by Chung Yiu Cho. / Parallel title in Chinese characters. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1988. / Bibliography: leaves 124-131.

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In modern local area networks, the communication signals sent from one computer to another across the lines of transmission are degraded because of reflection at the receiver. This reflection can be characterized through the impedances of the transmitter and the receiver, and is defined by the Institute of Electrical and Electronic Engineers (IEEE) as the S11 return loss. The specifications for S11 return loss in Gigabit Ethernet are given in terms of magnitude only in the IEEE 802.3 guidelines. This does not fully take into account, however, the effects of frequency dependant impedances within the bandwidth of interest. With a range of 30% error in the category 5, or CAT5, transmission line impedance used in this specification and no further requirements for individual components within the Gigabit Ethernet port, such as the RJ45 magjack or the physical layer, the system can easily be out of tolerance for return loss error. A simple impedance matching circuit could match the CAT5 cable to the physical layer such that the return loss is minimized and the S21 transmission is maximized. The first part of the project was commissioned by Dell Computer to characterize the return loss of all of its platforms. This thesis goes further in the creation of a system that can balance these two impedances so that the IEEE specification failure rate is reduced with the lowest implementation cost, size, power and complexity. The return loss data were used in the second phase of the project as the basis for component ranges needed to balance the impedance seen at the front of the physical layer to the CAT5 transmission line. Using the ladder network theory, an impedance matching circuit was created that significantly reduced the S11 return loss in the passband of the equivalent ladder network. To manage this iterative process, a control loop was also designed. While this system does not produce the accuracy that a programmable finite impulse response (FIR) filter could, it does improve performance with relatively minimal cost, power, area and complexity.

Thesis (M.S.)--California Polytechnic State University, 2009. / Mode of access: Internet. Title from PDF title page; viewed on Jan. 19, 2010. Major professor: Dr. David Clague. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Engineering, Biomedical Concentration." "November 2009." Includes bibliographical references (p. 63-65).

Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains xi, 93 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 92-93).

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In this research, multiwalled carbon nanotube (MWNT) and paper composite materials were fabricated by dropcasting aqueous dispersions containing MWNTs onto filter paper using vacuum filtration, a highly unidirectional drying technique. By varying the pore size of the paper backbone as well as the number of deposited MWNT layers, composites with distinct architectures and properties were created. This thesis provides numerous examples that show how the processing methodology used influences the location of the MWNTs, the amount of MWNTs deposited, and the interaction between the MWNTs and the paper backbone. These three factors work in tandem to form the structures and properties presented. Understanding how the structures and properties come about allows for the tailorability of these composites for different applications and devices. The pore size of the backbone material combined with the directionality of the drying methodology controlled the location of MWNT deposition. MWNT deposition occurred in three ways: on the paper surface only, within the paper material only, or combined surface and internal deposition. By varying the number of deposition steps, the properties of the composite could be altered in the location of deposition. Surface charge, dispersion concentration, paper pore size, drying methodology, MWNT length, the number of deposited MWNT layers, and post-processing techniques were all factors studied in this thesis which could successfully vary the interaction between the MWNTs and between the MWNT and paper materials and, ultimately, alter the properties of the composite. Regardless of the processing methodology employed and the starting materials used, structure and property evolutions in the composite materials were characterized using impedance spectroscopy, optical microscopy, scanning electron microscopy, and Current-AFM. Combining equivalent circuit fitting of the impedance data with the information obtained from the imaging techniques allowed for the elucidation of structural mechanisms which contribute to the electronic response measured for each composite. An overall equivalent circuit was built for each composite plane which could then be used to extract the electrical properties of the individual conduction mechanisms within the composite. In the in-plane, the electrical properties of the paper backbone, MWNT-MWNT junctions, MWNT bundles, and MWNT curved bundles could be determined. In the thru-plane, the electrical properties within the paper thickness, either paper-dominated or MWNT-dominated, could be measured. The resistance through the thickness of a bulk MWNT surface network could be also measured when the density of the MWNT network is sufficiently high.

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Electrical impedance tomography is an imaging method with applications to geophysics and medical imaging. A new approximation is presented based on Nachman's 2-dimensional construction for closed domains. It improves upon existing approximations by extending the range of application from resolving 2 times the surface conductivity to imaging perfect conductors and insulators. With perfect knowledge of boundary data, this approximation exactly resolves a single conductive disc embedded in a homogenous domain. The problem, however, is ill-posed, and imaging performance degrades quickly as the distance from the boundary increases. The key to the approximation lies in (a) approximating Fadeev's Green's function (b) pre-processing measured voltages based on a boundary-integral equation (c) solving a linearized inverse problem (d) solving a d-bar equation, and (e) scaling the resulting image based on analytical results for a disc. In the development of the approximation, a new formula for Fadeev's Green's function is presented in terms of the Exponential Integral function. Also, new comparisons are made between reconstructions with and without solving the d-bar equation, showing that the added computational expense of solving the d-bar equation is not justified for radial problems. There is no discernible improvement in image quality. As a result, the approximation converts the inverse conductivity problem into a novel one-step linear problem with pre-conditioning of boundary data and scaling of the resulting image. Several extensions to this work are possible. The approximation is implemented for a circular domain with unit conductivity near the boundary, and extensions to other domains, bounded and unbounded should be possible, with non-constant conductivity near the boundary requiring further approximation. Ultimately, further research is required to ascertain whether it is possible to extend these techniques to imaging problems in three dimensions.

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