S.M. Richie

Simulation of Elevated T-Waves of an ECG Inside a Static Magnetic Field (MRI)

In MRI, the flow of blood in the patient is subjected to a strong static magnetic field (B0). The movement of charge carriers in a magnetic field causes a magnetofluid dynamic (MFD) effect that induces a voltage across the artery. This induced voltage distorts the ECG signal of the patient and appears as an elevation of the T-wave of the ECG signal. Flow of blood through the aortic arch is perpendicular to the magnetic field and coincides with the occurrence of the T-wave of the ECG. Based on these facts, it is proposed that the elevation in the T-wave occurs because of the voltage induced across the aortic arch. In this paper, the elevation is computed mathematically using the equations of MFD. A method is developed to measure this induced voltage based on discretization of the aortic arch and measuring the blood flow profile in the aorta. The results are compared to the ECG signals measured in humans in the bore of 1.5 T imaging magnet. The computed ECG signals at the 12 leads are very similar to the measured values.

ZnO/diamond/Si SAW filter properties including velocity dispersion

The surface acoustic wave (SAW) filter properties of ZnO/diamond/Si structure are calculated including velocity dispersion. It is well known that the pole width of a SAW filter response and the number of electrodes have a reciprocal relation for bulk piezoelectric materials. However, the pole width of layered structures tends to be narrower than that of expected bulk SAW devices and the reason is due to the velocity dispersion of layered structures. The pole width of layered structures was calculated by the delta function model including the velocity dispersion and was compared with the experimental results. The dispersion effect is also calculated by using the Smiths equivalent circuit model. The results of this analysis are presented and agree well with the experimental results.

Gap-Based Estimation: Choosing the Smoothing Parameters for Probabilistic and General Regression Neural Networks

Probabilistic neural networks (PNN) and general regression neural networks (GRNN) represent knowledge by simple but interpretable models that approximate the optimal classifier or predictor in the sense of expected value of the accuracy. These models require the specification of an important smoothing parameter, which is usually chosen by cross-validation or clustering. In this article, we demonstrate the problems with the cross-validation and clustering approaches to specify the smoothing parameter, discuss the relationship between this parameter and some of the data statistics, and attempt to develop a fast approach to determine the optimal value of this parameter. Finally, through experimentation, we show that our approach, referred to as a gap-based estimation approach, is superior in speed to the compared approaches, including support vector machine, and yields good and stable accuracy.

Description and development of a SAW filter CAD system

The authors present a description of the appropriate device models, design methods, and analysis techniques for a real-time surface acoustic wave (SAW) computer-aided design (CAD) system. The approaches presented have been successfully implemented in the creation of a fully integrated SAW filter CAD system for the design of bidirectional and three-phase unidirectional filters on a DEC VAX 11/750 system and for the design of bidirectional filters on an IBM PC-AT computer, which acts as an independent workstation. The focus is on bidirectional transducer design and analysis using the PC-based computer system. CAD analysis of a SAW bidirectional filter is compared to measured parameters. >

Experiments with Safe µARTMAP: Effect of the network parameters on the network performance

Fuzzy ARTMAP (FAM) is currently considered to be one of the premier neural network architectures in solving classification problems. One of the limitations of Fuzzy ARTMAP that has been extensively reported in the literature is the category proliferation problem. That is, Fuzzy ARTMAP has the tendency of increasing its network size, as it is confronted with more and more data, especially if the data are of the noisy and/or overlapping nature. To remedy this problem a number of researchers have designed modifications to the training phase of Fuzzy ARTMAP that had the beneficial effect of reducing this category proliferation. One of these modified Fuzzy ARTMAP architectures was the one proposed by Gomez-Sanchez, and his colleagues, referred to as Safe muARTMAP. In this paper we present reasonable analytical arguments that demonstrate of how we should choose the range of some of the Safe muARTMAP network parameters. Through a combination of these analytical arguments and experimentation we were able to identify good default parameter values for some of the Safe muARTMAP network parameters. This feat would allow one to save computations when a good performing Safe muARTMAP network is needed to be identified for a new classification problem. Furthermore, we performed an exhaustive experimentation to find the best Safe muARTMAP network for a variety of problems (simulated and real problems), and we compared it with other best performing ART networks, including other ART networks that claim to resolve the category proliferation problem in Fuzzy ARTMAP. These experimental results allow one to make appropriate statements regarding the pair-wise comparison of a number of ART networks (including Safe muARTMAP).

