3,374 research outputs found
Shelley Stokes-Hammond interview, 15 September 2017
No full textShelley Stokes-Hammond is the oldest daughter of Louis Stokes. She is a graduate of The Ohio State University and Goucher College. She is a historic preservationist, author and public relations manager at Howard University. This 2017 interview was collected as part of a yearlong, community-wide commemoration of the 50th anniversary of Carl Stokes\u27 election as mayor of Cleveland
Shelley Stokes-Hammond interview, 15 September 2017
No full textShelley Stokes-Hammond is the oldest daughter of Louis Stokes. She is a graduate of The Ohio State University and Goucher College. She is a historic preservationist, author and public relations manager at Howard University. This 2017 interview was collected as part of a yearlong, community-wide commemoration of the 50th anniversary of Carl Stokes\u27 election as mayor of Cleveland
Shaping drops with magnetic fields
No full textThe control of small volumes of fluids (or drops) is important for a wide range of
applications, including lab-on-chip devices, where drops are transported and merged
for sensing and chemical mixing; liquid lenses, where drops are shaped to set optical
properties; and printing, where drops are generated by nozzles. Electric techniques
are widely used to generate, transport, split and merge drops. Equivalent magnetic
techniques are less well-known. Similarly to electric dipoles in electric fields, magnetic
dipoles experience a force in magnetic fields. This effect, called magnetophoresis,
is used to shape ferrofluids in magnetic valves and seals. Interest in shaping
drops with magnetic fields for microfluidics has recently increased, and ferrofluids
and paramagnetic salt solutions have been studied. The rich phenomenology of the
interaction of magnetic fields and fluids offers ample opportunities for exploration.
Diamagnetic fluids for example have no natural electric equivalent and are rarely
studied as a tool for microfluidics.
In this thesis, I study the shaping of drops with magnetic fields. My research focus
is on para- and diamagnetic salt solutions. Deformation of drops using external fields
and induced magnetism has not been fully explored in the literature. I study here
how induced magnetism can shape the liquid-vapour interface of drops and control
solids that float on them. This thesis includes (i) an introduction to the background
of the interaction of electromagnetic fields and fluids; (ii) a derivation of an expression
for the shape of drops in electromagnetic fields; (iii) experimental validation of
this expression through the measurement of the shape of para- and diamagnetic axisymmetric
sessile drops in homogeneous magnetic fields; (iv) demonstration of the
transport of para- and diamagnetic drops in magnetic field gradients; (v) explorations
of the use of shaping drops with magnetic fields for rheological measurements, and
for the controlled driving of objects floating on drops.
In summary, I explore how drops can be shaped in homogeneous magnetic fields,
and how the drops can be transported by magnetic field gradients. These fundamental
investigations may help stimulate novel applications of the controlled shaping of
drops with magnetic fields. In particular, I explore how this technique can be used in
rheology for food or medical research
HoverBot: a manufacturable swarm robot that has multi-functional sensing capabilities and uses collisions for two-dimensional mapping
No full textSwarm robotics is the study of developing and controlling large
groups of robots. Collectives of robots possess advantages over single robots
such as being robust to mission failures due to single-robot errors. Experimental
research in swarm robotics is currently limited by swarm robotic technology.
Current swarm robotic systems are either small groups of sophisticated
robots or large groups of simple robots due to manufacturing overhead,
functionality-cost dependencies, and their need to avoid collisions, amongst
others. It is therefore useful to develop a swarm robotic system that is easy to
manufacture, that utilises its sensors beyond standard usage, and that allows
for physical interactions. In this work, I introduce a new type of low-friction
locomotion and show its first implementation in the HoverBot system. The
HoverBot system consists of an air-levitation and magnet table, and a HoverBot agent. HoverBots are levitating circuit boards which are equipped with
an array of planar coils and a Hall-effect sensor. HoverBot uses its coils to
pull itself towards magnetic anchors that are embedded into a levitation table.
These robots consist of a Printed Circuit Board (PCB), surface mount components,
and a battery. HoverBots are easily manufacturable, robots can be
ordered populated; the assembly consists of plugging in a battery to a robot. I
demonstrate how HoverBot’s low-cost hardware can be used beyond its standard
functionality. HoverBot’s magnetic field readouts from its Hall-effect sensor
can be associated with successful movement, robot rotation and collision
measurands. I build a time series classifier based on these magnetic field readouts,
I modify and apply signal processing techniques to enable the online
classification of the time-variant magnetic field measurements on HoverBot’s
low-cost microcontroller. This method allows HoverBot to detect rotations,
successful movements, and collisions by utilising readouts from its single Hall-effect
sensor. I discuss how this classification method could be applied to other
sensors and demonstrate how HoverBots can utilise their classifier to create an
occupancy grid map. HoverBots use their multi-functional sensing capabilities
to determine whether they moved successfully or collided with a static object
to map their environment. HoverBots execute an "explore-and-return-to-nest"
strategy to deal with their sensor and locomotion noise. Each robot is assigned
to a nest (landmark); robots leave their nests, move n steps, return and share
their observations. Over time, a group of four HoverBots collectively builds a
probabilistic belief over its environment.
