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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.
161

Real-time integral based structural health monitoring

Singh-Levett, Ishan January 2006 (has links)
Structural Health Monitoring (SHM) is a means of identifying damage from the structural response to environmental loads. Real-time SHM offers rapid assessment of structural safety by owners and civil defense authorities enabling more optimal response to major events. This research presents an real-time, convex, integral-based SHM methods for seismic events that use only acceleration measurements and infrequently measured displacements, and a non-linear baseline model including hysteretic dynamics and permanent deformation. The method thus identifies time-varying pre-yield and post-yield stiffness, elastic and plastic components of displacement and final residual displacement. For a linear baseline model it identifies only timevarying stiffness. Thus, the algorithm identifies all key measures of structural damage affecting the immediate safety or use of the structure, and the long-term cost of repair and retrofit. The algorithm is tested with simulated and measured El Centro earthquake response data from a four storey non-linear steel frame structure and simulated data from a two storey non-linear hybrid rocking structure. The steel frame and rocking structures exhibit contrasting dynamic response and are thus used to highlight the impact of baseline model selection in SHM. In simulation, the algorithm identifies stiffness to within 3.5% with 90% confidence, and permanent displacement to within 7.5% with 90% confidence. Using measured data for the frame structure, the algorithm identifies final residual deformation to within 1.5% and identifies realistic stiffness values in comparison to values predicted from pushover analysis. For the rocking structure, the algorithm accurately identifies the different regimes of motion and linear stiffness comparable to estimates from previous research. Overall, the method is seen to be accurate, effective and realtime capable, with the non-linear baseline model more accurately identifying damage in both of the disparate structures examined.
162

PATTERN EVALUATION FOR IN-PLANE DISPLACEMENT MEASUREMENT OF THIN FILMS

Thota, Phanikrishna 01 January 2003 (has links)
The term Gossamer is used to describe ultra-lightweight spacecraft structures that solve the aerospace challenge of obtaining maximum performance while reducing the launch costs of the spacecraft. Gossamer structures are extremely compliant, which complicates control design and ground testing in full scale. One approach is to design and construct smaller test articles and verify their computational models experimentally, so that similar computational models can be used to predict the dynamic performance of full-scale structures. Though measurement of both in-plane and out-of-plane displacements is required to characterize the dynamic response of the surface of these structures, this thesis lays the groundwork for dynamic measurement of the in-plane component. The measurement of thin films must be performed using non-contacting sensors because any contacting sensor would change the dynamics of the structure. Moreover, the thin films dealt with in this work are coated with either gold or aluminum for special applications making the film optically smooth and therefore requiring a surface pattern. A Krypton Fluoride excimer laser system was selected to fabricate patterns on thin-film mirror test articles. Parameters required for pattern fabrication were investigated. Effects of the pattern on the thin-film dynamics were studied using finite element analysis. Photogrammetry was used to study the static in-plane displacement of the thin-film mirror. This was performed to determine the feasibility of the photogrammetric approach for future dynamic tests. It was concluded that photogrammetry could be used efficiently to quantify dynamic in-plane displacement with high-resolution cameras and sub-pixel target marking.
163

