Browsing by Subject "Induction"
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Item A longitudinal trend study of a university-based teacher induction program: observable behaviors of urban teachers and their perceptions of program components five years after participation(Texas A&M University, 2006-10-30) Moon Merchant, Vickie VThis longitudinal trend study (Gall, Borg & Gall, 1996) examined the effectiveness of a one-semester university-based teacher induction program as compared to a two-semester university-based teacher induction program based on the observation scores of classroom teaching behaviors urban novice teachers exhibited during the first year of teaching. These scores were further analyzed in relation to the socio-economic level of the school and the grade level taught. Additionally, the study explored the past participants?????? perceptions of the teacher induction program components of a one-semester program and a two-semester program during their fifth year of teaching. Their perceptions were also examined in relation to the socio-economic level of the school and the grade level taught. The study examined the observation scores of classroom teaching behaviors of 145 urban novice teachers participating in either a one-semester or two-semester universitybased teacher induction program. The urban novice teachers demonstrated growth over time as measured by the first and final observation scores of classroom teaching behaviors. However, the length of the university-based teacher induction program did not affect the observation scores of classroom teaching behaviors. Further, neither the socio-economic level of the school nor the grade level taught affected the observation scores of classroom teaching behaviors. Although the three components of the university-based teacher induction program received high means, 82 past participants of a one-semester or a two-semester teacher induction program responding to the Teacher Induction Program Participant Survey (TIPPS) recognized formative observation as the most effective component. Peer support and professional development were perceived second and third respectively. No statistical significant differences of the one-semester or two-semester past participants?????? perceptions of peer support, professional development or formative observation were found related to the socio-economic level of the school or the grade level taught.Item Design of vibrational and solar energy harvesting systems for powering wireless sensor networks in bridge structural health monitoring applications(2014-12) Adams, Jacob Allan; Crawford, Richard H.Structural health monitoring systems provide a promising route to real-time data for analyzing the current state of large structures. In the wake of two high-profile bridge collapses due to an aging highway infrastructure, the interest in implementing such systems into fracture-critical and structurally deficient bridges is greater now than at any point in history. Traditionally, these technologies have not been cost-effective as bridges lack existing wiring architecture and the addition of this is cost prohibitive. Modern wireless sensor networks (WSN) now present a viable alternative to traditional networking; however, these systems must incorporate localized power sources capable of decade-long operation with minimal maintenance. To this end, this thesis explores the development of two energy harvesting systems capable of long-term bridge deployment with minimal maintenance. First, an electromagnetic, linear, vibrational energy harvester is explored that utilizes the excitations from passing traffic to induce motion in a translating permanent magnet mass. This motion is then converted to electrical energy using Faraday’s law of induction. This thesis presents a review of vibrational energy harvesting literature before detailing the process of designing, simulating, prototyping, and testing a selected design. Included is an analysis of the effects of frequency, excitation amplitude, load, and damping on the power production potential of the harvester. Second, a solar energy harvester using photovoltaic (PV) panels is explored for powering the critical gateway component of the WSN responsible for data aggregation. As solar energy harvesting is a more mature technology, this thesis focuses on the methodologies for properly sizing a solar harvesting system and experimentally validating the selected design. Fabrication of the prototype system was completed and field testing was performed in Austin, TX. The results validate the selected system’s ability to power the necessary 14 W DC load with a 0° panel azimuth angle (facing direct south) and 45° tilt.Item Electrohydrodynamic induction and conduction pumping of dielectric liquid film: theoretical and numerical studies(Texas A&M University, 2007-04-25) Al Dini, Salem A. S.Electrohydrodynamic (EHD) pumping of single and two-phase media is attractive for terrestrial and outer space applications since it is non-mechanical, lightweight, and involves no moving parts. In addition to pure pumping purposes, EHD pumps are also used for the enhancement of heat transfer, as an increase in mass transport often translates to an augmentation of the heat transfer. Applications, for example, include two-phase heat exchangers, heat pipes, and capillary pumping loops. In this research, EHD induction pumping of liquid film in annular horizontal and vertical configurations is investigated. A non-dimensional analytical model accounting for electric shear stress existing only at the liquid/vapor interface is developed for attraction and repulsion pumping modes. The effects of all involved parameters including the external load (i.e. pressure gradient) and gravitational force on the nondimensional interfacial velocity are presented. A non-dimensional stability analysis