Masters Theses

Permanent link for this collection

https://hdl.handle.net/10292/5

The Masters Theses collection contains digital copies of AUT University masters theses deposited with the Library since 2002 and made available open access. From 2007 onwards, all theses for masters degrees awarded are required to be deposited in Tuwhera Open Theses & Dissertations unless subject to an embargo.

For theses submitted prior to 2007, open access was not mandatory, so only those theses for which the author has given consent are available in Tuwhera Open Theses & Dissertations. Where consent for open access has not been provided, the thesis is usually recorded in the AUT Library catalogue where the full text, if available, may be accessed with an AUT password. Other people should request an Interlibrary Loan through their library.

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Now showing 1 - 20 of 25

A simulation model of infant-incubator-feedback system with humidification and temperature control
(Auckland University of Technology, 2006) Al-Taweel, Yasser Amer; Al-Jumaily, Ahmed
A comprehensive simulation model for the infant-incubator-feedback system was developed in a Matlab/Simulink® environment to investigate all heat exchange relationships, variables and factors that have an influence on the overall thermo-neutrality of the environment. The model was also used to determine the benefits and limitations of using a convectively heated single-walled incubator in nursing preterm infants with very low birth weight < 1000 grams and low gestational age 28 weeks. The infant was modelled as one-lump with two layers; core and skin. The infant shape was approximated to a cylinder. The model incorporated all compartments of the infant-incubator system including core, skin, incubator air space, mattress, incubator walls, air-circulating fan, heating element, added oxygen (for resuscitation purposes), and humidification chamber, which has not previously been considered. The results of the simulation were in terms of the temperature variation over time, of the following parts of the system: core and skin temperatures and incubator air space temperature. Results of the simulation with added humidity showed that the body temperature of a 900 gram infant, with an initial body temperature of 35.5 ºC, did not reach the thermo-neutral range between 36.5-37.5 ºC in two hours, on air mode. Whereas, on skin mode, both core and skin temperature reached to 36.87 ºC and 36.5 ºC in two hours, and thus a thermo-neutral environment was achieved. These outcomes are consistent with clinical empirical reports. The simulation model is a closed-loop system with a PID controller for each mode; air servo controlled and skin servo controlled. The controller parameters were virtually estimated by the Zeigler-Nichols Method as real values were not available. Nevertheless, the overall stability of the whole system has been achieved by applying a step input which was verified by the Root Locus Method.
An investigation into 5-lobe lung modelling
(Auckland University of Technology, 2005-01-01) Vuong, Xuan Tung; Al-Jumaily, Ahmed
To understand how the input impedance of the respiratory system relates to pressure and volume airflow of the airway branched structure, this thesis focuses on developing a mathematical model of the branched airway including trachea and branching airways. The 5-Lobe lung model is developed mathematically and experimentally. A computer model is constructed in the MathlabTM programming environment. It accounts for the effects of airways with varying cross-sectional area, flexible wall properties, and the bronchial tree within the lung using the mathematical methods developed in previous researches. The terminal impedances are determined by proposed idealized lobe models. A range of frequencies up to 256 Hz are tested on this model. Cases of study on obstructions by varying lung stiffness from healthy to unhealthy conditions are investigated.Mathematical model is validated by experiment investigations on the mechanical lung simulator, which is built in Diagnostic & Control Research Centre at Auckland University of Technology. The results conclude that mathematical methods used in this research are capable to produce predictable results of the input impedance.
An investigation into the dynamic response of vocal folds
(Auckland University of Technology, 2006-11-26) Lan, Hai; Al-Jumaily, Ahmed
During phonation, the vocal folds collision during the glottal closure is considered to be a risk factor for pathological development. This thesis is aimed at designing a dependable finite element analysis (FEA) model of the vocal folds for frequency and dynamic analysis and for calculating the impact stress between the vocal folds during glottal closure. A three-dimensional model with irregular geometry and a layered structure was designed. The measured viscoelastic properties of the vocal-fold mucosa and the transverse isotropic elastic properties of the vocal fold muscle are applied to the model. The boundary conditions are assumed to be fixed on lateral, anterior and posterior surfaces based on anatomical structure analysis. This model is symmetrical about the right and left vocal folds.The frequency and dynamic characters are presented using the software ABAQUS. The FEA model is validated by both experimental modal analysis (EMA) model results and in-vivo experimental results from the literature.In the vibration analysis, the eigenfrequency and eigenmode of the FEA model are determined. The model results compare well with the experiments performed on a silicone vocal fold model. The eigenmodes show the vibration direction at different excitation frequencies. In the closure process, the closure and collision dynamic results are obtained. The results show that: (1) the closure process is independent of the subglottal pressure; (2) the glottal opening amplitude and closing velocity vary approximately linear with the subglottal pressure; (3) the maximum impact stress occurs on the mid area of the inferior surfaces; (4) the impact stress is approximately linear with the subglottal pressure; and (5) the impact stress will cause vocal fold tissue damage when the subglottal pressure is over 800 Pa.It is anticipated that the model will help to identify voice disorders such as vocal-fold paralysis and vocal-fold nodules.