Static axial pile foundation response using seismic piezocone data

Niazi, Fawad Sulaman 27 August 2014 (has links)
Ever since the use of cone penetration testing (CPT) in geotechnical site investigations, efforts have been made to correlate its readings with the components of static axial pile capacity: unit base resistance (qb) and unit shaft resistance (fp). Broadly, the pile capacity analysis from CPT data can be accomplished via two main approaches: rational (or indirect) methods, and direct methods. The rational methods require a two-step approach, whereby CPT data are first used to provide assessments of geoparameters that are further utilized as input values within a selected analytical framework to enable the evaluation of the pile capacity components. In contrast, direct CPT methods use the measured penetrometer readings by scaling relationships or algorithms in a single-step process to obtain fp and qb for full-size piling foundations. The evolution of the CPT from mechanical to electrical to electronic versions and single-channel readings (i.e., measured tip resistance, qc) to the piezocone penetration test (CPTu), that provides three readings of point stress (qt), sleeve friction (fs), and porewater pressure (u1 or u2), has resulted in the concurrent development of multiple CPT-based geotechnical pile design methods. It is noted, however, that current CPT-based methods focus only on an estimate of "axial pile capacity", corresponding to a limiting load or force at full mobilization. A more comprehensive approach is sought herein utilizing the CPT readings towards producing a complete nonlinear load-displacement-capacity (Q-w-Qcap) on axial pile response. In particular, the seismic cone penetration test (SCPT) provides the profile of shear wave velocity (Vs) that determines the fundamental small-strain shear modulus: Gmax = gt?Vs2, where gt = total mass density of soil. With the penetrometer readings useful in assessing foundation capacity, the stiffness Gmax finds application within elastic continuum solutions towards evaluating the load-displacement (Q-w) response. In this study, a concise review of the deep foundation systems is presented, including pile types and characteristics, various arrangements of axial pile load testing in static mode, and interpretations of the load test data. In addition a comprehensive state-of-the-art review of CPT-based rational and direct methods of pile capacity evaluations is compiled. It is recognized that the direct methods offer more convenience in their straightforward approach in estimation of the pile capacity. The piezocone-based UniCone direct method proposed by Eslami and Fellenius (1997) is selected for further refinements, as it utilizes all three CPT readings in its design formulations. Concerning the analysis of pile deformations under axial loading, a brief review covers designs employing empirical formulations, analytical solutions, load-transfer (t-z) methods, numerical simulations, variational approaches, and those using hybrid methods. Specifically, the analytical elastic solution by Randolph and Wroth (1978; 1979) is covered in more detail since it is simple and convenient in application with extended applications to uplift and bidirectional O-cell types of loadings. This elastic approach also serves well in modeling a stacked pile solution for layered soil profiles. The last part of the review covers various shear modulus reduction schemes, since evaluation of the applicable stiffnesses is considered to be the most delicate phase in the nonlinear Q-w response analysis of axially loaded piles. It is identified that the most appropriate scheme applicable to static axial loading of pile foundations is the one that can be derived from the back-analyses of actual load tests within the framework of analytical elastic solution. In order to conduct a comprehensive research study on the axial Q-w-Qcap response of deep foundations from CPT readings, a large database is compiled. This includes 330 case records of pile load tests at 70 sites from 5 continents and 19 different countries of the world, where pile foundations were load tested under top-down compression or top-applied uplift (tension) loading, or both, or by bi-directional Osterberg cell setups. All test sites had been investigated using CPT soundings; in most cases by the preferred SCPTu that provides all four readings from the same sounding: qt, fs, u2, and Vs. In a few cases, sites were subjected to CPT or CPTu and the profiles of shear wave velocities were obtained by other field geophysical techniques, otherwise by empirical estimations. Results of the new correlation efforts are offered to derive coefficients Cse for shaft component and Cte for base component of the axial pile capacity from CPTu data. The UniCone type of soil classification chart is refined by delineating 11 soil sub-zones along with their respective Cse, in contrast to the 5 zones originally proposed. The CPT material index, Ic (Robertson, 2009) is then used to establish direct correlations linking Cse vs. Ic and Cte vs. Ic. Statistical relationships offer continuous functions for estimating the coefficients over a wide range of Ic values, thereby eliminating the need for use of the soil classification chart as well as improving the reliability in the evaluations of fp and qb. The effects of the pile loading direction (compression vs. uplift) and loading rate are also incorporated in the proposed design formulations. New sets of shear stiffness reduction curves are developed from the back-analysis of pile load tests and Gmax profiles obtained from the SCPT data. Alternative functions formats are provided in terms of hyperbolic tangent expressions or exponential curves, developed as normalized shear stiffness (G/Gmax) vs. logarithm of percent pseudo-strain (gp = w/d, where w = pile displacement and d = pile diameter). These charts offer convenience in the axial Q-w analysis of different pile categories within the framework of analytical elastic solution. The results also account for the plasticity characteristics of the soil formations within the database. A stacked pile model for Q-w analysis is presented in which certain adaptations are proposed in the elastic continuum solution. These adaptations enable plotting of separate modulus reduction curves (G/Gmax vs. gp) as function of depth for each layer, and treating pile as a stack of smaller pile segments embedded in a multi-layered soil media. The solution can be used to address the question of progressive failure with depth in a multi-layer soil media that exhibits nonlinear soil stiffness response. Finally, the closed-from analytical elastic pile solution for predicting the Q-w response is decoupled and modified to account for different setup cases and multi-stage loading of bi-directional O-cell tests. The decoupling accounts for separate assessments of the response to axial loading for different segments of pile shaft and different stages of loading, while the modifications include: (1) reduced maximum radius of influence for the upward displacements of the upper shaft segment, and (2) modeling the non-linear ground stiffness from the back-analysis of a well-documented dataset of O-cell load tests.
164