Characteristics of ZnO/diamond/Si SAW resonators

The surface acoustic wave (SAW) resonator response of ZnO/diamond/Si layered structures are calculated and discussed including velocity dispersion. Smiths second equivalent circuit including energy storage effects is used to calculate the resonator response. The effect of velocity dispersion appears for the shift of resonant frequency to the expected center frequency, and appears for the bandwidth of resonator becoming narrower than that of the nondispersive case. The coupling of modes equation is modified for the velocity dispersion to explain these effects. The reflection coefficients of gratings are calculated for velocity dispersive case and the non velocity dispersive case. These results agree with the response calculated by the equivalent circuit model. Assuming the deviation of velocity dispersion is small neighboring the resonance area, the effect of velocity dispersion is explained theoretically. The ZnO/diamond/Si SAW resonators provide high frequency operation and high quality factor (Q) SAW resonators due to the velocity dispersion.

Characteristics and fabrication of a narrow gap transducer

The fundamental characteristics of a narrow gap transducer are investigated theoretically and experimentally. A surface acoustic wave (SAW) transducer with narrow gaps between electrodes, with a metallization ratio of greater than 90%, has potential application to high frequency devices. A narrow gap transducer doubles the center frequency for a given line width as compared with a conventional transducer. It relaxes the restriction on fabrication and lowers the resistance of the electrodes. The test devices are fabricated by a self-aligned liftoff process without using anodization. The experiment shows no internal reflections and a strong series of harmonics.<<ETX>>

The development of a first pass verification module for a SAW filter design automation system

The continuing developments of a non-interactive surface acoustic wave (SAW) filter design automation system, called SAWCOM, are presented. An automation system has been developed by S.M. Richie and D.C. Malocha (1989) for the design and analysis of SAW bidirectional transducers and filters. All dominant SAW acoustic and electrical effects have been modeled for non-reflecting transducers in a modular architecture. Synthesis and analysis tools form the core of the design automation system around which an automation shell is used to form the basis of a SAW compiler which is capable of non-interactive SAW filter design. The SAW filter design rules are implemented in a declarative language which provides logical decision control of the CAD system. The design automation system controls the execution and iteratively evaluates options, corrects errors, and decides on an optimal design choice within the set of design rules.<<ETX>>

Experiments with Safe ARTMAP and Comparisons to Other ART Networks

Fuzzy ARTMAP (FAM) is currently considered as one of the premier neural network architectures in solving classification problems. Safe muARTMAP, a modified version of FAM, was introduced to remedy the category proliferation problem that has been extensively reported in the literature. However, Safe muARTMAPs performance depends on a number of parameters. In this paper, we analyzed each parameter to set up the candidate values for evaluation. We performed an exhaustive experimentation to identify good default values for these parameters for a variety of problems, and compared the best performing Safe muARTMAP network with other best performing ART networks, including those that claim to solve the category proliferation problem.

On the design of an ellipsoid ARTMAP classifier within the fuzzy adaptive system ART framework

In this paper we present the design of fuzzy adaptive system ellipsoid ARTMAP (FASEAM), a novel neural architecture based on ellipsoid ARTMAP (EAM) that is equipped with concepts utilized in the fuzzy adaptive system ART (FASART) architecture. More specifically, we derive a new category choice function appropriate for EAM categories that is non-constant in a categorys representation region. Additionally, we augment the EAM category description with a centroid vector, whose learning rate is inversely proportional to the number of training patterns accessing the category. Finally, we demonstrate the merits of our design choices by comparing FASART, EAM and FASEAM in terms of generalization performance and final structural complexity on a set of classification problems.