You limited your search to:

  Partner: UNT Libraries
 Department: Department of Engineering Technology
 Collection: UNT Theses and Dissertations
Dynamic Behaviors of Historical Wrought Iron Truss Bridges – a Field Testing Case Study

Dynamic Behaviors of Historical Wrought Iron Truss Bridges – a Field Testing Case Study

Access: Use of this item is restricted to the UNT Community.
Date: December 2015
Creator: Hedric, Andrew C.
Description: Civil infrastructure throughout the world serves as main arteries for commerce and transportation, commonly forming the backbone of many societies. Bridges have been and remain a crucial part of the success of these civil networks. However, the crucial elements have been built over centuries and have been subject to generations of use. Many current bridges have outlived their intended service life or have been retrofitted to carry additional loads over their original design. A large number of these historic bridges are still in everyday use and their condition needs to be monitored for public safety. Transportation infrastructure authorities have implemented various inspection and management programs throughout the world, mainly visual inspections. However, careful visual inspections can provide valuable information but it has limitations in that it provides no actual stress-strain information to determine structural soundness. Structural Health Monitoring (SHM) has been a growing area of research as officials need to asses and triage the aging infrastructure with methods that provide measurable response information to determine the health of the structure. A rapid improvement in technology has allowed researchers to start using new sensors and algorithms to understand the structural parameters of tested structures due to known and unknown loading scenarios. ...
Contributing Partner: UNT Libraries
Impact of Green Design and Technology on Building Environment

Impact of Green Design and Technology on Building Environment

Date: December 2015
Creator: Xiong, Liang
Description: Currently, the public has a strong sense of the need for environment protection and the use of sustainable, or “green,” design in buildings and other civil structures. Since green design elements and technologies are different from traditional design, they probably have impacts on the building environment, such as vibration, lighting, noise, temperature, relative humidity, and overall comfort. Determining these impacts of green design on building environments is the primary objective of this study. The Zero Energy Research (ZOE) laboratory, located at the University of North Texas Discovery Park, is analyzed as a case study. Because the ZOE lab is a building that combines various green design elements and energy efficient technologies, such as solar panels, a geothermal heating system, and wind turbines, it provides an ideal case to study. Through field measurements and a questionnaire survey of regular occupants of the ZOE lab, this thesis analyzed and reported: 1) whether green design elements changed the building’s ability to meet common building environmental standards, 2) whether green design elements assisted in Leadership in Energy and Environmental Design (LEED) scoring, and 3) whether green design elements decreased the subjective comfort level of the occupants.
Contributing Partner: UNT Libraries
Comparative Analysis and Implementation of High Data Rate Wireless Sensor Network Simulation Frameworks

Comparative Analysis and Implementation of High Data Rate Wireless Sensor Network Simulation Frameworks

Date: December 2015
Creator: Laguduva Rajaram, Madhupreetha
Description: This thesis focuses on developing a high data rate wireless sensor network framework that could be integrated with hardware prototypes to monitor structural health of buildings. In order to better understand the wireless sensor network architecture and its consideration in structural health monitoring, a detailed literature review on wireless sensor networks has been carried out. Through research, it was found that there are numerous simulation software packages available for wireless sensor network simulation. One suitable software was selected for modelling the framework. Research showed that Matlab/Simulink was the most suitable environment, and as a result, a wireless sensor network framework was designed in Matlab/Simulink. Further, the thesis illustrates modeling of a simple accelerometer sensor, such as those used in wireless sensor networks in Matlab/Simulink using a mathematical description. Finally, the framework operation is demonstrated with 10 nodes, and data integrity is analyzed with cyclic redundancy check and transmission error rate calculations.
Contributing Partner: UNT Libraries
Spray Cooling with Hfc-134a and Hfo-1234yf for Thermal Management of Automotive Power Electronics

Spray Cooling with Hfc-134a and Hfo-1234yf for Thermal Management of Automotive Power Electronics

