University of Sydney. Aerospace, Mechanical and Mechatronic Engineering, 2005
I hereby declare that this submission is my own work and that, to the best of my knowledge and be... more I hereby declare that this submission is my own work and that, to the best of my knowledge and belief, it contains no material previously published or written by another person nor material which to a substantial extent has been accepted for the award of any other degree or diploma of the University or any other institute of higher learning, except where due acknowledgement has been made in the text.
The nonlinear mechanical behaviour of cervical tissue causes unpredictable changes in measured el... more The nonlinear mechanical behaviour of cervical tissue causes unpredictable changes in measured elastograms when pressure is applied. These uncontrolled variables prevent the reliable measurement of tissue elasticity in a clinical setting. Measuring the nonlinear properties of tissue is difficult due to the need for both shear modulus and strain to be taken simultaneously. A simulation-based method is proposed in this paper to resolve this. This study describes the nonlinear behaviour of cervical tissue using the hyperelastic material models of Demiray–Fung and Veronda–Westmann. Elastograms from 33 low-risk patients between 18 and 22 weeks gestation were obtained. The average measured properties of the hyperelastic material models are: Demiray–Fung—A1α = 2.07 (1.65–2.58) kPa, α = 6.74 (4.07–19.55); Veronda–Westmann—C1C2 = 4.12 (3.24–5.04) kPa, C2 = 4.86 (2.86–14.28). The Demiray–Fung and Veronda–Westmann models performed similarly in fitting to the elastograms with an average root me...
Noise is the unwanted energy that interferes with the ability of the receiver to detect the wante... more Noise is the unwanted energy that interferes with the ability of the receiver to detect the wanted signal. It may enter through the antenna along with the desired signal or it may be generated within the receiver itself. In underwater sonar systems, external acoustic noise is generated by waves and wind on the water surface, by biological agents (fish, prawns, etc.), and by man-made sources such as engine noise. In radar and lidar sensors the external electromagnetic noise is generated by various natural mechanisms such as the sun and lightning, among others. Man-made sources of electromagnetic noise are myriad, from car ignition systems and fluorescent lights to other broadcast signals. The deliberate transmission of noise in an attempt to mask a target echo or otherwise deceive a sensor is known as jamming.
2008 3rd International Conference on Sensing Technology, 2008
I. INTRODUCTION Having information about the internal structure of an ob-ject is important for me... more I. INTRODUCTION Having information about the internal structure of an ob-ject is important for medicine [1], [2], dentistry, material or building inspection, quality assurance, security [3], search and rescue, intelligent surveillance and reconnaissance (ISR) [4], astronomy, ...
The mechanical characteristics of tissue can reflect its biochemical content and, therefore, be a... more The mechanical characteristics of tissue can reflect its biochemical content and, therefore, be a powerful tool in the diagnosis of diseases. Many different methods have been developed for testing the mechanical properties of tissue, such as aspiration, indentation and shear wave elastography. Soft tissues are, however, more complex in behaviour than current commercial tissue-mimicking materials and the models used in measurement methods. Complex behaviours of the tissue include anisotropy and heterogeneous elasticity. The oversimplified models assumed in different measuring methods often neglect the effects of these behaviours, resulting in inaccuracies. The aim of this study was to develop a tissue-mimicking material able to capture the complexity of tissue mechanical behaviour. It will be used to improve mechanical property measuring methods by quantitatively determining how complexities in tissue behaviour affect the measurements made and evaluating the effectiveness of methods designed to overcome it, and will be used to train users for consistency in measurement. The tissue-mimicking material designed in this study focuses on the mechanical properties of the cervix as measured by shear wave elastography. The characteristic behaviours of cervical tissues highlighted are anisotropy, a wide range of elasticity that changes with gestational age and an elasticity gradient across the tissue. Magnetorheological gels were used as their elastic properties can be tuned with the application of magnetic fields. The sample was simulated with the finite-element software COMSOL before being tested by shear wave elastography and the INSTRON universal material testing machine. It had an elasticity range of 6.75-11.06 kPa, which is similar to that of cervical tissue. It was determined that a change in the orientation of the probe with respect to the orientation of anisotropy can cause up to a 30 % increase in measured elasticity. There was a 16% decrease in elasticity across the sample.