Multimodal treatment of women with mitral valve prolapse syndrome

Nevin, Doris Eileen Jacobs January 1997 (has links)
Mitral valve prolapse is the most commonly occurring cardiac condition. It is a benign condition which affects as many as 10% of the population. Some patients have symptomatic mitral valve prolapse. This condition is referred to as mitral valve prolapse syndrome. Symptoms include: chest pain, tachycardia, palpitations, fatigue, dizziness, shortness of breath, headaches, low exercise tolerance, feelings of anxiety, panic attacks, and mood swings. These symptoms adversely effect the patient's quality of life.The purpose of this study was to investigate the response of patients with mitral valve prolapse syndrome to treatment that includes the accepted treatment for panic disorder, and to determine the roles of self-efficacy and of level of spousal support in enhancing the ability of identified patients to cope with mitral valve prolapse syndrome.Thirty-one subjects initially agreed to participate in this study. Of these subjects, fifteen left the study. The leading causes of dropout were lack of spousal support and multiple role stress. The remaining sixteen subjects completed the study. Subjects were randomly divided into three treatment conditions, individual multimodal therapy, couples multimodal therapy, and a waiting list/control group. Treatment consisted of attending a five session psychoeducational program and completing prescribed exercises at home between sessions. The first two sessions examined self-care lifestyle changes that patients could make to alleviate symptoms. The remaining three sessions focused on the over reactiveness of the autonomic nervous system for these patients and the efficacy of learned relaxation procedures. Dependent measures included a Symptom Checklist, Anxiety Sensitivity, Strength and Magnitude of Self-Efficacy and Strength and Magnitude of Interactive Efficacy.Data was analyzed in a two-step process. First, it was analyzed using a multiple single case design format. This was followed by a quantitative analysis of grouped data. In general, the multiple single case design complemented the quantitative analysis. Individual findings in the multiple single case design indicated issues for future research.Participation in treatment was found to aid in decreasing global physical symptoms, decreasing anxiety sensitivity symptoms, and increasing the subject's confidence in her ability to manage her symptoms. The increased level of self-confidence was related significantly to decreasing global physical symptoms. There was a weak, non-statistically significant correlation between increased confidence of self-efficacy and decreased anxiety sensitivity symptoms. Participation in couples multimodal treatment or any treatment was not significantly linked to increased interactive efficacy. Increased interactive efficacy was correlated with increased self-efficacy and decreased global physical symptoms. / Department of Counseling Psychology and Guidance Services
165

Migrasie en verplasing in Anderkant die stilte (André P. Brink), De reis van de lege flessen (Kader Abdolah) en Idil, een meisje (Tasmine Allas) :|b'n genderbeskouing / Rochelle Marais