Artificial neonatal airway model
(Auckland University of Technology, 2011) Mussa, Jibril Siraj; Al-Jumaily, Ahmed; Bold, Geoff
The main aim of this project is to establish the effectiveness of Bubble CPAP in transmitting pressure oscillations through the neonatal tracheobronchial tree. As it is very difficult to establish how much of the pressure oscillation delivered to the mouth can reach the various branches during in-vivo measurements, this research focuses in developing an in-vitro experiment on the lung model. Hollow lung models for 128 and 142 day gestation lambs were created from existing silicon lung casts. An experimental setup using a lung simulator and pressure sensors was developed. Different combinations of respiratory rate and frequencies with different amplitudes were used to perform experimental tests. The current ovine respiratory system which was available at IBTec was modified to reflect the current experimental setup. Computer simulations were performed and compared with the experimental results. The study indicates that pressure waves with different frequencies can be delivered to different locations of the lung by controlling the pressure oscillation source to the lung.
Breathing Therapy Air Delivery Unit: Simulation, Design and Development
(Auckland University of Technology, 2003) White, David Edward; Al-Jumaily, Ahmed
Although constant positive airway pressure therapy is currently the most effective form of non-invasive treatment to relieve obstructive sleep apnea symptoms, it has relatively low treatment compliance due to pressure related side effects. Existing commercial continuous positive airway pressure (CPAP) devices rely on the combined airflow characteristics of both the air delivery unit and nasal mask vent to regulate treatment pressure. Fluctuation in mask pressure occurs however, due to patient breathing, presenting an opportunity to develop an alternative breathing therapy device capable of achieving dynamic control of mask pressure. Within this research, a computer model of a proposed patient breathing therapy device, based on characteristics of a prototype system, is developed to determine the breathing system air delivery requirements whilst operating under a simulated patient breathing load. This model initially utilises an idealised, zero order, air delivery unit behaviour, since this system element is yet to be built. A review of different types of air compressors is undertaken and the diaphragm type compressor selected as being best suited for practical implementation within the air delivery unit of the breathing system, based on constraints of air quality, available machining resource and materials. Thermodynamic design of the compressor is undertaken to determine physical dimensions and a range of actuation methods are reviewed, based on force and speed requirements. A speed controlled 3 phase AC induction motor is selected to actuate the compressor. The diaphragm compressor is built and tested under both steady state and dynamic conditions and proven capable of meeting the breathing system air supply for both air pressure and flow requirements. The air delivery unit within the model simulation, previously based on an idealised, zero order element, is characterised with the same dynamic behaviour as the prototype unit built, established during testing, and shown by simulation to meet the breathing system requirements under dynamic patient breathing load. Implementation of the air delivery unit within the completed prototype breathing system shows the mask pressure to fluctuate outside the desire pressure tolerance range; however, to remedy this situation, the compressor requires the development of an appropriate control scheme which is beyond the scope of this work.