In summary, I build manufacturable swarm robots that detect collisions
through a time series classifier and map their environment by colliding with
their surroundings. My work on swarm robotic technology pushes swarm
robotics research towards studies on collision-dependent behaviours, a research
niche that has been barely studied. Collision events occur more often in
dense areas and/or large groups, circumstances that swarm robots experience.
Large groups of robots with collision-dependent behaviours could become a
research tool to help invent and test novel distributed algorithms, to understand
the dependencies between local to global (emergent) behaviours and
more generally the science of complex systems. Such studies could become
tremendously useful for the execution of large-scale swarm applications such
as the search and rescue of survivors after a natural disaster
The Limpet: A ROS-Enabled Multi-Sensing Platform for the ORCA Hub
No full textThe oil and gas industry faces increasing pressure to remove people from dangerous offshore environments. Robots present a cost-effective and safe method for inspection, repair, and maintenance of topside and marine offshore infrastructure. In this work, we introduce a new multi-sensing platform, the Limpet, which is designed to be low-cost and highly manufacturable, and thus can be deployed in huge collectives for monitoring offshore platforms. The Limpet can be considered an instrument, where in abstract terms, an instrument is a device that transforms a physical variable of interest (measurand) into a form that is suitable for recording (measurement). The Limpet is designed to be part of the ORCA (Offshore Robotics for Certification of Assets) Hub System, which consists of the offshore assets and all the robots (Underwater Autonomous Vehicles, drones, mobile legged robots etc.) interacting with them. The Limpet comprises the sensing aspect of the ORCA Hub System. We integrated the Limpet with Robot Operating System (ROS), which allows it to interact with other robots in the ORCA Hub System. In this work, we demonstrate how the Limpet can be used to achieve real-time condition monitoring for offshore structures, by combining remote sensing with signal-processing techniques. We show an example of this approach for monitoring offshore wind turbines, by designing an experimental setup to mimic a wind turbine using a stepper motor and custom-designed acrylic fan blades. We use the distance sensor, which is a Time-of-Flight sensor, to achieve the monitoring process. We use two different approaches for the condition monitoring process: offline and online classification. We tested the offline classification approach using two different communication techniques: serial and Wi-Fi. We performed the online classification approach using two different communication techniques: LoRa and optical. We train our classifier offline and transfer its parameters to the Limpet for online classification. We simulated and classified four different faults in the operation of wind turbines. We tailored a data processing procedure for the gathered data and trained the Limpet to distinguish among each of the functioning states. The results show successful classification using the online approach, where the processing and analysis of the data is done on-board by the microcontroller. By using online classification, we reduce the information density of our transmissions, which allows us to substitute short-range high-bandwidth communication systems with low-bandwidth long-range communication systems. This work shines light on how robots can perform on-board signal processing and analysis to gain multi-functional sensing capabilities, improve their communication requirements, and monitor the structural health of equipmen
Screen-printed platinum electrodes for measuring crevice corrosion: Nickel aluminium bronze as an example
No full textScreen-printed platinum electrodes were used to monitor crevice corrosion processes. The electrodes, printed on an inert alumina substrate, formed the bottom of an artificial crevice when mechanically clamped to a rectangular block of nickel-aluminium bronze (NAB). Cyclic differential pulse voltammetry was used to detect corrosion products over time whilst the assembly was immersed in a 3.5% by weight aqueous solution of sodium chloride. Cupric (Cu2+), ferric (Fe3+) and ferrous (Fe2+) ions were detected with evolution profiles indicative of selective phase corrosion
Development of an integrated complex 3D fluidic device assembled from fully characterised functional blocks: Michaelis-Menten enzyme kinetics analysis as a case study
No full textThe work presented in this thesis demonstrates a new approach to the design of integrated
uidic devices. Most `lab-on-a-chip' are in fact `chips-in-a-lab'. The equipment
used to operate them, such as microscopes and syringe pumps, is bulky, expensive and
the portability is non-existent. Fluidic devices operate on multiple domains, such a fludics, pneumatics, sensing, control, etc. By integrating the domains to a single device,
cost can be reduced and portability increased.
