The dissertation focuses on estimating the uncertainty associated with stress/strain prediction procedures from dynamic test data used in turbine blade analysis. An accurate prediction of the maximum response levels for physical components during in-field operating conditions is essential for evaluating their performance and life characteristics, as well as for investigating how their behavior critically impacts system design and reliability assessment. Currently, stress/strain inference for a dynamic system is based on the combination of experimental data and results from the analytical/numerical model of the component under consideration. Both modeling challenges and testing limitations, however, contribute to the introduction of various sources of uncertainty within the given estimation procedure, and lead ultimately to diminished accuracy and reduced confidence in the predicted response. The objective of this work is to characterize the uncertainties present in the current response estimation process and provide a means to assess them quantitatively. More specifically, proposed in this research is a statistical methodology based on a Bayesian-network representation of the modeling process which allows for a statistically rigorous synthesis of modeling assumptions and information from experimental data. Such a framework addresses the problem of multi-directional uncertainty propagation, where standard techniques for unidirectional propagation from inputs' uncertainty to outputs' variability are not suited. Furthermore, it allows for the inclusion within the analysis of newly available test data that can provide indirect evidence on the parameters of the structure's analytical model, as well as lead to a reduction of the residual uncertainty in the estimated quantities. As part of this work, key uncertainty sources (i.e., material and geometric properties, sensor measurement and placement, as well as noise due data processing limitations) are investigated, and their impact upon the system response estimates is assessed through sensitivity studies. The results are utilized for the identification of the most significant contributors to uncertainty to be modeled within the developed Bayesian inference scheme. Simulated experimentation, statistically equivalent to specified real tests, is also constructed to generate the data necessary to build the appropriate Bayesian network, which is then infused with actual experimental information for the purpose of explaining the uncertainty embedded in the response predictions and quantifying their inherent accuracy.

Les matériaux composites à matrice organique sont de plus en plus utilisés par l'industrie des transports pour la réalisation d'éléments structuraux. Afin de permettre un dimensionnement optimal de ces structures, il est nécessaire d'améliorer la compréhension et la modélisation du comportement de ces matériaux sur une large gamme de vitesses de sollicitation et de températures d'environnement. Pour cela, plusieurs campagnes expérimentales ont été réalisées sur le T700GC/M21, un composite stratifié à matrice organique, dans le cadre de ces travaux. Tout d'abord, des essais dynamiques sur un vérin hydraulique, ainsi que des essais de fluage, ont été menés afin de caractériser la dépendance à la vitesse du comportement de ce matériau. Ensuite, la dépendance à la température a été mise en évidence à l'aide d'essais à basse température sur vérin hydraulique, complétés d'essais DMA.Les résultats de ces essais ont été utilisés afin de justifier physiquement le développement d'un modèle visco-élastique bi-spectral pour la description de la dépendance à la vitesse du T700GC/M21 sur une large gamme de vitesses de déformation. L'influence de la température d'environnement sur le comportement a quant à elle été introduite à l'aide d'une loi d'Arrhénius. Ce modèle thermo-visco-élastique permet finalement de rendre compte du comportement du stratifié T700GC/M21 sur une large gamme de vitesses et de températures / Organic matrix composite materials are more and more used in the transportation industry to design strutural components. In order to reach an optimal design, improvements in the understanding and the modelling of the behaviour of these materials under various strain rates and temperatures conditions are required.Therefore, a campaign of various mechanical tests has been performed on the T700GC/M21 organic matrix composite laminate in this work. On one hand, dynamic tests have been performed using hydraulic jacks, as well as creep tests, to characterise the material strain rate dependency. On the other hand, low temperatures and DMA tests have been performed to exhibit the temperature effect.Experimental results have been used to physically justify a bi-spectral visco-elactic model which describes the strain rate dependency of T700GC/M21 on a large range of strain rates. Introducing an Arrhenius like law for the viscous mechanisms, the temperature dependency has also been taken into account. The obtained thermo-visco-elastic model finally describes the behaviour of the T700GC/M21 laminate on a large range of strain rates and temperatures

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This thesis aims to develop a new type of highly stretchable strain sensor to measure large deformation of a specimen subjected to dynamic loading. The sensor was based on the piezo-resistive response of carbon nanotube(CNT)/polydimethysiloxane (PDMS) composites thin films, some nickel particles were added into the sensor composite to improve the sensor performance. The piezo-resistive response of CNT composite gives high frequency response in strain measurement, while the ultra-soft PDMS matrix provides high flexibility and ductility for large strain measuring large strain (up to 26%) with an excellent linearity and a fast frequency response under quasi-static test, the delay time for high strain rate test is just 30 μs. This stretchable strain sensor is also able to exhibit much higher sensitivities, with a gauge factor of as high as 80, than conventional foil strain gauges.