Marais, Rochelle January 2012 (has links)
Migration and the concomitant crossing of borders is a growing world wide theme in literature. This phenomenon can be attributed to growing mobility and globalisation which allow people to move freely across national borders. Mobility is a key concept for the 21st century and can be used as an umbrella term for the crossing of borders and migration, also connecting with concepts such as displacement, diaspora, nomad, travel, exile and (post)colonialism. Migration as demographic phenomenon does not only include the borders of countries but also social, cultural, psychological and language borders. Memory as border can be added to this since it acts as a link between time and space. The crossing of (national) borders also holds certain consequences, amongst others the problem of origin and identity, outsidership and/or marginalization as well as the experience of loss. Two novels which can be classified as migrant literature – Idil, een meisje (Yasmine Allas) and De reis van de lege flessen (Kader Abdolah), and one novel which explores the problem of migration thematically – Anderkant die stilte (André P. Brink) – are analysed in this dissertation. Idil, een meisje (Yasmine Allas) portrays a female perspective by a female migrant writer, while De reis van de lege flessen (Kader Abdolah) offers a male perspective by a male migrant writer. Anderkant die stilte (André P. Brink) adds an additional dimension to gender analysis since a female perspective is portrayed by a male writer. These three novels, one from Afrikaans and two from Dutch literature, will be analysed to determine the manifestation of migration and displacement and the outcome(s) thereof with emphasis on gendered experience in these literature texts. / Thesis (MA (Afrikaans en Nederlands))--North-West University, Vaal Triangle Campus, 2013
166

Experimental and numerical study of an indoor displacement ventilation system

Fatemiardestani, Seyediman Jr 07 February 2013 (has links)
This thesis reports a new set of experimental data and presents an in-depth analysis of the flow physics of a jet stream produced by a large quarter-round corner-mounted displacement diffuser. The air velocity, temperature and turbulence intensity inside the displacement ventilation (DV) jet have been thoroughly analyzed and compared with the reported findings of previous studies and model predictions. Furthermore, thermal comfort has been analyzed using the measured data following the ASHRAE standard. This thesis also aims at establishing an accurate numerical approach for simulating the heat and fluid flow in a room ventilated by a DV system. The supply boundary condition has been thoroughly investigated, which includes tests of the conventional box and momentum modeling methods, and proposal of a more accurate modeling approach. In addition, the predictive accuracy of the standard k-ϵ, RNG k-ϵ, SST k-ω and RSM turbulence models has been examined against the experimental data.
167

To Cue or Not to Cue: Beacons and Landmarks in Object-displacement Tasks

Mangalindan, Diane Marie 08 August 2013 (has links)
Two experiments examined the role of various cues on children’s performance in a well-known object-displacement task. In this task, children observed a toy rolling down a ramp whose trajectory was occluded by an opaque screen with doors. A barrier was placed along the ramp, behind one of the doors, to stop the toy. The top portion of the barrier was visible above the screen. To search successfully, children had to retrieve the hidden toy by opening the correct door. Previous work had found that the barrier was an ineffective cue among children less than three years of age. According to a landmark-based account, this was because the barrier was only an indirect cue to object location. If a cue directly marked the location, then it would be more likely attended and utilized. This model underscores the spatial relation between cue and the target. Other cue properties are important in so far that they modify this spatial relation. In Experiment 1, a cue’s distance from the target object was manipulated (i.e., short vs. long), but the location marked by the cue was kept constant (i.e., correct door was directly below). The search performances of 24- and 30-month old children were compared under no cue, short-cue/short-door, and long-cue/long-door conditions. Both age groups performed equally well under both cued conditions. In Experiment 2, a cue’s movement (i.e., coincident with the car vs. not coincident with the car) down the ramp was manipulated. The performance of 24- and 30-month old children were compared under attached-direct cue and unattached-direct cue conditions. Both age groups performed well under both conditions. Collectively, the results provide support for the landmark-based account. The spatial relation between cue and target underlies toddlers’ search. Properties of the cue matter to the extent that they impact how well the cue marks its target.
168

