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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

An investigation into the psychometric properties of the proportional reduction of mean squared error and augmented scores

Stephens, Christopher Neil 01 December 2012 (has links)
Augmentation procedures are designed to provide better estimates for a given test or subtest through the use of collateral information. The main purpose of this dissertation was to use Haberman's and Wainer's augmentation procedures on a large-scale, standardized achievement test to understand the relationship between reliability and correlation that exist to create the proportional reduction of mean squared error (PRMSE) statistic and to compare the practical effects of Haberman's augmentation procedure with the practical effects of Wainer's augmentation procedure. In this dissertation, Haberman's and Wainer's augmentation procedures were used on a data set that consisted of a large-scale, standardized achievement test with tests in three different content areas, reading, language arts, and mathematics, in both 4th and 8th grade. Each test could be broken down into different content area subtests, between two and five depending on the content area. The data sets contained between 2,500 and 3,000 examinees for each test. The PRMSE statistic was used on the all of the data sets to evaluate two augmentation procedures, one proposed by Haberman and one by Wainer. Following the augmentation analysis, the relationship between the reliability of the subtest to be augmented and that subtest's correlation with the rest of the test was investigated using a pseudo-simulated data set, which consisted of different values for those variables. Lastly, the Haberman and Wainer augmentation procedures were used on the data sets and the augmented data was analyzed to determine the magnitude of the effects of using these augmentation procedures. The main findings based on the data analysis and pseudo-simulated data analysis were as follows: (1) the more questions the better the estimates and the better the augmentation procedures; (2) there is virtually no difference between the Haberman and Wainer augmentation procedures, except for certain correlational relationships; (3) there is a significant effect of using the Haberman or Wainer augmentation procedures, however as the reliability increases, this effect lessens. The limitations of the study and possible future research are also discussed in the dissertation.
2

Design and Testing of a Flight Control System for Unstable Subscale Aircraft

Sobron, Alejandro January 2015 (has links)
The primary objective of this thesis was to study, implement, and test low-cost electronic flight control systems (FCS) in remotely piloted subscale research aircraft with relaxed static longitudinal stability. Even though this implementation was carried out in small, simplified test-bed aircraft, it was designed with the aim of being installed later in more complex demonstrator aircraft such as the Generic Future Fighter concept demonstrator project. The recent boom of the unmanned aircraft market has led to the appearance of numerous electronic FCS designed for small-scale vehicles and even hobbyist-type model aircraft. Therefore, the purpose was not to develop a new FCS from scratch, but rather to take advantage of the available technology and to examine the performance of different commercial off-the-shelf (COTS) low-cost systems in statically unstable aircraft models. Two different systems were integrated, calibrated and tested: a simple, gyroscope-based, single-axis controller, and an advanced flight controller with a complete suite of sensors, including a specifically manufactured angle-of-attack transducer. A flight testing methodology and appropriate flight-test data analysis tools were also developed. The satisfactory results are discussed for different flight control laws, and the controller tuning procedure is described. On the other hand, the different test-bed aircraft were analysed from a theoretical point of view by using common aircraft-design methods and conventional preliminary-design tools. The theoretical models were integrated into a flight dynamics simulator, which was compared with flight-test data obtaining a reasonable qualitative correlation. Possible FCS modifications are discussed and some future implementations are proposed, such as the integration of the angle-of-attack in the control laws.
3

A New Subscale for the Personality Assessment Inventory (PAI) to Screen Adults for Attention-Deficit/Hyperactivity Disorder (ADHD)

