve an individualâs mobility, motor
capabilities and coordination. Within this context, this paper describes the development of a wireless sensor
network and its application in a human motion capture system based on wearable inertial and magnetic sensors.
The goal is to enable, through continuous real-time monitoring, the creation of a personalized home-based
rehabilitation system for the elderly population and/or injured people. Within this system, the user can benefit
from an assisted mode, in which their movements can be compared to a reference motion model of the same
movements, resulting in visual feedback alerts given by the application. This motion model can be created
previously, in a âlearning phaseâ, under supervision of a caregiver.Project âAAL4ALLâ, co-financed by the
European Community Fund FEDER through
COMPETE â Programa Operacional Factores de
Competitividade (POFC). This work is funded by
FEDER funds through the COMPETE 2020
Programme and National Funds through FCT -
Portuguese Foundation for Science and Technology
under the projects UID/CTM/50025/2013 and
UID/EEA/04436/2013.info:eu-repo/semantics/publishedVersio
Black-hole horizons as probes of black-hole dynamics II: geometrical insights
In a companion paper [1], we have presented a cross-correlation approach to
near-horizon physics in which bulk dynamics is probed through the correlation
of quantities defined at inner and outer spacetime hypersurfaces acting as test
screens. More specifically, dynamical horizons provide appropriate inner
screens in a 3+1 setting and, in this context, we have shown that an
effective-curvature vector measured at the common horizon produced in a head-on
collision merger can be correlated with the flux of linear Bondi-momentum at
null infinity. In this paper we provide a more sound geometric basis to this
picture. First, we show that a rigidity property of dynamical horizons, namely
foliation uniqueness, leads to a preferred class of null tetrads and Weyl
scalars on these hypersurfaces. Second, we identify a heuristic horizon
news-like function, depending only on the geometry of spatial sections of the
horizon. Fluxes constructed from this function offer refined geometric
quantities to be correlated with Bondi fluxes at infinity, as well as a contact
with the discussion of quasi-local 4-momentum on dynamical horizons. Third, we
highlight the importance of tracking the internal horizon dual to the apparent
horizon in spatial 3-slices when integrating fluxes along the horizon. Finally,
we discuss the link between the dissipation of the non-stationary part of the
horizon's geometry with the viscous-fluid analogy for black holes, introducing
a geometric prescription for a "slowness parameter" in black-hole recoil
dynamics.Comment: Final version published on PR
Black-hole horizons as probes of black-hole dynamics I: post-merger recoil in head-on collisions
The understanding of strong-field dynamics near black-hole horizons is a
long-standing and challenging prob- lem in general relativity. Recent advances
in numerical relativity and in the geometric characterization of black- hole
horizons open new avenues into the problem. In this first paper in a series of
two, we focus on the analysis of the recoil occurring in the merger of binary
black holes, extending the analysis initiated in [1] with Robinson- Trautman
spacetimes. More specifically, we probe spacetime dynamics through the
correlation of quantities defined at the black-hole horizon and at null
infinity. The geometry of these hypersurfaces responds to bulk gravitational
fields acting as test screens in a scattering perspective of spacetime
dynamics. Within a 3 + 1 approach we build an effective-curvature vector from
the intrinsic geometry of dynamical-horizon sections and correlate its
evolution with the flux of Bondi linear momentum at large distances. We employ
this setup to study numerically the head-on collision of nonspinning black
holes and demonstrate its validity to track the qualita- tive aspects of recoil
dynamics at infinity. We also make contact with the suggestion that the
antikick can be described in terms of a "slowness parameter" and how this can
be computed from the local properties of the horizon. In a companion paper [2]
we will further elaborate on the geometric aspects of this approach and on its
relation with other approaches to characterize dynamical properties of
black-hole horizons.Comment: final version published on PR
Project results presentation (deliverable D18)
This document is a report which collects together the CYCLOPS project results for dissemination to different interested audiences such as Grid communities and Civil Protection agencies. It also reports on national and international initiatives and projects, SMEs, training activities and related projects.
The structure of this document shows the approach used in the project. Following an introduction, it describes a set of related projects, namely grid- based technologies/EGEE, risk management, and GMEs-based services. It then presents the business of Civil Protection and the use cases selected. These highlight the grid requirements for Grid-based CP applications. The research strategies and enhancements needed for the EGEE infra-structure are identified, based on the use cases. Dissemination of training and knowledge to different communities are also key points of the project.FP
Scouting Benefits and Developing Innovations in Temperate Grassland to Sustainable Agriculture Production
Agricultural intensification raises concern about land use and future effects to natural resources. The world demand for grain, meat and forest products is increasing constantly. Changes are occurring at large scale, being a compromise for policy makers to contribute to identify opportunities to readdress the productive scenario. There is available technology to reduce impacts, without restricting necessarily productivity. Grasslands provide a large series of economical and ecological benefits to the agricultural systems, being the literature exhaustive in examples. Ley-farming and cover crops technologies are good examples of environmentally sound soil management practices. The society is also worried about an improper use of the natural resources involved. The drastic increase in the grain crops area leaded by soybean in Uruguay, determined that the government implemented Sustainable Soil Use and Management Plans, based on erosion estimation using the USLE-RUSLE model adapted locally by research conducted over more than 50 years on a series of long term experimental platforms. There is an opportunity for this type of local innovative initiatives to be widely diffused, adopted or adapted. In essence, grasslands will continue playing a key role in maintaining a sustainable production
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