Search

We describe a ‘clock control unit’ based on a dual-axis cubic cavity (DACC) for the frequency stabilisation of lasers involved in a strontium optical lattice clock. The DACC, which ultimately targets deployment in space applications, provides a short-term stable reference for all auxiliary lasers—i.e. cooling, clear-out, and optical lattice—in a single multi-band cavity. Long-term cavity drift is compensated by a feed-forward scheme exploiting a fixed physical relation to an orthogonal second cavity axis; either by reference to an ultrastable 698 nm clock laser, or by exploiting the differential drift between orthogonal axes extracted by a single laser in common view. Via a change of mirror set in the cavity axis accessed by the clock laser, the system could also provide stabilisation for sub-Hz linewidths at the 698 nm clock wavelength, fulfilling all stabilisation requirements of the clock.

The development of a portable strontium lattice clock is discussed. Solutions to many of the engineering challenges required to build the next generation of portable and ultraprecise clocks will be presented. In particular, a) the realisation of a compact laser module which produces multiple stable laser frequencies required for the experiment and b) the progress made in the development of the atomics module.

A non-invasive and portable bioimpedance method and a device for detecting superior to inferior closure of the pharynx during swallowing have been developed. The 2-channel device measures electric impedance across the neck at two levels of the pharynx via injected currents at 40 and 70 kHz. The device has been trialled on both healthy and dysphagic subjects. Results from these trials revealed a relationship (r = 0.59) between the temporal separation of the second peaks in the bioimpedance waveforms and descending pressure sequence in the pharynx as measured by pharyngeal manometry. However, these features were only clearly visible in the bioimpedance waveforms for 64% of swallows. Further research is underway to improve the bioimpedance measurement reliability and validate waveform feature correlation to swallowing to maximise the device's efficacy in dysphagia rehabilitation.

The precise rotation of suspended cells is one of the many fundamental manipulations used in a wide range of biotechnological applications such as cell injection and enucleation in nuclear transfer (NT) cloning. Noticeably scarce among the existing rotation techniques is the three-dimensional (3D) rotation of cells on a single chip. Here we present an alternating current (ac) induced electric field-based biochip platform, which has an open-top sub-mm square chamber enclosed by four sidewall electrodes and two bottom electrodes, to achieve rotation about the two axes, thus 3D cell rotation. By applying an ac potential to the four sidewall electrodes, an in-plane (yaw) rotating electric field is generated and in-plane rotation is achieved. Similarly, by applying an ac potential to two opposite sidewall electrodes and the two bottom electrodes, an out-of-plane (pitch) rotating electric field is generated and rolling rotation is achieved. As a prompt proof-of-concept, bottom electrodes were constructed with transparent indium tin oxide (ITO) using the standard lift-off process and the sidewall electrodes were constructed using a low-cost micro-milling process and then assembled to form the chip. Through experiments, we demonstrate rotation of bovine oocytes of ~120 μm diameter about two axes, with the capability of controlling the rotation direction and the rate for each axis through control of the ac potential amplitude, frequency, and phase shift, and cell medium conductivity. The maximum observed rotation rate reached nearly 140° s⁻¹, while a consistent rotation rate reached up to 40° s⁻¹. Rotation rate spectra for zona pellucida-intact and zona pellucida-free oocytes were further compared and found to have no effective difference. This simple, transparent, cheap-to-manufacture, and open-top platform allows additional functional modules to be integrated to become a more powerful cell manipulation system.

The approach taken during restructuring the Mechatronics Program at the University of Canterbury is described, along with challenges faced. The background of the University of Canterbury Mechatronics program is examined, as are the challenges of integrating the program within the Department of Mechanical Engineering and the Department of Electrical & Computer Engineering. The new Mechatronics program features integrative projects during each of three Professional Education years to reinforce students’ “mechatronic” thinking and hands-on abilities. The project-based course “Introduction to Mechatronics Design” features a series of application-oriented laboratory projects using a Programmable Logic Controller (PLC). The restructured program of balanced essential skills training coupled with focus streams of specialization may signal a paradigm shift in engineering education.

