PhD, EngD, MPhil and MSc by research theses (CDS)

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Open Access
Bistatic SAR for Building Wall Material Characterisation
(Cranfield University, 2020-07) Elgy, James; Andre, Daniel
This thesis addresses the problem of using radar to extract interpretable information concerning both the structure and electrical properties of a wall, and the environment behind it. This is broken down into two subproblems: how to determine the thickness and electromagnetic properties of the wall without being in direct contact with it, and how to obtain the most accurate images of what lies beyond the wall. Existing research in the area is evaluated and a theoretical study is presented on the use of monostatic, bistatic, and multistatic Synthetic Aperture Radar (SAR) in both one and two dimensional apertures. New methods of determining the wall properties are evaluated by both computer simulation and with laboratory radar measurements, where a wall of concrete blocks is constructed. The robustness of the asymmetric SAR geometry approach is evaluated with the addition of complex objects placed behind the wall. The uncertainty associated with estimating the wall properties is evaluated and consequential improvements to image quality are discussed. It was found that an asymmetric bistatic SAR geometry accurately extracts the refractive index and thickness of a wall. The method is applicable to both cluttered environments and non-parallel wall trajectories without loss of accuracy. Applying a compensation for refraction in the SAR imagery results in better positional accuracy but does not necessarily result in better image focusing. Volumetric multistatic image formation benefits from applied refraction compensation. SAR image formation, and in particular volumetric image formation, can be significantly accelerated via a spatially variant basebanding technique followed by zero padding. Spatially variant basebanding is sub optimal when applied to a Through-Wall radar scenario where there is a visible wall signature in the image. Keywords: Through-Wall radar, Multistatic radar, Multidimensional signal processing, Electromagnetic propagation, Radar imagin
Open Access
Towards a robust slam framework for resilient AUV navigation
(Cranfield University, 2021-03) Issartel, Mathieu; Chermak, Lounis P; Le Caillec, Jean-Marc; Richardson, Marrk
Autonomous Underwater Vehicles (AUVs) are playing an increasing part in modern navies, to the point that the control of oceans will soon be decided by their strategic use. In face of more complex missions occurring in potentially hostile environments, the resilience of such systems becomes critical. In this study, we investigate the following scenario: how does a lone AUV could recover from a temporary breakdown that has created a gap in its measurements, while remaining beneath the surface to avoid detection? It is assumed that the AUV is equipped with an active sonar and is operating in an uncharted area. The vehicle has to rely on itself by recovering its location using a Simultaneous Localization and Mapping (SLAM) algorithm. While SLAM is widely investigated and developed in the case of aerial and terrestrial robotics, the nature of the poorly structured underwater environment dramatically challenges its effectiveness. To address such a complex problem, the usual side scan sonar data association techniques are investigated under a global registration problem while applying robust graph SLAM modelling. In particular, ways to improve the global detection of features from sonar mosaic region patches that react well to the MICR similarity measure are discussed. The main contribution of this study is centered on a novel data processing framework that is able to generate different graph topologies using robust SLAM techniques. One of its advantages is to facilitate the testing of different modelling hypotheses to tackle the data gap following the temporary breakdown and make the most of the limited available information. Several research perspectives related to this framework are discussed. Notably, the possibility to further extend the proposed framework to heterogeneous datasets and the opportunity to accelerate the recovery process by inferring information about the breakdown using machine learning.
Open Access
Internally bevelled conoidal entry wounds in sandwich bones; their genesis, impact dynamics and macroscopic and microscopic morpholog
(Cranfield University, 2021-01) Rickman, John; Painter, Jonathan; Hazael, Rachael
Projectile trauma to the sandwich bones of the neurocranium is of considerable forensic anthropological importance due to the high lethality associated with gunshot wounds to this anatomical region. The internally bevelled conoidal wound that typically results from perpendicular projectile impact has long been considered diagnostic of bullet involvement and is utilised in both differential diagnosis of gunshot trauma and in making trajectory determinations using the direction of bevel asymmetry as an indicator. However, despite the importance of these activities in forensic anthropological casework the fracture mechanisms underlying bevel formation have remained elusive, with multiple hypotheses presented but few empirical investigations carried out to test them. Further diagnostic complexity has been introduced by the recognition that bevelling also results from low-velocity impacts and that taphonomic agencies can both modify and create internally bevelled fractures. Despite the fact that bone is a complex hierarchical material the majority of analyses of projectile entry wounds in sandwich bones have been conducted at the macroscopic scale, leaving important questions as to whether lower scales of organisation may yield signatures of diagnostic importance. This thesis presents the findings of an experimental investigation into the fracture mechanisms that underlie internal bevelling and presents an analysis of the relationships between the dynamics of impact and quantitative wound morphology. A refined nomenclature for the components of internally bevelled fractures is presented and the layers composing the bevel formally defined. This thesis also presents a Scanning Electron Microscope (SEM) analysis of the effects of projectile impact on compact bone at lower hierarchical scales of bone organisation. Examination of fracture morphology with micro-computerised tomography (µ-CT) coupled with high-speed videography of the impact events revealed a novel cone cracking mechanism that fundamentally changes our understanding of bevel morphology. This mechanism explains how internal bevelling results from both low- and high-velocity impact events and suggests caution should be applied to trajectory determinations made using bevel asymmetry alone. Quantitative analysis of the perforation event revealed, for the first time in sandwich bones, a power relationship between incident velocity and absorbed kinetic energy. SEM analysis of cortical bone around the entry captured the early genesis of conoidal wounds through ring crack formation. Analysis of the periphery of the entry revealed two types of plastic deformation that are suggestive of changes to hydroxyapatite (HA) crystal structure that may be of diagnostic utility. Collectively, the findings presented in this thesis will enhance the diagnosis and interpretation of conoidal wounds in both forensic and archaeological contexts.