Date: December 2015
Creator: Yaddanapudi, Satvik Janardhan
Description: This study aims to experimentally investigate the spray cooling characteristics for active two-phase cooling of automotive power electronics. Tests are conducted on a small-scale, closed loop spray cooling system featuring a pressure atomized spray nozzle. Two types of refrigerants, HFC-134a (R-134a) and HFO-1234yf, are selected as the working fluids. The test section (heater), made out of oxygen-free copper, has a 1-cm2 plain, smooth surface prepared following a consistent procedure, and would serve as a baseline case. Matching size thick film resistors, attached onto the copper heaters, generate heat and simulate high heat flux power electronics devices. The tests are conducted by controlling the heat flux in increasing steps, and recording the corresponding steady-state temperatures to obtain cooling curves. The working fluid is kept at room temperature level (22oC). Performance comparisons are made based on heat transfer coefficient (HTC) and critical heat flux (CHF) values. Effects of spray characteristics and liquid flow rates on the cooling performance are investigated with the selected coolants. Three types of commercially available nozzles that generate full-cone sprays with fine droplets are utilized in the tests. Effect of liquid flow rate is evaluated varying flow rates at 2, 3, 4 ml/s. The experimental results obtained from ...
Contributing Partner: UNT Libraries
Control and Automation of a Heat Shrink Tubing Process

Control and Automation of a Heat Shrink Tubing Process

Access: Use of this item is restricted to the UNT Community.
Date: August 2014
Creator: Yousefi Darani, Shahrokh
Description: Heat shrink tubing is used to insulate wire conductors, protect wires, and to create cable entry seals in wire harnessing industries. Performing this sensitive process manually is time consuming, the results are strongly dependent on the operator’s expertise, and the process presents safety concerns. Alternatively, automating the process minimizes the operators’ direct interaction, decreases the production cost over the long term, and improves quantitative and qualitative production indicators dramatically. This thesis introduces the automation of a heat shrink tubing prototype machine that benefits the wire harnessing industry. The prototype consists of an instrumented heat chamber on a linear positioning system, and is fitted with two heat guns. The chamber design allows for the directing of hot air from the heat guns onto the wire harness uniformly through radially-distributed channels. The linear positioning system is designed to move the heat chamber along the wire harness as the proper shrinkage temperature level is reached. Heat exposure time as a major factor in the heat shrink tubing process can be governed by controlling the linear speed of the heat chamber. A control unit manages the actuator position continuously by measuring the chamber’s speed and temperature. A model-based design approach is followed to design ...
Contributing Partner: UNT Libraries
The Use of Optical Metrology in Active Positioning of a Lens

The Use of Optical Metrology in Active Positioning of a Lens

Date: August 2014
Creator: Ji, Zheng
Description: Precisely positioned optical lenses are currently required for many highly repetitive mechanics and applications. Thus the need for micron-scale repetition between opto-mechanical units is evident, especially in industrial manufacturing and medical breakthroughs. In this thesis, a novel optical metrology system is proposed, designed, and built whose purpose is to precisely locate the center of a mechanical fixture and then to assemble a plano-convex optical lens into the located position of the fixture. Center location specifications up to ±3 µm decenter and ±0.001° tilting accuracy are required. Nine precisely positioned lenses and fixtures were built with eight units passing the requirements with a repetitive standard deviation of ±0.15 µm or less. The assembled units show satisfactory results.
Contributing Partner: UNT Libraries
Analytical Model for Lateral Deflection in Cold-formed Steel Framed Shear Walls with Steel Sheathing

Analytical Model for Lateral Deflection in Cold-formed Steel Framed Shear Walls with Steel Sheathing

Date: December 2014
Creator: Yousof, Mohamad
Description: An analytical model for lateral deflection in cold-formed steel shear walls sheathed with steel is developed in this research. The model is based on the four factors: fastener displacement, steel sheet deformation, and hold-down deformation, which are from the effective strip concept and a complexity factor, which accounts for the additional influential factors not considered in the previous three terms. The model uses design equations based on the actual material and mechanical properties of the shear wall. Furthermore, the model accounts for aggressive and conservative designers by predicting deflection at different shear strength degrees.
Contributing Partner: UNT Libraries
Direct Immersion Cooling Via Nucleate Boiling of Hfe-7100 Dielectric Liquid on Hydrophobic and Hydrophilic Surfaces

Direct Immersion Cooling Via Nucleate Boiling of Hfe-7100 Dielectric Liquid on Hydrophobic and Hydrophilic Surfaces