Background : Electroporation is now a common tool in biotechnology and is used in a number of medical treatments. Until recently, the development of theoretical models of electroporation has lagged behind the experimental research. In order to optimize the efficiency of electroporation, it is important to consider as many biological and physical aspects as possible and it is a necessity that a variety of electric pulse parameters be tried. Thus a comprehensive model which can predict electropermeabilization as a result of any form of applied electric field and other important electroporation parameters is necessary. Results : A numerical model for a single cell electroporated by application of arbitrary external electric field pulses has been developed. The model is used to compare the transmembrane potential Vm , and pore density N , developed in response to the pulses. Vm and N are calculated via a piece-wise step response method that enables solutions to be obtained for any practical applied electric field waveform. Pore density is shown to increase so long as a threshold Vm is maintained by the electric field, and effectively clamps Vm to just over 1 V while N is increasing. Short unipolar pulses are also shown to create asymmetrical N between the two cell polar regions, whereas bipolar pulses result in a symmetrical N . Conclusions : The model presented here helps predict dynamic non-linear results of electropermeabilization, given any form of applied electric field and other important electroporation system parameters. This model can be used as a tool for the determination of starting parameters in biological applications.

We describe a distributed face recognition strategy that is implemented across a set of independent wireless sensor nodes which have no shared storage. Each node contains a camera of limited aperture, whose images are matched against a randomly selected feature of each face in a statically defined training set. The training set is represented in a distributed in-network storage device that emerges based on a shared protocol running on the sensor nodes. Nodes communicate their findings to other nodes in their immediate vicinity, and eventually the network aggregates these findings to conclude on the identity of the observed target. The independence of the recognition processes on nodes gives rise to the possibility that conflicting results may arise. We compare two consensus building strategies that we have designed to allow the entire network to arrive at a consistent conclusion using efficient communications. Our consensus strategies are based respectively on an optimization of gossiping, and on a distributed feature aggregation process that allows the recognition confidence on each node to monotonically increase.

Today. in the United Kingdom, approximately one in seven infants are diagnosed with asthma in the first six months of life. There has been a dramatic increase in recent years, and asthma-related drugs now account for approximately 11% of the total prescription costs to the National Health in the UK (Department of Health, Asthma and Epidemiology, HMSO, 1995). In addition to medication, preventative measures include attempts to exclude the allergen from the domestic environment. This requires careful control of the most common asthma allergen, Der p1,which is conveyed by the waste products produced by the house dust mite (Dermatophagoides pteronyssinus). Acaricides may be used to kill the dust mites,but these have to be combined with allergen denaturing agents if eradication of the allergen is sought. Mechanical barriers such as mattress and pillow covers offer some protection from contact with the allergen, but often with a varying degree of success. High levels of allergen carriers are also known to exist in carpeting, and this can lead to a particularly undesirable environment for infants who frequently crawl with their faces close to, and sometimes in contact with, the carpet pile. Inhalation of allergen is usually unavoidable in this situation. Research has indicated that the use of electret fibres can dramatically enhance the anchoring of allergen carriers in the carpet pile. Electrostatic adhesion of the carriers to the electret fibres ensures that for normal traffic conditions, such as walking, crawling, playing etc, much less dust is released from the carpet; thus reducing the probability of inhalation. Dispensing domestic products in aerosol form has undoubtedly been a commercial success; offering considerable consumer advantages in applications ranging from paints, polishes and insecticides. The targeting of products in aerosol form may not, however, be optimised with a high proportion of the product often missing its target. It is well known that electrostatic spraying can enhance targeting, but this technology is normally limited to industrial processes such as paint and powder coating. A novel and unique aerosol package has been developed which charges the aerosol on delivery in a controlled manner. The Smartseeker-(-Smartseeker is a trademark of Reckitt Benckiser) insect seeking technology is now incorporated into a commercial aerosol insecticide, and is the world's first electrostatically optimised aerosol can which requires no active energy source. Flying insect knock-down is enhanced by up to 34% with this technology.

