No description available.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 77-78). Also available via the Internet.

Thesis--University of Washington. / Vita. Description based on print version record. Includes bibliographical references (leaves [147]-156).

The transport of particulate in a gas flow or pneumatic conveying system 1s widespread in many areas of industry, for example chemical, food processing, cement industries and transportation of pulverised coal in coal-fired power plants. However, a simple and reliable method for monitoring the flow parameters, particularly the mass flow rate, velocity and size of particulate solids in the pipeline, has yet to be developed. This is mainly due to the fact that numerous problems, including insufficient signal generation, particle deposition in sensing vicinity, inhomogeneous particle and velocity profile, can be encountered by flow meters which may affect their readings. Being able to monitor the flow parameters, especially the particulate mass flow rate for example, allows accurate delivery of particulates and hence a better product quality in food processing industrials. In coal-fired power plants, being able to monitor and subsequently control the flow parameters will result in higher combustion efficiency and lower pollutants emission. Furthermore, optimum conveying conditions could also be set, which would result in reduced energy consumption and wear on equipment. This thesis is concerned with the generation of the Acoustic Emission (AE) from particulate flow and an investigation of the potential of implementing AE for flow parameters, namely the solid feed rate, particle velocity and size monitoring. A series of experiments has been conducted to gather AE signals from a laboratory scale single flow-loop pneumatic conveying system. Initially, AE sensors were attached to two steel meshes, which were placed with a fixed axial distance in the pipeline to study the generation of the AE and subsequently the possibility of using those generated AE to determine particle velocity in the pipeline. Particle velocities measured from this approach were compared with theoretical predictions. The results indicated that more than 90% of the measured particle velocities fall within ±10% of the theoretical particle velocity predicted using the modified Hinkle correlation. Since time alone is measured, no calibration is required. The generation of AE on five different sensor mounting locations was also studied. The results showed that sensors mounted on all those locations were able to respond to changes in the flow parameters. However, only two optimum sensor locations (mesh and outer bend) were chosen, based on the higher strength and repeatability, for further investigation. The final experimental results indicated that the AE features, namely Root-Mean-Square (RMS) and energy of the AE, are related to the changes in the flow parameters and good correlations were found. Good correlations between the RMS and energy of the AE with the momentum and kinetic energy of the particles, respectively, were also found. Ringdown count of the time domain signal and centroid frequency and energy ratio of the Power Spectral Density (PSD) are independent of variation in the solid feed rate and conveying air velocity. However, they varied significantly with changes in the mean particle size. This clearly marks the potential of the AE method to detect particle size variation inside pipes and hence the performance of the pulverising mill. Overall, all those features of AE have great potential in gas-solid two phase flow parameter monitoring.

Acoustic Emission Analysis (AEA) is the study of the sonic (and ultrasonic) energy released by chemical systems in the form of transient waves, as the system attempts to (re)attain equilibrium. This area of chemistry, and chemical analysis, is ripe for fundamental studies since it has been little explored. The high potential of the technique as a non-invasive, non-destructive reaction monitoring scheme suggests that numerous applications will follow. In this work, an apparatus and software have been constructed to monitor acoustic emission (AE) and collect and process AE data. A broad-band piezoelectric transducer was used to convert the acoustic signals to electrical waveforms which could be captured by a digital storage oscilloscope. These waveforms were then stored on an IBM-compatible computer for further analysis. Analysis of the data was performed using pattern recognition techniques. The signals were characterized through the use of descriptors which can map each signal onto a multi-dimensional feature space. Visualization of the data structure in multidimensional space was accomplished using several methods. Hierarchical clustering was used to produce tree structures, known as dendrograms, which attempt to show clustering of the signals into various groups. Abstract factor analysis (AFA) - also called principal components analysis (PCA) - was used to project the data onto a two dimensional factor space to allow for direct viewing of structure in the multidimensional data. Sodium hydroxide dissolution, aluminum chloride hydration and heat activation of Intumescent Flame Retardants (IFR's) were used to test the assembled hardware and to provide data to submit to the pattern recognition algorithms coded as part of this work. The solid-solid phase transition of trimethylolethane (Trimet), and the liquid crystal phase transitions of two liquid crystals (α-ѡ-bis(4-n-decylaniline-benzilidene-4'-oxyhexane), and 4-n-pentyloxybenzylidene-4'-n-heptylaniline) were also monitored and the signals analyzed. The pattern recognition software was able to extract much information from the acoustically emitting samples - information which would not have been apparent by using standard (uni- and bi-variate) methods of analysis. Chemical acoustic emission, coupled with pattern recognition analysis, will be able to provide the chemist with knowledge (qualitative, quantitative, kinetic, etc.) about chemical systems which are often difficult or impossible to monitor and analyze by other means. / Science, Faculty of / Chemistry, Department of / Graduate

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 84-86). Also available via the Internet.

