22,069 research outputs found
Online Movement Correlation of Wireless Sensor Nodes
Sensor nodes can autonomously form ad-hoc groups based on their common context. We propose a solution for grouping sensor nodes attached on the same vehicles on wheels. The nodes periodically receive the movement data from their neighbours and calculate the correlation coefficients over a time history. A high correlation coefficient implies that the nodes are moving together. We demonstrate the algorithm using two types of movement sensors: tilt switches and MEMS accelerometers. We place the nodes on two wirelessly controlled toy cars, and we observe in real-time the group membership via the LED colours of the nodes. In addition, a graphical user interface running on the base station shows the movement signals over a recent time history, the latest sampled data, the correlation between each two nodes and the group membership
Movement-based Group Awareness with Wireless Sensor Networks
We propose a method through which dynamic sensor nodes
determine that they move together, by communicating and correlating their movement information. We describe two possible solutions, one using inexpensive tilt switches, and another one using low-cost MEMS accelerometers. We implement a fast, incremental correlation algorithm,
with an execution time of 6ms, which can run on resource constrained devices. The tests with the implementation on real sensor nodes show that the method is reliable and distinguishes between joint and separate movements. In addition, we analyze the scalability from four different
perspectives: communication, energy, memory and execution speed. The solution using tilt switches proves to be simpler, cheaper and more energy efficient, while the accelerometer-based solution is more reliable, more
robust to sensor alignment problems and, potentially, more accurate by using extended features, such as speed and distance
Finite H2 concentrations in superfluid 4He
We have studied the solubility of molecular hydrogen in bulk liquid He at
zero temperature using the diffusion Monte Carlo method and realistic
interatomic potentials between the different species of the mixture. Around the
He equilibrium density, the H_2 molecules clusterize in liquid-like drops
blocking the existence of a uniform dilution. On the contrary, at higher
densities the cluster formation is less feasible and metastable dilute
solutions may exist.Comment: 2 pages, 2 eps figures, contribution to the LT22 Conferenc
Power in the Multinational Corporation in Industry Equilibrium
Recent theories of the multinational corporation introduce the property rights model of the firm and examine whether to integrate our outsource firm activities locally or to a foreign country. This paper focus instead on the internal organization of the multinational corporation by examining the power allocation between headquarters and subsidiaries. We provide a framework to analyse the interaction between the decision to serve the local market by exporting or FDI, market acces and the optimal mode of organization of the multinational corporation. We find that subsidiary managers are given most autonomy in their decision how to run the firm at intermediate levels of local competition. We then provide comparative statics for changes in fixed FDI entry costs and trade costs, information technology, the number of local competitors, and in the size of the local market
Distributed Service Discovery for Heterogeneous Wireless Sensor Networks
Service discovery in heterogeneous Wireless Sensor Networks is a challenging research objective, due to the inherent limitations of sensor nodes and their extensive and dense deployment. The protocols proposed for ad hoc networks are too heavy for sensor environments. This paper presents a resourceaware solution for the service discovery problem, which exploits the heterogeneous nature of the sensor network and alleviates the high-density problem from the flood-based approaches. The idea is to organize nodes into clusters, based on the available resources and the dynamics of nodes. The clusterhead nodes act as a distributed directory of service registrations. Service discovery messages are exchanged among the nodes in the distributed directory. The simulation results show the performance of the service discovery protocol in heterogeneous dense
environments
Demo Abstract: Service Oriented Wireless Sensor Networks - A Cluster-based Approach
In this paper we demonstrate a service-oriented solution for heterogeneous WSNs. The main operations are service discovery and service usage. Our solution is integrated with mobile platforms (smartphones and PDAs), that act as gateways to the GSM network and the Internet
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