Open Access
Development of an analytical framework to assess the risks posed to soil by emerging contaminants and chemicals of military concern.
(Cranfield University, 2022-11) Persico, Federica; Temple, Tracey J.; Coulon, Frederic
Soil provides multiple essential functions, such as provision of food and raw materials, a platform for urban development and human wellbeing and as a filtering and transforming medium. Many unregulated contaminants, often termed emerging contaminants, are globally released on soil creating potential risks, especially when undetected leading to significant impact on environmental receptors. The UK ministry of Defence plays an important role in soil protection as the biggest holder of Sites of Special Scientific Interest (SSSI) in the UK as well as being an active polluter in these protected areas through essential training activities. Therefore, there is a need to improve methods for early identification of emerging contamination to avoid long term environmental impacts and costly remediation. The research undertaken for this thesis has contributed to the development of a soil analytical framework to facilitate early identification of the deleterious effects of emerging contaminants and chemicals of military concern on soil. During this research two different scenarios were considered, firstly, when there is a significant body of ecotoxicological data available for a specific contaminant in the literature and secondly, when ecotoxicological data is not available. A scale based on potential hazards was created for the first scenario, which aims to classify chemicals into three categories - low, medium, and high environmental hazards. This scale serves as an inexpensive method to identify the risk of soil degradation. Results from this research showed that for the contaminants of interest (e.g. 1,3,5-trinitro-1,3,5-triazine - RDX, 2,4,6-Trinitrotoluene - TNT, Perfluorooctanoic Acid - PFOA, Perfluorooctane Sulfonate - PFOS and Cypermethrin) the low-level hazard values were lower than expected. These values were expected to correspond to existing Soil Screening Values (SSVs) and Ecological Soil Screening Levels (Eco-SSL), meaning that the contaminants are likely to have a negative impact on the soil at lower concentrations. For the second case, when data is not available experiments need to be undertaken to generate primary data. Insensitive High Explosives (IHE) compositions were identified as lacking data and explosive residues were collected and soil mesocosms were carried out to define the long-term consequences on soil. Field experiments were used to quantify IHE residue deposition concentrations from a standard 155 mm artillery shell, which was then used to estimate potential contamination after 100 detonations. These values were used to estimate low, medium and high contaminant concentration for soil mesocosm studies to quantify the impact on soil using indicators identified through literature review. A standardised procedure was developed based on this, which quantifies the consequences of explosives on soil. This procedure revealed that soils that are already degraded are more susceptible to the impact of explosives, which primarily affects the chemical and biological properties of the soil. . Specifically, this work has shown that the frequent use of IHE filled munitions on training ranges will have an effect on the quality of the soil even when low quantities of energetic residue are deposited. Results for this thesis represent a first step towards a more comprehensive soil analytical framework development providing early identification tools for soil protection.
Open Access
Effects of Particulate Contamination and Jet Fuel Chemistry on the Nucleation of Water and Ice in Aircraft Fuel Systems
(Cranfield University, 2022-04) Ugbeh-Johnson, Judith; Carpenter, Mark; Mai, Nathalie; Williams, Mike
The aviation industry is currently facing increasing environmental and energy challenges regarding its fuel use. Research is therefore currently under way to develop new sustainable aviation fuels. Understanding the properties of these fuels (along with the changing properties of existing fuel types) is required to understand their impact on aircraft fuel systems. Water solubility, water settling and ice formation in fuel are such properties of interest. The presence of water in jet fuel/fuel systems has been a long-standing issue in the aviation industry. Therefore, it is important to precisely identify the conditions and features that may exacerbate this phenomenon, understanding how fuel composition, temperature, water droplet sizes, flowrate and pipe surface affect ice formation and water solubility. Currently, there is relatively limited data regarding water solubility/settling rate and ice formation in sustainable fuels, specifically those specified in ASTM D7566. This work gives a comprehensive account of the recent advances and technologies in the literature indicating conditions that might lead to the nucleation of water and ice in aircraft fuel systems. These conditions have then been applied to characterizing dispersed water droplets in alternative fuels and conventional Jet A-1. Subsequently, the requirements have been applied to the design, set up, and effectiveness of an ice test rig to understand the types and amounts of ice that can be produced from different sustainable aviation fuel blends. In doing so, this work has helped shed light on the role of fuel composition in ice accretion and whether ice accumulation on a pump inlet strainer may impact pump performance. Furthermore, the results from this work will serve as a basis for design guidelines to minimise ice formation within an aircraft fuel system and help identify some potential/sustainable jet fuel candidates for ASTM D7566 certified jet fuels.