Date: December 2014
Creator: Joshua, Nihal E
Description: This study experimentally investigated the effect of hydrophobic and hydrophilic surfaces characteristics on nucleate boiling heat transfer performance for the application of direct immersion cooling of electronics. A dielectric liquid, HFE – 7100 was used as the working fluid in the saturated boiling tests. Twelve types of 1-cm2 copper heater samples, simulating high heat flux components, featured reference smooth copper surface, fully and patterned hydrophobic surface and fully and patterned hydrophilic surfaces. Hydrophobic samples were prepared by applying a thin Teflon coating following photolithography techniques, while the hydrophilic TiO2 thin films were made through a two step approach involving layer by layer self assembly and liquid phase deposition processes. Patterned surfaces had circular dots with sizes between 40 – 250 μm. Based on additional data, both hydrophobic and hydrophilic surfaces improved nucleate boiling performance that is evaluated in terms of boiling incipience, heat transfer coefficient and critical heat flux (CHF) level. The best results, considering the smooth copper surface as the reference, were achieved by the surfaces that have a mixture of hydrophobic/hydrophilic coatings, providing: (a) early transition to boiling regime and with eliminated temperature overshoot phenomena at boiling incipience, (b) up to 58.5% higher heat transfer coefficients, and (c) ...
Contributing Partner: UNT Libraries
The Measurement of the Third-order Elastic Constants for La3ga5sio14 (Lgs) and La3ga55ta05o14 (Lgt) Single Crystal

The Measurement of the Third-order Elastic Constants for La3ga5sio14 (Lgs) and La3ga55ta05o14 (Lgt) Single Crystal

Date: December 2013
Creator: Karim, Md Afzalul
Description: Recently, the development of electronic technology towards higher frequencies and larger band widths has led to interest in finding new piezoelectric materials, which could be used to make filters with larger pass band widths and oscillators with better frequency stability. Langasite (La3Ga5SiO14, LGS) and its isomorphs have enticed considerable attention of researchers as a potential substrate material for piezoelectric device applications because of its high frequency stability and fairly good electromechanical coupling factors for acoustic wave devices. Nonlinear effect including drive level dependence, mode coupling, force-frequency effect and electroelasic effect are critical for the design of these devices. Third-order elastic constants (TOEC) play an important role in a quantitative analysis of these nonlinear effects. In particular these elastic constants are of great importance when the BAW (Bulk Acoustic Wave) and SAW (Surface Acoustic Wave) sensors of force, acceleration and so on are designed. Until now Langasite (LGS) and Langatate (LGT) crystal resonators have been qualified in terms of quality factor, temperature effect, isochronism defect and material quality. One of the most important advantages of those crystals is that they will not undergo phase transitions up to its melting temperature of 1450°. Presently there is no data on TOEC of LGT ...
Contributing Partner: UNT Libraries
Energy Harvesting Wireless Piezoelectric Resonant Force Sensor

Energy Harvesting Wireless Piezoelectric Resonant Force Sensor

Date: December 2013
Creator: Ahmadi, Mehdi
Description: The piezoelectric energy harvester has become a new powering option for some low-power electronic devices such as MEMS (Micro Electrical Mechanical System) sensors. Piezoelectric materials can collect the ambient vibrations energy and convert it to electrical energy. This thesis is intended to demonstrate the behavior of a piezoelectric energy harvester system at elevated temperature from room temperature up to 82°C, and compares the system’s performance using different piezoelectric materials. The systems are structured with a Lead Magnesium Niobate-Lead Titanate (PMN-PT) single crystal patch bonded to an aluminum cantilever beam, Lead Indium Niobate-Lead Magnesium Niobate-Lead Titanate (PIN-PMN-PT) single crystal patch bonded to an aluminum cantilever beam and a bimorph cantilever beam which is made of Lead Zirconate Titanate (PZT). The results of this experimental study show the effects of the temperature on the operation frequency and output power of the piezoelectric energy harvesting system. The harvested electrical energy has been stored in storage circuits including a battery. Then, the stored energy has been used to power up the other part of the system, a wireless resonator force sensor, which uses frequency conversion techniques to convert the sensor’s ultrasonic signal to a microwave signal in order to transmit the signal wirelessly.
Contributing Partner: UNT Libraries
FIRST PREV 1 2 3 4 5 NEXT LAST