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Sleep and Mental Health Issues in Saudi Arabian Women: Development and Testing of an Online Cognitive Behaviour Therapy Treatment
No full textBackground: Mental health problems and sleep disorders can lead to chronic health conditions and low work performance, compromising the overall health and well-being of women. The lack of sufficient data on women’s well-being, mental health, sleep and shiftwork profiles, especially in Saudi Arabia, has continuously undermined Saudi Arabia’s efforts to prevent and mitigate the detrimental health effects arising from these conditions. This research aimed to investigate the prevalence of sleep problems, marital dissatisfaction, mental health and general health problems among Saudi Arabian women.Methodology: The research included three distinct studies. Study 1 compared survey data from 389 Saudi women on demographic information and validated questionnaires including the Short Form Health Survey (SF-36), Morningness Eveningness Questionnaire (MEQ), International Restless Legs Syndrome questionnaire (IRLS), Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), Insomnia Severity Index (ISI), Berlin Questionnaire (BQ), Depression, Anxiety and Stress Scale (DASS), and the Couples Satisfaction Index (CSI), with secondary data on the same variables from various sources with women from other countries. Study 2 aimed to investigate the prevalence of sleep disorders and general health (e.g., obesity, diabetes, hypertension) among Saudi men and women by investigating the medical records of patients from a local sleep centre in King Khalid University Hospital. Study 3 aimed to develop a sleep education intervention for sleep problems and mental health delivered to a sample of Saudi women. A second aim was to evaluate the effectiveness of this intervention concerning a basic sleep education control group. A quasi-experimental design consisting of 39 women participants, each in a Control group and an Intervention group, was used. The intervention consisted of Cognitive Behavioural Therapy for Insomnia (CBT-I) adapted from Jacobs (2009). It consisted of five stages delivered across five weeks with the topics being: Basic Facts About Sleep, Sleep Scheduling and Stimulus Control, Cognitive Restructuring Techniques, Stress Reduction, and Bedtime Relaxation Techniques.Results: Study 1 established a significantly higher risk of sleep disorders (ISI and PSQI scores) and mental health issues (DASS and CSI scores) was indicated among Saudi Arabian women compared to studies of women from other countries. Hierarchical regression analyses examined predictors of sleep quality PSQI, insomnia severity ISI, and daytime sleepiness ESS using demographic, general health, mental health, and sleep-specific variables. Generally, the strongest predictors were sleep-specific measures (e.g. MEQ and IRLS scores); however, other minor contributors such as time spent cooking, highest education qualification and employment status emerged as a marginally significant predictors. Study 2 found that women presented with a higher Body Mass Index (BMI), systolic blood pressure and hip circumference, whereas males were taller and had a larger neck circumference. Females took more medications unrelated to sleep or mental health, whereas more males were smokers. More females presented with diabetes, asthma and hypothyroidism. From the overnight sleep study, females had poorer sleep efficiency but more Stage 3 Sleep (N3). They also had a lower average Apnoea Hypopnea Index (AHI), indicating less severe Obstructive Sleep Apnoea (OSA) in general. From clinical interviews (self-reports by patients during clinical interviews with the doctors and logged in the medical records), females reported a greater rate of insomnia, gastric acidity, choking at night, tachycardia, headaches, ankle swelling and heart problems, whereas males reported a higher rate of snoring, stopping breathing during sleep, chest pain and previous broken nose. Presentation characteristics such as being an active smoker, having asthma and reporting ankle swelling were also predictors. Regarding the interrelationships of these variables within the female sample, physical characteristics such as weight, BMI, and abdominal and hip circumference were related to time in bed and total sleep time from the sleep study. AHI was also related to hypertension. No mental health variables were predictive of sleep problems. Within the male sample physical characteristics such as weight, BMI, abdominal and hip circumference were related to reported ankle swelling. Anxiety was related to reported sleep problems, but none of the sleep study variables. Study 3 results showed consistent interaction effects with significant pre-post reductions in ESS, PSQI, SHI and all three subscales of the DASS in the intervention group compared to the control. However, the intervention did not show a significantly greater pre-post decline compared to the control on the ISI, with both groups showing significant pre-post declines in ISI.Conclusion: Overall, the research from this thesis showed that Saudi women report more sleep and mental health issues compared to women of other countries. Saudi women also have a different health profile to Saudi men when presenting at a sleep clinic. Following this, a tailored cognitive behavioural therapy was successfully adapted to address the mental health and sleep problems of a group of Saudi women. In conclusion, these differing characteristics and treatment needs of Saudi women may be due to a range of socioeconomic and cultural factors that should be taken into consideration for developing more individualised treatment and interventions moving forward.</p
Scalable electrochemical grafting of anthraquinone for fabrication of multifunctional carbon fibers
