Multiple-indicators multiple-causes (MIMIC) modeling is often employed for measurement invariance testing under the structural equation modeling framework. This Monte Carlo study explored the behaviors of MIMIC as a measurement invariance testing method in different research situations. First, the performance of MIMIC under the factor loading noninvariance conditions was investigated through model fit evaluations and likelihood ratio tests. This study demonstrated that the violation of factor loading invariance was not detected by any of the typically reported model fit indices. Consistently, the likelihood ratio tests for MIMIC models exhibited poor performance in identifying noninvariance in factor loadings. That is, MIMIC was insensitive to the presence of factor loading noninvariance, which implies that factor loading invariance should be examined through other measurement invariance testing techniques. To control Type I error inflation in detecting the noninvariance of intercepts or thresholds, this simulation study with both continuous and categorical variables employed the likelihood ratio test with two critical value adjustment strategies, Oort adjustment and Bonferroni correction. The simulation results showed that the likelihood ratio test with Oort adjustment not only controlled Type I error rates below the basal Type I error rates but also maintained high power across study conditions. However, it was observed that power to detect the noninvariant variables slightly attenuated with multiple (i.e., two) noninvariant variables in a model. Given that the modification index is the chi-square difference after relaxing one parameter for estimation, this study investigated modification indices under four research scenarios based on a combination of the cutoffs of modification indices and the procedures of model modification: (a) the noniterative method (i.e., modification indices at the initial stage of model modification) using the conventional critical value, (b) the noniterative method using the Oort adjusted critical value, (c) the iterative procedure of model modification using the conventional critical value, and (d) the iterative procedure using the Oort adjustment. The iterative model search procedure using modification indices showed high performance in detecting noninvariant variables even without critical value adjustment, which indicates that iterative model search specification does not require critical value adjustment in identifying the noninvariance correctly. On the other hand, when the noniterative procedure was used, the Oort adjustment yielded adequate results.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1990. / Includes bibliographical references (leaves 121-125) / Microfiche. / xv, 125 leaves, bound ill. 29 cm

Thesis (Ph. D.)--University of Hawaii at Manoa, 1995. / Includes bibliographical references (leaves 136-141). / Microfiche. / xi, 141 leaves, bound ill., maps 29 cm

Typescript. / Bibliography: leaves 57-62. / viii, 62 l graphs, maps (4 fold. in pocket)

Thesis (MEng)--University of South Australia, 2000

The creep of materials is a research topic of major significance in the life assessment and design of many modern engineering components of advance technology such as: power generation plant, chemical plant, gas turbines, jet engines, spacecrafts, components made of plastics and polymers, etc. To predict the creep lives of such components, one necessary ingredient is a creep damage model. The current creep damage models are either too cumbersome to be readily employed and/or not sufficiently accurate for practical applications. This thesis describes a new creep damage model to overcome some of the major shortcomings in current creep damage/life prediction methods. The proposed model is relatively simple and readily applicable to industrial cases yet it is sufficiently accurate. The proposed model assumes that, on a macroscopic level, the energy dissipated in the material may be taken as a measure of creep damage induced in the material. In another words, creep damage is directly proportional to the absorbed internal energy density (IED), i.e., the internal energy per unit of volume. In this way, the model takes into account both multiaxial loading and deformation. The model is formulated when the creep constitutive relationships may be expressed by primary plus steadystate or steady-state alone (IED-SS) as well as for the cases when the material behaviour includes the creep tertiary region (IED-T). The proposed model has been verified by applying it to various components for which the experimental creep lives are available from literature including thick/thin cylindrical vessels, notch bars with various notch-root radii and materials, multi-material cross welds bars, and perforated biaxial plates. The predicted creep lives of these components by the proposed model (IED-SS and IED-T) are compared with the experimental results and those obtained by the Reference Stress Method (RSM). It is shown that the maximum errors in relation to the creep lives of the above-mentioned components are: 18% when IED-SS is applied, 38% when IED-T is applied, and 301% when RSM is applied. To estimate the effects of uncertainties in material data on the predicted creep life, a sensitivity analysis has been conducted. To this end and in relation to Norton creep law, material parameters such as creep stress coefficient and stress exponent are considered. In addition, the sensitivity analysis included the uncertainties related to the uniaxial creep rupture data. As might be expected, the results suggest that the predicted creep life is most sensitive to the creep stress. Finally, the present research reveals that the proposed model is simple, practical and can be used in conjunction with any commercial finite element code with creep analysis capabilities.

