The primary objective of this research was to investigate the feasibility of calibrating ultrasound scanners to measure surface impedance from reflection data. The method proposed uses calibration curves from known impedance interfaces. This plot, or calibration curve, may then be used, with interpolation, to relate measured grey level to impedance for the characterization of tissue specimens with unknown properties. This approach can be used independent of different medical ultrasound scanner systems to solve for reproducible tissue impedance values without offline data processing and complicated custom electronics. <p>Two medical ultrasound machines from different manufacturers were used in the experiment; a 30 MHz and a 7.5 MHz machine. The calibration curves for each machine were produced by imaging the interfaces of a vegetable oil floating over varying salt solutions. <p>To test the method, porcine liver, kidney, and spleen acoustical impedances were determined by relating measured grey levels to reflection coefficients using calibration curves and then inverting the reflection coefficients to obtain impedance values. The 30 MHz ultrasound machines calculated tissue impedances for liver, kidney, and spleen were 1.476 ± 0.020, 1.486 ± 0.020, 1.471 ± 0.020 MRayles respectively. The 7.5 MHz machines tissue impedances were 1.467 ± 0.088, 1.507 ± 0.088, and 1.457 ± 0.088 MRayles respectively for liver, kidney and spleen. The differences between the two machines are 0.61%, 1.41%, and 0.95% for the impedance of liver, kidney, and spleen tissue, respectively. If the grey level is solely used to characterize the tissue, then the differences are 45.9%, 40.3%, and 39.1% for liver, kidney, and spleen between the two machines. The results support the hypothesis that tissue impedance can be determined using calibration curves and be consistent between multiple machines.

As modern power systems operate closer to the limits due to load growth and financial imperatives, voltage stability becomes a more important issue and there have been more incidents caused by voltage collapse. For example, there have been 11 outages affecting more than 4000MW between 1984 and 2000 in North America [1]. In power systems, load voltages decrease as the supplied loads increase until the maximum power transfer point is reached. The voltage will collapse if the load is increased above this limit. Therefore, it is important to monitor the loadability of a system to avoid voltage collapse. The loadability of a system can be calculated when the Thevenin impedance is available as the maximum power transfer occurs when the Thevenin impedance and the load impedance are the same in magnitude. This thesis suggests a method to estimate the Thevenin impedance of a system. ABB corporation suggests the Voltage Stability Predictor (VIP) method to estimate the Thevenin impedance, but there are problems with this method and it is not gaining popularity in industry. In this thesis, a method is suggested to estimate the Thevenin impedance by taking advantage of the existance of negative sequence components in the system. The concept of this method has been proved mathematically. Simulations were performed on simple systems and on the modified IEEE 13 bus power flow test case to verify the feasibility of the method and the results are promising. Then, the method was verified with field measurements for a 25kV substation. The voltages and currents were analyzed to estimate the Thevenin equivalent impedance of the power system and the results were compared with the design Thevenin equivalent impedance. The result confirms the viability of the method as the estimated Thevenin impedance matched the design value.

The primary objective of this research was to investigate the feasibility of calibrating ultrasound scanners to measure surface impedance from reflection data. The method proposed uses calibration curves from known impedance interfaces. This plot, or calibration curve, may then be used, with interpolation, to relate measured grey level to impedance for the characterization of tissue specimens with unknown properties. This approach can be used independent of different medical ultrasound scanner systems to solve for reproducible tissue impedance values without offline data processing and complicated custom electronics. <p>Two medical ultrasound machines from different manufacturers were used in the experiment; a 30 MHz and a 7.5 MHz machine. The calibration curves for each machine were produced by imaging the interfaces of a vegetable oil floating over varying salt solutions. <p>To test the method, porcine liver, kidney, and spleen acoustical impedances were determined by relating measured grey levels to reflection coefficients using calibration curves and then inverting the reflection coefficients to obtain impedance values. The 30 MHz ultrasound machines calculated tissue impedances for liver, kidney, and spleen were 1.476 ± 0.020, 1.486 ± 0.020, 1.471 ± 0.020 MRayles respectively. The 7.5 MHz machines tissue impedances were 1.467 ± 0.088, 1.507 ± 0.088, and 1.457 ± 0.088 MRayles respectively for liver, kidney and spleen. The differences between the two machines are 0.61%, 1.41%, and 0.95% for the impedance of liver, kidney, and spleen tissue, respectively. If the grey level is solely used to characterize the tissue, then the differences are 45.9%, 40.3%, and 39.1% for liver, kidney, and spleen between the two machines. The results support the hypothesis that tissue impedance can be determined using calibration curves and be consistent between multiple machines.