Simulating the radar illumination of large scenes generally relies on a geometric model of light ... more Simulating the radar illumination of large scenes generally relies on a geometric model of light transport which largely ignores prominent wave effects. This can be remedied through coherence ray-tracing, but this requires the Wigner transform of the aperture. This diffraction function has been historically difficult to generate, and is relevant in the fields of optics, holography, synchrotron-radiation, quantum systems and radar. In this paper we provide the Wigner transform of arbitrary polygons through geometric transforms and the Stokes Fourier transform; and display its use in Monte-Carlo rendering.
Introduction to Sensors for Ranging and Imaging, 2009
The range resolution of a sensor is defined as the minimum separation (in range) of two targets o... more The range resolution of a sensor is defined as the minimum separation (in range) of two targets of equal cross section that can be resolved as separate targets. It is determined by the bandwidth of the transmitted signal, Δf (Hz), which is generated by widening the transmitter bandwidth using one of the following modulation forms: amplitude modulation, frequency modulation, phase modulation.
2017 Eleventh International Conference on Sensing Technology (ICST), 2017
The paper describes the development, calibration and testing of a custom made photometric-thermom... more The paper describes the development, calibration and testing of a custom made photometric-thermometric sensor used to measure the penetration of NIR radiation from an intraoral therapeutic LED source, and the resultant temperature increase in tooth sockets. The difficulty of producing this novel device resides in its small dimensions. However a judicious choice of probes enabled successful development, calibration and in vivo testing. Apart from photometric and thermometric data the heart rate of the patients was also apparent, due to swelling of the capillaries in the gum tissue during systole — the contraction phase — of the cardiac cycle.
The concept of blackbody radiation was introduced in Chapter 3. It was shown that the total power... more The concept of blackbody radiation was introduced in Chapter 3. It was shown that the total power emitted by an object is a function of the temperature, and the emissivity of the material is proportional to T4 as described by the Stefan-Boltzmann law. It was also shown that if the power is measured in a region far from the emission peak, the source brightness, Bf (W/m2/Hz/ sr), is directly proportional to the temperature, T (K), according to the relationship described by the Rayleigh-Jean law (Currie and Brown 1987): Bf = 2kT/λ2 , (4.1) where k is Boltzmann's constant (1.3804 x 10-23 J/K), T is the source temperature (K), and l is the wavelength (m). This approximation is accurate to within 1% for frequencies below 100 GHz, and to within 3% for frequencies below 300 GHz. It can therefore be applied to both microwave and millimeter wave systems (Ulaby 1987).
2003 Proceedings of the International Conference on Radar (IEEE Cat. No.03EX695)
Conical-scam implementations for three antenna types are discussed in terms of the beam nuiatioa ... more Conical-scam implementations for three antenna types are discussed in terms of the beam nuiatioa method, reference signal generation and angle error demodulation Various applications for these antennas including their use in teaching are discussed. Inder Terms-..eoaical-sean, millimetre wave, antenna I. IN'RODUCiTON Tracking radars require a mechanism to determine the offset of a target from the antenna boresight. At millimetre wavelengths, implementation of the monopulse technique is both difficult and expensive in contrast to the elegant simplicity of the conical-scan technique. This simplicity and ease of implementation makes the latter an ideal tool to teach a wide range of sensing concepts.
In this example, it can be seen that the retroreflective return will easily be visible above the ... more In this example, it can be seen that the retroreflective return will easily be visible above the returns from the backscattered laser signal, the backscatter from the sun, the dark current, and the shot noise. The SNR of 47 dB is limited by the photodiode shot noise.
