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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

Condition monitoring of reciprocating compressors and rolling element bearings

Johnston, Andrew Beaton January 1985 (has links)
The prefailure detection of faults in operating plant can effect major rewards in both safety and economy. A successful on-condition maintenance philosophy would pay great dividends particularly in the offshore oil industry where -until recently, only token methods have been employed. Many techniques are available for monitoring mechanical plant and several of these are considered in general terms. Industrial methods are subsequently evaluated on reciprocating compressor and rolling element bearing faults. Bearing fault analysis is considered in two stages. Initially, a series of vibration based techniques are evaluated on a large relatively noise free rotating machine. The techniques of greatest worth carrier spectra, autospectra, time signature analysis and statistical assessments - are then applied to bearings in the hostile environment of a reciprocating machine. It is shown that while discrete faults often produce predictable periodic vibrational patterns, a monitoring system aimed solely at such vibrational phenomena cannot be relied upon. To this end, a diagnostic system must encompass a series of techniques, including carrier spectrum, time signature and statistical analyses. A series of valve and piston faults in reciprocating machines are also studied. By using a number of monitoring techniques, a catalogue of fault characteristics is constructed, and the methods of greatest worth are high-lighted. It is noted that due to the complexities of a reciprocating machine, fault characteristics vary with load, and this must be borne in mind when interpreting the various parameter displays. No single technique can provide a complete cover for all compressor faults, and it is shown that those of greatest worth are acoustic emission, combined pressure and vibration plots, temperature and performance analysis. An indication of compressor temperature and internal cylinder pressure can greatly ease the detection and diagnostic process, and for the latter, bolt load determinations may be a valuable aid.
2

Fault detection using transfer function techniques

Paterson, Neil Ewing January 1987 (has links)
No description available.
3

A generalised transients program for power system protection studies

Wong, Kwok-Tung January 1986 (has links)
No description available.
4

Some aspects of time series analysis with application to on-line inspection in the gas industry

Coates, David January 1984 (has links)
No description available.
5

On-line proctection of electrical machines by microcomputer analysis of axial leakage flux

Dey, M. N. January 1983 (has links)
No description available.
6

Computer Modeling and Simulation of Power Electronics Systems for Stability Analysis

Ahmed, Sara Mohamed 19 February 2008 (has links)
This works focuses on analyzing ac/dc hybrid power systems with large number of power converters that can be used for a variety of applications. A computer model of a sample power system is developed. The system consists of various detailed/switching models that are connected together to study the sample system dynamic behavior and to set conditions for safe operation. The stability analysis of this type of power systems has been approached using time domain simulations. There are three types of stability analysis that are studied: steady-state, small-signal analysis and large signal analysis. The steady-state stability analysis is done by investigating the nominal operation of the power electronics system proposed. The small-signal stability of this system is studied by running different parametric case studies. First, the safe values of the main system parameters are defined from the view of the stability of the complete system. Then, these different critical parameters of the system are mapped together to predict their influence on the system. The large signal stability is examined through the response of the power system to different types of transient changes. There are different load steps applied to the critical parameters of the system at the maximum or minimum stability boundary limit found by the mapping section. The maximum load step after which the system can recover and remain stable is defined. The other type of large signal stability analysis done is the study of faults. There are different faults to be studied; for example, over voltage, under voltage and over current. / Master of Science
7

Incremental Fault Analysis: A New Differential Fault Attack on Block Ciphers

Pogue, Trevor January 2019 (has links)
Electronic devices such as phones and computers use cryptography to achieve information security. However, while cryptographic algorithms may be strong theoretically, their physical implementations in hardware can leak unintentional side information as a byproduct of performing their computations. A device's security can be compromised from this leakage through side-channel attacks. Research in hardware security reveals how dangerous these attacks can be and provides security countermeasures. This thesis focuses on a category of side-channel attacks called fault attacks, and contributes a new fault attack method that can compromise a cryptographic device more rapidly than the previous methods when using practical fault injection techniques. We observe that as a circuit is further overclocked, new faults are often superimposed upon previous ones. We analyze the incremental changes rather than the total sum in order to extract more secret information. Unlike many previous methods, ours does not require precise fault injection techniques and requires no knowledge of when the internal state is in a specific algorithmic stage. Results are confirmed experimentally on hardware implementations of AES-128, 192, and 256. / Thesis / Master of Applied Science (MASc)
8

Launch Vehicle and Satellite Independent Failure Analysis Using Telemetry Prognostic Algorithms

Losik, Len 10 1900 (has links)
ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, California / Unique vehicle designs encourage the use of the builder to complete its own failure analysis. Current failure analysis practices use telemetry and diagnostic technology developed over the past 100 years to identify root-cause. When telemetry isn't available speculation is used to create a list of prioritized, potential causes. Prognostic technology consists of generic algorithms that identify equipment that has failed and is going to fail while the equipment is still at the factory allowing the equipment to be repaired or replaced while it is still on the ground for any spacecraft, satellite, launch vehicle and missile.
9

Techniques of Side Channel Cryptanalysis

Muir, James January 2001 (has links)
The traditional model of cryptography examines the security of cryptographic primitives as mathematical functions. This approach does not account for the physical side effects of using these primitives in the real world. A more realistic model employs the concept of a <I>side channel</I>. A side channel is a source of information that is inherent to a physical implementation of a primitive. Research done in the last half of the 1990s has shown that the information transmitted by side channels, such as execution time, computational faults and power consumption, can be detrimental to the security of ciphers like DES and RSA. This thesis surveys the techniques of side channel cryptanalysis presented in [Kocher1996], [Boneh1997], and [Kocher1998] and shows how side channel information can be used to break implementations of DES and RSA. Some specific techniques covered include the timing attack, differential fault analysis, simple power analysis and differential power analysis. Possible defenses against each of these side channel attacks are also discussed.
10

Techniques of Side Channel Cryptanalysis

Muir, James January 2001 (has links)
The traditional model of cryptography examines the security of cryptographic primitives as mathematical functions. This approach does not account for the physical side effects of using these primitives in the real world. A more realistic model employs the concept of a <I>side channel</I>. A side channel is a source of information that is inherent to a physical implementation of a primitive. Research done in the last half of the 1990s has shown that the information transmitted by side channels, such as execution time, computational faults and power consumption, can be detrimental to the security of ciphers like DES and RSA. This thesis surveys the techniques of side channel cryptanalysis presented in [Kocher1996], [Boneh1997], and [Kocher1998] and shows how side channel information can be used to break implementations of DES and RSA. Some specific techniques covered include the timing attack, differential fault analysis, simple power analysis and differential power analysis. Possible defenses against each of these side channel attacks are also discussed.

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