Embracing Localization Inaccuracy: A Case Study

In recent years, indoor localization has become a hot research topic with some sophisticated solutions reaching accuracy on the order of ten centimeters. While certain classes of applications can justify the corresponding costs that come with these solutions, a wealth of applications have requirements that can be met at much lower cost by accepting lower accuracy. This paper explores one specific application for monitoring patients in a nursing home, showing that sufficient accuracy can be achieved with a carefully designed deployment of low-cost wireless sensor network nodes in combination with a simple RSSI-based localization technique. Notably our solution uses a single radio sample per period, a number that is much lower than similar approaches. This greatly eases the power burden of the nodes, resulting in a significant lifetime increase. This paper evaluates a concrete deployment from summer 2012 composed of fixed anchor motes throughout one floor of a nursing home and mobile units carried by patients. We show how two localization algorithms perform and demonstrate a clear improvement by following a set of simple guidelines to tune the anchor node placement. We show both quantitatively and qualitatively that the results meet the functional and non-functional system requirements

Programming Wireless Sensor Networks with Logical Neighborhoods: A Road Tunnel Use Case

Wireless sensor networks (WSNs) involving actuation are increasingly envisioned in a range of fields [1]. Among these, there is considerable interest in leveraging off WSNs to improve safety in road tunnels [4]. Researchers are envi- sioning tunnels equipped with WSN nodes that gather physi- cal readings such as temperature and light, monitor the struc- tural integrity of the tunnel, and sense the presence of vehi- cles to detect a possible traffic congestion. Based on sensed data, the system operates a variety of devices, such as ven- tilation fans inside the tunnel, and traffic lights at the en- trances. For instance, when a sensor detects the presence of a fire in a sector, the fans in the same sector are activated, and the traffic lights are turned red to prevent further vehicles from entering the tunnel

Critical interfaces in the random-bond Potts model

We study geometrical properties of interfaces in the random-temperature q-states Potts model as an example of a conformal field theory weakly perturbed by quenched disorder. Using conformal perturbation theory in q-2 we compute the fractal dimension of Fortuin Kasteleyn domain walls. We also compute it numerically both via the Wolff cluster algorithm for q=3 and via transfer-matrix evaluations. We obtain numerical results for the fractal dimension of spin cluster interfaces for q=3. These are found numerically consistent with the duality kappa(spin) * kappa(FK)= 16 as expressed in putative SLE parameters.Comment: 4 page

Pervasive Games in a Mote-Enabled Virtual World Using Tuple Space Middleware

Pervasive games are a new and exciting field where the user experience benefits from the blending of real and virtual elements. Players are no longer confined to computer screens. Rather, interactions with devices embedded within the real world and physical movements become an integral part of the gaming experience. Several prototypes of pervasive games have been proposed by both industry and academia. However, in such games the issues arising from the integration of players and real world, the management of the context surrounding the players, and the need for communication and distributed coordination are often addressed in an ad-hoc fashion. Therefore, the underlying software fabric is often not reusable, ultimately slowing down the diffusion of pervasive games. In this paper we describe the design and implementation of a pervasive game on top of TinyLIME, a middleware system supporting data sharing among mobile and embedded devices. By illustrating the design of a pervasive game we developed, we argue concretely that the programming abstractions supported by TinyLIME greatly simplify the data and context management characteristics of pervasive games, and provide an effective and reusable building block for their development. TinyLIME was originally designed to support applications where mobile users collect data from sensors scattered in the physical environment. We build upon this capability to put forth a second contribution, namely, the use of wireless sensor devices (or motes) as a computing platform for pervasive games. Besides reporting physical data for the sake of the game, we use motes to store information relevant to the game plot, e.g., virtual objects. Motes are typically very small in size, and therefore can be hidden in the environment, enhancing the sense of immersion in a virtual world. To the best of our knowledge, this original use of wireless sensor devices is novel in the scientific and gaming literature. Furthermore, it is naturally supported by TinyLIME, yielding a unified programming abstraction that spans the heterogeneous gaming platform we propose