Implantable devices are used extensively in the medical field for treatment and rehabilitation. H... more Implantable devices are used extensively in the medical field for treatment and rehabilitation. However, one key issue with the use of implantable medical devices is the absence of a safe, reliable method of evaluating the effectiveness of the device during the period of implantation. Majority of the current monitoring methods rely on the use of imaging techniques and analysis of chemical composition of fluids. The information provided by these methods lack information on the physical performance and condition of the implants. Additionally, the discrete nature of these methods limits the amount of information provided and risks the late discovery of complications. The concept of using sensors to keep track of implants is found in various applications, but the challenges in designing the ideal sensor have yet to be solved. These problems are the disruption of transmission by the tissue barrier, the longevity and safety of the battery source, and the danger of infection of artificial ...
2019 13th International Conference on Sensing Technology (ICST), Dec 1, 2019
There are numerous examples in which the introduction of expensive medical equipment into the dev... more There are numerous examples in which the introduction of expensive medical equipment into the developing world fail for lack of a basic understanding of the device operation, lack of spare parts and poor maintenance. This paper describes the development of a Fleisch pneumotachograph and cellphone based telespirometer that can easily be built from "junk box" medical and electronic components available in the developing world. This approach should introduce a sense of local ownership to the project as well as encouraging participation by the local electronics repair industry. Experimental results confirm that the forced expiratory flow data are reliably modulated onto an audio signal and transmitted by cellphone to a base station for examination by a district nurse or doctor. Flow measurement and data transmission accuracies are sufficiently good for remote diagnoses of chronic obstructive pulmonary disease.
The purpose of this paper is to outline a novel method of using template based cross-correlation ... more The purpose of this paper is to outline a novel method of using template based cross-correlation to identify and track uterine contractions during labour. A purpose built six-channel Electromyography (EMG) device was used to collect data from consenting women during labour and birth. A range of templates were constructed for the purpose of identifying and tracking uterine activity when cross-correlated with the EMG signal. Peak finding techniques were applied on the cross-correlated result to simplify and automate the identification and tracking of contractions. The EMG data showed a unique pattern when a woman was contracting with key features of the contraction signal remaining consistent and identifiable across subjects. Contraction profiles across subjects were automatically identified using template based cross-correlation. Synthetic templates from a rectangular function with a duration of between 5 and 10 s performed best at identifying and tracking uterine activity across sub...
2016 International Symposium on Fundamentals of Electrical Engineering (ISFEE), 2016
The paper investigates the effects of using coax-to-microstrip line transition with different mou... more The paper investigates the effects of using coax-to-microstrip line transition with different mounting techniques and coaxial line terminals for measuring the characteristics of microstrip antenna. The investigations reveal that the antenna return losses and magnitude of characteristic impedance are least effected by vertically mounted tab terminal coaxial line. However, all the coaxial lines shift the phase of the characteristic impedance which requires phase correction.
2016 International Symposium on Fundamentals of Electrical Engineering (ISFEE), 2016
The paper presents a waveguide-to-probe transition for testing millimeter wave band planar harmon... more The paper presents a waveguide-to-probe transition for testing millimeter wave band planar harmonic tag antennas. It discusses in detail the design and the tuning approach for developing the waveguide transition. The transition limits the radiation leakage and is easy to fabricate. However, it is narrow band and could not be used for testing multiple antennas simultaneously. The working of the transition is validated by measuring the return losses of 77 GHz planar harmonic antenna which are in good agreement with the simulated results.
Proceedings of the 5th European Conference on Antennas and Propagation, Apr 11, 2011
The paper presents some recent developments in harmonic radar tracking systems. These are widely ... more The paper presents some recent developments in harmonic radar tracking systems. These are widely used for monitoring and tracking of low flying insects like honey bees, butterflies, snail and carabid beetles, and come under the category of individual marking techniques and use harmonic range detection or range finding for tracking insects tagged with harmonic transponders. In most cases the transponder is, however, a vertical rod or trailing wire both of which hinder insect movement. This paper presents recommendations for improving the harmonic radar, detectable range and minimizing the weight and size of transponder. It presents externally biased microstrip antenna based prototype harmonic transponder.
