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Design and Simulation of Next-Generation Datacentre Transceivers based on Ultrafast Laser Inscription
No full textAbstract unavailable. Please refer to PDF. Previously restricted until 30.09.24. Restricted access extended until 28.2.2027
Generic wireless sensor network for dynamic monitoring of a new generation of building material
Get PDFExisting testing methods for building materials before deployment include a series of
procedures as stipulated in British Standards, and most tests are performed in a controlled
laboratory environment. Types of equipment used for measurements, data logging, and
visualisation are commonly bulky, hard-wired, and consume a significant amount of
power. Most of the off-the-shelf sensing nodes have been designed for a few specific
applications and cannot be used for general purpose applications. This makes it difficult
to modify or extend the sensing features when needed. This thesis takes the initiative of
designing and implementing a low-powered, open-source, flexible, and small-sized
Generic wireless sensor network (GWSN) that can continuously monitor the building
materials and building environment, to address the limitations of the conventional
measurement methods and the technological gap.
The designed system is comprised of two custom-made sensor nodes and a gateway, as
well as purpose designed firmware for data collection and processing. For the proof of
concept and experimental studies, several measurement strategies were designed, to
demonstrate, evaluate, and validate the effectiveness of the system. The data was
collected from selected case study areas in the School of Energy, Geoscience,
Infrastructure and Society (EGIS) laboratories by measuring and monitoring building
structures and indoor environment quality parameters using the designed GWSN. The
measured data includes heat flux through the material, surface and air temperatures on
both sides of the material/structure, moisture variation, ambient temperature, relative
humidity, carbon dioxide, volatile organic compounds, particulate matter, and
sound/acoustic levels.
The initial results show the potential of the designed system to become the new
benchmark for tracking the variation of building materials with the environment and
investigating the impact of variation of building materials on indoor environment quality.
Based on the estimates of the thermal performance data, the sample used in the
experiment had a typical U-value between 4.8 and 5.8 W/m2K and a thermal resistance
value of 0.025m2
·K/W[1][2]. Thermal resistance values from the GWSN real-time
measurement were between 0.025 and 0.03 m2K/W, with an average of 0.025 m2K/W,
and thermal transmission values varied between 4.55 and 5.11 W/m2K. Based on the data
obtained, the results are within the range of typical values[3]. For thermal comfort measurements, the results of humidity and temperature from GWSN
were compared to values in the Kambic climatic chamber in the EGIS laboratory, and the
accuracies were 99 % and 98 % respectively. For the IAQ measurements, the values of
CO2 and TVOCs were compared to the commercial off-the-shelf measuring system, and
the accuracies were 98 %, and 97 %. Finally, the GWSN was tested for acoustic
measurements in the range of 55 dB to 106 dB. The results were compared to class one
Bruel & Kjaer SLM. The accuracy of GWSN was 97 %. The GWSN can be used for in lab and in-situ applications, to measure and analyse the thermal physical properties of
building materials/building structures (thermal transmittance, thermal conductivity, and
thermal resistance). The system can also measure indoor air quality, thermal comfort, and
airborne sound insulation of the building envelope. The key point here is to establish a
direct link between how building materials vary with the environment and how this
impacts indoor environment quality. Such a link is essential for long-term analysis of
building materials, which cannot be achieved using current methods.
Regarding increasing the power efficient of the implemented GWSN as well as its
performance and functionality, a new sensing platforms using backscatter technology
have been introduced. The theory of modulation and spread spectrum technique used in
backscattering has been explored. The trade-off between hardware complexity/power
consumption and link performance has been investigated.
Theoretical analysis and simulation validation of the new sensing technique, using
backscatter communication, has been performed. A novel multicarrier backscatter tag
compatible with Wireless Fidelity has been implemented and an IEEE 802.11g OFDM
preamble was synthesized by simulation. The tag consists of only two transistors with
current consumption no larger than 0.2 μA at voltage of less than 0.6 V.
Novel harmonic suppression approaches for frequency-shifted backscatter
communication has been proposed and demonstrated. The proposed approaches
independently manipulate mirror harmonics and higher order harmonics whereby;
specified higher order harmonics can be removed by carefully designing the real-valued
(continuous and discrete) reflection coefficients-based backscatter tags.
