5,747 research outputs found
Design, Fabrication and Characterization of a Piezoelectric Microgenerator Including a Power Management Circuit
We report in this paper the design, fabrication and experimental
characterization of a piezoelectric MEMS microgenerator. This device scavenges
the energy of ambient mechanical vibrations characterized by frequencies in the
range of 1 kHz. This component is made with Aluminum Nitride thin film
deposited with a CMOS compatible process. Moreover we analyze two possible
solutions for the signal rectification: a discrete doubler-rectifier and a full
custom power management circuit. The ASIC developed for this application takes
advantage of diodes with very low threshold voltage and therefore allows the
conversion of extremely low input voltages corresponding to very weak input
accelerations. The volume of the proposed generator is inferior to 1mm3 and the
generated powers are in the range of 1W. This system is intended to supply
power to autonomous wireless sensor nodes.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/EDA-Publishing
Comparison of spectrum occupancy measurements using software defined radio RTL-SDR with a conventional spectrum analyzer approach
In the present day Cognitive Radio has become a realistic option for solution of the spectrum scarcity problem in wireless communication. Recently, the TV band has attracted attention due to the considerable potential for exploitation of available TV white space which is not utilized based on time and location. In this paper, we investigate spectrum occupancy of the UHF TV band in the frequency range from 470 to 862MHz by using two different devices, the low cost device RTL-SDR and high cost spectrum analyzer. The spectrum occupancy measurements provide evidence of the utility of using the inexpensive RTL SDR and illustrate its effectiveness for detection of the percentage of spectrum utilization compared with results from the conventional high cost Agilent spectrum analyzer, both systems employing various antennas
Method of computation of energies in the fractional quantum Hall effect regime
In a previous work, we reported exact results of energies of the ground state
in the fractional quantum Hall effect (FQHE) regime for systems with up to
electrons at the filling factor by using the
method of complex polar coordinates. In this work, we display interesting
computational details of the previous calculation and extend the calculation to
electrons at . Moreover, similar exact results
are derived at the filling for systems with up to electrons. The results that we obtained by analytical calculation are in
good agreement with their analogues ones derived by the method of Monte Carlo
in a precedent work.Comment: 9 pages, 1 figur
Video Data Visualization System: Semantic Classification And Personalization
We present in this paper an intelligent video data visualization tool, based
on semantic classification, for retrieving and exploring a large scale corpus
of videos. Our work is based on semantic classification resulting from semantic
analysis of video. The obtained classes will be projected in the visualization
space. The graph is represented by nodes and edges, the nodes are the keyframes
of video documents and the edges are the relation between documents and the
classes of documents. Finally, we construct the user's profile, based on the
interaction with the system, to render the system more adequate to its
references.Comment: graphic
Spectrum occupancy measurements and lessons learned in the context of cognitive radio
Various measurement campaigns have shown that numerous spectrum bands are vacant even though licenses have been issued by the regulatory agencies. Dynamic spectrum access (DSA) based on Cognitive Radio (CR) has been regarded as a prospective solution to improve spectrum utilization for wireless communications. Empirical measurement of the radio environment to promote understanding of the current spectrum usage of the different wireless services is the first step towards deployment of future CR networks. In this paper we present our spectrum measurement setup and discuss lessons learned during our measurement activities. The main contribution of the paper is to introduce global spectrum occupancy measurements and address the major drawbacks of previous spectrum occupancy studies by providing a unifying methodological framework for future spectrum measurement campaigns
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