University of Sydney. Aerospace, Mechanical and Mechatronic Engineering, 2005
I hereby declare that this submission is my own work and that, to the best of my knowledge and be... more I hereby declare that this submission is my own work and that, to the best of my knowledge and belief, it contains no material previously published or written by another person nor material which to a substantial extent has been accepted for the award of any other degree or diploma of the University or any other institute of higher learning, except where due acknowledgement has been made in the text.
The nonlinear mechanical behaviour of cervical tissue causes unpredictable changes in measured el... more The nonlinear mechanical behaviour of cervical tissue causes unpredictable changes in measured elastograms when pressure is applied. These uncontrolled variables prevent the reliable measurement of tissue elasticity in a clinical setting. Measuring the nonlinear properties of tissue is difficult due to the need for both shear modulus and strain to be taken simultaneously. A simulation-based method is proposed in this paper to resolve this. This study describes the nonlinear behaviour of cervical tissue using the hyperelastic material models of Demiray–Fung and Veronda–Westmann. Elastograms from 33 low-risk patients between 18 and 22 weeks gestation were obtained. The average measured properties of the hyperelastic material models are: Demiray–Fung—A1α = 2.07 (1.65–2.58) kPa, α = 6.74 (4.07–19.55); Veronda–Westmann—C1C2 = 4.12 (3.24–5.04) kPa, C2 = 4.86 (2.86–14.28). The Demiray–Fung and Veronda–Westmann models performed similarly in fitting to the elastograms with an average root me...
Noise is the unwanted energy that interferes with the ability of the receiver to detect the wante... more Noise is the unwanted energy that interferes with the ability of the receiver to detect the wanted signal. It may enter through the antenna along with the desired signal or it may be generated within the receiver itself. In underwater sonar systems, external acoustic noise is generated by waves and wind on the water surface, by biological agents (fish, prawns, etc.), and by man-made sources such as engine noise. In radar and lidar sensors the external electromagnetic noise is generated by various natural mechanisms such as the sun and lightning, among others. Man-made sources of electromagnetic noise are myriad, from car ignition systems and fluorescent lights to other broadcast signals. The deliberate transmission of noise in an attempt to mask a target echo or otherwise deceive a sensor is known as jamming.
2008 3rd International Conference on Sensing Technology, 2008
I. INTRODUCTION Having information about the internal structure of an ob-ject is important for me... more I. INTRODUCTION Having information about the internal structure of an ob-ject is important for medicine [1], [2], dentistry, material or building inspection, quality assurance, security [3], search and rescue, intelligent surveillance and reconnaissance (ISR) [4], astronomy, ...
The mechanical characteristics of tissue can reflect its biochemical content and, therefore, be a... more The mechanical characteristics of tissue can reflect its biochemical content and, therefore, be a powerful tool in the diagnosis of diseases. Many different methods have been developed for testing the mechanical properties of tissue, such as aspiration, indentation and shear wave elastography. Soft tissues are, however, more complex in behaviour than current commercial tissue-mimicking materials and the models used in measurement methods. Complex behaviours of the tissue include anisotropy and heterogeneous elasticity. The oversimplified models assumed in different measuring methods often neglect the effects of these behaviours, resulting in inaccuracies. The aim of this study was to develop a tissue-mimicking material able to capture the complexity of tissue mechanical behaviour. It will be used to improve mechanical property measuring methods by quantitatively determining how complexities in tissue behaviour affect the measurements made and evaluating the effectiveness of methods designed to overcome it, and will be used to train users for consistency in measurement. The tissue-mimicking material designed in this study focuses on the mechanical properties of the cervix as measured by shear wave elastography. The characteristic behaviours of cervical tissues highlighted are anisotropy, a wide range of elasticity that changes with gestational age and an elasticity gradient across the tissue. Magnetorheological gels were used as their elastic properties can be tuned with the application of magnetic fields. The sample was simulated with the finite-element software COMSOL before being tested by shear wave elastography and the INSTRON universal material testing machine. It had an elasticity range of 6.75-11.06 kPa, which is similar to that of cervical tissue. It was determined that a change in the orientation of the probe with respect to the orientation of anisotropy can cause up to a 30 % increase in measured elasticity. There was a 16% decrease in elasticity across the sample.