Combined map personalisation algorithm for delivering preferred spatial features in a map to everyday mobile device users
(Auckland University of Technology, 2010) Bookwala, Avinash Turab; Al-Jumaily, Ahmed; Zhou, Helen
In this thesis, we present an innovative and novel approach to personalise maps/geo-spatial services for mobile users. With the proposed map personalisation approach, only relevant data will be extracted from detailed maps/geo-spatial services on the fly, based on a user’s current location, preferences and requirements. This would result in dramatic improvements in the legibility of maps on mobile device screens, as well as significant reductions in the amount of data being transmitted; which, in turn, would reduce the download time and cost of transferring the required geo-spatial data across mobile networks. Furthermore, the proposed map personalisation approach has been implemented into a working system, based on a four-tier client server architecture, wherein fully detailed maps/services are stored on the server, and upon a user’s request personalised maps/services, extracted from the fully detailed maps/services based on the user’s current location, preferences, are sent to the user’s mobile device through mobile networks. By using open and standard system development tools, our system is open to everyday mobile devices rather than smart phones and Personal Digital Assistants (PDA) only, as is prevalent in most current map personalisation systems. The proposed map personalisation approach combines content-based information filtering and collaborative information filtering techniques into an algorithmic solution, wherein content-based information filtering is used for regular users having a user profile stored on the system, and collaborative information filtering is used for new/occasional users having no user profile stored on the system. Maps/geo-spatial services are personalised for regular users by analysing the user’s spatial feature preferences automatically collected and stored in their user profile from previous usages, whereas, map personalisation for new/occasional users is achieved through analysing the spatial feature preferences of like-minded users in the system in order to make an inference for the target user. Furthermore, with the use of association rule mining, an advanced inference technique, the spatial features retrieved for new/occasional users through collaborative filtering can be attained. The selection of spatial features through association rule mining is achieved by finding interesting and similar patterns in the spatial features most commonly retrieved by different user groups, based on their past transactions or usage sessions with the system.
Design and development of an optimised telemetry control system
(Auckland University of Technology, 2011) Salig, Avinash; Al-Jumaily, Ahmed
Designing an optimised telemetry control system will improve the quality of service for Supervisory Control And Data Acquisition (SCADA) systems implemented by CSE-W. Arthur Fisher and enable system expansion thus minimising revenue for their future system designs. The telemetry control system ensures a high degree of data reliability and integrity to meet SCADA operational requirements. This thesis presents the design and development of an optimised telemetry control system using Kingfisher Remote Terminal Units (RTU’s) with Kingfisher Series 2 protocol. To determine the system response for data transmission over the bandwidth, quantitative research methods were undertaken to evaluate communication blocks within the Kingfisher protocol. There are usually different techniques used to collect data from remote stations. The Kingfisher S2 protocol implements two techniques namely “Exception Reporting” and the “Polling” technique for data acquisition. The polling technique was the most efficient in terms of bandwidth utilization for transferring data therefore the system was designed using a pure polling system approach. It also enabled the communication links for remote stations to be monitored and enabled a deterministic system design approach to be implemented. Research focused on polling system optimization whereby efficient polling frequencies were calculated based on theory presented by (O. J. Boxma, Levy, & Weststrate, 1991). The aim was to efficiently allocate the limited bandwidth resource to a number of remote stations thus optimising the system performance. The proposed theory was implemented for system optimisation. It enables efficient polling frequencies to be calculated for a polling cycle hence optimising the bandwidth utilisation and eliminating fairness problems for the medium access control. Bandwidth optimisation enables system expansion thus reducing the networks need for additional resources. A pure polling telemetry communication system was implemented in this design using point to multipoint network topology over half duplex radio channel. Empirical data modelling enabled the design of the service duration period to allow for time sharing between the remote stations to share the bandwidth. The bandwidth was designed to share real time data and event log for SCADA systems monitoring and control. Queuing analysis was performed to establish system parameters and enable system optimisation. From the literature review the implemented design methodology uses the “mean delay approximation” method which was used to calculate efficient visit frequencies and enabled the optimisation of the bandwidth to the remote stations based on the workload of each remote site. The software for the telemetry control system was developed and tested using ladder logic. The results prove that the bandwidth utilisation can be efficiently controlled thus optimising the telemetry control system. The implemented design improves the quality of service for the SCADA system by providing regular real time system status poll requests for control purposes and was given the highest priority for medium access. It also performs a polling of individual sites according to the “mean delay approximation method” to efficiently allocate bandwidth amongst the remote stations depending on their workload thus optimising the system. The system was designed to be responsive to high priority event log data thus enabling system flexibility.