Indiana University-Purdue University Indianapolis (IUPUI) / Predictability of tooth displacement in response to specific orthodontic load system directly links to the quality and effectiveness of the treatment. The key questions are how the tooth’s environment changes in response to the orthodontic load and how the biological tissues respond clinically. The objectives of this study are to determine the mechanical environment (ME) changes and to quantify the biological tissues’ response. Eighteen (18) patients who needed maxillary bilateral canine retractions were involved in the study. A method was developed to quantify the 3D load systems on the canine, which allowed the treatment strategies to be customized in terms of orthodontic loading systems to meet either translation (TR) or controlled tipping (CT) requirement. Dental casts were made before and after each treatment interval, and the Cone Beam Computed Tomography (CBCT) scans were taken prior to and following the entire treatment for control of treatment strategy and post treatment evaluations. Finite element method (FEM) was applied to calculate the location of center of resistance (CRes) for tooth movement control. The location and variation of CRes were recorded and compared with previous studies. A quick CRes assessment method that locates CRes by calculating the centroid of the contact surface (CCS) and the centroid of the projection of root surface (CPCS) in certain direction was also tested and compared with the results from FEM. Customized T-loop spring, a kind of orthodontic appliance, was designed, fabricated, and calibrated on a load measuring system to ensure that the load met the clinician’s prescription. The treatment outcomes in terms of tooth displacement and root resorption characterized by the changes of tooth length and volume as well as the bone mineral density (BMD) represented by the Hounsfield units (HU) change were recorded and analyzed. The ME in terms of stress were also calculated by using FEM. Paired t-test and mixed model ANOVA methods were used to analyze the relationships between the mechanical inputs (quantified and customized load, and corresponding stress) and clinical outcomes (root resorption and BMD change). It was found that the overall root resorption is not significant for canine retraction, but apical root resorption does occur, meaning that orthodontic load is not a sufficient factor. Also, it was observed that HU distribution changed significantly in both root and alveolar bone. The maximum reduction was on the coronal level in the direction perpendicular to the direction of movement in root, and in the direction of the tooth movement at the coronal level in bone. In addition, it was determined that the locations of the CRes in the MD and BL directions were significantly different. The locations of the CRes of a human canine in MD and BL directions can be estimated by finding the CPCSs in the two directions. Finally, it was shown that the stress invariants can be used to characterize how the osteocytes feel when ME changes. The stress invariants in the alveolar bone are not significantly affected by different M/F. The higher bone modeling/remodeling activities along the direction of tooth movement may be related to the initial volumetric increase and decrease in the alveolar bone.

In this study the description and development of intensity-based laser interferometric techniques for the detection and measurement of ultrasonic stress waves and their small displacement amplitudes is presented. The dynamic displacement sensitive interferometers described in the following chapters allow the quantitative point-by-point measurement of both in-plane and out-of-plane components of surface displacement motion. These uniquely developed interferometric sensors are: 1) an optical system design for the detection of the surface acoustic wave (Rayleigh wave). The technique is based on the Fourier analysis of coherent light and diffraction imaging properties of an illuminated grating; 2) the design and construction of a two-beam unequal-path laser interferometer for the measurement of out-of-plane surface displacement of ultrasonic waves; 3) extension of a flexible fiber optic probing device which is optically coupled to the test arm of the above two-beam interferometer. This permits scanning of the test surface which may be at some distance from the main optical system components; 4) the design and construction of a laser speckle interferometer for retro-reflective diffusing surfaces in which the in-plane displacements of the ultrasonic wave are interrogated. The inherent advantages of these newly designed optical configurations in terms of their greater simplicity, feasibility, and sensitivity over the conventional counterparts (classical/speckle laser interferometers) are explained. The function-response limitations of these interferometric sensors on lateral displacement resolution, on upper and lower-bound displacement sensitivity (dynamic range), on high-frequency bandwidth probing capability, on low-frequency environmentally associated noise disturbance, and on specularly reflective or diffusively retro-reflective specimen surface preparation are also mentioned. Finally, in a series of experimental observations, the application of a couple of these acoustic sensors in pulsed-excitation ultrasonic Specifically, the optically testing methods is cited. detected ultrasonic signals revealing the true nature of the various surface displacement modes of vibration are presented. / Ph. D.