Evaluation of short-term geomorphic changes in differently impacted gravel-bed rivers using improved dems of difference

The evaluation of the morphological dynamics of rivers is increasingly focusing, in recent years, on the achievement of quantitative estimates of change in order to identify geomorphic trends and forecast targeted restoration actions. Thanks to the development of more effective and reliable survey technologies, more accurate Digital Elevation Models (DEM) can be produced and, through their consequent differencing (DoD), extremely useful geomorphic analyses can be carried out. In this situation, a major role is played by uncertainty, especially in the final volumetric rates of erosion and deposition processes, that may lead to misinterpretation of spatial and temporal changes. This paper aims at achieving precise geomorphic estimates derived from subsequent hybrid (LiDAR and bathymetric points) surface representations. The study areas consist of gravel-bed reaches of two differently impacted fluvial environments, Piave and Tagliamento rivers, that were affected by two severe flood events (Piave, R.I. of 7 and 10 years and Tagliamento, R.I. of 15 and 12 years) in the inter-surveys period. The basic Hybrid Digital Elevation Models (HDTM) were processed accounting for spatially variable uncertainty and considering, beside slope and point density input variables, a novel component measuring the quality of the bathymetric derived points. In fact, since the major changes occur within river channels, the integration of this variable evaluating the precision of the bathymetric channel elevations in the HDTMs, has allowed, through the creation of targeted FIS (Fuzzy Inference System) rules, to obtain reliable geomorphic estimates of change. Volumes and erosion and deposition patterns were then analyzed and compared to outline the different dynamics among the sub-reaches and the two river systems

Algal Viruses: The (Atomic) Shape of Things to Come

This is the final version. Available on open access from MDPI via the DOI in this recordVisualization of algal viruses has been paramount to their study and understanding. The direct observation of the morphological dynamics of infection is a highly desired capability and the focus of instrument development across a variety of microscopy technologies. However, the high temporal (ms) and spatial resolution (nm) required, combined with the need to operate in physiologically relevant conditions presents a significant challenge. Here we present a short history of virus structure study and its relation to algal viruses and highlight current work, concentrating on electron microscopy and atomic force microscopy, towards the direct observation of individual algae⁻virus interactions. Finally, we make predictions towards future algal virus study direction with particular focus on the exciting opportunities offered by modern high-speed atomic force microscopy methods and instrumentation.The previously unpublished AFM images shown in this manuscript were generated in the Plymouth Marine Laboratory and University of Exeter Environmental Single Cell Genomics Facility which was supported by the UK’s Natural Environment Research Council (NERC) and The Wolfson Foundation. C.T.E. is supported by an EPSRC and Bristol Nano Dynamics Ltd PhD studentship

A Flexible and Modular Framework for Implementing Infrastructures for Global Computing

We present a Java software framework for building infrastructures to support the development of applications for systems where mobility and network awareness are key issues. The framework is particularly useful to develop run-time support for languages oriented towards global computing. It enables platform designers to customize communication protocols and network architectures and guarantees transparency of name management and code mobility in distributed environments. The key features are illustrated by means of a couple of simple case studies

LIME: A Middleware for Physical and Logical Mobility

LIME is a middleware supporting the development of applications that exhibit physical mobility of hosts, logical mobility of agents, or both. LIME adopts a coordination perspective inspired by work on the Linda model. The context for computation, represented in Linda by a globally accessible, persistent tuple space, is represented in LIME by transient sharing of the tuple spaces carried by each individual mobile unit. Linda tuple spaces are also extended with a notion of location and with the ability to react to a given state. The hypothesis underlying our work is that the resulting model provides a minimalist set of abstractions that enable rapid and dependable development of mobile applications. In this paper, we illustrate the model underlying LIME, present its current design and implementation, report about its initial evaluation in applications that involve physical mobility, and discuss lessons learned and future enhancements that will drive its evolution