Simulating the radar illumination of large scenes generally relies on a geometric model of light ... more Simulating the radar illumination of large scenes generally relies on a geometric model of light transport which largely ignores prominent wave effects. This can be remedied through coherence ray-tracing, but this requires the Wigner transform of the aperture. This diffraction function has been historically difficult to generate, and is relevant in the fields of optics, holography, synchrotron-radiation, quantum systems and radar. In this paper we provide the Wigner transform of arbitrary polygons through geometric transforms and the Stokes Fourier transform; and display its use in Monte-Carlo rendering.
Introduction to Sensors for Ranging and Imaging, 2009
The range resolution of a sensor is defined as the minimum separation (in range) of two targets o... more The range resolution of a sensor is defined as the minimum separation (in range) of two targets of equal cross section that can be resolved as separate targets. It is determined by the bandwidth of the transmitted signal, Δf (Hz), which is generated by widening the transmitter bandwidth using one of the following modulation forms: amplitude modulation, frequency modulation, phase modulation.
2017 Eleventh International Conference on Sensing Technology (ICST), 2017
The paper describes the development, calibration and testing of a custom made photometric-thermom... more The paper describes the development, calibration and testing of a custom made photometric-thermometric sensor used to measure the penetration of NIR radiation from an intraoral therapeutic LED source, and the resultant temperature increase in tooth sockets. The difficulty of producing this novel device resides in its small dimensions. However a judicious choice of probes enabled successful development, calibration and in vivo testing. Apart from photometric and thermometric data the heart rate of the patients was also apparent, due to swelling of the capillaries in the gum tissue during systole — the contraction phase — of the cardiac cycle.
The concept of blackbody radiation was introduced in Chapter 3. It was shown that the total power... more The concept of blackbody radiation was introduced in Chapter 3. It was shown that the total power emitted by an object is a function of the temperature, and the emissivity of the material is proportional to T4 as described by the Stefan-Boltzmann law. It was also shown that if the power is measured in a region far from the emission peak, the source brightness, Bf (W/m2/Hz/ sr), is directly proportional to the temperature, T (K), according to the relationship described by the Rayleigh-Jean law (Currie and Brown 1987): Bf = 2kT/λ2 , (4.1) where k is Boltzmann's constant (1.3804 x 10-23 J/K), T is the source temperature (K), and l is the wavelength (m). This approximation is accurate to within 1% for frequencies below 100 GHz, and to within 3% for frequencies below 300 GHz. It can therefore be applied to both microwave and millimeter wave systems (Ulaby 1987).
2003 Proceedings of the International Conference on Radar (IEEE Cat. No.03EX695)
Conical-scam implementations for three antenna types are discussed in terms of the beam nuiatioa ... more Conical-scam implementations for three antenna types are discussed in terms of the beam nuiatioa method, reference signal generation and angle error demodulation Various applications for these antennas including their use in teaching are discussed. Inder Terms-..eoaical-sean, millimetre wave, antenna I. IN'RODUCiTON Tracking radars require a mechanism to determine the offset of a target from the antenna boresight. At millimetre wavelengths, implementation of the monopulse technique is both difficult and expensive in contrast to the elegant simplicity of the conical-scan technique. This simplicity and ease of implementation makes the latter an ideal tool to teach a wide range of sensing concepts.
In this example, it can be seen that the retroreflective return will easily be visible above the ... more In this example, it can be seen that the retroreflective return will easily be visible above the returns from the backscattered laser signal, the backscatter from the sun, the dark current, and the shot noise. The SNR of 47 dB is limited by the photodiode shot noise.
