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Ganeriwal S. Tsigkogiannis I. Shim H. Tsiatsis V. Srivastava M.B. Ganesan D. 《Networking, IEEE/ACM Transactions on》2009,17(3):843-856
Radio duty cycling has received significant attention in sensor networking literature, particularly in the form of protocols for medium access control and topology management. While many protocols have claimed to achieve significant duty-cycling benefits in theory and simulation, these benefits have often not translated into practice. The dominant factor that prevents the optimal usage of the radio in real deployment settings is time uncertainty between sensor nodes which results in overhead in the form of long packet preambles, guard bands, and excessive control packets for synchronization. This paper proposes an uncertainty-driven approach to duty-cycling, where a model of long-term clock drift is used to minimize the duty-cycling overhead. First, we use long-term empirical measurements to evaluate and analyze in-depth the interplay between three key parameters that influence long-term synchronization: synchronization rate, history of past synchronization beacons, and the estimation scheme. Second, we use this measurement-based study to design a rate-adaptive, energy-efficient long-term time synchronization algorithm that can adapt to changing clock drift and environmental conditions, while achieving application-specific precision with very high probability. Finally, we integrate our uncertainty-driven time synchronization scheme with the BMAC medium access control protocol, and demonstrate one to two orders of magnitude reduction in transmission energy consumption with negligible impact on packet loss rate. 相似文献
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Biomimetic total syntheses of glyantrypine, fumiquinazoline F, fumiquinazoline G, and fiscalin B were achieved in four steps from tryptophan methyl ester. In the key step, the anthranilamide residue in a linear tripeptide is dehydrated to a benzoxazine by reaction with triphenylphosphine, iodine, and a tertiary amine. The benzoxazines subsequently undergo rearrangement to the natural products via an amidine intermediate. This dehydrative oxazine to quinazoline route is applicable to a broad range of N-acylanthranilamides, including sterically hindered cases. 相似文献
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A numerical solution for the transient natural convection flow over a vertical cylinder under the combined buoyancy effect
of heat and mass transfer is presented. The velocity, temperature and concentration profiles, local and average skin-friction,
Nusselt number and Sherwood number are shown graphically. It is observed that time taken to reach steady state increases with
Schmidt number and decreases as combined buoyancy ratio parameter N increases. Stability and convergence of the finite difference scheme are established.
Received on 8 July 1997 相似文献
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Karthik Arumugam Mallikarjuna Rao Chamallamudi Ravindranath Reddy Gilibili Ramesh Mullangi Subramanian Ganesan Sidhartha S Kar Ranjithkumar Averineni Gopal Shavi Nayanabhirama Udupa 《Biomedical chromatography : BMC》2011,25(3):353-361
A sensitive, specific and accurate HPLC method for the quantification of rivastigmine (RSM) in rat urine was developed and validated. The method involves the simple liquid–liquid extraction of RSM and pyridostigmine as an internal standard (IS) from rat urine with tertiary methyl butyl ether. The chromatographic separation of RSM and IS was achieved with 20 mm ammonium acetate buffer (pH 6.5) and acetonitrile (65:35, v/v) delivered at flow‐rate of 1 mL/min on a Kromasil KR‐100. The method was in linear range from 50 to 5000 ng/mL. The validation was done as per FDA guidelines and the results met the acceptance criteria. The method was successfully applied for the quantification of RSM in rat urine. Besides method validation, we have identified two metabolites of RSM in urine. Both the metabolites were characterized by HPLC‐PDA and LC‐MS/MS and it was found that one metabolite is novel. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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M. Ganesan 《Ionics》2009,15(5):609-614
The lithiated transition metal oxide has been used as the cathode materials for lithium ion rechargeable batteries. Among
the various cathode materials, LiCoO2 has been widely used. There are lot of reports on the substituted LiCoO2 replacing small amount of Cobalt with other transition and nontransitional metals. Here, we focus on to a tetravalent transition
metal atom such as titanium, as an addition in LiCoO2 and studied its performance. The titled cathode material was synthesized by solid-state reaction method. Thermogravimetric/differential
thermal analysis, X-ray diffraction, X-ray fluorescence, scanning electron microscopy, and particle size analysis were carried
out to assess the effect of addition of titanium on LiCoO2. Electrochemical studies were carried out by cyclic voltammetry and life cycle analyzer. 相似文献