Calmenson, Nina E 08 1900 (has links)
The Personality Assessment Inventory (PAI) is a widely used and available self-report measure designed to assess clinical syndromes and has the potential to assist in the process of ADHD assessment. Since the PAI's inception, several researchers have attempted to create other supplemental indicators, some so effective and useful that they were added to the second edition of the Personality Assessment Inventory Professional Manual. Previous researchers have offered important insights into the possibility of the creation of an ADHD item-level index for the PAI that would effectively decrease false positive rates and increase accurate detection of ADHD in the adult population. Previous researchers were not successful in creating an item-level subscale that reliably detected adult ADHD. Four experts in ADHD assessment rated PAI items that they believed could discriminate adults with ADHD from adults without ADHD. After performing a PCA on the top 16 items chosen by the experts, 12 items sufficiently loaded onto one factor that has clear face validity by conceptually matching the DSM-5 description of inattention and impulsivity commonly seen in adults with ADHD as well as the "internalized restlessness" Hallowell and Ratey describe for adult ADHD. The PAI-ADHD was found to have good internal consistency, a = .84. The PAI-ADHD has good convergent validity with the Conners' Adult ADHD Rating Scale – Self-Report – Long Version (CAARS-Self) and Wender Utah Rating Scale (WURS). The PAI-ADHD also has good concurrent validity. Two cut scores are suggested, 13 and 22, to maximize sensitivity (.88) and specificity (.89), create three screening groups: ruled-out, at-risk, and probable ADHD, and increase utility for clinicians.
4

Design and manufacturing of a thrust measurement system for a micro jet engine : Enabling in-flight drag estimation for subscale aircraft testing

Martinez, Anna January 2018 (has links)
Good estimation of aerodynamic coefficients is of fundamental importance in the design and development process of an aircraft. Generally, these parameters are obtained using analytical, numerical and experimental methods, which are sometimes either inaccurate or very expensive. The use of subscale aircraft is becoming increasingly common in the study and evaluation of new aircraft concepts. Flight testing results in an efficient solution for obtaining parameters that can define drag characteristics. This project presents a solution for achieving the drag aerodynamic model from the design and manufacturing of a micro engine thrust measuring system integrated on subscale aircraft. Strain gauge technology permits to identify the stresses that the engine forces cause to the aircraft internal structure by analysing the strain of several strategic zones of the engine mounting created for this purpose. Different structural support geometries have been presented and stress-analysed together with the design of the appropriate strain gauge model conguration in order to select and manufacture a system that represents a good compromise between all the requirements while ensuring the quality and accuracy of the data acquired. After calibration, installation and set-up, the system is ready for real in-flight measurements.
5

Modeling and Scaling of a Flexible Subscale Aircraft for Flight Control Development and Testing in the Presence of Aeroservoelastic Interactions

Ouellette, Jeffrey Alan 18 September 2013 (has links)
The interaction of an aircraft's structure and the flight dynamics can degrade the performance of a controller designed only considering the rigid body flight dynamics. These concerns are greater for the next generation adaptive controls. These interactions lead to an increase in the tracking error, instabilities in the control parameters, and significant structural excitations. To improve the understanding of these issues the interactions have been examined using simulation as well as flight testing of a subscale aircraft. The scaling required for such a subscale aircraft has also been examined. For the simulation a coordinate system where the non-linear flight dynamics are orthogonal to the linear structural dynamics was defined. The orthogonality allows the use of separates models for the aerodynamics. For the non-linear flight dynamics, preexisting table lookups with extended vortex lattice are used to determine the aerodynamic forces. Strip theory is then used to determine the smaller, but still important, unsteady aerodynamic forces due to the flexible motion. Because the orientation of the engines is dependent on the structural deformations, the propulsive force is modeled as a non-conservative follower force. The simulation of the integrated dynamics is then used to examine the effects of the aircraft flexibility and resultant ASE interactions on the performance of adaptive controls. For the scaling, the complete similitude of a flexible aircraft was examined. However, this complete similitude is unfeasible for an actual model, so partial similitude is investigated using two approaches. First, the classical approximations of the flight dynamic modes are used to reduce the order of the coupled model, and consequently the number of scaling parameters required to maintain the physics of the system. The second approach uses sensitivity of the response to errors in the aircraft's nondimensional parameters. Both methods give a consistent set of nondimensional parameters which do not have significant influence on the aeroservoelastic interaction. These parameters do not need to be scaled, thus leading to a viable scaled model. A subscale vehicle has been designed which shows significant coupling between the flight dynamics and structural dynamics. This vehicle was used to validate the results of the scaling theory. Output error system identification was used to identify a model from the flight test data. This identified model provides the frequency of the short-period mode, and the effects of the Froude number on the flexibility. / Ph. D.
6

Thermo-fluid effects associated with modelling subscale automotive heat exchangers