When successfully implemented, the backscatter system will reduce sensor node power
consumption by shifting the power-consuming radio frequency carrier synthesis functions
to carrier emitters.Engineering and Physical Sciences Research
Council (EPSRC) Funding EP/H009612/
Advanced quantum light sources for quantum networking
Get PDFAll of quantum photonics relies on being able to reliably generate quantum states
encoded in a particular degree of freedom of light. A key piece of technology is
therefore the photon source.
The choice of which degree of freedom to encode information in is an interesting one,
there is no universal best option. The historically common option of polarisation
is straightforward to manipulate and detect, but is restricted to a two dimensional
Hilbert space. More modern choices such as orbital angular momentum and path
encodings have become popular as they are high dimensional and offer greater information capacity per photon. The downside of these options is they are difficult
to integrate into existing communication networks.
Time and frequency are in a unique position of being naturally high dimensional
and compatible with single-mode fibre which makes them compatible with standard telecommunication equipment. The first half of this thesis is about generating time-frequency encoded quantum states in a scalable, lossless and arguably
simpler way than other techniques commonly used to generate time-frequency encoded states. This is done through the process of domain-engineering in parametric
downconversion. This thesis will walk through the basics of nonlinear optics and
particular three-wave mixing before going on to discuss the principles of domain-engineering and how it can be used to manipulate the time-frequency structure of
photon pairs produced in parametric downconversion. The experimental characterisation of a high dimensional frequency-bin entangled source is discussed along
with other potential time-frequency states which could be generated using the same
domain-engineering techniques.
The second half of the thesis is centred around building a bright and low noise
single-photon source at telecommunication wavelengths using a frequency converted
quantum dot. The performance of the source before and after conversion is compared
with the end result that the frequency conversion process does not significantly
alter the single-photon nature of the source. Using the mathematical machinery
developed to describe three-wave mixing, we show how the time-frequency properties
of quantum dots can be improved using frequency conversion.
With a bright and low noise source realised, a demonstration of quantum key distribution is carried out. The range and key rate of this demonstration compare
favourably to to other single-photon sources in the literature. Finally, theoretical
predictions of a decoy state quantum key distribution protocol using this source are
carried out which extends the range by around 100 km compared to the protocol
without decoy states
Optical investigation of many-body interactions in transition metal dichalcogenide heterostructures
Get PDFTwo-dimensional transition metal dichalcogenide (TMD) heterostructures have emerged
as a novel platform for the investigation of many-body physical phenomena. In these
systems, tightly bound excitons dressed by a gate-tunable Fermi sea form exciton-polarons, which are sensitive to Coulomb and spin interactions. In addition, TMD
moir´e devices provide a highly tunable platform to study strongly correlated electronic states. This thesis describes the use of magneto-optical polarisation-resolved
white-light confocal reflection spectroscopy at cryogenic temperatures (4 K) to probe
different many-body interactions in TMD heterostructure devices. First, monolayer
and bilayer tungsten diselenide (WSe2) and molybdenum diselenide (MoSe2) are investigated under varying carrier concentration. The doping dependent dispersions of
the exciton-polarons are shown to be excellent probes of the distinctive band structures of these materials. Then, in a moir´e heterobilayer MoSe2/WSe2 structure, optically injected excitons are shown to interact with itinerant carriers occupying narrow
moir´e bands to form exciton-polarons sensitive to strong correlations. At a multitude of fractional fillings of the moir´e lattice, the ordering of both electrons and holes
into stable correlated electronic states is observed, leading to extraordinary Zeeman
splittings of the exciton-polarons. Next, in heterotrilayer bilayer WSe2/monolayer
MoSe2, the energetic ordering of the moir´e bands is shown to be highly tunable with
applied vertical electric field, leading to the demonstration of hole transfer between
correlated states in K and Γ valley derived moir´e bands. Finally, the moire lattice
uniformity of MoSe2/WSe2 moir´e heterostructures is probed by spatial mapping of
the electronic correlations, leading to a measured variation in twist angle of 0.6 degrees across the device. These results establish WSe2 and MoSe2 heterostructures
as an exciting platform for investigations of exciton-polarons, Fermi-Hubbard or
Bose-Hubbard physics
Novel optical fibres for on-chip optical tweezing and bio-applications
Get PDFOptical trapping of a single cell is a technique widely used in many scientific sectors
due to the benefits of isolating and examining a single cell in isolation. Studies that use
a conventional microscope-based tweezing system demonstrate optical trapping based
on strongly focused laser light delivered through a high Numerical Aperture objective.
