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 Degree Discipline: Engineering Technology
Fracture Toughness Testing of Plastics under Various Environmental Conditions

Fracture Toughness Testing of Plastics under Various Environmental Conditions

Date: December 1997
Creator: Velpuri, Seshagirirao V.
Description: The primary objective of this study is to test the applicability to plastics of a fracture toughness testing tool developed for metals. The intent is to study pre-test conditioning of several plastic materials and the effect of the depth of the razor notch cut in the chevron notched fracture toughness test specimens. The study includes the careful preparation of samples followed by conditioning in various environments. Samples were subjected to laboratory air for a specific duration or to a controlled temperature-humidity condition as per the ASTM D1870. Some of the samples were subjected to vacuum conditioning under standard test specifications. Testing was conducted using the conventional three-point bend test as per ASTM D5045-95. ASTM E1304, which sets a standard for short rod and bar testing of metals and ceramics provides some basis for conducting chevron notched four-point bend tests to duplicate the toughness tool. Correlation of these results with the ASTM test samples is determined. The four-point bend test involves less specimen machining as well as time to perform the fracture toughness tests. This study of fracture toughness testing has potential for quality control as well as the fracture property determination.
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Increasing the Dynamic Range of Audio THD Measurements Using a Novel Noise and Distortion Canceling Methodology

Increasing the Dynamic Range of Audio THD Measurements Using a Novel Noise and Distortion Canceling Methodology

Access: Use of this item is restricted to the UNT Community.
Date: May 2003
Creator: Dunipace, Richard Alan
Description: The objective of this study was to determine how a new experimental methodology for measuring Total-Harmonic-Distortion (THD) of operational amplifiers functioned when compared with two standard methodologies, and whether the new methodology offers any improvement in noise floor and dynamic range along with distortion canceling of the sine-wave source used in the testing. The new methodology (THD) is being tested against two standard methodologies: Spectral Analysis using a tuned receiver type Spectrum Analyzer with Notch Filter pre-processing, and a digitized Fast Fourier Transform (FFT) using Notch Filter pre-processing. The THD results appear to agree across all methodologies, and across all items of the sample within all methodologies, to within a percent or less. The distortion and noise canceling feature of the new methodology appeared to function as expected and in accordance with theory. The sample tested in the study consisted of thirty-five NE5534 operational amplifiers produced by Texas Instruments, Inc. and purchased from a local store. The NE5534 is a low-noise, low-distortion, operational amplifier that is widely used in industry and is representative of today's best audio amplifiers.
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Indoor Propagation Modeling at 2.4 GHz for IEEE 802.11 Networks

Indoor Propagation Modeling at 2.4 GHz for IEEE 802.11 Networks

Date: December 2005
Creator: Tummala, Dinesh
Description: Indoor use of wireless systems poses one of the biggest design challenges. It is difficult to predict the propagation of a radio frequency wave in an indoor environment. To assist in deploying the above systems, characterization of the indoor radio propagation channel is essential. The contributions of this work are two-folds. First, in order to build a model, extensive field strength measurements are carried out inside two different buildings. Then, path loss exponents from log-distance path loss model and standard deviations from log-normal shadowing, which statistically describe the path loss models for a different transmitter receiver separations and scenarios, are determined. The purpose of this study is to characterize the indoor channel for 802.11 wireless local area networks at 2.4 GHz frequency. This thesis presents a channel model based on measurements conducted in commonly found scenarios in buildings. These scenarios include closed corridor, open corridor, classroom, and computer lab. Path loss equations are determined using log-distance path loss model and log-normal shadowing. The chi-square test statistic values for each access point are calculated to prove that the observed fading is a normal distribution at 5% significance level. Finally, the propagation models from the two buildings are compared to validate the ...
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Investigation of the feasibility of non-invasive carbon dioxide detection using spectroscopy in the visible spectrum.

Investigation of the feasibility of non-invasive carbon dioxide detection using spectroscopy in the visible spectrum.

Date: December 2007
Creator: Marks, Damian
Description: Pulse oximeters are used in operating rooms and recovery rooms as a monitoring device for oxygen in the respiratory system of the patient. The advantage of pulse oximeters over other methods of oxygen monitoring is that they are easy to use and they are non-invasive, which means it is not necessary break the skin to extract blood for information to be obtained. The standard for the measurement of partial pressure of CO2 and O2 is an arterial blood gas analysis (ABG). However routine monitoring using this method on a continuous basis is impractical since it is slow, painful and invasive. Measuring carbon dioxide is critical to preventing ailments such as carbon dioxide poisoning or hypoxia. The problem is, currently there is no known effective non-invasive method for accurately measuring carbon dioxide in the body to properly assess the adequacy of ventilation. The objective of this study was to experimentally use spectroscopy in the visible spectrum and the principles of operation of a pulse oximeter to incorporate a method of non-invasive real-time carbon dioxide monitoring that is as quick and easy to use.
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Laser Cutting Machine: Justification of initial costs