Searching a wilderness environment for missing persons is a task that is well suited to a swarm of miniature UAVs, given the high availability of low cost drones and the large geographic area that is to be covered. The use of a swarm for detection provides an alternative to automated detection solutions that require high processing power to search all images encountered for all possible combinations of items that may be detected. Challenges faced in implementation include limited storage and processing capacity per node, the designation of data storage points when the swarm is far from any base station, and inhospitable wilderness environments that may destroy UAVs. The solution that we employ leverages on the use of distributed in-network storage that allows each UAV to behave as a sensor node which is specialized to the task of detecting certain features. Our data storage strategy self organizes in an efficient way using a randomized selection of backup addresses, and is robust to the loss of data even after events that cause the destruction of a large number of nodes. Analysis and simulations show the survivability of data, how the communication latency varies with the number of backup addresses and that a set of simple processors can be used to collaboratively perform distributed searches with relatively high accuracy.

The generation of monoclonal antibodies by electrofusion techniques has advanced the efficiency of B-cell immortalisation over ‘PEG’ fusion techniques by greater than 100 fold and also allows for the manipulation of hundreds of cells compared to millions as in the later technique. Most researchers in this field at present have equipment which is highly specialised and machined ‘in-house’ or expensive commercial electrofusion apparatus which precludes small laboratories with limited access to either machine shops or research facilities from using this technique. We present here data showing that it is possible to make a small switching device and couple this to readily available commercial electroporation instruments making an efficient electrofusion device that a competent electronics technician could accomplish readily.

This paper describes a novel design of a high voltage, high frequency, bipolar pulse generator, for experimental use in electrochemotherapy and irreversible electroporation, using RF MOSFETs (DE375-102N12A) in a cascaded multilevel inverter topology. Its pulsing regime is fully programmable and is con-trolled by an FPGA. A systematic development approach was followed. The UCC37321 gate driver and the HCPL-2400 opto-coupler were selected. Damping resistors and RCD snubbers were employed to mitigate excessive ringing in the output circuit. Practical EMC reduction guidelines were followed. The pulse generator operated satisfactorily, producing a typical cascaded 5-level output of 1250 V peak at 1 MHz into a load of 80 ohm in parallel with 235 pF. Higher room temperature caused a slight “indent” into the output pulses.

Distributed approaches to face recognition have been widely studied for over a decade. One of the remaining problems with these approaches is that of coordinating the heavy storage requirements in a distributed way. We present a modification of existing facial recognition algorithms deployed on a self organizing, reliable and robust platform composed of wireless sensor nodes that should yield a self-organizing algorithm for face recognition, which manages its storage in an entirely distributed way. Our preliminary results, though tentative, suggest that these expectations are plausible. As an effective facial recognition algorithm, our implementation is still a work in progress; but the modest computational requirements of the storage platform, coupled with the parallelizable operations already in current distributed face recognition techniques should eventually yield a distributed algorithm that can be scaled up to run on a very large system of simple processors.

A theoretical evaluation of cellular transmembrane potential is used to investigate the effect of dynamic high magnitude electric fields specific to the electrofusion process. A numerical computer model is designed for the purpose. Conventional DC impulse techniques for electrofusion are found to be less efficient than AC electric fields in both an electrical and a biological sense.

This paper will detail the processes in the design, revamp and commissioning of an existing 12 kV–4.16 kV 15 MVA secondary-selective substation for a major refinery with its N-1 capacity already exceeded due to load creep. The project installs a third 15 MVA transformer with associated switchgear, bus ducts, protection and transfer control system. The paper will briefly outline the conceptual plan and engineering for the project. The primary focus of the paper will be to detail the effort in modification of the existing power system configuration, developing a startup and commissioning plan, factory acceptance testing, and the actual startup and commissioning. The management directive was to complete a “flawless” startup and commissioning of the substation within a compressed refinery turnaround window. A flawless startup was important to management because a functional failure in a main electrical substation was unacceptable. The business cost of such a failure could easily exceed the capital cost of the substation. It was deemed as cost effective by management and engineering personnel to insure that the design, construction and testing of the substation was as thorough as possible. The design was completed by one team and reviewed by the fresh eyes of a completely independent team. The paper will review important tests performed during the startup and commissioning, along with the benefits and usefulness it provided. The complicated system was checked by the vendor, checked again by the startup team, and then completely checked for functionality at the end user's facility. The testing included the normal functional and secondary injection testing, but additionally used primary injection to test relays and CTs and test certain relay functions. The paper will conclude with a discussion of the lessons learned during the testing.

