Browsing by Author "Wang, Li Chun"

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A Zero Flow Entry Expiration Timeout P4 Switch
(2018-01-01)
He, Cheng-Hung
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Chang, Brian Y.
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Chakraborty, Suchandra
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Chen, Chien
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Wang, Li Chun
Existing OpenFlow based flow expiry mechanisms rely on a fixed timeout after which the switch proactively removes the flow entries from its flow table. Assigning an appropriate value to this timeout presents a tradeoff between efficient flow table utilization and controller overhead.We propose a simple addition of a zero flow entry expiration timeout scheme to idle timeout mechanism on a P4 based switch that identifies the last packet of a TCP flow, and removes the corresponding flow entry from the flow table. It enables connections to be deleted from the flow table right after it finishes, instead of waiting to expire after it reaches the timeout threshold and causing unnecessary flow table occupation.
Development of a high performance integrated sensor chip with a multi-walled carbon nanotube assisted sensing array
(2013-02-01)
Chuang, Pi Kai
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Wang, Li Chun
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Kuo, Cheng Tzu
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材料科學與工程學系
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Department of Materials Science and Engineering
For room temperature toxic gas sensing, a system chip with a MWCNT (multi-walled carbon nanotube)-assisted array of 30 sensors (two sensors for each of 15 sensor types) was developed. Gases tested include four simulants of chemical warfare agents: dichloromethane, acetonitrile, 2-chloroethyl ethyl sulfide, and dimethyl-methyl phosphonate (DMMP). By selecting 15 different functional polymer materials, each composite sensor composed of 15 sensing stacks (polymer/MWCNTs/Si(001), wafer) was fabricated by a solution droplet casting method to simplify the process. The principle of gas sensing is basically to measure the resistivity change of the composite sensor device upon contact with a target gas. One of the advantages of the sensing stack having a polymer overlayer above the MWCNT layer is being able to protect the MWCNT from direct interaction with the gas to improve sensor life and sensitivity. The results indicate that a fingerprint pattern of the sensor radar plot can be determined for each testing run, and that specificity can be achieved through a 3-D principal component analysis of the radar plots. The results also show that a linear relationship between the resistance response and concentration is clearly evident for these four toxic gases. By extrapolation and careful process monitoring, a sensitivity much lower than 43 ppm for DMMP vapor is likely. The gas sensing mechanisms are discussed in the text. (C) 2012 Elsevier B.V. All rights reserved.