A new manufacturing process was developed to allow for the integration of multiple domains. The vast majority of fluidic devices are two-dimensional, made via soft
lithography, which limits the complexity and integration of other components. Three-
dimensional fluidic devices can be used to create complex intricate networks and can
include sensors, actuators and optics. A negative mould was 3D printed in Acrylonitrile Butadiene Styrene (ABS), encased in Polydimethylsiloxane (PDMS) before being
placed in an acetone bath. Because of the swelling properties of ABS in solvents, Acetone could reach the embedded ABS. ABS was liquefied in the presence of acetone,
making it possible to be flushed from the PDMS, leaving a void.
Following the development of the manufacturing process, functional fluidic blocks were
developed to create more complex devices based on usage. Each block was designed to
perform a given task, including a photometric sensor, a proportional valve, a turbulent
flow mixer, and storage wells. Using the blocks that were developed, a device designed
to perform Michaelis-Menten enzyme kinetics analysis was demonstrated. The device
was operated by a combination of a custom PCB and a Matlab GUI, thus creating an
integrated system. Enzyme kinetics were analysed by determining the initial reaction
rate of the enzyme-catalysed reactions for various concentration of its substrate. In
order to determine reaction rates, it is common to monitor the opacity of the reaction
product over time. This is often achieved by using a substrate (or a substrate analogue)
which produces a product with a unique optical absorbance, thus the opacity of the
product can be monitored by absorption spectroscopy. The experiment was repeated
for multiple concentrations before the kinetics were extrapolated. The device created
can perform the same task, as well as automating the mixing of any concentration
necessary for the kinetic analysis, at fraction of the cost of commercial equipment
Large-time behavior of the weak solution to 3D Navier-Stokes equations
No full textThe weak solution to the Navier–Stokes equations in a bounded domain D ⊂ R[superscript 3] with a smooth boundary is proved to be unique provided that it satisfies an additional requirement. This solution exists for all t ≥ 0. In a bounded domain D the solution decays exponentially
fast as t → ∞if the force term decays at a suitable rat
Review on the development of truly portable and in-situ capillary electrophoresis systems
No full textCapillary electrophoresis (CE) is a technique which uses an electric field to separate a mixed sample into its constituents. Portable CE systems enable this powerful analysis technique to be used in the field. Many of the challenges for portable systems are similar to those of autonomous in-situ analysis and therefore portable systems may be considered a stepping stone towards autonomous in-situ analysis. CE is widely used for biological and chemical analysis and example applications include: water quality analysis; drug development and quality control; proteomics and DNA analysis; counter-terrorism (explosive material identification) and corrosion monitoring. The technique is often limited to laboratory use, since it requires large electric fields, sensitive detection systems and fluidic control systems. All of these place restrictions in terms of: size, weight, cost, choice of operating solutions, choice of fabrication materials, electrical power and lifetime. In this review we bring together and critique the work by researchers addressing these issues. We emphasize the importance of a holistic approach for portable and in-situ CE systems and discuss all the aspects of the design. We identify gaps in the literature which require attention for the realization of both truly portable and in-situ CE systems
Synergy of debris mitigation and removal
No full textAt the beginning of the twenty-first century there was considerable effort made using evolutionary models to assess the effectiveness of post-mission disposal (PMD) and other mitigation measures to stabilise the growth of the debris population in low Earth orbit (LEO). Subsequently, this activity led to the recommendation of a “25-year rule” for the post-mission disposal of spacecraft and orbital stages intersecting the LEO region. At the time, it was anticipated that the 25-year rule, together with passivation and suppression of mission-related debris, would be sufficient to prevent the continued growth of the LEO debris population. However, in the last decade both the LEO debris environment and the debris modelling capability have seen significant changes. In particular, recent population growth has been driven by a number of major break-ups, including the intentional destruction of the Fengyun-1C spacecraft and the collision between Iridium 33 and Cosmos 2251. State-of-the-art evolutionary models now indicate that mitigation measures alone are insufficient to stabilise the LEO debris population. Consequently, this has led to considerable interest in the remediation of the debris environment and, especially, in debris removal. Yet there is a reluctance to revisit the role of PMD within the wider goal of remediation even though it does not provide the solution that was expected. Thus, there is a risk that the approach to remediation will follow a sequential, “over-the-fence” philosophy, which tends to deliver costly, and less than optimal solutions. In this paper, we present a new and large study of debris mitigation and removal using the University of Southampton’s evolutionary model, DAMAGE, together with the latest MASTER model population of objects > 10 cm in LEO. Here, we have employed a concurrent approach to remediation, whereby changes to the PMD rule and the inclusion of other mitigation measures have been considered alongside multiple removal strategies. In this way, we have been able to demonstrate the synergy of these measures and to identify aggregate solutions to the space debris problem. The results suggest that reducing the PMD decay rule offers benefits that include an increase in the effectiveness of debris removal and a corresponding increase in the confidence that these combined measures will lead to the stabilisation of the LEO debris population
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