A micro-electrophysiological analysis system (-EPAS) using various microfabrication techniques for single cell study was developed. Conventional microfabrication techniques combined with plastic and polymer microfabrication techniques have been used to realize the system. The system is capable of performing patch clamp recording and whole cell electrical impedance spectroscopy (EIS) on a single cell. Methodologies for single cell manipulation were developed. The ion channel activities of primary cultured bovine chromaffin cells were measured in both the patch clamping mode and the whole cell EIS mode. Membrane capacitance of the chromaffin cell was calculated from these measurements. Increases in the capacitances were observed when certain ion channels were blocked using toxins. The dielectric properties of human breast cancer cell lines from different pathological stages were measured and compared to a normal human breast cell line in the whole cell EIS mode. The measured properties were correlated to the pathological stages of the breast cancer cell lines. Decreases in the membrane capacitances were observed for the more pathologically progressed cancer cell lines.

As variation in pork tenderness has increased, identification of tenderness has become an industry need. This study consisted of 1208 pork loins randomly selected to test the efficacy of four automated grading techniques. Visible and near-infrared spectroscopy (VVNIR) (350-1830 nm wavelengths), bioelectrical impedance (EI) (resistance, reactance, phase angle, and partial capacitance), pH, and CIE L*, a* and b* color space values were used to predict chemical moisture and lipid, pH, Warner-Bratzler shear force (WBSF), and Slice shear force (SSF) on 13 d aged pork loins. The means and standard deviations for WBSF were (22.95 and 5.16) and SSF were (165.49 and 58.15). Prediction was based on stepwise linear regression and partial least squares regression. VNIR, pH, and color, when in combination, had the highest R^2 (0.19 and 0.21) for the prediction of WBSF and SSF, respectively. Partial least squares regression (PLSR) was used to remove autocorrelation between VNIR values. By using PLSR, with an R ^2 value of 0.49, 100 percent of the "tender" chops were correctly classified, 93 percent of the "intermediate" chops were correctly classified, and 92 percent of the "tough" chops were correctly classified into its category for WBSF. However, SSF was much lower (R^2 = 0.24) with only correctly placing 62 percent of the "tender" chops and only 48 percent of the "intermediate" and "tough" chops. Electrical impedance, alone or in combination with other technologies, either did not improve predictability of linear regression equations (increase R^2) or of PLSR models (increase R^2). Equations and models that included EI values had low R^2. When adding EI to the regression equation involving all variables, R^2 increased slightly from 0.19 to 0.21 in predicting WBSF, and from 0.21 to 0.25 for SSF. When pH or CIE L* color space values were included in linear regression or PLSR models to predict WBSF and SSF, R^2 values increased from 0.14 to 0.19 for WBSF, and 0.14 to 0.21 for SSF. pH played a large role in predicting WBSF and SSF, along with CIE L*. Thus, for an on-line situation, use of VNIR, pH, and color could be used to predict tenderness. Utilization of VNIR alone could be effective in predicting pork tenderness (WBSF). Using EI alone, or in combination with VNIR, would not provide acceptable prediction of WBSF or SSF. Use of VNIR with pH and color would improve the ability to predict tender and intermediate pork WBSF and SSF, but the additional improvement in accuracy may not be warranted based on the cost and additional time needed when using more than one technology.