Recent political and social changes in South Africa have created the need for culture-fair tests for cross-cultural measurement of cognitive ability. This need has been highlighted by the professional, legal and research communities. For cognitive assessment, dynamic assessment is more equitable because it involves a test-train-retest procedure, which shows what performance levels individuals are able to attain when relevant training is provided. Following Binet’s thinking, dynamic assessment aims to identify those individuals who are likely to benefit from additional training. The theoretical basis for learning potential assessment is Vygotsky’s concept of the zone of proximal development. This thesis describes the development, standardisation and evaluation of the Learning Potential Computerised Adaptive Test (LPCAT), for measuring learning potential in the culturally diverse South African population by means of nonverbal figural items. In accordance with Vygotsky’s view, learning potential is defined as a combination of present performance and the extent to which performance is increased after relevant training. This definition allows for comparison of individuals at different levels of initial performance and with different measures of improvement. Computerised adaptive testing based on item response theory, as used in the LPCAT, is uniquely suitable for increasing both measurement accuracy and testing efficiency of dynamic testing, two aspects that have been identified as problematic. The LPCAT pretest and the post-test are two separate adaptive tests, hence eliminating the role of memory in post-test performance. Several multicultural groups were used for item analysis and test validation. The results support the LPCAT as a culture-fair measure of learning potential in the nonverbal general reasoning domain. For examinees with a wide range of ability levels, LPCAT scores correlate strongly with academic performance. For African examinees, poor proficiency in English (the language of teaching) hampers academic performance. The LPCAT ensures the equitable measurement of learning potential, independent of language proficiency and prior scholastic learning and can be used to help select candidates for further training or developmental opportunities. / Psychology / D. Litt. et Phil. (Psychology)

Recent political and social changes in South Africa have created the need for culture-fair tests for cross-cultural measurement of cognitive ability. This need has been highlighted by the professional, legal and research communities. For cognitive assessment, dynamic assessment is more equitable because it involves a test-train-retest procedure, which shows what performance levels individuals are able to attain when relevant training is provided. Following Binet’s thinking, dynamic assessment aims to identify those individuals who are likely to benefit from additional training. The theoretical basis for learning potential assessment is Vygotsky’s concept of the zone of proximal development. This thesis describes the development, standardisation and evaluation of the Learning Potential Computerised Adaptive Test (LPCAT), for measuring learning potential in the culturally diverse South African population by means of nonverbal figural items. In accordance with Vygotsky’s view, learning potential is defined as a combination of present performance and the extent to which performance is increased after relevant training. This definition allows for comparison of individuals at different levels of initial performance and with different measures of improvement. Computerised adaptive testing based on item response theory, as used in the LPCAT, is uniquely suitable for increasing both measurement accuracy and testing efficiency of dynamic testing, two aspects that have been identified as problematic. The LPCAT pretest and the post-test are two separate adaptive tests, hence eliminating the role of memory in post-test performance. Several multicultural groups were used for item analysis and test validation. The results support the LPCAT as a culture-fair measure of learning potential in the nonverbal general reasoning domain. For examinees with a wide range of ability levels, LPCAT scores correlate strongly with academic performance. For African examinees, poor proficiency in English (the language of teaching) hampers academic performance. The LPCAT ensures the equitable measurement of learning potential, independent of language proficiency and prior scholastic learning and can be used to help select candidates for further training or developmental opportunities. / Psychology / D. Litt. et Phil. (Psychology)