Development of a novel humidifier for air breathing devices
(Auckland University of Technology, 2011) Brizio, Pablo Joaquin; Al-Jumaily, Ahmed; Somervell, Andrew
Continuous positive pressure of air on the airways (CPAP) is the most common treatment for the obstructive sleep apnea syndrome. Humidification of the air applied to the patient improves patient compliance by preventing congestion and nasal and throat dryness. Most humidifiers used in CPAP systems are traditional heating-type humidifiers which consume large amount of energy. In this thesis, a non-traditional humidification technique was developed to be used in various respiratory supportive device applications such as CPAP therapy. Atomization processes were reviewed and ultrasonic atomizers were found to be the most suitable in terms of power consumption, droplets size distribution of the spray generated and size of the device. Four setups were used for experiments with these atomizers using five frequencies (1.5, 1.7, 2.1, 2.6 and 3.0 MHz). The experiments demonstrated that excitation with sine pulses has better efficiency than square pulses. In order to avoid overheating of the ultrasonic atomizer, the pulses must be sent in bursts and the frequency at which this bursts are sent (duty cycle) was proportional to the heating of the transducer. The droplet size distribution was measured by three different methods (photographic, impact and optic) and it did not have a significant change with the power applied to the transducer. The power did have a direct relationship with the atomization rate. Ultrasonic transducers with resonant frequency of 1.5 MHz are recommended for this application since the generated droplets have a small diameter (which facilitates its evaporation). The complexity of a driving circuit also increases with the frequency. Ideally there should be no water droplets in the air supplied to the patient. The evaporation of the droplets was mathematically modelled and experimentally tested to determine if the air that will be supplied needs to be heated to reach the fully evaporation. With an airflow rate of 60 L/min, the full evaporation of the droplets was reached in a relatively short distance (0.05 m) compared with the normal separation between the equipment and the patient (1.50m). There is no need to use a heater achieve such evaporation of the droplets. In this device, the pathogen risk could be reduced with the use of hydrophobic filters. This work demonstrates that ultrasonic transducers are capable of atomizing sufficient quantities of water for this application with low power consumption.
Effect of Mechanical Pulse Oscillations on Airway Smooth Muscle
(Auckland University of Technology, 2011) Theodore, Solomon; Al-Jumaily, Ahmed
The airway smooth muscle (ASM) plays an important role in the mechanism of respiratory system. Asthma, a common respiratory disease is associated with ASM hyper-contraction and shortening of airway diameter. This results in occlusion of the airway lumen leading to breathing difficulties. Various studies have shown that ASM can be relaxed by length oscillations. Previous experiments on ASM by applying sinusoidal oscillation at low frequencies and high amplitudes have showed a clear reduction in active force. Similar tests for a larger frequency range on ASM have also shown large reduction in dynamic force. But, it is not well known what parameters induce relaxation the most on ASM. The purpose of our research is to see the degree of relaxation when superimposed oscillations are applied on breathing and see which parameter relaxes smooth muscle the most. This research also focuses on investigating the effect of pulse oscillation rather than sinusoidal oscillation on contracted ASM. Isolated ASM were tested using pulse oscillations with wide range of frequency, amplitude and duration. Results obtained from these experiments showed that pulse oscillation with short duration had significant effect on the relaxation of ASM compared to sinusoidal oscillations with longer duration.
Effects of combined bronchodilators and oscillations on the the airway smooth muscle response
(Auckland University of Technology, 2011) Mathur, Meha; Al-Jumaily, Ahmed; Cairns, Simeon
The current study aims to investigate the combined effects of oscillations and bronchodilators on the dynamics of the isolated contracted airway smooth muscle. Current day asthma treatments commonly use bronchodilators such as Isoproterenol to reduce the symptoms of asthma. Previous studies have shown the ability of length oscillations (such as those occurring during tidal breathing and deep inspirations) to have a bronchodilatory effect on normal activated airway smooth muscle both in vitro and in vivo. However, this effect is absent or transient in asthmatic airway smooth muscle. Although, many studies have been conducted to possibly understand the role of oscillations on the airway smooth muscle (ASM) dynamics, the exact mechanism is still unclear. Many studies have been conducted to look at the effects of length oscillations or perturbations on the contracted ASM dynamics, along with separate set of studies investigating the behaviour of ASM in the presence of bronchodilators. This study is novel in the sense that it experimentally investigates the effects of bronchodilators combined with length oscillations of varying parameters on the isolated airway smooth muscle. The experimental data suggest that the combined effect of the bronchodilator Isoproterenol and length oscillations is higher than that of each when applied alone. This response has been tested by varying the amplitudes and frequencies of the oscillations. The relaxation of the ASM subsequent to the application of oscillations was found to be proportional to the amplitude, but independent of the frequency of oscillations. This study gives more insight into the role of bronchodilators and oscillations (such as while breathing) on the contracted airways in an optimal goal of developing a new treatment methodology for asthma.