of EHD induction pumping of liquid film in a vertical annular configuration in the presence of external load for repulsion mode is carried out. A general non-dimensional stability criterion is presented. Stability maps are introduced allowing classification of pump operation as stable or unstable based on the input operating parameters. An advanced numerical model accounting for the charges induced throughout the bulk of the fluid due to the temperature gradient for EHD induction pumping of liquid film in a vertical annular configuration is derived. A non-dimensional parametric study including the effects of external load is carried out for different entrance temperature profiles and in the presence of Joule heating. Finally, a non-dimensional theoretical model is developed to investigate and to understand the EHD conduction phenomenon in electrode geometries capable of generating a net flow. It is shown that with minimal drag electrode design, the EHD conduction phenomenon is capable of providing a net flow. The theoretical model is further extended to study the effect of EHD conduction phenomenon for a two-phase flow (i.e. a stratified liquid/ vapor medium). The numerical results presented confirm the concept of liquid film net flow generation with the EHD conduction mechanism.Item Forward Modeling of the Induction Log Response of a Fractured Geologic Formation(2013-05-02) Bray, Steven HunterInduction logging is a well-developed geophysical method with multiple applications. It has been used extensively in academic research as well as in industry. Induction logging is a controlled-source electromagnetic (CSEM) exploration method. It characterizes geologic formations through the measurements of induced magnetics fields. The purpose of this research project is to better understand induction logs and the effects fractured geologic formations have on them. Computer modeling is used to generate synthetic logs for analysis in this research project. The original program required certain modifications to fit this research project?s goals. The computer program, Seatem is based on the finite element method. It is able to use a layered Earth model that is the basis for the synthetic log analysis. The geologic layers in this model are assigned various conductivities and also have the option of being assigned a geologic roughness value. The geologic roughness parameter is used to simulate fractured rocks in the subsurface. The synthetic logs generated by the modified Seatem program produce some encouraging results. In a thinning bed analysis, it is shown that as a conductive bed is thinned in a step-size procedure, the resulting induction log underestimates the actual conductivity of the layer. It also shows that the boundary layers around the thinned layer are better characterized in the log. The next synthetic log was calculated for a fractured resistive layer. This log shows that as the layer becomes more fractured, there is an increase in the underestimation of the actual conductivity. This layer is then thinned down and another synthetic log is calculated. The resulting log shows similar traits to the thinning bed analysis and shows an underestimation of the apparent conductivity. The same procedure is performed for a fractured conductive layer. The analysis produce similar results; however, that are much more drastic changes in the induction logs. As the unit becomes more fractured, the apparent conductivity is lower then the actual conductivity, as in the resistive case. However, smaller increases in the roughness parameter produced more severe underestimations than larger increases in the roughness parameter did for the resistive layer.Item Investigation on cutting metals using induced currents(2014-12) Sitzman, Alex Joseph; Becker, Michael F.; Bourell, David LeeNon-contact magnetic cutting (NCMC) is a recently developed metal-cutting technology that uses pulsed magnetic fields to advance and steer fine cuts in metal sheet. With this process, a coil is used to induce currents in a workpiece that has a starter feature such as a notch or slit. The induced currents are forced to bend tightly around the starter feature, which enhances the current and magnetic field density. Under the right conditions, resistive heating and large J × B forces cause localized melting and ejection of material. Each cut is only a fraction of a millimeter long; however, the process can be repeated and the coil can be moved to cut arbitrary lengths and shapes. While some promising results have been obtained, the operating space for making controlled cuts appears to be narrow. Furthermore, the process by which cutting occurs is not well understood. The objective of this dissertation is to provide the scientific underpinnings of NCMC by experimentally assessing the conditions for controlled cutting, developing a method for predicting conditions for optimal cutting, and identifying a path to reduce NCMC to practice.Item Market study and design of an induction heating product to warm weighlifting barbells(2014-05) Doglio, Jean Marie; Crawford, Richard H.; Hall, Matthew JIn order to solve the problem of discomfort and injury caused by weightlifting with barbells in cold temperatures, an induction heater product was designed to warm cold barbells in 15 minutes or less; currently no other product exists to address this issue. The primary market identified for the product is lifters located in cold climates who train in their home garages, and the secondary market is unheated membership-based gyms. Product development steps documented in this thesis include customer needs gathering and analysis, concept generation and variant development, and heating performance simulation.Item Operating Characteristics of a Two-Stator Induction Machine(Texas Tech University, 1973-05) Kauss, Walmar LacerdaNot Available.Item