Integrating RFID and WLAN for indoor positioning and IP movement detection

Location awareness in an indoor environment and wireless access to Internet applications are major research areas towards the overwhelming success of wireless and mobile communications. However, the unpredictable indoor radio propagation and handover latency due to node mobility are the main challenging issues that need to be addressed. For tackling efficiently both problems of indoor localization and handover management, we propose combining key benefits of two outstanding wireless technologies, i.e. radio frequency identification (RFID) and a wireless local area network (WLAN) infrastructure. WLANs, such as IEEE 802.11 (WiFi), are now very common in many indoor environments for providing wireless communication among WiFi-enabled devices by accessing an Access Point (infrastructure mode) or through peer to peer connections (ad hoc mode). However, the small cell size of the Access Points (APs) in a WiFi-based network drives the need for frequent handovers leading to increased latency. RFID is an emerging technology consisting of two basic components, a tag and a reader, and its main purpose is the automatic identification of tagged objects by a reader. However, in the presence of multiple readers, RFID suffers from the so-called reader collision problem, mainly due to the inability for direct communication among them. In this paper, we propose a hybrid RFID and WLAN system; the RFID technology is employed for collecting information that is used for both localization and handover management within the WLAN, whereas the WLAN itself is utilized for controlling and coordinating the RFID reading process. In our system architecture, tag IDs of a RFID tag deployment are correlated with both location and topology information in order to determine the position and predict the next subnetwork of a Mobile Node (MN) with a reader attached to its mobile device. The role of the WLAN is to coordinate the readers when accessing the RFID channel for retrieving tags?? IDs, hence compensating the persisting RFID collision problem among multiple readers. Numerical results based on extensive simulations validate the efficiency of the proposed hybrid system in providing accurate and time efficient localization and reducing the IP handover latency.     

On the response of thin-walled CFRP composite tubular components subjected to static and dynamic axial compressive loading: experimental

In this work the crushing response and crashworthiness characteristics of thin-wall square FRP (fibre reinforced plastic) tubes that were impact tested at high compressive strain rate are compared to the response of the same tubes in static axial compressive loading. The material combination of the tested specimens was carbon fibres in the form of reinforcing woven fabric in epoxy resin, and the tested tubes were constructed trying three different laminate stacking sequences and fibre volume contents on approximately the same square cross-section. Comparison of the static and dynamic crushing characteristics is made by examining the collapse modes, the shape of the load–displacement curves, the peak and average compressive load and the absorbed amount of crushing energy in both loading cases. In addition, the influence of the tube geometry (axial length, aspect ratio and wall thickness), the laminate material properties-such as the fibre volume content and stacking sequence-and the compressive strain rate on the compressive response, the collapse modes, the size of the peak load and the energy absorbing capability of the thin-wall tubes is extensively analysed.     

Scene analysis indoor positioning enhancements

The emergence of innovative location-oriented services and the great advances in mobile computing and wireless networking motivated the development of positioning systems in indoor environments. However, despite the benefits from location awareness within a building, the implicating indoor characteristics and increased user mobility impeded the implementation of accurate and time-efficient indoor localizers. In this paper, we consider the case of indoor positioning based on the correlation between location and signal intensity of the received Wi-Fi signals. This is due to the wide availability of WLAN infrastructure and the ease of obtaining such signal strength (SS) measurements by standard 802.11 cards. With our focus on the radio scene analysis (or fingerprinting) positioning method, we study both deterministic and probabilistic schemes. We then describe techniques to improve their accuracy without increasing considerably the processing time and hardware requirements of the system. More precisely, we first propose considering orientation information and simple SS sample processing during the training of the system or the entire localization process. For dealing with the expanded search space after adding orientation-sensitive information, we suggest a hierarchical pattern matching method during the real-time localization phase. Numerical results based on real experimental measurements demonstrated a noticeable performance enhancement, especially for the deterministic case which has additionally the advantage of being less complex compared to the probabilistic one.     

Development and implementation of an optimisation model for biofuels supply chain

Biofuels supply chain comprises a wide set of activities involving a rather complex set of parameters. Cultivation of the raw materials is closely related to the agricultural sector whereas the production of the final product presumes the operation of a conversion plant. The distribution network aims at delivering the final product close to the consumption. The extent of the involvement of each one of the previously mentioned sectors is the result of strategic and operational planning of the whole supply chain and, in the general case, determines the efficiency of the biofuels sector. Taking also into account the very rapidly changing opinions related to the environmental behaviour of the whole biofuels supply chain, it becomes very clear that the parameters in the sector are continuously changing. Therefore, the consideration of an integrated supply chain appropriately modelled is believed to be very critical and could result in the optimal solution per case, economically and/or environmentally speaking. In this paper the development of a mathematical model for the optimal design and operation of Biofuels Supply Chain is proposed as an integrated approach that can take into account both technical and economic parameters affecting the performance of the whole value chain. Model implementation would facilitate and support the decision taking in various planning and operational issues such as infrastructure investments, the quantities of raw materials to be cultivated, the quantities of biofuels to be produced in the domestic market or imported, identifying the best available solution for the optimal design and operation of the biofuels supply chain.     