No full textCarbon fiber electrodes were prepared by grafting anthraquinone molecules via a scalable electrochemical approach which simultaneously increased interfacial and electrochemical capacitance properties. In this work, anthraquinone diazonium salts were synthesized and grafted onto carbon fiber tows at various concentrations. These modified fibers were subsequently evaluated mechanically and electrochemically to analyze their suitability in structural supercapacitors. Compared to control fibers, the grafted anthraquinone groups resulted in a 30% increase in interfacial shear strength (IFSS) and 6.6x increase in specific capacitance. Industry application was also a focus thus carbon fibers were also modified with in-situ generated diazonium salts to determine the applicability to an in-line industrial process. Specifically, potentiostatic functionalization of fibers with in-situ generated diazonium salts AQ-1 and AQ-2, showed 3x and 4.3x increase in specific capacitance, respectively, relative to unmodified carbon fiber (CF). We expect that implementing a scalable method to introduce a conductive and electrochemically active covalently bound surface chemistry layer onto carbon fiber exhibits a higher specific capacitance than carbon fiber grafted with most other small molecules reported in literature. This will open new avenues for manufacturing multifunctional and high-performance fibers with tailored properties for specific/targeted applications.</p
Complex Aviation Systems Equipment Evaluation and Selection: Case Study of Airport Outbound Hold-Baggage Processing Systems
No full textThe escalating demand for air travel places significant stress on the operational capacities of airport infrastructure. This impact is particularly pronounced in the Baggage Handling System (BHS), which constitutes a pivotal aspect of an airport's functional architecture. This study, framed within the context of Melbourne Airport, embarks on a qualitative exploration to unravel the complexities associated with optimising BHS technology selection and integration while ensuring alignment with security requirements and varying baggage dimensions.The underpinning theoretical framework amalgamates institutional and stakeholder theory paradigms. This theoretical synthesis sheds light on the socio-institutional undercurrents and stakeholder dynamics that influence the adoption and assimilation of BHS technology in airport environments. This theoretical foundation enables a comprehensive understanding of the multifaceted challenges that emerge during the modernisation of Baggage Handling Systems.Methodologically, this study adopted a qualitative research approach, employing thematic analysis as its primary analytical vehicle. Semi-structured interviews were conducted with a cohort of airport authorities, staff, and technology suppliers using purposive sampling. This methodological rigour ensures the acquisition of rich and contextually relevant insights while upholding ethical considerations.Within the thematic analysis framework, 18 distinct themes emerged, encompassing critical facets such as regulatory compliance, operational efficiency enhancement, technological decision-making, integration complexities, and strategic implications. The analytical discourse uncovered intricate patterns and trends interwoven within these themes, delineating the multidimensional landscape shaping BHS technology choices. These 18 identified themes provide a comprehensive framework for understanding the management of Baggage Handling Systems, representing a principal outcome of this research project.The research results emphasise the importance of ensuring BHS systems align with ever-changing security regulations. An important finding indicates that employing single BHS processing systems can streamline operations when dealing with diverse baggage types. Additionally, the study examines the complexities of assessing and integrating security scanning technologies, which play a crucial role in ensuring passenger safety and BHS operational effectiveness.The tangible implications of this study traverse a practical spectrum. Airports navigating the challenges of BHS expansion will draw insights from the delineated operational parameters. The strategic selection of BHS technology suppliers assumes heightened prominence in minimising technological entrenchment risks. Furthermore, building upon the aforementioned thematic framework, this study develops a 15-step operational roadmap for future-proofing airport operations, particularly in the Baggage Handling System, airside operations involving ground handler movements, and for enhancing the customer experience concerning evolving security dynamics and passenger expectations.In practical terms, the insights gleaned from this study can significantly inform the decisions of Melbourne Airport authorities and support the decision-making and evaluation processes of a broader set of aviation professionals and policymakers aiming to enhance baggage handling efficiency, passenger experience, and security measures at airports. The implications extend to the strategic selection of BHS suppliers and security scanning technologies, and to the adoption of dual supplier strategies to ensure operational resilience. Additionally, this study contributes academically by offering a comprehensive understanding of the multifaceted aspects involved in selecting, implementing, and integrating advanced BHS technology to meet requirements for handling different-sized baggage securely.</p
Developing the Next Generation of Neural Stimulation Devices
No full textThe cochlear implant is a one of the best bionic devices ever developed and is a life-changing technology for many people, yet it has limitations. Electrical current spread within the cochlea hinders precise neural stimulation, affecting speech understanding in noisy environments and music. If two or more electrodes (‘channels’) are simultaneously stimulated, the broad current spread causes summation of electric fields, leading to high interaction between channels. Consequently, commercial cochlear implants use sequential rather than simultaneous stimulation. However, simultaneous stimulation would be more beneficial, as it would be more representative of the sound. Stimulating with greater precision would enable the delivery of spectral and fine temporal information to the auditory system, ultimately improving cochlear implant performance.