Reduction of Shaft Voltages and Bearing Currents in Five-Phase Induction Motor(2012-07-16) Hussain, HussainInduction motors are commonly used in numerous industrial applications. To maintain a reliable operation of the motor, it is important to identify the potential faults that may cause the motor to fail. Bearing failures are one of the main causes of motor breakdown. The causes of bearing damage have been studied in detail for a long time. In some cases, bearing failed due to the current passing through them. In this thesis, bearing currents in an inverter driven five-phase induction motor are studied and a new solution is proposed. First, theory of shaft voltage and bearing current are presented. The causes are identified and current solutions are discussed. Then, new switching patterns are proposed for the five-phase induction motor. The new schemes apply a modified algorithm for the space vector pulse-width-modulation (SVPWM). The system is simulated and the results of the new switching patterns are compared with the conventional switching pattern. Finally, the new schemes are experimentally tested using a digital signal processor (DSP) to drive the five-phase IGBT inverter. The experimental results verified that the new switching pattern could reduce shaft voltages and bearing current without affecting the performance.Item Reevaluating the determinants of category-based induction(2010-05) Rein, Jonathan Raymond, 1983-; Markman, Arthur B.; Griffin, Zenzi; Legare, Cristine; Loewenstein, Jeffrey; Maddox, ToddWhat makes one more or less likely to project a novel property from an item to that item’s broader category? Research on category-based induction has documented a consistent typicality effect: typical exemplars promote stronger inferences than atypical exemplars. This work has been largely confined to categories whose central tendencies are the most typical members of the category. Experiments 1 and 2, using natural and artificial categories, showed that central tendencies have greatest induction strength even for categories that are best represented by ideal exemplars. Experiments 3-7 investigate the role of familiarity in induction. Experiments 3 and 4 directly contrast statistical averageness against familiarity through category learning procedures. Experiment 5 creates this contrast through frequency differences across stimuli. Experiments 6 and 7 investigate how the familiarity advantage found in Experiments 3-5 can be modified through fluency manipulations, independent of actual experience. Taken together, these studies suggest that category-based induction is driven largely by a familiarity heuristic.Item Studies on submerged cotton fiber growth : induction and characterization, effects of Congo Red and auxin(2003-12) Feng, Rong; Brown, R. Malcolm (Richard Malcolm), 1939-Induction of growth of submerged cotton (Gossypium hirsutum L.) fibers from cultured ovules has been investigated for the first time. Both exogenous plant hormone levels and the age of the ovules at induction play important roles in induction of submerged cotton fiber growth. The diameter of submerged fibers was about same as that of air-grown fibers but was smaller than that of fibers grown in vivo. Submerged fibers were shorter in the fiber length, stronger in the tensile strength, and they had thicker secondary cell walls and smaller crystallite sizes compared with air-grown fibers and fibers in vivo. Helical secondary cell wall thickenings were exclusively found in submerged fibers. Congo Red is a natural dye that has a high affinity for the biopolymer cellulose. The addition of Congo Red to the culture medium had an influence only on submerged cotton fibers and not on air-grown cotton fibers. When Congo Red was applied in the early primary wall stage, fiber cell elongation was inhibited, but amyloplast production was induced. When Congo Red was applied in late primary wall or early secondary wall stage (about 14-16 DPA), the effects were less severe, but a significant increase in birefringence of secondary cell walls was observed. In both conditions of treatment with Congo Red in the primary wall and the secondary wall stages, a "nodulation" occurred on the wall surface. Neither cellobiohydrolase CBH I or CBH II had affinity for the external wall materials, implying that there was no cellulose present or binding sites for CBH had been occupied by Congo Red. X-ray diffraction data showed that Congo Red decreased the crystallite size of cellulose in submerged cotton fibers. The preliminary investigation with auxin (indole-3-acetic acid) depletion in the culture medium was to study whether or not amyloplasts were produced under this condition. No amyloplasts were observed in submerged fibers grown in the auxindepleted medium, but cellulose microfibrils in the secondary cell wall were greatly disorganized. Possibly, indole-3-acetic acid might play an important role in regulating the arrays of microtubules, which, in turn, may help to organize the patterns of cellulose deposition.Item Wireless power transfer in the classroom(2013-08) O'Dell, David Harrison; Ling, HaoTraditional methods of teaching magnetic induction with lab investigations using a battery, wire and compass are best reserved for demonstration purposes to introduce this particular topic. The modern student who sits in a physics course also lives in a world filled with an increasing number of small portable devices that will eventually be charged wirelessly using some form of magnetic induction. The topic of magnetic induction needs to be placed in the modern context it deserves since the future of transmitting power will eventually be through wireless means. The wireless power transfer kit described in this report is designed to improve student understanding and the application of magnetic induction in an engaging, relevant manner.