Open Access
Investigation into the fate and transport of Insensitive High Explosives in sandy soils to inform the development of a computational simulation
(Cranfield University, 2022-08) Gutierrez Carazo, Encina; Ladyman, Melissa; Coulon, Frederic
The use of less-sensitive energetic formulations for military training activities has driven the replacement of traditional explosive fills by a new generation known as Insensitive High Explosives (IHE). Due to their novelty, little is understood about their behaviour in the environment when deposited as part of a formulation, specifically how long they may persist and the likelihood of transport of significant concentrations to groundwater. However, it is impractical to empirically investigate the behaviour of IHE in all possible environmental conditions and scenarios, and as of yet, there is no single computational model that enables simulation of persistence of IHE in soil. Therefore, the aim of this thesis was to provide insight into the chemical behaviour of IHE to simulate their fate and transport in sandy soils. To achieve this, the key parameters governing IHE dissolution, transport through soil and degradation were identified, highlighting that the partitioning coefficient regulated IHE mobility through soil; rainwater pH modified IHE dissolution and soil temperature had a significant influence on IHE degradation. These parameters were used to develop a stochastic model able to simulate breakthrough times and concentrations in sandy soil environments. Comparison of simulated breakthrough concentrations of IHE to empirical soil columns proved that the model was able to representatively predict how IHE behaved in soil specifically concentration in leachate over time, which would be invaluable in evaluation of the environmental risks posed by IHE residues and to support soil remediation strategies in contaminated areas.
Open Access
A Nonlinear, Unsteady, Aerodynamic Model for Insect-like Flapping Wings in the Hover with Micro Air Vehicle Applications
(Cranfield University, 2004) Ansari, Salman Ahmad; Knowles, Kevin
The essence of this PhD thesis is the analytical, aerodynamic modelling, as opposed to using grid-based methods such as CFD, of insect-like flapping wings in the hover for micro air vehicle applications. A key feature of such flapping-wing flows is their unsteadiness and the formation of a leading-edge vortex in addition to the conventional wake shed from the trailing edge. What ensues is a complex interaction between the shed wakes which, in part, determines the forces and moments on the wing. In an attempt to describe such a flow, two coupled, nonlinear, wake integral equations are derived and these form the foundation upon which the rest of the work stands. The model so developed is unsteady and inviscid in nature and essentially two-dimensional. It is converted to a 'quasi-three-dimensional' model using a blade-element-type analogy but with radial chords. The governing equations developed in the study are exact but do not have a closed form. Solutions are, therefore, found by numerical methods and implemented in FORTRAN. The model is validated against existing experimental data and remarkable agreement is found both in terms of flow field representation and force prediction. The importance of including the effect of the leading-edge vortex for such problems is also established. The model is then used for a parametric study to analyse the effects of various wing geometry and wing kinematics parameters. From these results, a preferred wing design for a flapping-wing MAV is proposed which is the ultimate aim of this work. The results from the unsteady, aerodynamic model are also compared with earlier work in the PhD using a simple quasi-steady model and good agreement is found in terms of the relative merits of the various wing parameters, thereby establishing the usefulness of using such simple models for initial design studies.
Open Access
Transforming the Kafala in Saudi Arabia: Turning weaknesses into opportunities
(2023-01) Al-Saud, Madawi A; Matthews, Ron
The research sought to find out what is really going on in the modern Kafala and to create solutions for reform based on what is right for Saudi instead of being led by outside voices. The research focuses on migrant domestic workers as one of the most marginalized and vulnerable groups in Saudi, with Kafala practices that amount to modern slavery. The value of this lies in, firstly, promoting the interests of Saudi and the GCC; secondly, upholding human rights and associated principles; thirdly, contributing to an international understanding of Islam and the GCC; and fourthly, providing a culturally specific solution to reforming the Kafala. The selected research methodology consists of mainly qualitative interviews of government officials and other professionals. The research has identified cross-cutting issues that must be addressed by reforms of the Kafala, and that are borne out of the intersecting issues of slavery, Islam, and gender. These cross-cutting issues include: culture (in particular the fact that the status of women and foreigners means that their exploitation may be culturally accepted); migration (which includes the global context of migration and Saudi’s own aims in relation to the system); and access to justice (such as the problem of ensuring that legal reforms are implemented and people are able to exercise their rights).
Open Access
Agent-Based Modelling of O ensive Actors in Cyberspace
(2021-12) Sidorenko, Tatjana; Hodges, D; Buckley, O
With the rise of the Information Age, there has also been a growing rate of attacks targeting information. In order to better defend against these attacks being able to understand attackers and simulate their behaviour is of utmost importance. A recent approach of using serious games provides an avenue to explore o ensive cyber attacks in a safe and fun environment. There exists a wide range of cyber attackers, with varying levels of expertise whose motivations are di erent. This project provides a novel contribution in using games to allow people to role play as malicious attackers and then using these games as inputs into the simulation. A board game has been designed that emulates a cyber environment, where players represent o ensive actors, with seven roles - Cyber Mercenary (low and high capability), State-backed (low and high capability), Script Kiddy, Hacktivist and Counter-culture (not motivated by nances or ideology). The facilitator or the Games Master (GM) represents the organisation under attack, and players use the Technique cards to perform attacks on the organisation, all cards are sourced from existing Tools, Techniques and Procedures (TTPs). Along with the game, players also provided responses to a questionnaire, that encapsulated three individual dif ferences: Sneider's self-report, DOSPERT and Barratt's Impulsiveness scale. There was a total of 15 players participating in 13 games, and three key groups of individual di erences players. No correlation was identi ed with the individual Technique card pick rate and role. However, the complexity of the attack patterns (Technique card chains) was modulated by roles, and the players' individual di erences. A proof-of-concept simulation has been made using an Agent-Based Modelling framework that re-plays the actions of a player. One of the aspects of future work is the exploitation of the game data to be used as a learning model to create intelligent standalone agents.