Gerova, Klementina January 2015 (has links)
Automotive components are tested extensively in wind tunnels by automotive manufacturers and race teams. This is usually achieved using an accurate scale model representation of the component within the wind tunnel. Automotive heat exchangers, however, are comprised of numerous intricate geometries and are therefore impractical to produce at model scale. Instead they are simply modelled as pressure drops, achieved using a thin mesh or honeycomb of known porosity. Most commercial computational fluid dynamics solvers ignore the geometry of the heat exchanger and instead model it as a discontinuity with a known pressure drop and heat transfer. The pressure drop across an automotive heat exchanger, however, was found to vary with both the coolant temperature and the angle of inclination of the heat exchanger. This thesis initially presents a relationship between the pressure drop coefficient and the inclination angle for varying media porosities. Mathematical relationships for inclination angles of 0°, 15°, 30° and 45°. were derived relating this pressure drop coefficient to the porosity of the media. Weighted least squares is proposed over ordinary least squares when obtaining the Forchheimer equation coefficients from experimental measurements. Investigation extends into the thermo-fluid effects on a full scale automotive heat exchanger when inclined at 0 °, 15°, 30° and 45°. It was found, depending on the angle, that there was a difference in the pressure drop of up to 10% between the unheated and heated (100 C) heat exchanger. Based on the proposed mathematical relationship, this correlated to a 4% decrease in porosity in order to accurately model the automotive heat exchanger at subscale. The thesis concludes with experimental and numerical investigation into the heat transfer on a hydrodynamically and thermally developing ow within a radiator channel. Laser doppler anemometry measurements recorded a 1.5% increase in the centreline velocity compared to 0.8% obtained from numerical simulation.
7

Simulation of the Inertia Friction Welding Process Using a Subscale Specimen and a Friction Stir Welder

Dansie, Ty Samual 01 April 2018 (has links)
This study develops a method to simulate a full-scale inertia friction weld with a sub-scale specimen and modifies a direct drive friction stir welder to perform the welding process. A torque meter is fabricated for the FSW machine to measure weld torque. Machine controls are modified to enable a force control during the IFW process. An equation is created to measure weld upset due to deflection of the FSW machine. Data obtained from a full-scale inertia friction weld are altered to account for the geometrical differences between the sub-scale and full-scale specimens. The IFW are simulated with the sub-scale specimen while controlling spindle RPM and matching weld power or weld RPM. The force used to perform friction welding is scaled to different values accounting for specimen size to determine the effects on output parameters including: HAZ, upset, RPM, torque, power and energy of the weld. Increasing force has positive effects to upset, torque, power and energy of the welds, while reducing the size of the HAZ.
8

Career Adaptability as a predictor of retention among undecided students

Kotlan, Nicole M. 28 April 2022 (has links)
No description available.
9

Marriage Moments: An Evaluation of an Approach to Strengthen Couples' Relationships During the Transition to Parenthood, in the Context of a Home Visitation Program

Lovejoy, Kimberly Ann Rose 09 August 2004 (has links) (PDF)
This study evaluates the efficacy of a self-guided, low-intensity curriculum, Marriage Moments, based on Fowers' (2000) virtues model of marital quality that emphasizes friendship, generosity, justice and loyalty. The Marriage Moments program consists of a guidebook and a video that were designed to strengthen marriages during the transition to parenthood and is used in the context of a home visitation program for first-time parents. Participants in the study included 119 married couples who had recently given birth to their first child. They were assigned to either a treatment, comparison or control group. The treatment group received the Marriage Moments curriculum as well as the Welcome Baby home visitation curriculum, the comparison group only received the Welcome Baby curriculum and the control group received neither program. Data were gathered through a battery of self- and spouse-report measures given at 3-months, 4-months, and 9-months postpartum. Relationship outcome measures included in this study were the Marital Virtues Profile, Revised-Dyadic Adjustment Scale, RELATE Satisfaction subscale, Transition Adjustment Scale, Father Involvement Scale, Household Labor Scale, and Maternal Depression Scale. Despite positive evaluations of the program from participants, analyses revealed a lack of significant, positive effects for members of the treatment group. Further research is needed before reliable conclusions can be drawn about the value of a marital virtues model as a guide for low intensity intervention.

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