However, this approach poses restrictions to the range of the applications of the
tweezing system due to the use of the imaging optics for tweezing beam delivery. To
overcome these restrictions, optical fibre-based systems to optically trap a single cell
have been studied. In this thesis, an optical tweezing system based on machined four core optical fibres has been developed and applied to a variety of cells.
Mirrors, with an angle slightly higher than the critical angle for the fibre to medium
interface, have been fabricated on the end of a four-core fibre, to alter the propagation
of the laser beam exiting the four cores. The four beams are directed to overlap, and the
optical fibre trap acts in a manner similar to a conventional optical tweezer. The
multicore fibre (MCF) trap is composed of four diverging beams which overlap to form
a trapping volume, as opposed to the trapping volume of an optical tweezer which is
formed by tightly focusing a single beam via a high numerical aperture objective lens. It
is shown that micron-scale particles can be optically trapped in this overlap region of
the MCF trap.
Optical trapping of yeast cells, and also a wider range of cells such as red blood cells,
U87 cells and mouse embryonic stem cells is reported in this thesis. The optical
trapping system has been used also below a Raman microscope. This demonstrates the
ability to trap cells under an analytical microscope without modifying the microscope
optics, and to capture the Raman spectra from single trapped cells.
The work presented in the thesis demonstrates a flexible system of small dimension, to
trap cells for use under a wide range of microscopes, circumventing the need to focus a
trapping beam through a high numerical aperture objective lens. The trap has been
characterised by measuring the maximum trapping velocities and trap strengths, which
are comparable to conventional optical tweezers.
The trapping system has also been used to investigate alternative optical manipulation
of 'special' particles, such as hollow glass spheres, that cannot be optically trapped with
a conventional optical tweezers system due to their low refractive index. The machined multicore fibre uses the region between the beam overlap area and the fibre end face, to
hold these low refractive index particles in place.
The primary objectives of the work described in this thesis were to optimise the FIB
fabrication of the mirrors on the MCF trap, build a robust, portable system capable of
cell trapping and manipulation under different analytical microscopes, characterise the
beam propagation characteristics, demonstrate stable trapping of some exemplar cell
types, and compare the trap strength with conventional optical tweezers
Hierarchical 1-3D titania Hyper-Branched Nanorods (HBNs) thin films for photocatalytic CO2 utilisation applications
Get PDFDespite our efforts, the concentration of CO2 in the atmosphere is constantly rising at an
alarming rate. It is of paramount importance to develop technologies that will expedite the
reduction of the rate that CO2 is released into the atmosphere. CO2 utilisation technologies
consider CO2 as a valuable carbon building block in a circular carbon economy approach,
where the released CO2 is captured, and utilised to produce valuable chemicals. One of these
technologies is the photocatalytic utilisation of CO2 for the production of solar fuels and value
added chemicals, which has the added advantage of utilising light with mild reaction
conditions. However, photocatalysis is limited to the absorbed light energy and CO2 is a very
stable molecule which requires a large amount of energy for its conversion. Therefore,
designing highly efficient materials as photocatalysts becomes a very important task.
