CMOS Hyperbolic Sine ELIN filters for low/audio frequency biomedical applications

Hyperbolic-Sine (Sinh) filters form a subclass of Externally-Linear-Internally-Non- Linear (ELIN) systems. They can handle large-signals in a low power environment under half the capacitor area required by the more popular ELIN Log-domain filters. Their inherent class-AB nature stems from the odd property of the sinh function at the heart of their companding operation. Despite this early realisation, the Sinh filtering paradigm has not attracted the interest it deserves to date probably due to its mathematical and circuit-level complexity. This Thesis presents an overview of the CMOS weak inversion Sinh filtering paradigm and explains how biomedical systems of low- to audio-frequency range could benefit from it. Its dual scope is to: consolidate the theory behind the synthesis and design of high order Sinh continuous–time filters and more importantly to confirm their micro-power consumption and 100+ dB of DR through measured results presented for the first time. Novel high order Sinh topologies are designed by means of a systematic mathematical framework introduced. They employ a recently proposed CMOS Sinh integrator comprising only p-type devices in its translinear loops. The performance of the high order topologies is evaluated both solely and in comparison with their Log domain counterparts. A 5th order Sinh Chebyshev low pass filter is compared head-to-head with a corresponding and also novel Log domain class-AB topology, confirming that Sinh filters constitute a solution of equally high DR (100+ dB) with half the capacitor area at the expense of higher complexity and power consumption. The theoretical findings are validated by means of measured results from an 8th order notch filter for 50/60Hz noise fabricated in a 0.35μm CMOS technology. Measured results confirm a DR of 102dB, a moderate SNR of ~60dB and 74μW power consumption from 2V power supply

Magneto-inductive magnetic resonance imaging duodenoscope

A magnetic resonance imaging (MRI) duodenoscope is demonstrated, by combining non- magnetic endoscope components with a thin-film receiver based on a magneto-inductive waveguide. The waveguide elements consist of figure-of-eight shaped inductors formed on either side of a flexible substrate and parallel plate capacitors that use the substrate as a dielectric. Operation is simulated using equivalent circuit models and by computation of two- and three-dimensional sensitivity patterns. Circuits are fabricated for operation at 127.7 MHz by double-sided patterning of copper-clad Kapton and assembled onto non-magnetic flexible endoscope insertion tubes. Operation is verified by bench testing and by 1 H MRI at 3T using phantoms. The receiver can form a segmented coaxial image along the length of the endoscope, even when bent, and shows a signal-to-noise-ratio advantage over a surface array coil up to three times the tube diameter at the tip. Initial immersion imaging experiments have been carried out and confirm an encouraging lack of sensitivity to RF heating

Numerical analysis of different heating systems for warm sheet metal forming

The main goal of this study is to present an analysis of different heating methods frequently used in laboratory scale and in the industrial practice to heat blanks at warm temperatures. In this context, the blank can be heated inside the forming tools (internal method) or using a heating system (external method). In order to perform this analysis, a finite element model is firstly validated with the simulation of the direct resistance system used in a Gleeble testing machine. The predicted temperature was compared with the temperature distribution recorded experimentally and a good agreement was found. Afterwards, a finite element model is used to predict the temperature distribution in the blank during the heating process, when using different heating methods. The analysis also includes the evaluation of a cooling phase associated to the transport phase for the external heating methods. The results of this analysis show that neglecting the heating phase and a transport phase could lead to inaccuracies in the simulation of the forming phase.The authors gratefully acknowledge the financial support of the Portuguese Foundation for Science and Technology (FCT) under project PTDC/EMS-TEC/1805/2012 and by FEDER funds through the program COMPETE—Programa Operacional Factores de Competitividade, under the project CENTRO-07-0224-FEDER-002001 (MT4MOBI). The authors would like to thank Prof. A. Andrade-Campos for helpful contributions on the development of the finite element code presented in this work.info:eu-repo/semantics/publishedVersio

MRI for Noninvasive Thermometry

MRI was recognized for its potential use as a noninvasive in vivo thermometer 30 years ago. Today, the most popular application of MR thermometry is the guidance of thermal therapies for the treatment of cancer and other pathologies. These minimally invasive operations are routinely performed on patients who are not eligible for surgery in approximately 40 medical centers globally. The aim is to deliver or abduct thermal energy in order to cause local tissue necrosis or to sensitize a lesion to chemotherapy or radiotherapy without causing harm to the surrounding healthy tissue. Here we explain the principles of operation of MR thermometry and provide a critical review of the proposed methods, highlighting remaining fundamental and technical issues as well as recent progress. Emphasis is placed on hardware advances (RF receivers) for improved signal-to-noise ratio (SNR) which would lead to better accuracy, spatiotemporal resolution, and precise calibration. We conclude with a general outlook for the field