To Cue or Not to Cue: Beacons and Landmarks in Object-displacement Tasks

Mangalindan, Diane Marie 08 August 2013 (has links)
Two experiments examined the role of various cues on children’s performance in a well-known object-displacement task. In this task, children observed a toy rolling down a ramp whose trajectory was occluded by an opaque screen with doors. A barrier was placed along the ramp, behind one of the doors, to stop the toy. The top portion of the barrier was visible above the screen. To search successfully, children had to retrieve the hidden toy by opening the correct door. Previous work had found that the barrier was an ineffective cue among children less than three years of age. According to a landmark-based account, this was because the barrier was only an indirect cue to object location. If a cue directly marked the location, then it would be more likely attended and utilized. This model underscores the spatial relation between cue and the target. Other cue properties are important in so far that they modify this spatial relation. In Experiment 1, a cue’s distance from the target object was manipulated (i.e., short vs. long), but the location marked by the cue was kept constant (i.e., correct door was directly below). The search performances of 24- and 30-month old children were compared under no cue, short-cue/short-door, and long-cue/long-door conditions. Both age groups performed equally well under both cued conditions. In Experiment 2, a cue’s movement (i.e., coincident with the car vs. not coincident with the car) down the ramp was manipulated. The performance of 24- and 30-month old children were compared under attached-direct cue and unattached-direct cue conditions. Both age groups performed well under both conditions. Collectively, the results provide support for the landmark-based account. The spatial relation between cue and target underlies toddlers’ search. Properties of the cue matter to the extent that they impact how well the cue marks its target.
169

Invisible displacement understanding in dogs (Canis familiaris), chimpanzees (Pan troglodytes), and other primates

Collier-Baker, E. Unknown Date (has links)
The Piagetian invisible displacement task has been used extensively in the filed of comparative cognition to measure representational capacity. In the task a desirable object is hidden beneath one of several hiding boxes via a displacement device, such as a small opaque container. Success on the task is deemed to require that the invisible trajectory of the object be mentally represented and its current location inferred. That is, the task is supposed to measure the ability to “think” of something that is occurring outside of direct perception. However, simple associative strategies may also lead to success in the absence of stringent control conditions. Among mammals, only great apes and domestic dogs have consistently performed above chance on the invisible displacement task. There is much converging evidence from other tasks to suggest that great apes have a capacity for representational thought. However, dogs have shown few signs of possessing the representational abilities generally though necessary to pass the task. Thus, in Chapter 2, four experiments investigated how dogs (n=35) find an object that has been invisibly displaced behind one of three opaque boxes under four control conditions devised to separate associative search strategies from performance based on mental representation. Strategies involving experimenter cue-use, search at the last or first box visited by the displacement device, and search at boxes adjacent to the displacement device were systematically controlled for. Dogs passed invisible displacement’s but only if the device used to displace the object was adjacent to the target box following displacements. These results suggest that the search behaviour of dogs was guided by simple associative rules rather than mental representation of past trajectory of the object. In contrast, Experiment 5 found that, on the same task, 18- and 24-moth-old children (n=21) showed no disparity between trials in which the displacement device was adjacent or non-adjacent to the target box. In Chapter 3, two chimpanzees were tested on single invisible displacements under the same four control conditions that were administered to dogs. In contract to dogs, chimpanzees showed no indication of utilizing these simple strategies, suggesting that their capacity to mentally represent single invisible displacements is comparable to that of 18- to 24-month-old children. Chapter 4 followed up reports of children and apes’ difficulty with double invisible displacements in which an object is hidden at two non-adjacent boxes in a linear array. Experiment 1 eliminated the possibility that chimpanzees’ previous poor performance was due to the hiding direction of the displacement device. Subjects failed double non-adjacent displacements, showing a tendency to select adjacent boxes. In Experiments 2 and 3, chimpanzees and 24-month-old children were tested on a new adaptation of the task involving four hiding boxes presented in a diamond-shaped array on a vertical plane. Both species performed above change on double invisible displacements using this format, suggesting that previous poor performance was due to a response bias or inhibition problem rather than a fundamental limitation in representational capacity. In Chapter 5, I conducted a pilot study examining the performance of siamangs and a spider monkey on single and double invisible displacements. Performance was mixed but provides some promising evidence that invisible displacements are within the capacity of siamangs. In contrast to siamangs and chimpanzees, but like dogs, the spider monkey showed a significant tendency to search at a box adjacent to the displacement device on simple invisible displacements. However, the spider monkey performed above chance on an impromptu test of single invisible displacements presented in the vertical format. Further study is needed to eliminate alternative associative strategies in these two species. In Chapter 6, I discuss the findings of the study with dogs, chimpanzees, 2-year-old children, siamangs, and a spider monkey on invisible displacement understanding. The results highlight the importance of associative strategies and inhibition problems. The thesis presents strong evidence of stage 6 invisible displacement understanding, and thus representational thought, in chimpanzees and 2-year-old children, but suggests that dogs are capable of only stage 5 objective permanence understanding.
170

