Master of Science

thesisAs unattended, remote controlled, and self-driving aerial and ground vehicles become increasingly prevalent, the need for real-time structural health monitoring (SHM) systems that can sense, localize, and quantify internal structural damage with low latency, low power, and small size and weight requirements, is increasing. One such methodology, electrical impedance tomography (EIT), shows promising results, but is limited in its scalability and portability due to lack of hardware support outside of expensive and bulky laboratory-grade equipment. In this master's thesis, a data acquisition system of low cost and small form factor is designed and prototyped to rapidly and efficiently collect EIT measurements for SHM applications. System scalability is abstracted to small data acquisition modules that communicate to a host computer via a USB connection. Fitting the palm of your hand, and at a cost of only 250 USD, each module is capable of collecting EIT data at a rate of 10,000 voltage measurements per second with 10-bit resolution. This study describes the design process that attempts to achieve the desired data collection rate, transfer speed, and size requirements for this application using only readily available commercial off-the-shelf electronic components. The performance, precision, accuracy, and EIT reconstruction results of the designed EIT measurement system are characterized and compared to a laboratory-grade EIT data acquisition system

Mathematical Models for Natural Gas Forecasting

It is vital for natural gas Local Distribution Companies (LDCs) to forecast their customers\u27 natural gas demand accurately. A significant error on a single very cold day can cost the customers of the LDC millions of dollars. This paper looks at the financial implication of forecasting natural gas, the nature of natural gas forecasting, the factors that impact natural gas consumption, and describes a survey of mathematical techniques and practices used to model natural gas demand. Many of the techniques used in this paper currently are implemented in a software GasDayTM, which is currently used by 24 LDCs throughout the United States, forecasting about 20% of the total U.S. residential, commercial, and industrial consumption. Results of GasDay\u27sTM forecasting performance also is presented

A comparison of spectral analysis and adaptive exponential smoothin forecasting models

Two basically different approaches to forecasting, spectral analysis and adaptive exponential smoothing, are compared by measuring squared error of forecasts on controlled computer-generated time series

Application of Probabilistic Methods to Assess Risk Due to Resonance in the Design of J-2X Rocket Engine Turbine Blades

The LOX-Hydrogen J-2X Rocket Engine, which is proposed for use as an upper-stage engine for numerous earth-to-orbit and heavy lift launch vehicle architectures, is presently in the design phase and will move shortly to the initial development test phase. Analysis of the design has revealed numerous potential resonance issues with hardware in the turbomachinery turbine-side flow-path. The analysis of the fuel pump turbine blades requires particular care because resonant failure of the blades, which are rotating in excess of 30,000 revolutions/minutes (RPM), could be catastrophic for the engine and the entire launch vehicle. This paper describes a series of probabilistic analyses performed to assess the risk of failure of the turbine blades due to resonant vibration during past and present test series. Some significant results are that the probability of failure during a single complete engine hot-fire test is low (~1%) because of the small likelihood of resonance, but that the probability increases to around 30% for a more focused turbomachinery-only test because all speeds will be ramped through and there is a greater likelihood of dwelling at more speeds. These risk calculations have been invaluable for use by program management in deciding if risk-reduction methods such as dampers are necessary immediately or if the test can be performed before the risk-reduction hardware is ready