Typescript (photocopy) / xiv, 296 leaves, [3] leaves of plates : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics, 1980

128 leaves : ill. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1969) from the Dept. of Physics, University of Adelaide

Typescript (photocopy) / v, 256 leaves, [2] leaves of col. plates : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.) Dept. of Plant Physiology, University of Adelaide, 1982

The rapid settling nature of some industrial mineral slurries can cause problems in the measurement of their rheological properties. To address this problem a flow rheometer based on the principles of helical flow was developed. The rheometer designed, is a modified Couette flow system, whereby slurries are circulated through the concentric cylinders by the addition of an axial flow. The purpose of this axial flow is to prevent particles from settling and to maintain a homogeneous suspension. However, the addition of an axial flow component to Couette flow complicates the analysis procedure for non-Newtonian fluids particularly in wide gap geometries. Thus a specific emphasis in this study was placed on developing a correct analysis procedure for helical flow that eliminated the need for rudimentary calibration procedures. Experimental measurements with different liquids, including those with Newtonian and non-Newtonian flow properties showed good agreement between data obtained from the flow rheometer and data obtained using other standard laboratory instruments. Typical differences between the results from the flow rheometer and results from other laboratory instrument varied between 1-2%, with standard deviations in the flow rheometer data of between 2-4%. The flow properties of several non-Newtonian slow settling slurries were examined using the flow rheometer and also with a specially modified tube rheometer. As with the pure liquid results good agreement was obtained between the results from the flow rheometer and those obtained with the modified tube rheometer. Several rapid settling slurries were examined using the flow rheometer, but due to the rapid settling nature of these slurries they could not be examined with any other laboratory instruments. However, internally consistent results were obtained from different tests with the flow rheometer using different values of axial flow rate. These results demonstrate that the correct data analysis method was developed for the helical flow of non-Newtonian fluids Particle migration is a phenomenon known to affect the results of both rotational and axial flow rheological equipment. Whilst the motion of particles within the helical The University of Adelaide Continuous Flow Rheometry for Settling Slurries flow geometry could not be directly observed, careful examination of the results from several experiments with slurries showed that the effects of particle migration were minimal or non-existent within the flow rheometer. It is presumed that the circulation of the fluid through the geometry minimises the residence time in the geometry, which reduces the likelihood of particle migration. The development of Taylor vortices in a Couette type geometry can cause substantial errors in any rheological measurements. The flow rheometer is based on helical flow, which is a combination of both Couette and axial flow and as such may also suffer from measurement errors if instabilities develop in the flow. A stability criterion for the helical flow of non-Newtonian fluids is therefore required to ensure measurements from the flow rheometer were obtained in the laminar flow region. The stability criterion for laminar Couette flow of a Newtonian fluid was well known, as was the effect of imposing axial flow on Newtonian Couette flow. However, the effect of the rate of acceleration of the inner cylinder and the effect of non-Newtonian fluids on the onset of Taylor vortices was unknown. An increase in the rate of acceleration of the inner cylinder was found to have a destabilising effect on Couette flow. A modified Taylor number was developed for non-Newtonian fluids using the power-law model and was experimentally validated for a range of non-Newtonian fluids. These results were then used to develop a laminar flow stability criterion for rheological measurements of non-Newtonian fluids in the flow rheometer. To test the suitability of the results from the flow rheometer for use in the design and optimisation of process units, the power requirements to turn an impeller in a small baffled mixing vessel were investigated. Good agreement was obtained in the laminar and turbulent flow regions for a variety of Newtonian and non-Newtonian fluids between measured values of impeller power and those predicted using rheological measurements from the flow rheometer. Altering the density of the solid particles in a slurry is known to affect the overall rheological properties of the slurry. However, the effects of changing the liquid density were not so clearly defined and thus several artificial slurries of PMMA (poly-methylmethacrylate) spheres in water/NaCl and water/glycerol solutions were used to investigate this phenomenon. It was found that the slurry rheology was altered by The University of Adelaide Continuous Flow Rheometry for Settling Slurries changes in the suspending liquid density, however, these changes could be entirely attributed to changes in the liquid viscosity associated with the changes in liquid density. To summarise, the work presented in this Thesis provides a fundamental approach for the absolute measurement of the rheological properties of settling slurries, under conditions that more accurately represent those found in actual mineral processing operations. / Thesis (Ph.D.)--School of Chemical Engineering, 2004.