Open Access
Non-Parametric Spatial Spectral Band Selection methods
(2021-05) Torres, Ruben M; Yuen, Peter W. T.; James, David
This project is about the development of band selection (BS) techniques for better target detection and classification in remote sensing and hyperspectral imaging (HSI). Conventionally, this is achieved just by using the spectral features for guiding the band compression. However, this project develops a BS method which uses both spatial and spectral features to allow a handful of crucial spectral bands to be selected for enhancing the target detection and classification performances. This thesis firstly outlines the fundamental concepts and background of remote sensing and HSI, followed by the theories of different atmospheric correction algorithms — in order to assess the reflectance conversion for band selection — and BS techniques, with a detailed explanation of the Hughes principle, which postulates the fundamental drawback for having high-dimensional data in HSI. Subsequently, the thesis highlights the performances of some advanced BS techniques and to point out their deficiencies. Most of the existing BS work in the field have exhibited maximal classification accuracy when more spectral bands have been utilized for classification; this apparently disagrees with the theoretical model of the Hughes phenomenon. The thesis then presents a spatial spectral mutual information (SSMI) BS scheme which utilizes a spatial feature extraction technique as a pre-processing step, followed by the clustering of the mutual information (MI) of spectral bands for enhancing the BS efficiency. Through this BS scheme, a sharp ’bell’-shaped accuracy-dimensionality characteristic has been observed, peaking at about 20 bands. The performance of the proposed SSMI BS scheme has been validated through 6 HSI datasets, and its classification accuracy is shown to be ~10% better than 7 state-of-the-art BS algorithms. These results confirm that the high efficiency of the BS scheme is essentially important to observe, and to validate, the Hughes phenomenon at band selection through experiments for the first time.
Open Access
Multimodal Navigation for Accurate Space Rendezvous Missions
(2021-05) Rondao, Duarte O De M A; Aouf, Nabil; Richardson, Mark A
Relative navigation is paramount in space missions that involve rendezvousing between two spacecraft. It demands accurate and continuous estimation of the six degree-of-freedom relative pose, as this stage involves close-proximity-fast-reaction operations that can last up to five orbits. This has been routinely achieved thanks to active sensors such as lidar, but their large size, cost, power and limited operational range remain a stumbling block for en masse on-board integration. With the onset of faster processing units, lighter and cheaper passive optical sensors are emerging as the suitable alternative for autonomous rendezvous in combination with computer vision algorithms. Current vision-based solutions, however, are limited by adverse illumination conditions such as solar glare, shadowing, and eclipse. These effects are exacerbated when the target does not hold cooperative markers to accommodate the estimation process and is incapable of controlling its rotational state. This thesis explores novel model-based methods that exploit sequences of monoc ular images acquired by an on-board camera to accurately carry out spacecraft relative pose estimation for non-cooperative close-range rendezvous with a known artificial target. The proposed solutions tackle the current challenges of imaging in the visible spectrum and investigate the contribution of the long wavelength infrared (or “thermal”) band towards a combined multimodal approach. As part of the research, a visible-thermal synthetic dataset of a rendezvous approach with the defunct satellite Envisat is generated from the ground up using a realistic orbital camera simulator. From the rendered trajectories, the performance of several state-of-the-art feature detectors and descriptors is first evaluated for both modalities in a tailored scenario for short and wide baseline image processing transforms. Multiple combinations, including the pairing of algorithms with their non-native counterparts, are tested. Computational runtimes are assessed in an embedded hardware board. From the insight gained, a method to estimate the pose on the visible band is derived from minimising geometric constraints between online local point and edge contour features matched to keyframes generated offline from a 3D model of the target. The combination of both feature types is demonstrated to achieve a pose solution for a tumbling target using a sparse set of training images, bypassing the need for hardware-accelerated real-time renderings of the model. The proposed algorithm is then augmented with an extended Kalman filter which processes each feature-induced minimisation output as individual pseudo measurements, fusing them to estimate the relative pose and velocity states at each time-step. Both the minimisation and filtering are established using Lie group formalisms, allowing for the covariance of the solution computed by the former to be automatically incorporated as measurement noise in the latter, providing an automatic weighing of each feature type directly related to the quality of the matches. The predicted states are then used to search for new feature matches in the subsequent time-step. Furthermore, a method to derive a coarse viewpoint estimate to initialise the nominal algorithm is developed based on probabilistic modelling of the target’s shape. The robustness of the complete approach is demonstrated for several synthetic and laboratory test cases involving two types of target undergoing extreme illumination conditions. Lastly, an innovative deep learning-based framework is developed by processing the features extracted by a convolutional front-end with long short-term memory cells, thus proposing the first deep recurrent convolutional neural network for spacecraft pose estimation. The framework is used to compare the performance achieved by visible-only and multimodal input sequences, where the addition of the thermal band is shown to greatly improve the performance during sunlit sequences. Potential limitations of this modality are also identified, such as when the target’s thermal signature is comparable to Earth’s during eclipse.