An Experimental Investigation Into Heatless Self-Humidifying Breathing System
(Auckland University of Technology, 2022) Al-Attar, Ahmed Kaleem Muez; Al-Jumaily, Ahmed
Many developments have been conducted on heat and moisture exchange devices to recover heat and moisture from expired air to condition the inspired air for lung supportive devices. Available methods typically require an external heat source to achieve the objectives. However, most available HME devices have limited capabilities, such as delivering insufficient heat and moisture to the patient, causing breathing restriction and increasing dead space levels in the system. The Institute of Biomedical Technologies (IBTec) at Auckland University of Technology (AUT) has developed a novel moisture exchanger material for a self-humidification feature. However, this material requires a micro-electrical heat generator as a heat source to achieve its objectives. The device absorbs water vapor from human exhalation when the surrounding temperature is lower than its thermal threshold and releases the vapor when temperature increases by the micro-electrical heat generator above that edge. This research aims to investigate further the possibilities of optimizing this respiratory supporting system to become a heatless system and eliminate the need for the micro-electrical heat generator by integrating a suitable self-heating element utilizing an exothermic chemical reaction to absorb heat during the exhalation process and delivers the heat in the inhalation process. Such development is expected to reduce device expense, power usage, and size of the breathing system, become user-friendly, and increase efficiency safely and securely. This research will investigate different approaches to develop and optimize a new system with self-humidification and heatless features.
Experimental techniques to determine the Young's Modulus of the trachea
(Auckland University of Technology, 2004-01-01) Hermawan, Vera; Al-Jumaily, Ahmed
In addition to its usefulness in modeling and simulation processes, the modulus of elasticity is an index which is highly used in biomedical identifications and tissue characterizations. For many composite and viscoelastic materials an "accurate modulus" is an idealistic hypothesis and an "equivalent modulus" is normally of a high biomechanical significance. The composite shape of the trachea, which consists of the smooth muscles and cartilage rings, renders the fact that an equivalent modulus is in place for many applications. In this paper three in-vitro nondestructive testing techniques are presented to determine the Young modulus of elasticity of the trachea and the results are compared with the standard uniaxial state of stress method. These techniques are based on: (1) simulating the trachea as a pressurized vessel and deducing a special relationship between the pressure and the radial strain; (2) using two hydrophones and studying the variation in acoustic transmittance caused by the presence of the trachea in a water-bath; (3) considering the trachea as a thin cylindrical shell and determining the resonance vibration response. Elaborate discussion is presented to identify the "pros" and "cons" of each technique and final practical recommendations are made.
Feasibility of using miniaturised electromagnetic actuator in small air pumps
(Auckland University of Technology, 2011) Wang, Lei; Al-Jumaily, Ahmed
The feasibility of using an electromagnetic actuator as an important part in a portable diaphragm air pump is investigated. The ideal electromagnetic actuator will have capabilities of producing large deflection and high tuneable frequency. These two characteristics make the actuator very attractive for the present application. Much effort has been put into the development of the proposed diaphragm air pump because it is easily integrated into the complex system. The characteristics of the magnetic field of the electromagnetic coils are thoroughly investigated in order to complete the design optimization for the proposed electromagnetic actuator. As the base of the design optimization for the proposed planar and cylindrical coils, the proposed model of magnetic field distribution for a circular current loop is developed. The design optimization for various parameters of planar coils was thoroughly investigated. Approximate approaches to determine the electromagnetic forces are discussed. Models for diaphragm deflection were determined. The fluid model for evaluation of flow rate form the output of diaphragm pump was developed. The feasibility of using nozzle/diffuser elements as components of air pumps is investigated. The geometry of nozzle/diffuser elements was designed and the chamber configuration for the proposed electromagnetic air pump was determined. The proposed air pumps, including the electromagnetic actuator, PDMS (polydimethylsiloxane) diaphragm, and chamber and nozzle/diffuser elements were built. Several experiments were conducted to investigate the performances of the proposed electromagnetic actuator including the deflection of diaphragm and frequency characteristics. The flow rate of the proposed air pump was measured. In conclusion this study supplies solid evidence of achievements using electromagnetic actuators in air pumps.
