1,016 research outputs found
Recent Advances on Implantable Wireless Sensor Networks
Implantable electronic devices are undergoing a miniaturization age, becoming more efficient and yet more powerful as well. Biomedical sensors are used to monitor a multitude of physiological parameters, such as glucose levels, blood pressure and neural activity. A group of sensors working together in the human body is the main component of a body area network, which is a wireless sensor network applied to the human body. In this chapter, applications of wireless biomedical sensors are presented, along with state-of-the-art communication and powering mechanisms of these devices. Furthermore, recent integration methods that allow the sensors to become smaller and more suitable for implantation are summarized. For individual sensors to become a body area network (BAN), they must form a network and work together. Issues that must be addressed when developing these networks are detailed and, finally, mobility methods for implanted sensors are presented
Specifications of a device interface for service-oriented automation control components
Service-oriented paradigm is being used to develop distributed and reconfigurable control solutions for factory automation environments. Since service-oriented automation control components are logical entities that provide and consume services, they may have an interface that maps the logical processes into the actions of the representative physical mechatronics. The inter-connection with the physical hardware devices, namely accessing I/Os, is a crucial issue to achieve the vertical IT-enterprise integration in these service-oriented systems, covering the shop floor device control level. This paper describes a device interface approach, in the context of a service-oriented control architecture, in which High-level Petri nets are used as the control description to access to the physical device. The outgoing features of the solution allow integrating the physical behavior into the control of automation components and consequently thereby incorporate it in the modular service-oriented control architecture
A Model to Improve the Accuracy of WSN Simulations
Simulation studies have been extensively adopted in the networking research community. Nevertheless, the performance of the software components running within the network devices is often not modeled by generic network simulators. This aspect is particularly important in wireless sensor networks (WSN). As motes present very limited computing resources, the overhead of the software components cannot be ignored. Consequently, WSN simulation results may diverge significantly from the reality. After showing experimentally the validity of this assumption, the paper proposes a set of generic equations to model the performance of WSN software components. Validation tests using contention and multiplexing-based MAC protocols show that the inclusion of the proposed model in a WSN simulator improves the confidence degree in the simulation results significantly
STATISTICAL PROPERTIES AND SENSITIVITY OF A NEW ADAPTIVE SAMPLING METHOD FOR QUALITY CONTROL
We present a new adaptive sampling method for statistical quality control. In this method, called LSI (Laplace sampling intervals), we use the probability distribution function of the Laplace standard distribution to obtain the sampling instants, depending on a k parameter that allows control of sampling costs. Several algebraic expressions concerning the statistical properties of the LSI method are presented. We compare the LSI method with fixed sampling intervals (FSI) and variable sampling intervals (VSI) methods using a Shewhart X-bar control chart and evaluate the sensitivity of these sampling methods when the lower sampling interval is truncated. The results obtained show that the new method is a viable alternative in various critical contexts and situations
Modelling the impact of software components on wireless sensor network performance
Network Simulators are often used to study multiple aspects of data communications in distinct scenarios, including wireless sensor networks (WSN). However, the performance of the software components running in the network nodes is normally neglected by the simulators. This aspect is particularly important in WSNs, as nodes have very limited computing resources. In order to study the impact of software components on WSN performance, a simulated WSN and a physical WSN were setup in the IEEE 802.15.4 domain. Tests revealed that the simulator must take into account the software components of the WSN to produce realistic results. To achieve this, new parameters are proposed to model the impact of the software components on a physical WSN. Tests measuring the packet round-trip delay, delivery error ratio, and duplicated packet ratio showed that the inclusion of this model in a simulator improves significantly the accuracy of the results when compared with those obtained in a physical WSN
A time-slot scheduling algorithm for e-health wireless sensor networks
http://www.ieee-healthcom.org/2010/about.htmlFor e-health wireless sensor networks presenting significant traffic loads, MAC protocols based on deterministic scheduling algorithms are consensually considered more adequate than protocols based on random access algorithms. Indeed, TDMA-based MAC protocols are able to control the delay bound and save power by eliminating collisions. However, these protocols always require some expedite scheme to assign the superframe time-slots to the network devices that need to transmit data. Knowing that patients of an e-health wireless network are normally monitored by the same number and types of motes, originating a regular traffic pattern, a simple collaborative time-slot allocation algorithm can be achieved, as introduced in this paper. In the proposed algorithm, the announcement of time-slot allocation by the network coordinator is avoided, which helps to improve the packet delivery ratio and reduce the energy consumption in the e–health wireless network.(undefined
Petri net-based approach for web service automation resource coordination
In industrial automation, control systems and mechatronic devices are from
diverse nature, supplied by different manufacturers and made of different
technologies. The adoption of web services principles in an automated
production system satisfies some requirements, namely the interoperability of
such heterogeneous and distributed environments and the basis for flexibility
and reconfigurability. Manufacturing processes require to access resources at
different precedence levels and time instances, but in the other way resources
may also be shared by different processes. A major challenge is then how
individual services may interact, coordinating their activities. Petri nets may be
used to describe complex system behaviour and therefore also applied to
coordinate such systems. The paper introduces a Petri net based approach for the
design, analysis and coordination of systems developed using web services to
represent individual and autonomous resources. For this purpose, it is presented
a Petri nets computational tool to support the design, validation and coordination
of web service based automation systems.info:eu-repo/semantics/publishedVersio
Avaliação experimental do comportamento sÃsmico de casas de madeira
As casas de madeira estão a ter um desenvolvimento rápido na Europa devido a aspetos
tais como a sustentabilidade e o elevado grau de industrialização e prefabricação, que se
traduzem em facilidade e rapidez de montagem. Os sistemas mais tradicionais de estruturas
de madeira e os sistemas inovadores recentes são agora aplicados não apenas no norte da
Europa mas, crescentemente, no sul da Europa, onde a perigosidade sÃsmica é mais
elevada. Neste artigo revêm-se brevemente o desempenho de edifÃcios de madeira em
sismos recentes, definem-se os aspetos que caracterizam a ação sÃsmica na regulamentação
europeia e apresentam-se os resultados de uma campanha extensa de ensaios realizados na mesa sÃsmica no Laboratório Nacional de Engenharia Civil
Revealing hidden symmetries and gauge invariance of the massive Carroll-Field-Jackiw model
In this paper we have analyzed the improved version of the Gauge Unfixing
(GU) formalism of the massive Carroll-Field-Jackiw model, which breaks both the
Lorentz and gauge invariances, to disclose hidden symmetries to obtain gauge
invariance, the key stone of the Standard Model. In this process, as usual, we
have converted this second-class system into a first-class one and we have
obtained two gauge invariant models. We have verified that the Poisson brackets
involving the gauge invariant variables, obtained through the GU formalism,
coincide with the Dirac brackets between the original second-class variables of
the phase space. Finally, we have obtained two gauge invariant Lagrangians
where one of them represents the Stueckelberg form.Comment: revised version. To appear in Europhysics Letter
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