This thesis relates to the feasibility of monitoring dental implants using the transmission of Acoustic Emission (AE) from an intra-oral source to a sensor mounted on the patient’s face. A number of in vitro and in vivo experiments have been carried using different AE sources on teeth and dental implants with the ultimate aim of defining the characteristics of the AE signatures in the time- and frequency-domains that are affected by the implant-bone interface. An initial feasibility study was carried out to assess the transmission of simulated AE signals through human teeth and hard and soft tissues by biting on different types of hard food. The tests demonstrated that the transmission of AE signals through human tissues was feasible. However, the source was not reproducible. Further preliminary experiments were carried out to assess the transmission of AE in various dental materials as well as in bone and bone-implant combinations in various states of hydration. The main systematic body of work centred around establishing whether AE signals could discriminate between implants with different amounts of contact with bone. AE signals were generated by applying a standard impulse source through a specially-designed abutment onto dental implants of various sizes (large and small) inserted in bovine ribs under tight and loose fitting conditions. The findings suggested that this simple transmission test was able to assess the quality of the contact between the implant and the bone in the in vitro situation and that it might be possible to extend this to the clinical environment. The (standard) pencil lead break method was not suitable for use intra-orally, so a more suitable source for in vivo testing needed to be developed. After considering various options a continuous source (based on an air jet) was developed and this was applied to dental implants in the same set of systematic tests as for the pencil lead source. The analysis revealed that the air jet source was a little better at discriminating between the various implant contact conditions. Finally, an in vivo study was conducted to assess the characteristics of the transmitted AE form air jet source applied to the dental implants of a number of volunteers. The findings demonstrated that the AE transmission through the implants, soft and hard tissues using an air jet source was feasible, with the degree of transmission depending on a number of variables, some related to the patients themselves and some related to other, tractable engineering factors. The overall conclusion of the work is that the technique is very likely to be successful for monitoring implant stability, and is feasible to apply with minimum invasion to patients whose implants have been newly installed. An in vivo study in which the test is applied to patients during the stages of stabilisation of their implants is required in order to validate the technique.

Barkhausen emission (B.E.) and Magneto-acoustic emission (M.A.E.) can be detected from specimens in a magnetic field varying at a few millihertz. Comparison of the two signals can indicate the nature of the domain walls responsible for the activity at any particular field. In order to characterize a specimen the strength of the emissions around the hysteresis loop are measured together with the distribution of Barkhausen event sizes. This technique has been used to measure the effects of: (A) Microstructure. Both B.E. and M.A.E. are sensitive to dislocations, and the effects of cold-working and its removal by isochronal annealing has been studied in alpha-iron. A simple model of domain wall pinning is presented which enables the dislocation density to be estimated. M.A.E. and B.E. are also sensitive to the growth of precipitates in Incoloy 904 alloy and, for a certain regime of sizes, can potentially be used to monitor the precipitate diameter. B.E. is sensitive to smaller precipitates (-100 nm) than M.A.E. but, unlike M.A.E., its dependence on precipitate size is not monotonic. An understanding of the signal dependence is obtained from Lorentz microscopy. (B) Radiation damage. The sensitivity of B.E. and M.A.E. to radiation damage is quite small by virtue of the small size of defects present. Nevertheless measurements on neutron irradiated alpha-iron specimens in several microstructural states indicate: (a) an accelerated recovery from the cold-worked condition on isochronal annealing and (b) dissolution of nitrides and carbides which formed in preparatory heat treatments. Measurements on a neutron irradiated iron-copper alloy which was subsequently isochronally annealed indicated effects which were consistent with: (a) removal of dislocation loops formed during irradiation at 550°C and (b) growth of precipitates (probably copper) at 600°C which presumably formed during the irradiation, (i.e. the effect was smaller in unirradiated control specimens). These results suggest that B.E. and M.A.E. might be useful tools for the characterization of radiation effects. (C) Tensile stress. Both B.E. and M.A.E. are sensitive to applied tensile stress and measurements on a number of different materials indicate that the dependence of M.A.E. is monotonic (except in nickel) whereas that of B.E. is generally quite complex. Since the microstructural and stress dependences are often interrelated it would be difficult to use the technique to measure say residual stress in a practical material unless the exact condition of the microstructure could be determined. Consequently B.E. and M.A.E. were measured from mild steel specimens (4360 steel) which had recieved a number of different heat treatments. The effects of applied tensile stress on the amplitude and shape of the B.E. and M.A.E. profiles were investigated with a view to be able to use the M.A.E. to measure stresses without prior knowledge of the microstructure. It was found that certain parameters in the signal profile were much more strongly dependent upon the stress than on the microstructure for many of the material conditions. Therefore M.A.E. is potentially useful for residual stress measurements.

No description available.

Thesis (M.S.)--Brigham Young University. Dept. of Physics and Astronomy, 2004. / Includes bibliographical references (p. 70-72).