An investigation into bicycle steering and roll responses
(Auckland University of Technology, 2004) Prince, John; Al-Jumaily, Ahmed
This research studies the dynamics of bicycles, in particular how they corner, balance upright and maintain directional control. It examines the design and performance of single front wheel steering, the geometry of which has up till now, been based on established practice rather than scientific investigation. A computer simulation model for bicycle dynamics was developed using Simulink™. The model combines all the key elements of a moving bicycle, the steering torque, the physical parameters that define the design and is based on Euler’s Equations of Motion. It can simulate a wide range of bicycle manoeuvres, particularly counter-steered cornering. The model can be changed to simulate different bicycles and riders so that comparisons can be made between different bicycle designs and different conditions of cornering. After running the computer model it is found that, the most important torque terms for yawing are; the castor torque, the Jones’ torque and the steering torque input by the rider. The most important torque terms for rolling are; the gravitational and centrifugal torques. The next most important terms are the various new torques added in this study due to the steering geometry. The negligible terms are the Coriolis torque and the gyroscopic torques (again the gyroscopic torques are shown to be unimportant). To validate the computer model it was compared firstly to existing theory and then secondly to the results of an experimental investigation. The experimental investigation used a bicycle fitted with sensors to measure steering and roll angles. The steering angle was measured with an electrical potentiometer mounted directly on the steering stem and the roll angle was measured using an infra-red (IR) distance measuring sensor mounted at the rear of the bicycle. A data logger recorded the steering and roll responses to a series of cornering manoeuvres. A main research objective was to improve steering performance in terms of the response, system stability and frequency response. It was found that small changes in system inputs and bicycle geometry can have a large effect on dynamic behaviour. Head tube angle, rake, trail, steering torque and damping are all important factors and to some extent interrelated. The computer model allows combinations of these factors to be trialed so that their effect can be quantified. Procedures for the design of bicycles have been prepared so that unstable designs can be avoided and steering problems with existing bicycles can be examined. A graph of rake against trail allows unstable combinations to be shown in an easily interpreted form. This graph allows bicycle designers and cycling enthusiasts to quickly grasp the importance of selecting appropriate geometry. The research has successfully achieved its objectives and identified areas for future developement. The computer model could be improved by adding rider steering feedback and by plotting the bicycle’s course. The experimental investigation could be improved by making the equipment easier to calibrate and use.
An investigation into the acoustic response of the arteries
(Auckland University of Technology, 2007) El-Aklouk, Essa; Al-Jumaily, Ahmed; Lowe, Andrew
In hypertension, aging and certain types of arterial disease, central elastic arteries become stiffer and hence the central pulse pressure is augmented due to the increase in pulse wave velocity (PWV) and the early return of reflected waves to the heart from the periphery. Valuable information on arterial properties such as stiffness can be obtained from both central (aortic) and peripheral (e.g. radial) pressure waveforms. A feasibility study for the non-invasive estimation of arterial stiffness using pressure waves detected by a pneumatic cuff wrapped around the upper arm is presented. The propagation and reflection of arterial pressure waves (generated by the heart) in the central elastic arteries are simulated using a simplified propagative acoustic model. Furthermore, a lumped parameter model is used to describe the transmission of the pressure waves from the brachial artery to the cuff external wall. By combining the two models, the brachial artery pressure contours under the pneumatic cuff were simulated. Also, the combined model was able to illustrate how these pressures transmit through the arm to the cuff’s external wall and produce a strain contour. The effects of aortic stiffness, aortic geometrical variations, heart rate and cuff pressure were investigated by simulating the model at different parameters and observing the pressure and strain augmentation and the timing of the return of the reflected wave. This work was done as part of the development of a non-invasive diagnostic device by Pulsecor Ltd. The model results obtained in this work are in agreement with published experimental results and the strain contours obtained using the device and hence can be used to develop the device’s stiffness estimation algorithm.