The current thesis is concerned with the growth of titania 1-3D hierarchical hyperbranched
nanorods (HBNs) on fluorine-doped tin oxide (FTO) conductive glass as thin films to be used
as photocatalysts for CO2 reduction reactions. This thesis is focused on investigating the
capabilities and photocatalytic behaviour of the titania HBNs material. The HBNs were found
to have improved light harvesting when compared to Degussa P25 TiO2 (48.2 to 28.6 μmol m 2
s
-1
), attributed to their 1-3D morphology. P25 is a blend of mainly anatase and traces of rutile
phase TiO2, commonly used as a benchmark for photocatalytic applications. P25 was supported
on FTO glass and its performance was compared with that of FTO supported HBNs. This
thesis is presented as a collection of published bodies of work, where the HBNs are
characterised, modified and tested in photocatalytic reactions. In more detail, two reactions are
presented, firstly the CO2 photoreduction to produce solar fuels such as CH4 and CO. The
HBNs were found to have superior conversion rates (up to 8.7 μmol gcat
-1 h
-1
) compared to P25
(6.9 μmol gcat
-1 h
-1
) but, more importantly, offer the ability to shift the selectivity of the reaction
product from CO to CH4, utilising a facile phase altering treatment. Additionally, the HBNs
were loaded with CuO and RuO2 and their performance was investigated and compared. CuO
has shown the ability to improve the optical properties of the material, while RuO2 exhibited
improved charge separation and suppressed the recombination rate, which led to further
improvement in the photocatalytic performance. The second reaction is the CO2 cycloaddition to epoxides, for the photogeneration of cyclic carbonates, which are primarily used as
electrolytes in Li-ion batteries amongst others. In the current thesis it is demonstrated that a
photocatalytic approach is possible for this reaction. Additionally, RuO2-HBNs are shown to
be the best performing photocatalyst in terms of conversion. The main appeal of the
photocatalytic approach is the significantly milder reaction conditions (below 55 °C and 200
kPa) when compared to the conditions currently being used in the industry (100-200 °C and 5-
10 MPa).Heriot-Watt University fundin
Meanings of Europe in the Scottish independence movement after the 2016 EU referendum : Brexit, (dis)integration and values
Get PDFThis thesis asks what the meaning of Europe is to the argument, purpose, and continuation of
the Scottish independence movement, to the everyday lives of independence supporters, and
to the narrative of what Scotland is today, and in the future. The theoretical framework of the
research is formed around the study of identity and small state theory. Data has been
collected by means of ethnographic fieldwork with members of the Scottish independence
movement.
I argue that there were mixed reactions to the EU referendum within the independence
movement. Many participants were frustrated, but there was also an awareness of
opportunities Brexit may bring to the movement. Some respondents who voted for Brexit felt
their opinion was not valued.
Brexit resulted in a growing awareness of European integration and has led to the formation
of trans-national narrative structures of European identity. The detriments of disintegration
present an opportunity to blame Westminster and to provide a potential alternative. But
Brexit also highlights Scotland’s vulnerabilities and dependency on a shelter relationship. I
examine participants’ understanding of vulnerability and how it is incorporated into a form of
trans-border nationalism.
Finally, I argue that a narrative is formed in which a myth of European values supports a
myth of Scottish values, while at the same time being contrasted to a myth of British values.
Thus, European values contribute to the formation of and differentiation with Britain as the
other. What appears is a supra-national European identity structure in which European values
have strategic value and are used to support the argument for independence.Heriot-Watt University scholarshi
Smart grid-integrated control of PV inverters for active voltage regulation and DER ancillary services
Get PDFThe increased penetration of grid-connected roof-top photovoltaic (PV) systems
distribution feeders is leading to technical issues to electric utilities, mainly voltage
fluctuations and violations to the grid codes limits. Furthermore, the legacy voltage
control devices such as transformer’s on-load tap changers (OLTC) and switched
capacitor banks need to be operated more frequently than usual with PV penetration and
could only alleviate slow-moving voltage fluctuations.
Ancillary services from Photovoltaic (PV) inverters can alleviate the impact of the rapidly
growing PV penetration by increasing distribution system flexibility and addressing
voltage regulation issues. However, the required communication infrastructure and
smart grid integration challenges limit broad deployments of PV ancillary services. This
thesis proposes a cost-effective volt/var (VVC) control scheme of multi-string PV
inverters for active voltage regulation and reactive power ancillary services using the
existing smart distribution infrastructure to avoid upfront costs of PV ancillary services.