Open Access
Understanding Insider Threats Using Natural Language Processing
(2021-02) Paxton-Fear, Kate; Hodges, D; Buckley, O
Insider threats are security incidents committed not by outsiders, such as malicious hack ers or advanced persistent threat groups, but instead an organisation’s employees or other trusted individuals. These attacks are often more impactful than incidents committed by outsiders. Insiders may have valid security credentials, knowledge relating to the organ isation they work for (such as competitors), knowledge of security controls in place and potentially how to bypass those controls. This activity could be unintentional, such as an employee leaving a laptop on public transport, or malicious, when an insider purposefully chooses to attack for some gain, such as selling IP to a competitor. When an outsider chooses to attack, they may leave digital breadcrumbs as they perform various stages of the cyber kill-chain. These breadcrumbs can allow organisations to detect and respond to an incident, flagging suspicious behaviour or access. Comparatively, an insider may be able to continue their attack for years for being caught. Therefore, insider threat activity can be considered co-spatial and co-temporal with legitimate activity; an insider conducts their attack during their work or very soon after leaving their jobs. There are three fundamental approaches to control the risk of malicious insider threats: organisational, technical, and psychological. More recently, insider threat models attempt to encapsulate all these factors into one approach, combining all these into a single frame work or model. However, one issue with these models is their static nature; models cannot adapt as insider threat changes. For example, during the COVID-19 Pandemic, many or ganisations had to support remote working, increasing the risk of attacks. This work attempts to address this flaw of models directly. Instead of attempting to supplant existing practices in these three domains, this work will support them, providing new techniques for exploring an insider threat attack to better understand the attack through the lens of strategic and tactical decision making. This dynamic, custom insider threat model can be constructed by leveraging natural language processing techniques, a type of machine learning completed on text, and a large corpus (body of documents) of news articles de scribing insider threat incidents. This model can then be applied to a new, previously unseen corpus of witness reports to offer an overview of the attack. The core technique this work uses is topic modelling, which uses word association to identify key themes across a document, similar to grounded theory approaches. By identifying themes across many different insider threat incidents, the core attributes of insider threat are recognised, such as methodologies, motivations, information about the insider’s role in an organisa tion or the weakness they exploited. These topics can be further enriched by identifying temporal, casual and narrative clues to place events on a graph and create a timeline or causal chain. The final output of this process is a collection of visualisations of the incident; this visualisation then aims to support the investigator as they ask critical questions about an incident, such as ”What was the motivation of the insider?” ”What assets did they target and how?” ”Were there any security controls in place?” ”Did they bypass those?” allowing for the full exploration of the attack. Informed organisations can make changes using the answers to these questions combined with existing controls, policies, and procedures. The work presented in this thesis has many implications for both insider threat spe cifically and the broader domains of sociology and cyber security. Primarily this work introduces a new approach to incident response, supporting the reflection stage of incid ent response. While this work represents a proof of concept for NLP to be used in this way, due to the technical nature of this work, it could be improved to produce an implement able and deployable piece of software, generating further impact, while there would be some necessary training required, this could offer a new tool for handling insider threat within an organisation. Aside from this direct impact in the insider threat domain, the methods developed and designed during this work will have a broader impact on cyber security, mainly due to its interdisciplinary nature within social science. With the ability to leverage witness reports or organic narratives and map these automatically to an exist ing framework, rather than ask a witness to adapt their narrative to a framework directly. Reports can then be collected on a large scale and analysed. These techniques provide a holistic view of an attack, considering many aspects of an insider threat attack by using reports already collected after an incident to create a better understanding of insider threat which leads to more techniques in prevention and detection.
Open Access
A novel dual-spin actuation mechanism for small calibre, spin stabilised, guided projectiles
(2021) Norris, James J.; Hameed, Amer; Economou, John T.