An investigation into the development of a miniature Piezoelectric pump
(Auckland University of Technology, 2012) Meng, Lei; Al-Jumaily, Ahmed; Ramos, Maximiano
This thesis is aimed at improving the understanding and effectiveness in operating of the micropump in CPAP system. The principle objectives were to understand the air flow rate and air pressure of a micropump designs for the CPAP System. The feasibility of developing a micropump using piezoelectric fans was investigated. Input frequencies and voltages were quantified for different chambers of micropump, discharge air flow rates and air pressure. The effect of these parameters on flow rate and air pressure was determined. To test the effect of air flow and air pressure produced by the micropump, a mathematical model of piezoelectric fan is developed. The experimental results with dynamic characteristics of air flow resulted in the following conclusions. 1. The vibration frequency is influential in determining the attainable pressure compared to the vibration amplitude. 2. The parallel configuration of two piezoelectric fans excited with the same phase yields more flow rate than excited with opposite phase. The parallel configuration yields more flow rate than series configuration, but the series configuration yields higher air pressure. 3. The shapes of the flow channel, inlet and outlet have significant influence on the air flow rate and pressure.
Modelling and optimization of Air Flow Sensor within CPAP System
(Auckland University of Technology, 2007) Huang, Junhai (Johnny); Al-Jumaily, Ahmed
The Continues Positive Airway Pressure (CPAP) therapy is the most popular noninvasive therapy used to treat Obstructive Sleep Apnoea symptoms (OSA). Recent sleep clinic research requires more CPAP functions during patient s sleep periods. It would be an advantage to operate the CPAP system at a lower pressure whilst monitoring the patient s air flow, and raise the pressure as the OSA is detected, rather than maintaining a fixed higher minimum pressure in order to reduce OSA symptoms. In order to detect OSA, an air flow sensor is considered ideally suited to assemble within the CPAP system and the characteristics of this type of sensors are investigated by creating and validating a mathematical model. Before determining the most suitable type of air flow sensor, several common methods of air flow measurement were investigated. Ultrasonic and hot wire air flow sensors were considered to be the most suitable sensors to be implemented. After setting up the simulation model and conducting experiments, some limitations of ultrasonic air flow sensor were found, so the hot wire sensor was selected for further investigation. Comparing the performances of three types of hot wire sensor, Constant Voltage (CV), Constant Current (CC) and Constant Temperature (CT), the CT hot wire sensor was found to be the most suitable type for CPAP systems. In order to achieve a precise measurement, different locations for the air flow sensor within CPAP system were investigated and the blower inlet was found to be the best location for air flow sensor. The simulation CT model hot wire sensor was developed. The experimental results were compared to the simulation model results. Comparison of the two results showed less than 1.5 % error when the air flow velocity exceeded 1.0 m/s (Average air speed is 5.0 m/s from the CPAP Blower). Environmental conditions of temperature, humidity and wire property effects were analysed by processing the simulation model under different conditions. The following conclusions were drawn out: The output current to the hot wire air flow sensor rise significantly as the hot wire diameter increases, however, the sensor response time increases significantly. It was found that platinum wire of a diameter 0.02 mm can meet the response time requirement for diagnosis of sleep disorders. Various wire lengths produce no significant effect on both aspects of output wire current and response time. Therefore wire length can be designed to fit the inlet channel of the CPAP blower. Higher wire temperature causes higher wire current flow at the same air flow velocity, however, lower wire temperatures achieve a faster response speed. The temperature range of 50 to 100oC over ambient was found to be an optional setting. To achieve the desired level of accuracy a temperature compensation circuit was required for the hot wire air flow sensor. Otherwise it was necessary to keep the sensor in a stable room temperature environment to gain the same result. The percentage error of ambient temperature was about 0.65% per oC.
Non-invasive blood pressure measurement algorithm for all age groups
(Auckland University of Technology, 2012) Ma, Xiaoqi; Al-Jumaily, Ahmed; Lowe, Andrew
The oscillometric method is the most common technique used in commercial non-invasive blood pressure monitoring. In this technique, devices record the pressure oscillations in the cuff as the cuff pressure decreases from supra-systolic to sub-diastolic. The values for systolic pressure (SP) and diastolic pressure (DP) are determined by analyzing the shape of the oscillometric envelope. In many oscillometric algorithms, fixed percentile algorithms are used to determine SP and DP but their accuracy has been questioned. In this research an algorithm has been developed based on a beat-by-beat pattern recognition approach using time and frequency domain signal processing to extract features and an artificial neural network (ANN) is designed for classification of each beat as supra-systolic, sub-diastolic or in between. Normalized beat shape is successful at determining SP and DP and it also shows good agreement with recommended gold standard blood pressure auscultatory measurement.
