338 research outputs found
Reliable Identification of RFID Tags Using Multiple Independent Reader Sessions
Radio Frequency Identification (RFID) systems are gaining momentum in various
applications of logistics, inventory, etc. A generic problem in such systems is
to ensure that the RFID readers can reliably read a set of RFID tags, such that
the probability of missing tags stays below an acceptable value. A tag may be
missing (left unread) due to errors in the communication link towards the
reader e.g. due to obstacles in the radio path. The present paper proposes
techniques that use multiple reader sessions, during which the system of
readers obtains a running estimate of the probability to have at least one tag
missing. Based on such an estimate, it is decided whether an additional reader
session is required. Two methods are proposed, they rely on the statistical
independence of the tag reading errors across different reader sessions, which
is a plausible assumption when e.g. each reader session is executed on
different readers. The first method uses statistical relationships that are
valid when the reader sessions are independent. The second method is obtained
by modifying an existing capture-recapture estimator. The results show that,
when the reader sessions are independent, the proposed mechanisms provide a
good approximation to the probability of missing tags, such that the number of
reader sessions made, meets the target specification. If the assumption of
independence is violated, the estimators are still useful, but they should be
corrected by a margin of additional reader sessions to ensure that the target
probability of missing tags is met.Comment: Presented at IEEE RFID 2009 Conferenc
The Course of O<sub>2</sub> Partial Pressure and Electric Potential Across an Oxide Electrolyte Cell
Dynamic Aspects of Solid Solution Cathodes for Electrochemical Power Sources
Battery systems based on alkali metal anodes and solid solution cathodes, i.e., cathodes based on the insertion of the alkali cation in a "host lattice," show considerable promise for high energy density storage batteries. This paper discusses the interaction between battery requirements, in particular for vehicle propulsion, and electrochemical nd constructional factors. It is argued that the energy obtainable at a given load is l imited by saturation of the surface layers of cathode particles with cations, and that the time before saturation occurs is determined by diffusion of cations and electrons into the host lattice. Expressions are developed for plane, cylindrical, and spherical particles, giving the relation between battery load and the amount of cath-ode material utilized before saturation. The particle shape and a: single pa-rameter Q is used to describe cathode performance. Q is the ratio between dis-charge time at 100 % utilization of the cathode at the given load, and the time constant for diffusion through the cathode particles. This description is ex
Single Electrode Heat Effects:I. Peltier Entropies of Gas Electrodes in Carbonate Paste Electrolytes
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