The energy costs of transferring data from sources in Wireless Sensor Networks (WSNs) to sinks at the edge of the network are high. These high costs have generated much interest in data storage strategies within the WSN. The frequently dangerous and power limited conditions in which nodes are required to operate can however result in the loss of nodes that are vital data storage points. We extend work on a reliability enhancing WSN data storage strategy called Address Coding that provides power efficient self organizing backup capability in networks of homogeneous nodes. We show that the asymptotic energy cost per backup is lower with Address Coding than it would be for a naive storage strategy based on AODV. We also show that probabilistic flooding can be applied to Address Coding, yielding significant reduction in energy cost with negligible loss in reliability.

The University of Canterbury has embedded design projects into each of the three professional education years (years 2-4 of the degree) in its new Mechatronics programme. The goal is to create an educational mechanism that links engineering sciences and individual class topics to integrated applications. A series of application-oriented laboratory projects using a Programmable Logic Controller is built into the second-year (1st professional year) curriculum. In the third year (2nd professional), a mobile robotic system design project encompasses electromechanical design, embedded control, software development and system integration. In the fourth and final year (3rd professional), students advance to working on mechatronics research projects that address real-life complex engineering problems facing the industrial sponsors. Embedding design projects progressively into multidisciplinary engineering education has proven to be an effective pedagogy to reinforce students' systems thinking, hands-on abilities, and cross-course linkage.

This paper will review the many factors involved in the successful selection and operation of medium voltage (2300V and above) induction and synchronous motors for use in the petrochemical industry. Among these are the power requirements of the driven load, start-up and normal operating conditions, and plant power restrictions. In addition, consideration must be given to maintenance requirements, necessary training and skills for site personnel, and the ability of the manufacturer to provide services to maximize the reliability of the machine. These areas will be discussed to give readers a better understanding of the subject, and field experiences from multiple petrochemical plants will be reviewed.

Nuclear transfer (NT) cloning involves manual positioning of individual donor-recipient cell couplets for electrofusion. This is time-consuming and introduces operator-dependent variation as a confounding parameter in cloning trials. In order to automate the NT procedure, we developed a micro-fluidic device that integrates automated cell positioning and electrofusion of isolated cell couplets. A simple two layer micro-fluidic device was fabricated. Thin film interdigitated titanium electrodes (300 nm thick, 250 microm wide and 250 microm apart) were deposited on a solid borosilicate glass substrate. They were coated with a film of electrically insulating photosensitive epoxy polymer (SU-8) of either 4 or 22 microm thickness. Circular holes ("micropits") measuring 10, 20, 30, 40 or 80 microm in diameter were fabricated above the electrodes. The device was immersed in hypo-osmolar fusion buffer and manually loaded with somatic donor cells and recipient oocytes. Dielectrophoresis (DEP) was used to attract cells towards the micropit and form couplets on the same side of the insulating film. Fusion pulses between 80 V and 120 V were applied to each couplet and fusion scored under a stereomicroscope. Automated couplet formation between oocytes and somatic cells was achieved using DEP. Bovine oocyte-oocyte, oocyte-follicular cells and oocyte-fibroblast couplets fused with up to 69% (n = 13), 50% (n = 30) and 78% (n = 9) efficiency, respectively. Fusion rates were comparable to parallel plate or film electrodes that are conventionally used for bovine NT. This demonstrates proof-of-principle that a micropit device is capable of both rapid cell positioning and fusion.