Optimization of the optical properties of electrostrictive polyurethane for a smart lens
(Auckland University of Technology, 2005) Abbas, Ibtisam; Al-Jumaily, Ahmed
Smart polymer material, such as electrostrictive polyurethane elastomer (PUE) with compliant electrodes (conductive polyyrrole PPy), is potentially useful as a small–scale, solid–state actuator technology in a changeable focal length lens in smart electroactive lens, (“EAL”). The limitation of the conventional lenses highlights the need to develop a new smart optical lens system that has the ability to change focal length according to the need of the wearer and to overcome the deficiency of using several conventional fixed focus length lenses. The basic principle of optical correction is to change the curvature and thickness of a lens, and so change the focal length. In this way, it would be possible to accommodate near and far distance visual tasks in one lens. Electrostrictive PUE with compliant electrodes has superior electromechanical coupling characteristics with application of an electric field and exhibit superior optical properties such as high index of refraction, transparent in the visible rang (400-700nm) and has adequate absorption of UV radiation (up to 380nm). It will be used as the smart material for an smart electroactive lens (EAL). In this thesis, both the optical and the electroactive properties of PUE film were investigated and developed for the proposed EAL. The governing equations for the dynamic performance of these characteristics were also derivative. In light of this, a new relationship was developed to provide a direct reading of the focal length, applied voltage, thickness and deflection. Attention was focused on the processing conditions which affect the film properties. These properties include optical transparency, electroactive response and Young’s modulus of elasticity. In this research, two techniques of producing PUE films were used, the first consists of moulding the PUE pellets under various pressure and temperature conditions while the second was based on producing films of various thickness by the solvent casting method using tetrahydrofuran (THF) as solvent followed by a 95°C annealing in vacuum for 30 min. Sample films of 50 mm diameter were rigidly attached to circular frames and tested under applied DC field in the range of 4-25 KV. The pellethane polyurethane elastomer (PellPUE polyether based polyurethane) film prepared by the first method has deformation response in the order of 0.8 mm; however, it was translucent. The PellPUE film prepared by the second method resulted in thinner film and reasonable electro-active response in the order of 0.3 mm. The transparency of the latter samples was excellent and closed the gap to produce a smart lens. The main goal of this project is to optimize the optical properties and the electroactive characteristic of smart PUE to suit different environmental conditions. This includes developing the dynamic response characteristics with the total transmitted light of the final composite films of over 83.4% in the visible range. PUE films with PPy electrode have demonstrated potential in developing smart lens materials.
PTCR effect in La2CO3 doped BaTiO2 ceramic sensors
(Auckland University of Technology, 2006-01-01) Puli, Venkata Sreenivas; Al-Jumaily, Ahmed
The positive temperature coefficient of resistivity (PTCR) sensors is resistor materials that undergo a sharp change in resistivity at a designed Curie temperature due to its unique structure and chemical composition. This effect serves important control functions in a wide variety of electronic circuitry and similar applications. Conventional calcining of mixed oxides method (CMO) is used for fabricating lanthanum doped barium titanate (BaTiO3) for PTCR behaviour through solid-state-sintering route, at 1100°C, 1350°C. Two batches of samples were fabricated at low and high sintering temperatures of 1100°C, 1350°C respectively. The effect of different concentrations of donor dopant on BaTiO3 on the electrical properties of Ba(1-x)LaxTiO3 with x= 0.0005, 0.001, 0.002, 0.0025, 0.003 mol%, is investigated at low sintering temperature. The influence of lantanum doping with Al2O3+SiO2+TiO2 (AST) as sintering aids on the electrical properties of Ba(1-x)LaxTiO3 with x= 0.0005, 0.001, 0.003 mol%, is also investigated. The results of the electrical characterization for the first batch of samples showed an increase in room temperature resistance with increaisng donor concentration. Also the results of the electrical characterization for the second batch of samples also showed the same increase in room temperature resistance with increasing donor concentration. For first batch of sensors the high room temperature resistance keeps the jump small and these materials showed V-shaped NTCR-PTCR multifunctional cryogenic sensor behavior with a strong negative coefficient of resistance effect at room temperature.Where as the second batch of sensors showed few orders of magnitude rise in resistivity values. The La-doped BaTiO3 ceramics co-doped with Mn gives an enhanced PTCR effect which can be exploited for various sensor applications.

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