Small calibre projectiles are spin-stabilised to increase ballistic stability, often at high frequencies. Due to hardware limitations, conventional actuators and meth ods are unable to provide satisfactory control at such high frequencies. With the reduced volume for control hardware and increased financial cost, incorporating traditional guid ance methods into small-calibre projectiles is inherently difficult. This work presents a novel method of projectile control which addresses these issues and conducts a systems level analysis of the underlying actuation mechanism. The design is shown to be a viable alternative to traditional control methods, Firstly, a 7 Degree-of-Freedom (DoF) dynamic model is created for dual-spin pro jectiles, including aerodynamic coefficients. The stability of dual-spin projectiles, gov erned by the gyroscopic and dynamic stability factors is given, discussed and unified across available literature. The model is implemented in a Matlab/Simulink simulation environ ment, which is in turn validated against a range of academic literature and experimental test data. The novel design and fundamental operating principle are presented. The actuation mechanism (AM) is then mathematically formulated from both a velocity change (∆V ) and a lateral acceleration (a˜) perspective. A set of axioms are declared and verified using the 7-DoF model, showing that the inherently discrete system behaviour can be controlled continuously via these control variables, ∆V or a˜. Control state switching is simplified to be instantaneous, then expanded to be generically characterised by an arbitrarily complex mathematical function. A detailed investigation, parametric analysis and sensitivity study is undertaken to understand the system behaviour. A Monte Carlo procedure is described, which is used to compare the correction cap abilities of different guidance laws (GLs). A bespoke Zero-Effort-Miss (ZEM) based GLis synthesised from the mathematical formulation of the AM, with innately more know ledge of the system behaviour, which allows superior error correction. This bespoke GL is discussed in detail, a parametric study is undertaken, and both the GL parameters and PID controller gains are optimised using a genetic algorithm. Artificial Intelligence (AI) Reinforcement learning methods are used to emulate a GL, as well as controlling the AM and operating as a GL, simultaneously. The novel GLs are compared against a traditional proportional navigation GL in a nominal system and all GLs were able to control the AMs, reducing the miss distance to a satisfactory margin. The ZEM-based GL provided superior correction to the AI GL, which in turn provided superior correction over proportional navigation. Example CAD models are shown, and the stability analysis is conducted on the geometry. The CAD model is then used in CFD simulations to determine aerodynamic coefficients for use in the 7-DoF dynamic model. The novel control method was able to reduce the 95% dispersion diameter of a traditional ballistic 7.62mm projectile from 70mm to 33mm. Statistical data analysis showed there was no significant correlation or bias present in either the nominal or 7-DoF dispersion patterns. This project is co-sponsored by BAE Systems and ESPRC (ref. 1700064). The con tents of this thesis are covered by patent applications GB2011850.1, GB 2106035.5 and EP 20275128.5. Two papers are currently published (DOI: 10.1016/j.dt.2019.06.003, the second DOI is pending) and one is undergoing peer review..
Open Access
The Boundaries of Flow: when the balance between a person’s challenges and capabilities becomes imbalanced, an empirical investigation of the relationship between subjective experience, capabilities and challenge.
(2022-08) Forsyth, Tim; Hilton, Jeremy; Dodd, Lorraine
The problematic situation this doctoral research project investigates concerns how the quality of a person’s lived subjective experience is affected by differing degrees of challenge: a product of pressures and demands that overwhelm a person’s knowledge, skills and experience (capability). The cost of stress and the ways stress make people vulnerable to illness is well documented. Therefore, the purpose of this doctoral research project is – to identify the thresholds (points) where the balance between challenges and capability moves to imbalance. This study uses Flow Theory and Complex Systems Theory as the foundation for this research. A literature review of flow theory pertaining to the research problem identified deficiencies in the models, methods and practices. As a result, the project is divided into two sections. The first section developed a new synthesised model of experience using an innovative suite of methods. The insights gained from this model were used to inform the second phase of the research project. The second phase utilises a novel multi-paradigmatic design strategy grounded in a realist philosophy of science. This approach facilitated the development of a quasi-experimental protocol and construct elicitation method to investigate the individual participant's subjective experience of varying degrees of challenge in the sensory and affective domains, respectively. This project contributes to the knowledge gap in two distinct yet complementary ways. Firstly, the research identified a relational link between challenge and subjective experience. Secondly, as experienced by the individual, challenge is incremental and cumulative. Moreover, this doctoral research project realises the overarching research objective by developing a codebook and a new synthesised model of experience. When the model and codebook are combined, they can identify when a person’s challenges and capabilities are aligned and misaligned through the various instances and absences of experiential states. This contribution represents a proof of concept. Future work is required to develop the method's applicability in organisational environments to support and enhance people’s lived experience of work.
Open Access
Supporting operational decision making concerning aircraft structural integrity damage identified during maintenance.
(2021-06-10) Green, Richard; McNaught, K. R.; Saddington, A.
Military aircraft operations balance delivery pressures and engineering risks. Aircraft structural damage incurred in-service creates complex risk decision problems for managers deliberating maintenance activity such as delaying rectification to continue operations, or grounding an aircraft or entire fleet. In many operational settings, aircraft availability demands restrict the time, information, or resources to analyse structural risks, making formal risk or decision analysis intractable. Exact solutions are information intensive and require specialist knowledge or machinery beyond the capabilities of generalist engineering managers, often compelling decision-makers to use their subjective judgement in an unsupported way. For actors deliberating aircraft maintenance structural risks in such circumstances, a novel approach based upon heuristics, argument and bounded rationality is proposed, which was informed by the results from a survey of engineering practitioners and case study analyses. Testing of the approach was carried-out with 21 aircraft engineering decision-makers with experience of structural integrity risks, split into three groups, using realistic but fictional textual simulations of aircraft maintenance. One group used existing decision justification approaches and were compared with a second group who provided decision justifications using the novel approach. Users of the novel approach felt supported and were very confident in their justifications. The third group of raters comparing the two sets of decision justifications indicated preferences using Likert scales against the criteria: which is easier to understand, which is more transparent, and which gives the better justification. Analysis of the comparative results using ANOVA provided evidence that the novel approach enabled better decision justification and transparency compared to existing approaches. The novel approach aids decision-makers compelled to use their unsupported subjective judgement, improving organisational resilience by improving robustness and stretching system process to handle surprises, and providing a clear record of the decision basis for post hoc review.