Axial collapse of hybrid square sandwich composite tubular components with corrugated core: numerical modelling

The present paper is dealing with the implementation of the explicit FE Code LS-DYNA to the simulation of the crash behaviour and energy absorption characteristics of thick-walled square tubular crashworthy components made of hybrid sandwich material with corrugated core subjected to axial compressive loading. The obtained numerical results are compared with actual experimental data from small-scale models in terms of deformation modes, energy absorption capability, load/deflection history and crush zone characteristics, showing very good agreement.     

Generalized flame surface density transport conditional on flow topologies for turbulent H2-air premixed flames in different regimes of combustion

Abstract

The generalized flame surface density (FSD) transport conditional on local flow topologies in premixed turbulent flames has been analyzed based on a detailed chemistry direct numerical simulation database of statistically planar turbulent hydrogen-air premixed flames with an equivalence ratio of 0.7 representing the corrugated flamelets, thin reaction zones and broken reaction zones regimes of combustion. The local flow topologies have been categorized by the values of the three invariants of the velocity gradient tensor and the statistical behaviors of the generalized FSD and different terms of its transport equation conditional on these flow topologies have been analyzed in detail for different choices of the reaction progress variable. The qualitative behavior of the different terms of the generalized FSD transport equation has been found to be similar for different choices of reaction progress variable but the statistical behaviors of the tangential strain rate term and its components have been found to be affected by the regime of combustion. The topologies, which exist for all values of dilatation rate, contribute significantly to the generalized FSD transport in premixed turbulent flames for all regimes of combustion. An unstable nodal flow topology, which is representative of a counter-flow configuration, has been found to be a dominant contributor to the FSD transport for all regimes of combustion irrespective of the choice of reaction progress variable. Moreover, a focal topology which is obtained only for positive values of dilatation rate, has been found to contribute significantly, especially to the curvature and propagation terms of the FSD transport equation for all regimes of combustion including the broken reaction zones regime. However, the contributions of the flow topologies to the turbulent transport and tangential strain rate term, which are obtained only for positive dilatation rates, have been found to weaken from the corrugated flamelets to the broken reaction zones regime.     

Path selection algorithms for fault tolerance in wireless mesh networks

Recently Wireless Mesh Networks (WMNs) have emerged as a key technology for providing high-bandwidth networking among peer nodes over a specific coverage area. Features such as low cost, ease of deployment, self-configuration and self-healing make them one of the most promising global telecommunication systems. Despite their advantages, however, several research challenges remain in all protocol layers. In this paper, we address the main challenging issues related to the routing aspects in a WMN. Routing in such networks is performed through multi-hop paths where intermediate nodes cooperatively make forwarding decisions based on their knowledge regarding the network topology. However, in an unideal dynamic environment due to frequent or rare node failures/misbehavior, traditional ad-hoc routing protocols suffer from high routing overhead or energy consumption. Motivated by this, we propose several path selection algorithms which adapt to such topology dynamics. The main objective of these routing schemes is to provide fault tolerance without sacrificing the energy and computational complexity efficiency. Numerical investigations, based on extensive simulations, validate the effectiveness of our proposals even when faulty nodes subsist in the environment.     

On the experimental investigation of crash energy absorption in laminate splaying collapse mode of FRP tubular components

In this experimental work the crash energy absorption of fibre reinforced plastic (FRP) tubular components that collapse in laminate splaying mode is investigated by means of a new testing method, the “curling test”. This test method was used trying rectangular carbon, aramid and glass FRP strips—in which the reinforcing fibres were in the form of reinforcing woven fabric (carbon and aramid FRP specimens) and multi-axial fibre reinforcements (glass FRP specimens). Apart from the analysis of the system of bending and friction forces acting on the specimens during the curling tests in comparison with the forces acting in the case the laminate splaying collapse mode and the observations related to the deformation and crushing induced on the FRP specimens by this force combination, the analysis of the test results focused on the influence of the most important geometric and laminate material properties—such as thickness, flexural rigidity, number of reinforcing fibre layers, laminate stacking sequence and constituent material mechanical properties—on the specific energy absorption and the peak load.