New applications for wireless sensor networks(WSNs) that demand stricter quality of service guarantees may require high levels of scalability, robustness, life expectancy and response time. Unfortunately, most sensor network communication protocols often guarantee several of these requirements at the risk of others. Caching provides a doorway to a solution, however works reviewed thus far in WSN caching involve the energy intensive practice of cache placement. We show that when applying a strategy of using random backup addresses in a sensor network, an emergent functionality that places data closer to required sinks can be achieved in an energy efficient way.

To hasten the process of saving lives after disasters in urban areas, autonomous robots are being looked to for providing mapping, hazard identification and casualty location. These robots need to maximise time in the field without having to recharge and without reducing productivity. This project aims to improve autonomous robot navigation through allowing comparison of algorithms with various weightings, in conjunction with the ability to vary physical parameters of the robot and other factors such as error thresholds/limits. The lack of a priori terrain data in disaster sites, means that robots have to dynamically create a representation of the terrain from received sensor range-data in order to path plan. To reduce the resources used, the affect of input data on the terrain model is analysed such that some points may be culled. The issues of identifying hazards within these models are considered with respect to the affect on safe navigation.

Automated lab on chip systems offer increased throughput and reproducibility, but the implementation of microelectrodes presently relies on miniaturization of parallel plate electrodes that are time consuming and costly to fabricate. Electric field modelling of open electrofusion chambers suggested that widely spaced (or =2 mm) coplanar film electrodes should result in similar cell fusion rates as parallel plate electrodes provided the cell positioning was roughly midway between the electrodes. This hypothesis was investigated by electrofusion trials of bovine oocyte-donor cell couplets used in nuclear transfer (NT) cloning. Comparative experiments with reference parallel plate electrodes were conducted as controls. Coplanar fusion ratesor = 90% were demonstrated for embryonic blastomeres, follicular cells and fetal and adult fibroblasts as NT donor cells. For embryonic and adult cell types, there was no significant difference in fusion rate between coplanar and parallel plate electrodes. For both electrode geometries, fusion efficiency with adult fibroblasts was highest at a calculated field strength of 2.33 kV/cm. The coplanar electrodes required a voltage pi/2 times greater than parallel plate electrodes to achieve equivalent field strength when the couplets are placed midway between the electrodes.

Research into various forms of sustainable power generation is required to address the rising problems associated with fossil fuel limitations. A new research programme aims to show that electric power generation using low-grade heat and Stirling engine technology can be made commercially viable. Using the Modified Beale Number, and preliminary software modelling, an initial prototype has been designed. This prototype will output approximately 1 kW of electric power with a temperature differential of around 30 K. The fundamental considerations for this prototype are the effects of engine parameters such as compression ratio, pressure, regenerator matrix composition, displacer/power piston phasing, and displacer velocity profile. The result here being a novel gamma-type engine configuration that complements a high pressure system. The prototype also has an electrically actuated displacer piston so that the phasing and velocity profile are finely variable, and a modular regenerator matrix.

We propose a protocol for a distributed sensor network of unreliable components that causes the network to behave collectively as a memory device. The reliability of this memory device is greater than that of the individual components. Nodes with redundant data are not spatially collocated, so the system is robust to spatially localized damage. Address-datum pairs are submitted to the network at a designated interface point. The address in the pair determines the nodes that are used to store the pair. Messages are transformed on each hop, based on differences in addresses between the source and destination of the hop. The composition of these transformations produces a path dependent transformation on messages that provides reliable communication on the ensemble of unreliable parts. The reliability of the memory device is a tunable parameter that is achieved by adjusting the redundancy. We show how reliability improves with redundancy. We also show that optimum reliability is achieved with relatively modest redundancy.