Implantable devices are used extensively in the medical field for treatment and rehabilitation. H... more Implantable devices are used extensively in the medical field for treatment and rehabilitation. However, one key issue with the use of implantable medical devices is the absence of a safe, reliable method of evaluating the effectiveness of the device during the period of implantation. Majority of the current monitoring methods rely on the use of imaging techniques and analysis of chemical composition of fluids. The information provided by these methods lack information on the physical performance and condition of the implants. Additionally, the discrete nature of these methods limits the amount of information provided and risks the late discovery of complications. The concept of using sensors to keep track of implants is found in various applications, but the challenges in designing the ideal sensor have yet to be solved. These problems are the disruption of transmission by the tissue barrier, the longevity and safety of the battery source, and the danger of infection of artificial ...
2019 13th International Conference on Sensing Technology (ICST), Dec 1, 2019
There are numerous examples in which the introduction of expensive medical equipment into the dev... more There are numerous examples in which the introduction of expensive medical equipment into the developing world fail for lack of a basic understanding of the device operation, lack of spare parts and poor maintenance. This paper describes the development of a Fleisch pneumotachograph and cellphone based telespirometer that can easily be built from "junk box" medical and electronic components available in the developing world. This approach should introduce a sense of local ownership to the project as well as encouraging participation by the local electronics repair industry. Experimental results confirm that the forced expiratory flow data are reliably modulated onto an audio signal and transmitted by cellphone to a base station for examination by a district nurse or doctor. Flow measurement and data transmission accuracies are sufficiently good for remote diagnoses of chronic obstructive pulmonary disease.
The purpose of this paper is to outline a novel method of using template based cross-correlation ... more The purpose of this paper is to outline a novel method of using template based cross-correlation to identify and track uterine contractions during labour. A purpose built six-channel Electromyography (EMG) device was used to collect data from consenting women during labour and birth. A range of templates were constructed for the purpose of identifying and tracking uterine activity when cross-correlated with the EMG signal. Peak finding techniques were applied on the cross-correlated result to simplify and automate the identification and tracking of contractions. The EMG data showed a unique pattern when a woman was contracting with key features of the contraction signal remaining consistent and identifiable across subjects. Contraction profiles across subjects were automatically identified using template based cross-correlation. Synthetic templates from a rectangular function with a duration of between 5 and 10 s performed best at identifying and tracking uterine activity across sub...
2016 International Symposium on Fundamentals of Electrical Engineering (ISFEE), 2016
The paper investigates the effects of using coax-to-microstrip line transition with different mou... more The paper investigates the effects of using coax-to-microstrip line transition with different mounting techniques and coaxial line terminals for measuring the characteristics of microstrip antenna. The investigations reveal that the antenna return losses and magnitude of characteristic impedance are least effected by vertically mounted tab terminal coaxial line. However, all the coaxial lines shift the phase of the characteristic impedance which requires phase correction.
2016 International Symposium on Fundamentals of Electrical Engineering (ISFEE), 2016
The paper presents a waveguide-to-probe transition for testing millimeter wave band planar harmon... more The paper presents a waveguide-to-probe transition for testing millimeter wave band planar harmonic tag antennas. It discusses in detail the design and the tuning approach for developing the waveguide transition. The transition limits the radiation leakage and is easy to fabricate. However, it is narrow band and could not be used for testing multiple antennas simultaneously. The working of the transition is validated by measuring the return losses of 77 GHz planar harmonic antenna which are in good agreement with the simulated results.
Proceedings of the 5th European Conference on Antennas and Propagation, Apr 11, 2011
The paper presents some recent developments in harmonic radar tracking systems. These are widely ... more The paper presents some recent developments in harmonic radar tracking systems. These are widely used for monitoring and tracking of low flying insects like honey bees, butterflies, snail and carabid beetles, and come under the category of individual marking techniques and use harmonic range detection or range finding for tracking insects tagged with harmonic transponders. In most cases the transponder is, however, a vertical rod or trailing wire both of which hinder insect movement. This paper presents recommendations for improving the harmonic radar, detectable range and minimizing the weight and size of transponder. It presents externally biased microstrip antenna based prototype harmonic transponder.
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Papers by Graham Brooker