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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Electrochemical impedance spectroscopy options for proton exchange membrane fuel cell diagnostics

Valenzuela, Jorge Ignacio 05 1900 (has links)
Electrochemical impedance spectroscopy (EIS) has been exploited as a rich source of Proton Exchange Membrane Fuel Cell (PEMFC) diagnostic information for many years. Several investigators have characterized different failure modes for PEMFCs using EIS and it now remains to determine how this information is to be obtained and used in a diagnostic or control algorithm for an operating PEMFC. This work utilizes the concept of impedance spectral fingerprints (ISF) to uniquely identify between failure modes in an operating PEMFC. Three well documented PEMFC failure modes, carbon monoxide (CO) poisoning, dehydration, and flooding were surveyed, modelled, and simulated in the time domain and the results were used to create a database of ISFs. The time domain simulation was realized with a fractional order differential calculus state space approach. A primary goal of this work was to develop simple and cost effective algorithms that could be included in a PEMFC on-board controller. To this end, the ISF was discretized as coarsely as possible while still retaining identifying spectral features using the Goertzel algorithm in much the same way as in dual tone multi-frequency detection in telephony. This approach generated a significant reduction in computational burden relative to the classical Fast Fourier Transform approach. The ISF database was used to diagnose simulated experimental PEMFC failures into one of five levels of failure: none (normal operation), mild, moderate, advanced, and extreme from one of the three catalogued failure modes. The described ISF recognition algorithm was shown to correctly identify failure modes to a lower limit of SNR = 1dB.
2

A study of negative-impedance converter compensation

Krohn, Howard Emil, 1939- January 1963 (has links)
No description available.
3

Electrochemical impedance spectroscopy options for proton exchange membrane fuel cell diagnostics

Valenzuela, Jorge Ignacio 05 1900 (has links)
Electrochemical impedance spectroscopy (EIS) has been exploited as a rich source of Proton Exchange Membrane Fuel Cell (PEMFC) diagnostic information for many years. Several investigators have characterized different failure modes for PEMFCs using EIS and it now remains to determine how this information is to be obtained and used in a diagnostic or control algorithm for an operating PEMFC. This work utilizes the concept of impedance spectral fingerprints (ISF) to uniquely identify between failure modes in an operating PEMFC. Three well documented PEMFC failure modes, carbon monoxide (CO) poisoning, dehydration, and flooding were surveyed, modelled, and simulated in the time domain and the results were used to create a database of ISFs. The time domain simulation was realized with a fractional order differential calculus state space approach. A primary goal of this work was to develop simple and cost effective algorithms that could be included in a PEMFC on-board controller. To this end, the ISF was discretized as coarsely as possible while still retaining identifying spectral features using the Goertzel algorithm in much the same way as in dual tone multi-frequency detection in telephony. This approach generated a significant reduction in computational burden relative to the classical Fast Fourier Transform approach. The ISF database was used to diagnose simulated experimental PEMFC failures into one of five levels of failure: none (normal operation), mild, moderate, advanced, and extreme from one of the three catalogued failure modes. The described ISF recognition algorithm was shown to correctly identify failure modes to a lower limit of SNR = 1dB.
4

Étude des paramètres affectant l'impédance électrique de certains métaux et minéraux / Study of the parameters affecting the electrical impedance of some metals and minerals.

Lambert, Roger. January 1974 (has links)
No description available.
5

A study of negative impedances

Meadows, Henry Emerson 08 1900 (has links)
No description available.
6

A general broadband matching theory and its application

Tsai, Cheng-Kwang. January 1981 (has links)
Thesis (Ph. D.)--Ohio University, August, 1981. / Title from PDF t.p.
7

Surface impedance on non-parallel stratified media

Hustig, Charles Harold, January 1969 (has links)
Thesis (M.S.)--University of Wisconsin--Madison, 1969. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
8

The origin of impedance pulse in the limbs and arterial compliance studies using impedance plethysmography

Shankar, T. M. Ravi. January 1982 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
9

Measurement errors and origin of electrical impedance changes in the limb

Swanson, David Keith, January 1976 (has links)
Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 196-203).
10

Electrochemical impedance spectroscopy options for proton exchange membrane fuel cell diagnostics

Valenzuela, Jorge Ignacio 05 1900 (has links)
Electrochemical impedance spectroscopy (EIS) has been exploited as a rich source of Proton Exchange Membrane Fuel Cell (PEMFC) diagnostic information for many years. Several investigators have characterized different failure modes for PEMFCs using EIS and it now remains to determine how this information is to be obtained and used in a diagnostic or control algorithm for an operating PEMFC. This work utilizes the concept of impedance spectral fingerprints (ISF) to uniquely identify between failure modes in an operating PEMFC. Three well documented PEMFC failure modes, carbon monoxide (CO) poisoning, dehydration, and flooding were surveyed, modelled, and simulated in the time domain and the results were used to create a database of ISFs. The time domain simulation was realized with a fractional order differential calculus state space approach. A primary goal of this work was to develop simple and cost effective algorithms that could be included in a PEMFC on-board controller. To this end, the ISF was discretized as coarsely as possible while still retaining identifying spectral features using the Goertzel algorithm in much the same way as in dual tone multi-frequency detection in telephony. This approach generated a significant reduction in computational burden relative to the classical Fast Fourier Transform approach. The ISF database was used to diagnose simulated experimental PEMFC failures into one of five levels of failure: none (normal operation), mild, moderate, advanced, and extreme from one of the three catalogued failure modes. The described ISF recognition algorithm was shown to correctly identify failure modes to a lower limit of SNR = 1dB. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

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