Lab on chip (LOC) systems often require the controlled movement of individual biological cells. Automated operation of these systems usually requires detectors to track individual cells. Electrical methods involving measurement of the conductivity or permittivity of regions between two electrodes are capable of providing this information. However, these detection systems can interfere with other dielectrophoretic LOC cell handling systems. Conversely optical systems are immune to electrical interference. Many LOC devices are fabricated with only the top surface of the device being transparent to light, precluding the use of transmitted optical detection. This is often due to the use of silicon, a favoured substrate. Here we present a low cost optical system suitable for detecting biological cells in microfluidic channels. A flow cell with a fluid microlayer approximately 105±10μm deep was fabricated having a 100±10μm thick glass window, and a reflective base layer. The reflective base was formed by thermal evaporation of gold onto a substrate. Particles within a microfluidic layer were epi-illuminated by a standard (red) laser DVD pickup unit. The flow cell permitted the laser beam to be focussed onto the gold reflector, and back through a beamsplitter onto a photodiode. This system was tested using polystyrene beads that were representative of biological cells. The position of the focal point significantly affected the base line reflected signal, but this micron scale position sensitivity could be overcome using the magnetic focussing coil of the DVD pickup. In this system, polystyrene beads down to 3μm in diameter were successfully detected.

There are applications where low-current inrush and/or high starting torque are specified for reducing disturbance on the electrical distribution network. There are also situations where it is required to successfully start large ac motors at reduced voltage conditions when only one substation transformer of a double-ended transformer is in service at petrochemical plants. The latter condition requires the motors to draw lower inrush current while producing high starting torque. These requirements can create unfavorable design characteristics where one or both requirements cannot be accomplished using standard techniques at the final design stage or motor test. The authors have accomplished the design and installation of magnetic material retaining rings on induction motors with significant improvement in inrush currents and starting torques. Inrush currents have been reduced from 600% to 508%, and starting torques have been increased up to 14%. Several case studies of using magnetic retaining rings on large induction motors are described in this paper for machines ranging from 6000 up to 14 000 hp and testing as low as 380% of inrush for machines with magnetic rings. The application of this concept is not limited to only ac induction motors. The same process can also be applied to synchronous motors. Very limited information is available on the benefits of applying magnetic retaining rings and what the consequences are for large ac motors. The application of magnetic retaining rings is a practical approach to solving inrush and torque problems at the manufacturing or design stage. The theory, test, concepts, and consequences along with electrical and mechanical considerations are described in this paper.

The bio-physical effect known as electroporation or electropermeabilization is becoming more widely used in medical treatment, especially for chemotherapy and gene therapy. The conventional electrical apparatus used is based on DC voltage pulses which may not be optimal. Indications are that AC pulses may provide significant improvements. A high voltage linear amplifier design incorporating vacuum tube valves is presented that could facilitate AC pulse experimentation. Valves are used as they most readily suit the desired electrical specifications of an output voltage of 4kV/sub p/, a bandwidth of 500 Hz-5 MHz, a voltage gain of 52 dB, and an output impedance of

Recent advances have resulted in the availability of a new generation of silicon carbide (SiC) junction field effect transistors (JFETs), which unlike previous generations, exhibit highly desirable normally off characteristics. Normally off SiC JFETs are characterised with particular focus on previously unknown reverse conduction characteristics. Refinements are proposed to JFET gate driving circuits that allow their implementation as a single-chip solution. Reverse recovery characteristics of SiC JFETs were measured using diode testing techniques and found to be significantly faster than typical silicon metal oxide semi-conductor field effect transistor (MOSFET) body diodes. SiC JFETs are compared with silicon MOSFETs in power factor correction boost converters, including a real-world application where superior power conversion efficiency utilising SiC JFETs is demonstrated.

A robotic system and specifically designed end-effector tool has been developed for the automation of a meat processing task. This tool replicates the operation of a human butcher, while providing improved aseptic conditions and an increase in the reliability, repeatability and quality of the process. The robotic system incorporates a neural network-based fault detection scheme, which uses a learning vector quantisation network to classify axial load signals. A proposed online adaptive learning algorithm will provide continuous optimisation of the robot cut-path, leading to the automation of the path tuning process. This will allow the system to respond to seasonal carcass variations automatically and maintain a consistently high level of performance.