Thin-film theorems are well developed and so are the fabrication processes. Yet under some special conditions, traditional methods (such as the ABCD matrix and the transmission matrix methods) will lead to a serious numerical error. In this thesis, we propose a new method called Couple E/H field formulation, which will overcome this numerical problem in simulating characteristics of complex multi-layered structures. We have verified both the algorithm and its results with the traditional techniques. By extending the impedance matching principle, we came out with a multi-layer anti-reflection coating design optimized for a time-harmonic plane wave incidence with any incident angle. Such a design allows for more plane waves with adjacent angles to pass through the coating layers with minimal reflection. Furthermore, we apply this AR coating design to facets of semiconductor lasers. Our calculation shows that multi-layer coating does a better job than a single layer coating. The reflectivity of a laser diode from single layer coating 0.085% to 5 layer coating 0.056%, which is a 33% improvement.

In this thesis, the design rule of the tag antenna and the properties of the high impedance surface structure are studied. We proceed to design the low profile and miniature high impedance surface structure. In order to be more competitive, we use PCB plates for fabrication to reduce the cost. The tags are intended to be placed inside two shorted metallic plates. In order to reduce the effect of the two parallel metallic plates, we use the slots to design the tag antenna. The EBG structure behaves as a high impedance surface and suppresses the surface wave. We add the EBG structure on the back of the antenna to reduce the back metallic effect. We use slot structure to design the non-planar RFID reader antenna that can be placed inside the three metallic plates to read the data. For the slot structure design, the electric field between the slots is perpendicular to the upper and lower metallic plates. According to the image theory, the induced image current will result in constructive effect to reduce the metallic effect. Finally, the hand-held RFID reader may not identify the RFID tag as the RFID tag placed at position deeper inside. The proposed non-planar reader can solve this problem to be used for more applications.

