Theses and Dissertations
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PublicationHardware and software design for the control of a new scanning pulsed eddy-current system( 2000)A new Scanning Pulsed Eddy-current (SPEC) system is designed and developed. The work involves designing software and algorithms to interface with and acquire data from the new PEC hardware. The project is based on an old SPEC instrument developed at the Center for NDE. In the new SPEC system, a current-driven circuit instead of the voltage-driven is used. The form of the coil current can be accurately controlled by the adjusting the input of the current driven circuit. The new hardware architecture is based on Peripheral Component Interconnection (PCI) buses to take the advantage of the new technologies of personal computers. PCI-PCI bridges and MXI-3 technologies are introduced to the new instrument for lowering the overall developing time while obtaining reliable performance. National Instruments[Superscript TM] PXI-1010 chassis is employed to host the PXI subsystem and the SCXI subsystem of the new SPEC instrument. The graphical user interface (GUI) is reengineered from the legacy code of the old SPEC software's GUI classes. The compiler has been upgraded and the legacy GUI classes are modulized into different Dynamic Linked Libraries (DLLs). The new software abandons all the 16-bit device drivers of the old SPEC software. 32-bit device drivers have been written to meet the specifications of the three PXI boards - data acquisition, digital I/O and motion controller. The exported functions and some internal functions for the three device drivers are described to show how the software exerts control to the hardware and how to coordinate them to make the whole system work well. Two important hardware control methods for the programming are used. They are callback functions and polling. Some signal processing algorithms such as the temperature compensation for the Hall-device probe has been derived and implemented. The comparison of the A-scan waveforms and C-scan images shows the effectiveness of the algorithm.
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PublicationUltrasonic NDE signal classification on steam generator tubes( 2000)This thesis presents a method for discriminating two different types of ultrasonic defect signals (cracks and deposits) collected from steam generator tubing using pulse-echo reflection techniques. The proposed method uses various signal processing and image processing techniques, such as the fast Fourier transform, deconvolution, the wavelet transform and binary morphology, to extract features from ultrasonic signals. Then several pattern recognition techniques, such as the K-mean clustering algorithm, univariate decision tree, oblique tree, and feed-forward back-propagation neural network are used to classify the flaws. Training and testing with these features results in improved performance in comparison with previous research projects concerning this data. In the feature extraction steps, a Wiener filter was used to get the impulse response of the defects. Then features from the time and frequency domains were extracted. A 1-D wavelet transform was also used to get multi-resolution representation of A-scans. Features from different decomposition levels were extracted. Image processing and binary morphology were also used to get features from 2-D images of defects. Useful features such as image area and image moments were extracted. An oblique tree and a feed-forward back-propagation neural network were shown to perform well in this project. Based on the features we obtained thus far, a feed-forward back-propagation neural network gives the best performance.
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PublicationGenetic and molecular analysis of Draf conserved regions in Drosophila early development( 2000)This work studied the role of Draf, a serine/threonine kinase, in two RTK pathways in Drosophila: DER, which establishes dorsal ventral polarity in both the eggshell and the embryo (Brand and Perrimon, 1994), and Torso, which patterns the terminal structures (Ambrosio, 1989a). Different regions of Draf were overexpressed under a heat shock promoter in a maternal background with one-half the normal dose of Draf and the effects on DER and Torso signaling were studied by examining the eggshell phenotype, hatching rate, and embryonic phenotype. It was found that overexpression of CR2 led to increased Draf activity, probably by binding to a negative regulator and thus releasing Draf from negative regulation. Overexpression of CR3K497M, K497M and CR1 led to a decrease in Draf activity. These three modules possibly bound to a positive regulator thus depriving endogenous wild type Draf from interaction, or they may participate in the formation of dead dimers/oligomers or dead protein complex, thus blocking the activation of wild type Draf. It was also found that Draf was more active in a background with one-half dose of wild type Draf than in a normal dose (2 copies) Draf background. The competition model is a possible model presented to explain this observation. The yeast two-hybrid screen identified Arf-like as a possible candidate protein for interacting with Draf and regulating its activity. Arf-like is a member of the small GTP-binding protein (SGBP) family which can bind and hydrolyze GTP. Mutant Arf-like is recessively lethal, indicating it is an essential gene in Drosophila (Tamkun et al. 1991). Our germline clone experiments showed that Arf-like is a possible negative regulator of the Torso RTK pathway (unpublished data). To find out more about this novel factor, Arf-like was subcloned into the plasmid pGEM7G3GLO to be transcribed in vitro. The transcribed mRNA then can be injected into the Drosophila early embryo and the effect of injected Arf-like on RTK signaling pathways can be analyzed.
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PublicationSynthesis and free radical polymerization of amino-functionalized diene derivatives( 2000)This thesis describes the synthesis of a series of amino-functionalized diene-based monomers, to produce and modify functional polymer materials. Because of the close relationship of structure and property, it was anticipated that the amino-functionalized diene-based monomers can be used potentially as a third comonomer in modifying existing materials (such as SBR or NBR) or the resulting polymers can be used as additives to make polymer blends with high compatibility. The homopolymers of 2-[(N,N-dialkylamino)methyl]-1,3-butadienes with methyl, ethyl and n-propyl substituents were synthesized via bulk free radical polymerization. For each monomer, the effects of polymerization initiator, initiator concentration and reaction temperature on the final polymer structure, molecular weight and glass transition temperature were examined. Homopolymers of 2-[(N-benzyl-N-methylamino)methyl]-1,3-butadiene (BMAMBD) were successfully made through bulk, solution and emulsion free radical polymerizations. Copolymers of BMAMBD with styrene were synthesized and fully characterized by 1H NMR, 13C NMR, GPC, DSC and TGA.
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PublicationEnhancing electricity auction mechanism with FACTS devices( 2000)In the U.S., the electrical industry has consisted of state-regulated vertically integrated monopolies for a long time. The results of monopolistic operation are high electricity price and low output level, which brings deadweight loss to the social welfare. In order to eliminate the deadweight and achieve high efficiency, the restructuring, i.e., deregulation, is an inevitable trend in the electrical industry. In the deregulated electric power market, auction is demonstrated to be an effective way to achieve the Pareto optimality. The auction scheme in this work is double-sided SPCA (single period commodity auction). The auction problem is formulated in a linear form and can be solved by LP (linear programming). Recent advances in the power electronics field bring the FACTS (flexible AC transmission system) devices and HVDC (high voltage DC) transmission to the power system. These devices are the power electronics based fast switching power flow controller. They have the ability to enhance the system controllability, capacity and stability. This work constructs linearized models for UPFC (unified power flow controller) and two-terminal HVDC link. This model can be easily incorporated into the SPCA formulation without losing much accuracy. The control parameters of FACTS devices and HVDC link are introduced to the formulation as new state variables. The test result shows the power flow solution with UPFC can converge in four to six iterations. The using of UPFC can enhance the trading surplus in the power auction market. This work also introduces a LP algorithm to solve the power auction problem with contingency. The expected remedial action cost (ERAC) for the contingencies cannot be known before getting the result of power auction. Thus, the ERAC cannot be formulated explicitly in the objective function of the power auction problem. The LP algorithm solves an optimal remedial action sub-problem after each LP iteration of the power auction problem. The ERAC is returned from the sub-problem and used to update the reduced cost coefficients (RCCs) in the main problem. The simplex pivot maybe changed after this updating. Thus, the global optimality of the power auction problem with the consideration of contingency can be gotten using this algorithm.