Open Access
First World War Grave Concentration on the Western Front: Hooge Crater Cemetery, Belgium
(2021-04) Martin, V; Shortland, A; Harrison, K; Braekmans, D
The First World War took place between 1914 and 1918, with conflict occurring in Europe and across the globe. By the end of the War, the bodies of the British and Commonwealth dead were scattered across France and Belgium. It was decided to move single graves or small cemeteries into bigger cemeteries that were being built by the Imperial War Graves Commission. This process was called “concentration”, and involved searching the battlefields for graves, then excavating and attempting to identify the bodies present, prior to their reburial in a concentration cemetery. This thesis focuses on the concentration process and specifically examines a sample of graves from Hooge Crater Cemetery, Belgium. The main research aim is to understand the range of errors that occurred during concentration and identification, and how prolific they were. A historical and literature review was completed, followed by the analysis of data from 109 graves from Hooge Crater Cemetery that were re-exhumed in 1920. This proved that within the sample, a high number of errors occurred in the original concentration work. Following this, 163 burial returns containing the details of 1013 graves from Hooge Crater Cemetery were selected for detailed analysis. The information from these burial returns was gathered and reviewed, and where possible was plotted onto First World War trench maps. This data provides new insights into where and when bodies were concentrated, the type of methods used for identification and how these methods changed over time. The research presented here demonstrates that identification rates varied, and were influenced by several factors including burial location, quantity of body present, time of concentration and primary identification method used. Overall, this thesis expands our knowledge of First World War grave concentration, including how the battlefields were searched and how bodes were identified.
Open Access
Investigation of early medieval pottery production in Lower Austria: an archaeological science approach
(2021-06) Polyak, T; Shortland, A; Braekmans, D; Herold, H
This thesis aims to contribute to a better understanding of early medieval pottery production in Lower Austria by the scientific analysis of ceramics. The investigation is based on 135 potsherds, including graphite-containing ceramics, which originate from the Erlauf Valley and other sites of Lower Austria and Vienna. The ceramics are dated to the 1st–12th centuries AD, with a majority of samples (n=123) from the 6th–11th centuries AD. The potsherds are studied, in addition to macroscopic analysis, by four scientific methods: petrographic thin section analysis, scanning electron microscopy (SEM), inductively coupled plasma optical emission spectrometry (ICP-OES) and X-ray diffraction (XRD). These methods are used to identify and characterise the origin and manufacturing technology of the ceramics in order to gain insight into wider aspects of pottery production such as the organisation of production, technological choices, traditions and innovation. The compositions of the studied ceramics are consistent with different parts of one geological unit, the Bohemian Massif. This information, together with the distribution of the pots, provides details about connectivity and suggests the presence of local, regional and supra-regional trade/exchange networks within the study area. Traces of the applied production techniques indicate a relatively low level of standardisation for most of the ceramics; observations in this regard along with scale, degree of control and specialisation are used to discuss organisation of production. Through the reconstruction of the ceramic making process, technological choices are examined, such as the use of a new raw material, graphite, from the 8th/9th centuries. The analysis of the manufacturing steps also sheds light on practices of different periods and reveals, for example, differences in raw material preparation between the 1st–7 th and 8th–9 th centuries, which suggest a more sophisticated technology of pottery production in the former than in the latter period in the Erlauf Valley.
Open Access
A framework for optical features selection and management for camera-only autonomous navigation in the proximity to small celestial objects
(2021-08) Di Fraia, Marco Z; Chemak, L; Sanchez Cuartielles, Joan Pau
Small celestial bodies such as asteroids and comets are abundantly present in the Solar System, yet their surfaces remain largely unexplored. Achieving regular access to these surfaces would have a major impact on capabilities such as planetary defence and in situ resource utilisation and lead to significant scientific insights. However, missions close to small celestial objects remain challenging in at least two aspects: technically, due to weak gravity fields, complex operational environments and latency from long communication times, and commercially, with the applications still being few and cost-ineffective. A potential solution to reducing development and operational costs and obtaining robust, scalable operations, could be using small, camera-only spacecraft with an elevated degree of autonomy. Enabling a camera-based autonomy requires building appropriate computer vision pipelines. All computer vision pipelines start with the detection of features - salient patterns within the scene. This thesis presents multiple methods and tools enabling the appropriate selection and management of different features for autonomous navigation in proximity to asteroids. To that end, relevant contributions developed during this work consist of:  The development of a software toolbox for prototyping and testing optical navigation technologies through a parametrisable synthetic 3D visual environment;  An analysis of the response of feature detectors to internal factors (e.g., feature model) and external factors (e.g., illumination). This response, once known, can be used for designing the system or to obtain situational awareness  An assessment of the response of template matching methods when the template (model) does not perfectly match the observed target (asteroid, with illumination). Through the above contributions, it was shown that considering environmental cues and the perception model helps in achieving robust camera-only navigation processes. This capability could lead to small satellites autonomously exploring hundreds or thousands of small celestial objects or be employed on more powerful spacecraft for redundancy.