This dissertation describes a new electrochemical synthesis of novel composite materials based on montmorillonite (MMT) clay and intrinsically conducting polyaniline (PANI). PANI was successfully incorporated into MMT galleries to form PANI−MMT nanocomposites. Electropolymerization of anilinium ions which are intercalated inside the clay layers have been carried out at a constant applied potential. The synthetic conditions have been optimized taking into account the effect of concentration of aniline, magnetic stirring and potential cycling. The resulting organic-inorganic hybrid material, PANI-MMT has been characterized by various physicochemical techniques. Results of elemental analysis show that nanocomposite contains only 10 % of conducting PANI. Formation of PANI inside the clay tactoid has been confirmed by the expansion of inter layer distance of MMT as revealed by X-ray diffraction studies. Relatively lower interlayer expansion for PANI-MMT than that of anilinium-MMT indicates the higher stereoregularity in PANI-MMT which has strong influence on electrical properties of nanocomposites. Infrared spectroscopy studies reveal the presence of physicochemical interaction, probably hydrogen bonding, between clay and polyaniline. Cyclic voltammetry studies indicate that presence of electroinactive clay does not influence the electrochemical activity of PANI. Electrochromic behaviour of PANI-MMT nanocomposites have been studied using in situ UV-Vis spectroscopy which reveals that electrochromism of PANI in the composite material has been retained. One of the main technological applications of conducting polymers, particularly PANI, is in the area of corrosion protection of active metals. PANI-MMT nanocomposites synthesized using the present method and a chemically synthesized PANI which is soluble in organic solvents have been used to protect C45 steel surface against corrosion. Corrosion studies have been performed using electrochemical impedance measurements(EIM)and anodic polarization studies. Electrochemical impedance data has been analyzed using a suitable equivalent circuit. Corrosion protection of steel offered by both PANI-MMT and organically soluble PANI is evident form the increase in the value of charge transfer resistance of the coated steel surfaces. Time dependent EIM measurements reveal that charge transfer resistance gradually decreases with time, however, the values are much higher than that of uncoated surfaces. Two capacitive loops, one at higher and another at lower frequencies, observed in the Nyquist plots have been assigned to the electrical properties of coating material (in the present case, PANI-MMT or soluble PANI) and electrochemical process at the interface, respectively. An anodic shift in the corrosion potential, a decrease in the corrosion rate and a significant increase in the polarization resistance indicate a significant anti-corrosion performance of both PANI-MMT nanocomposite and organically soluble PANI deposited on the protected steel surface. / Diese Dissertation beschreibt eine neue elektrochemische Synthese neuartiger Compositmaterialien basierend auf dem Tonmineral Montmorillonite (MMT) und intrinsisch leitfähigem Polyanilin (PANI). Die Elektropolymerisation von Aniliniumionen, welche in die Tonmineralschichten eingebaut sind, wurde bei einem konstanten Potenzial durchgeführt. Das resultierende organisch-anorganische Hybridmaterial PANI-MMT wurde mit verschiedenen physikochemischen Methoden charakterisiert. Die Ergebnisse der Elementaranalyse zeigen, dass nur 10 % des Nanocompositmaterials aus leitfähigem PANI bestehen. Die Vergrößerung des Zwischenschichtabstandes von MMT, die bei Röntgendiffraktometrieuntersuchungen beobachtet wurde, lässt auf die Bildung von PANI innerhalb der Tonmineral-Taktoide schließen. IR-spektroskopische Untersuchungen deuten auf das Vorhandensein von Wechselwirkungen physikochemischer Art, wahrscheinlich Wasserstoffbindungen zwischen dem Tonmineral und Polyanilin, hin. Untersuchungen mit zyklischer Voltammetrie zeigten, dass die Anwesenheit von elektroinaktivem Tonmineral die elektrochemische Aktivität von PANI nicht beeinflusst. Das elektrochrome Verhalten von PANI-MMT Nanocompositen wurde mit UV-Vis-Spektroskopie untersucht, wobei sich herausstellte, dass das elektrochrome Verhalten vom PANI im Compositmaterial erhalten bleibt. Eines der technologischen Hauptanwendungsgebiete von leitfähigen Polymeren, insbesondere von PANI, ist der Korrosionsschutz von aktiven Metallen. PANI-MMT Nanocomposite die mit der angegebenen Methode (elektrochemisch) synthetisiert wurden und chemisch synthetisiertes in organischen Medien lösliches PANI wurden zum Korrosionsschutz von C45 Stahl eingesetzt. Die Korrosionsuntersuchungen wurden mit Hilfe von elektrochemischen Impedanzmessungen (EIM) und anodischen Polarisationsuntersuchungen durchgeführt. Der von PANI-MMT und von in organischen Medien löslichem PANI gebotene Korrosionsschutz ist wahrscheinlich auf die Zunahme des Ladungsdurchtritts widerstandes der beschichteten Stahloberfläche zurückzuführen. Die anodische Verschiebung des Korrosionspotenzials, eine Verringerung der Korrosions-geschwindigkeit und eine deutliche Zunahme des Polarisationswiderstandes sind eindeutige Hinweise für das Antikorrosionsvermögen von PANI-MMT und auch von in organischen Medien löslichem PANI, welche auf der zu schützenden Stahloberfläche abgeschieden wurden.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 105-112).

This work is aimed at developing a high sensitivity salinity (conductivity) sensor for marine applications. The principle of sensing involves the use of parallel plate capacitors, which minimizes the proximity effects associated with inductive measurement techniques. The barrier properties of two different materials, AZ5214 and Honeywell's ACCUFLO T3027, were investigated for use as the insulation layer for the sensor. Impedance analysis performed on the two coatings using Agilent's 4924A Precision Impedance Analyzer served to prove that ACCUFLO was a better dielectric material for this application when compared to AZ5214.Two separate detection circuits have been proposed for the salinity sensor. In the Twin-T filter method, a variation in capacitance tends to shift the resonant frequency of a Twin-T oscillator, comprising the sensor. Simulations of the oscillator circuit were performed using Pspice. Experiments were performed on calibrated ocean water samples of 34.996 psu and a shift of 410 Hz/psu was obtained. To avoid the problems associated with the frequency drift in the oscillator, an alternate detection scheme is proposed which employs frequency-to-voltage converters. The sensitivity of this detection scheme was observed to be 10 mV/psu.