The proposed VVC model is developed in MATLAB/Simulink to adapt PV reactive
power compensation according to X/R characteristics of the distribution feeder for
effective voltage regulation. A volt/var optimisation model is proposed based on particle
swarm optimisation to coordinate the reactive power dispatch of PV inverters with the
legacy voltage regulation devices to resolve the operational issues of distribution feeders
at high PV penetration levels.
Transient voltage analysis and quasi-static time series (QSTS) simulation analysis are
conducted using Matlab/Simulink and OpenDSS co-simulation environment.
A porotype is designed based on the compiled Simulink PLC code and verified in
CODESYS IEC 61131-3 standardization tool to address the practical considerations of
controlling multi-string PV systems and smart grid integration challenges. The proposed
VVC scheme is implemented using remote terminal units (RTU) in a real-world PV
system with multi-string inverters for experimental validation. Quasi-static time-series simulation and experimental results demonstrate the validated
effectiveness of the proposed control scheme in controlling fast PV fluctuations, resolving
voltage issues, voltage flickers, and enabling higher PV penetration. Furthermore, the
proposed VVC control algorithm of PV inverters led to operational benefits for utilities
by alleviating voltage flickers, reducing feeder losses, and significantly reducing regulator
switching operations (up to 37.1% saving in SCB operations and 34.7% saving in OLTC
operations), thereby extending their lifespan and potentially deferring the investment in
new voltage regulators.
The techno-economic assessment showed that the proposed VVC ancillary services
achieved significant improvements of the benefits-cost ratio (BCR) and net present value
(NPV) economic metrics of the system. The proposed BCR value increase by 13.3% from
1.27 to 1.44 when the proposed VVC was implemented. The respective (NPV) increased
from 62,117.86 due to the additional benefits achieved from the proposed
VVC ancillary services. Additionally, the payback period was reduced to 8 years using
the proposed VVC compared to 12 years with the existing P/Pn method.Heriot-Watt University scholarshi
General Relativity analogues in nonlinear optical systems
Get PDFThis thesis presents the results of the experimental and numerical investigations of
nonlinear optical systems in relation to their analogy with some General Relativity
phenomena.
After a short introduction on the context of this work, the first Chapter starts
with an introduction on the Newton-Schrodinger Equation and its optical analogue,
then the investigations of two main effects (the analogue Newtonian gravitational
interaction of two optical beams, and violent relaxation process in analogue galaxy
formation) are illustrated. For these, the theoretical background is presented, then
experimental setups and results are compared with numerical simulations.
The second Chapter starts with a brief literature review on Penrose superradiance
and its optical analogue. This is followed by the experimental setup and results of the
investigation of the nonlinear optical properties of the medium and the measurement
of the time stability of a vortex beam in the medium, followed by the investigation
of the nonlinear interaction of a pump-probe setup by means of a four-wave mixing
mechanism, giving rise to superradiant scattering. The corresponding experimental
setups and results are illustrated in details, as well as the comparison with numerical
simulations.
A short conclusion summarises the whole work
Electricity spot market : game-theoretical approach
Get PDFWe study models where a finite number of profit-maximising generators compete in
the electricity spot market. Each generator chooses as its strategy a supply function,
which indicates how much a generator is willing to produce for any positive price.
Generators simultaneously submit these supply functions to a system operator, who
solves an allocation problem and clears the market.
We start with a study of a particular parameterized supply function bidding game
which was proved to possess certain good properties in the case of a single market.
Our first model is an extension of this game for the the case of several, in particular two, markets. First, for any given topology, Nash equilibrium existence and
uniqueness are characterised. We then focus on a case with symmetric players and
establish the price of anarchy bounds. Further, we compare resulting social welfare
across models with the same players but under different topological structures. A
Braess paradox is detected and investigated for the symmetric case.
The second model is a proposal of a novel payment rule, which leads to the non-uniform price auction. We prove that truthful bidding is a dominant strategy and
show the close relation of the proposed clearing rule in the context of supply function bidding with the Vickrey-Clarke-Groves (VCG) auction. Some further analytic
results are obtained for the symmetric case.
We conclude with a case study with actual data for the UK electricity spot market
in 2014/2015. Under some simplifications, we simulate the supply function game
under different mechanism designs, and analyse and compare outcomes across models
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