Open Access
Material Chemistry Control for the Additive Manufacture of Composite Propellants
(2022-06) Brash, J P A; Vrcelj, Ranko; Moniruzzaman, M
This thesis has sought to aid the additive manufacture of propellants using a novel dry powder printing system developed at Cranfield. The energetic performance and hazard safety of crystalline energetic materials is intrinsically linked to crystal properties such as size, morphology, and crystalline phase. By optimisation of cooling, antisolvent, sonocrystallisation, spray drying and microencapsulation, the properties of cyclotrimethylenetrinitramine (RDX) and ammonium perchlorate (AP) have been engineered towards better performance within our printing system. Crystallisation of AP from solution in water has been assessed as a means of producing particles with a controllable particle size and morphology. Slow cooling processes (−7.5 °C hr-1 ) failed to produce material suited for use in propellant formulations. However, by significantly increasing the nucleation rate using rapid cooling crystallisation processes (~ −5 °C min-1 ) the size of generated crystals was greatly reduced, with a d50 range of 79.1 - 152.3 µm, compared to ~ 500 – 2000 µm. The application of ultrasonic radiation via a horn to the rapid cooling crystallisation gave promising results – leading to particle size reduction (d50 range: 33.5 – 43.4 µm) and a reduced frequency of secondary nucleation. Moreover, the average particle size distribution width was reduced from 245 µm to 75 µm by the application of sonication. Flow character, as assessed by angle of repose measurements, was good for these sonicated materials (31.0° to 34.1°). Spray drying and micro encapsulation was assessed as a means of RDX particle size reduction. Initial studies using paracetamol as an inert simulant demonstrated that modifications to spray drying process parameters (flow, atomisation pressure, nozzle diameter and feed concentration) produced measurable changes in particle size and size distribution. However, attempts to rationalise these effects using a multifactorial design of experiment were inhibited with the significant errors retrieved from the model. Attempts to understand how particle properties impact the flow character of a powder led to the observation that increased particle size gave decreased angle of repose. However, the magnitude of change was negligible when compared to the effect of reformulation in the presence of known glidant nanomaterials. Microencapsulation of RDX with cellulose acetate butyrate (CAB) was conducted at a range of operating temperatures between 55 and 100 °C. Both particle morphology and impact Figure of insensitiveness were demonstrably affected by drying temperature, and both were minimised by the use of lower drying temperatures (d50 = 2.60 µm, FoI = 102.0). FoI values for RDX/CAB microparticles correlated negatively with drying temperature, suggesting that the strain imparted by this rapid crystallisation process may be retained in the material thereby acting to influence its hazardous nature. Crystallisation of RDX by antisolvent precipitation and spray drying was assessed with the inclusion of five different tailor-made additives (TMAs). Of the assessed TMAs, 2,4-dimethyl-1nitrobenzene and 1,2-diemthyl-3- nitrobenzene were noteworthy for causing significant particle size reduction of antisolvent precipitated RDX. Crystal size enlargement and aspect ratio elongation was most pronounced when 1,3,5-triazine-2,4-diamine impurity was present. A novel application of the Scherrer equation was employed, to study the effect of TMA inclusion on the constituent crystallites within spray dried microparticles. The investigation revealed reduced coherence length of the (002) plane and extension of the (210) plane when RDX was spray dried in the presence of TMAs.
Open Access
Conceptualizing, defining, and modelling supply chain management : an objective oriented approach.
(2022-08) Alkebaisi, Hussain K; Allen, Robert; Hameed, Amer
Although it has been more than three decades since the term Supply Chain Management (SCM) was first introduced, there are still divergent views and different interpretations amongst scholars and practitioners about its meaning. The literature lacks consensus on a precise definition of SCM and presents a plethora of different perspectives. A unified conceptual or theoretical model has not yet been acknowledged, and the existing frameworks lack the call for a holistic model that encompasses the essence of the concept. With this disagreement on what SCM is, there are repeated calls to achieve consensus on a unified definition, a unified understanding, a unified conceptual model, and a unified framework of SCM. The argument in the literature is that achieving consensus among scholars and practitioners will improve research and practice and the SCM discipline. The literature revealed that the prevalent and the most recommended approach of conceptualising SCM is the process orientation. However, there is no evidence in the literature that an objective-oriented approach was investigated in resolving those theoretical issues, and neither has a Grounded Theory research method been applied to that end.Through an objective-orientated approach and applying the grounded theory method, it is found that the majority of the theory behind SCM is about managing business activities and achieving business goals through the communication, cooperation, collaboration, and integration within and across firms in a supply chain or network. The proposed name of the identified theory is ‘Business Relations Management Theory.’ The theory states that individuals, organisations, societies and nations achieve better performance and outcomes through communication, cooperation, collaboration, and integration. A literature-based thematic analysis showed that SCM is being used as a synonym for Supply Management, Business Relations Management (BRM), or a combination of both. Also, an assessment survey that included more than 200 managers and employees from different countries showed unclear or limited understanding of the identified theory and perspective of BRM. Accordingly, this research presents the theory and perspective of BRM and asserts that the term Supply Chain Management (SCM) should be replaced with Business Relations Management (BRM). SCM, as a term, limits the benefits of communication, cooperation, collaboration, and integration to a chain or network of firms and enterprises within the production sector. In contrast, the Business Relations Management (BRM) concept generalises the benefits to all sectors and all stakeholders, including the final customers, consumers, and services recipients. In addition, universities or business schools are advised to replace SCM with ‘Supply Management’ or another name that combines supply and demand management fields. A Feedback survey included a group of managers and employees from different sectors in Bahrain showed a high level of satisfaction and acceptance of the outcomes of this research, the researcher’s argument, and recommendations. The feedback survey outcomes led to the conclusion that the objective orientation was an effective approach to conceptualise SCM, and there is a probability of higher acceptance of the outcomes of this research and, consequently, achieving consensus among academics and practitioners.