Laser Cutting Machine: Justification of initial costs

Date: May 2001
Creator: Nagaraja, Dwarakish
Description: The Industrial Laser is firmly established in metalcutting as the tool of choice for many applications. The elevator division of Montgomery KONE Inc., in an effort to move towards quality, ontime, complete deliveries and 100% customer satisfaction, decided to invest in new equipment to improve manufacturing processes. A huge investment is proposed for a laser-cutting machine. It is the responsibility of Manufacturing Engineering to direct the management by justifying its benefits, which includes payback time and financial gains. Factors such as common line cutting, automated material handling system and cutting time were involved in justification of the initial cost of a laser-cutting machine. Comparative statistics on appropriate factors accurately determine and justify the initial cost of a laser-cutting machine.
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Linearity and monotonicity of a 10-bit, 125 MHz, segmented current steering digital to analog converter

Linearity and monotonicity of a 10-bit, 125 MHz, segmented current steering digital to analog converter

Date: May 2000
Creator: Bittle, Charles C.
Description: The purpose of this research is to determine the linearity and monotonicity of the THS5651IDW digital to analog converter (DAC), a prototype of the future Texas Instruments TLV5651, 10-bit, 125 MHz communication DAC. Testing was conducted at the Texas Instruments facility on Forest Lane, Dallas, Texas. Texas Instruments provided test equipment, software and laboratory space to obtain test data. Analysis of the data found the DAC to be monotonic since the magnitude of the differential nonlinearity (DNL) was less than ± 1 least significant bit (LSB) and the integral nonlinearity (INL) was less than ± 0.5 LSB. The study also showed that the DAC has primarily negative DNL although the DNL is well within the desired specification.
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Liquid Nitrogen Propulsion Systems for Automotive Applications: Calculation of Mechanical Efficiency of a Dual, Double-acting Piston Propulsion System

Liquid Nitrogen Propulsion Systems for Automotive Applications: Calculation of Mechanical Efficiency of a Dual, Double-acting Piston Propulsion System

Date: May 2008
Creator: North, Thomas B.
Description: A dual, double-acting propulsion system is analyzed to determine how efficiently it can convert the potential energy available from liquid nitrogen into useful work. The two double-acting pistons (high- and low-pressure) were analyzed by using a Matlab-Simulink computer simulation to determine their respective mechanical efficiencies. The flow circuit for the entire system was analyzed by using flow circuit analysis software to determine pressure losses throughout the system at the required mass flow rates. The results of the piston simulation indicate that the two pistons analyzed are very efficient at transferring energy into useful work. The flow circuit analysis shows that the system can adequately maintain the mass flow rate requirements of the pistons but also identifies components that have a significant impact on the performance of the system. The results of the analysis indicate that the nitrogen propulsion system meets the intended goals of its designers.
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MBE Growth and Instrumentation

MBE Growth and Instrumentation

Date: May 2006
Creator: Tarigopula, Sriteja
Description: This thesis mainly aims at application of principles of engineering technology in the field of molecular beam epitaxy (MBE). MBE is a versatile technique for growing epitaxial thin films of semiconductors and metals by impinging molecular beams of atoms onto a heated substrate under ultra-high vacuum (UHV) conditions. Here, a LabVIEW® (laboratory virtual instrument engineering workbench) software (National Instruments Corp., http://www.ni.com/legal/termsofuse/unitedstates/usH) program is developed that would form the basis of a real-time control system that would transform MBE into a true-production technology. Growth conditions can be monitored in real-time with the help of reflection high energy electron diffraction (RHEED) technique. The period of one RHEED oscillation corresponds exactly to the growth of one monolayer of atoms of the semiconductor material. The PCI-1409 frame grabber card supplied by National Instruments is used in conjunction with the LabVIEW software to capture the RHEED images and capture the intensity of RHEED oscillations. The intensity values are written to a text file and plotted in the form of a graph. A fast Fourier transform of these oscillations gives the growth rate of the epi-wafer being grown. All the data being captured by the LabVIEW program can be saved to file forming a growth pedigree ...
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A model for designing a new telecommunication system in Mongolia

A model for designing a new telecommunication system in Mongolia

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Date: May 2001
Creator: Baatarjav, Enkhbat
Description: The objective of this research is to design, and determine the feasibility of, a telecommunication system for the city of Erdenet, Mongolia. The Mongolian Telecommunication Company, Telecommunication Company of Erdenet city, and the National Statistical Office of Mongolia provided the data required for telecommunication forecasting of Erdenet. The literature review and analysis of the telecommunication forecasting indicate the need for a model of a new Telecommunication system in Erdenet, Mongolia. The model, as indicated, should become a useful example for planning and updating the telecommunication system in Mongolia. The design of a proposed telecommunication network involves the following considerations: analyzing and forecasting telephone traffic, calculating the required number of channels, determining exchange locations, traffic matrix, and establishing a basic hierarchical structure.
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Nodal Resistance Measurement System

Nodal Resistance Measurement System

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Date: May 2005
Creator: Putta, Sunil Kumar
Description: The latest development in the measurement techniques has resulted in fast improvements in the instruments used for measurement of various electrical quantities. A common problem in such instruments is the automation of acquiring, retrieving and controlling the measurements by a computer or a laptop. In this study, nodal resistance measurement (NRM) system is developed to solve the above problem. The purpose of this study is to design and develop a compact electronic board, which measures electrical resistance, and a computer or a laptop controls the board. For the above purpose, surface nodal points are created on the surface of the sample electrically conductive material. The nodal points are connected to the compact electronic board and this board is connected to the computer. The user selects the nodal points, from the computer, between which the NRM system measures the electrical resistance and displays the measured quantity on the computer.
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