Impact of breath group control on the speech of normals and individuals with cerebral palsy

Yip, Fiona Pik Ying January 2008 (has links)
Dysarthria is one of the most common signs of speech impairment in the cerebral palsy (CP) population. Facilitating strategies for speech enhancement in this population often include training on speech breathing. Treatment efficacy studies with cross-system measures in this population are needed for improved understanding and management of the interrelationship between respiratory, phonatory, and articulatory systems. The purpose of this study was to investigate the effect of breath group control on the coordination of articulatory and phonatory muscles and the acoustic measures related to speech and voice quality. A simultaneous acoustic, electroglottographic (EGG), and marker-based facial tracking recording system was employed to monitor the speech production behaviors of four adults with CP and 16 neurologically healthy controls. Subjects were instructed to perform three tasks, each containing speech targets with a voiceless plosive (/p/, /t/, or /k/) preceding a vowel (/i/, /a/, /u/, or /ɔ/). Task 1 consisted of a short reading passage embedded with target vowels without cueing from breath group markers. Task 2 included reading a series of monosyllabic and 3-syllable or 5-syllable non-speech words with the speech targets. Task 3 included reading the same short passage from Task 1 with cueing from breath group markers separating the passage into phrases with no more than five syllables per phrase. Measures from the acoustic, EGG and facial tracking recordings of the first and last syllable of all syllable trains produced in the non-speech task and the target vowels in the passage reading task were examined. Acoustic measures included voice onset time (VOT), vowel duration, fundamental frequency (F0), percent jitter (%jitter), percent shimmer (%shimmer), signal-to-noise ratio (SNR), and frequencies of Formants one and two (F1 and F2). EGG measures included speed quotient (SQ) and open quotient (OQ). Facial tracking measures consisted of maximum jaw displacement. Individual and averaged data were submitted to a series of two-way Analysis of Variances (ANOVAs) or two-way Repeated Measures ANOVAs to determine the effects of the relative position of an utterance in the breath group and the place of articulation of the consonants involved. In addition, mean vowel spaces derived from all three tasks were examined. Results revealed significant changes of VOT, F1, F2, SNR and SQ as a function of position. Significant changes of VOT, vowel duration, F2, F0, %jitter, %shimmer, and maximum jaw displacement as a function of place of articulation were also evident. In particular, breath group control was found to result in expansion of vowel space, especially for individuals with CP. These findings suggest that proper phrasing enhances articulatory and phonatory stability, providing empirical evidences in support of its usage in treating individuals with CP.

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