Damage modelling of leaded free cutting steel under hot forming conditions

In this thesis the influence of stress-state on ductile damage in free cutting steel under hot forming conditions is examined. The industrial motivation for the project focuses on edge cracking in hot rolling. A brief outline of the hot rolling process conditions is necessary to define the important parameters affecting edge cracking. Triaxiality was, thus, identified as the key parameter relating to damage under hot rolling conditions. Based on a detailed literature review, the appropriate testing and modelling methodology were identified for this body of work. A high temperature, uniaxial tension test program was implemented to identify the effect of triaxiality on damage under hot forming conditions. Double notched bars with varying notch radii were utilised, thus inducing different stress triaxialities due to geometrical constraints. Based on the resultant stress-strain data the effect of triaxiality on ductility and the strain to failure was investigated. Subsequently, unbroken notches from tested double notched samples were sectioned and optically examined to reveal damage initiation sites. Interesting damage features were identified and correlated with sample geometry (i.e. triaxiality) and testing conditions. Finite element analysis of the double notched samples revealed the effect of triaxiality on the local stress-state. The accuracy of the mechanical analysis from such simulations was improved by incorporating the thermal gradients induced during high temperature Gleeble tests. Three stress parameters were examined in relation to their effect on the experimentally observed damage; maximum principal stress, effective stress and hydrostatic stress. The maximum principal stress and equivalent stress were most clearly correlated to damage development under multiaxial conditions for this particular free cutting steel. Based on the results of the stress-state investigation of the double notched samples, a multiaxial damage expression was developed that reproduced the experimentally observed damage characteristics. The new multiaxial damage model was calibrated using a combination of uniaxial and multiaxial stress-strain data and damage profiles. The model was shown to have good accuracy in predicting both the stress-strain data and the damage initiation sites as a function of geometry and damage conditions. Finally, an extensive range of temperature and strain rate conditions were simulated for all tested sample geometries, and an additional sample geometry, to fully understand how testing conditions affect damage characteristics and under what triaxialities this is prone to happen.Open Acces

CMOS Hyperbolic-Sine ELIN filters for low/audio frequency biomedical applications

Hyperbolic-Sine (Sinh) filters form a subclass of Externally-Linear-Internally-Non-Linear (ELIN) systems. They can handle large-signals in a low power environment under half the capacitor area required by the more popular ELIN Log-domain filters. Their inherent class-AB nature stems from the odd property of the sinh function at the heart of their companding operation. Despite this early realisation, the Sinh filtering paradigm has not attracted the interest it deserves to date probably due to its mathematical and circuit-level complexity. This Thesis presents an overview of the CMOS weak inversion Sinh filtering paradigm and explains how biomedical systems of low- to audio-frequency range could benefit from it. Its dual scope is to: consolidate the theory behind the synthesis and design of high order Sinh continuous–time filters and more importantly to confirm their micro-power consumption and 100+ dB of DR through measured results presented for the first time. Novel high order Sinh topologies are designed by means of a systematic mathematical framework introduced. They employ a recently proposed CMOS Sinh integrator comprising only p-type devices in its translinear loops. The performance of the high order topologies is evaluated both solely and in comparison with their Log domain counterparts. A 5th order Sinh Chebyshev low pass filter is compared head-to-head with a corresponding and also novel Log domain class-AB topology, confirming that Sinh filters constitute a solution of equally high DR (100+ dB) with half the capacitor area at the expense of higher complexity and power consumption. The theoretical findings are validated by means of measured results from an 8th order notch filter for 50/60Hz noise fabricated in a 0.35μm CMOS technology. Measured results confirm a DR of 102dB, a moderate SNR of ~60dB and 74μW power consumption from 2V power supply.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

SNR in MI catheter receivers for MRI

Internal coils have a signal-to-noise ratio (SNR) advantage during magnetic resonance imaging. However, coils with continuous cables are generally unsafe, due to the risk of RF heating. Segmented cables, such as magneto-inductive waveguides, should introduce inherent safety at the price of increased noise, from both the cable and the body. Here, we derive analytical SNR expressions for both types of noise, develop a model to compare the SNR of different types of receiver, and validate the model with data from imaging experiments at 3T. Experiments and theory confirm that body noise does not prevent an SNR gain compared with an eight-element external coil, even when a long section of waveguide is loaded with tissue