Objective: Lack of insight into illness is common in patients with schizophrenia diagnoses. It is supposed to reflect deficits of executive functioning that are frequently assessed with the Wisconsin Card Sorting Test. Studies on the remediability of WCST deficits in schizophrenia, however, raise doubts about its construct validity and suggest the use of a dynamic pretest-training-posttest paradigm (WCSTdyn) and single-case analysis (Reliable Change Index, RCI) in studies on insight. Moreover, a multifactorial etiology with neurocognitive and motivational factors, as suggested by Startup's (1996) model, has to be taken into consideration. The model hypothesizes a quadratic function of the relationship between insight and cognition, which means that both cognitively impaired and cognitively intact patients with low insight are to be expected. Method: Three interrelated studies on WCSTdyn and insight were conducted. In study 1, the split-half reliability of the WCST-128 was investigated in a non-psychiatric sample (N = 110). Study 2 compared different RCI single-case tests of significance of intraindividual change on data from N = 400 patients with schizophrenia diagnoses. Furthermore, a typology with three homogenous subgroups was developed and first steps toward an external validation were taken. In study 3, the three types of test-takers were compared on two measures of insight (Item G12 of the Positive and Negative Syndrome Scale [PANSS]; Osnabrueck Scale of Therapeutic Attitudes and Identification of Psychological Problems in Schizophrenia [OSSTI]). The model by STARTUP (1996) was tested by means of regression and cluster analyses including scales on coping (Freiburg Questionnaire of Coping with Illness, FKV: MUTHNY, 1989) and defensiveness (Eppendorf Schizophrenia Inventory, ESI-FR: MAß, 2001; N = 85). Results: The WCST-64 was sufficiently stable (r_tt = .70 [Total Number Correct]). Concordances of different RCI methods were high (kappa = .72 - .90). 45 % of the sample consisted of high scorers, in 43 % a low initial score could be normalized by a short training intervention (learners), and in only 12 % of the sample the WCST deficits were not amenable to training (nonlearners). Insight of nonlearners was significantly reduced (G12: g = 0,45). Finally, three clusters were identified with configurations of insight and WCSTdyn scores consistent with the prediction by STARTUP (1996). Patients with intact neurocognition but low insight responded in a significantly more defensive manner (g = 0,38). They did not differ in self-rated coping, however. A quadratic relationship could not be confirmed. Conclusion: The RCI-based performance typology developed in studies 1 and 2 is a universally applicable analytic tool for future studies on insight-limiting neurocognitive deficits with the WCSTdyn. Results from study 3 point in the direction of a multifactorial etiology of lack of insight in schizophrenia with differential contributions of neurocognitive deficits (e.g., interference control) and defensiveness.

Indiana University-Purdue University Indianapolis (IUPUI) / Quantification of treatment outcomes (tooth displacement and bony changes) is the key to advance orthodontic research and improve clinical practices. Traditionally, treatment outcome were quantified by using two-dimensional (2D) cephalometric analysis. However, there are problems inherent in 2D analysis, such as tracing errors and inability to detect side-effects. Thus, a reliable three-dimensional (3D) image analysis method for treatment outcome quantification is of high interest. Systematic 3D image analysis methods were developed for digital dental cast models and Cone-Beam Computed Tomography (CBCT) models. A typical analysis procedure includes image reconstruction, landmarks identification, coordinate system setup, superimposition, and displacement or change calculation. The specified procedures for maxillary teeth displacements and anatomical landmarks movements were presented and validated. The validation results showed that these procedures were accurate and reliable enough for clinical applications. The 3D methods were first applied to a human canine retraction clinical study. The purposes of this study were to quantify canines and anchorage tooth movements, and to compare two commonly used canine retraction strategies, controlled tipping and translation. The canine results showed that (1) canine movements were linear with time; (2) the initial load system was not the only factor that controlled the canine movement pattern; and (3) control tipping was significantly faster than translation. The anchorage tooth results showed that (1) anchorage losses occurred even with transpalatal arch (TPA); (2) there was no significant difference in anchorage loss between the two treatment strategies; and (3) compared with removable TPA, fixed TPA appliance can significantly reduce the amount of anchorage loss in the mesial-distal direction. The second clinical application for the 3D methods was a mandibular growth clinical trial. The purposes of this study were to quantify skeletal landmark movements, and compare two widely used appliances, Herbst and MARA. The results showed that (1) the Herbst appliance caused mandibular forward movement with backward rotation; and (2) the treatment effects had no significant differences by using either Herbst or MARA appliances. The two clinical applications validated the methods developed in this study to quantify orthodontic treatment outcomes. They also demonstrated the benefits of using the 3D methods to quantify orthodontic treatment outcomes and to test fundamental hypotheses. These 3D methods can easily be extended to other clinical cases. This study will benefit orthodontic patients, clinicians and researchers.