This study explored novel optogenetic stimulation methods, whereby light is to control neurons that are genetically modified with opsins, to improve the spectral and temporal resolution of the stimulus, which may lead to enhanced cochlear implant performance compared to traditional monopolar electrical stimulation. A hybrid cochlear implant was fabricated for the mouse cochlea that consisted of micro-LEDs and electrodes and suitable coatings to safeguard the electrical components. In vitro tests were conducted to test and characterise the hybrid array. Then this hybrid array was used to test the hypotheses in vivo using a transgenic mouse model expressing an excitatory opsin (the H134R variant of channelrhodopsin-2). Responses to the stimuli were recorded through multi-channel recordings in the inferior colliculus of the midbrain.
A series of acoustic, electrical and optogenetic stimulation acute experiments were conducted to evaluate the spread of activation and interactions between channels during multi-channel simultaneous stimulation in mice. Results demonstrated that the spread of activation from optical stimulation was approximately half that of monopolar electrical stimulation (measured at two set levels above threshold, normalised between stimulation modalities), and similar to that during acoustic stimulation. Channel interactions during simultaneous optogenetic stimulation were significantly lower, with 13-fold less influence on threshold of adjacent channels compared to electrical stimulation alone.
Additionally, a series of hybrid stimulation was performed by combining sub-threshold electrical with the sub-threshold optogenetics stimulation to address the temporal limitations of optogenetic-only stimulation. The spread of activation, measured at the same levels above the threshold, was significantly lower compared to electrical stimulation. Interactions between channels were significantly lower compared to electrical stimulation at same levels. Moreover, the electrical current required to achieve the threshold of activation (i.e. activity that is 30% greater than normalised spontaneous activity) during hybrid stimulation was reduced by 35% compared to electrical-only stimulation.
Finally, optical stimulation was combined with the electrical current steering across two channels to determine if the reduction in activation threshold over the hybrid channel could be enhanced. Hybrid current steering demonstrated the ability to form virtual channels between physical electrodes. The study also explored which current steering ratio resulted in the highest hybrid interaction (i.e. highest interaction with the optical channel) by examining the threshold change. Although the reduction in activation threshold varied with different current ratios, there was no significant difference between these reductions. This suggests that current steering was too coarse to have an impact on the hybrid channel. Having an alternating array of LEDs and electrodes would be as effective as channels that occupy the same position.
Overall, this study provides significant advancements in precise neuromodulation that could be applied to cochlear implant technology. This study explores a paradigm-shifting approach for cochlear implants, addressing both the temporal limitations of optical stimulation and the spatial limitations of electrical stimulation through the combination of optogenetic and hybrid stimulation. The research also contributes insights into critical design considerations such as electrode/LED positioning and coating technologies.</p
The application of low-cost proximal remote sensing technologies for the biophysical measurement of forest structure
No full textStructural measurements, that form part of forest inventories, are critical to the effective management of forest ecosystems at multiple levels. Proximal Three-Dimensional (3D) remote sensing approaches have been investigated, and more recently adopted for operational use, to meet growing inventory demands. This has largely been enabled by Light Detection and Ranging (LiDAR) technologies. Conventional LiDAR, however, is cost prohibitive to operational use outside established organisations overseeing the care of large extents of forested land. Due to this, there has been continued exploration into low-cost alternative hardware that provide 3D representations of forests. Modern Colour and Depth (RGB-D) sensors offer new opportunities due to advancements within sensor hardware, computational resources and spatial mapping algorithms. RGB-D sensors are now often integrated into consumer devices, increasing their accessibility for untrained operators. Presented across four Research Questions (RQ), this thesis aimed to explore the feasibility and application of RGB-D devices for the acquisition of biophysical forest measurements within both urban and native forest environments.
RQ1 reviewed the current state of research surrounding the application of terrestrial low-cost 3D remote sensing technologies for forest inventory tasks and how this relates to current operational requirements. This was conducted through the examination of past literature and surveying forestry professionals regarding the importance and capture complexity of different structural forest measurements. Current research focus regarding inventory measurements captured by low-cost sensors was found to align with metrics identified on average as important, defined as ≤ 4 on a 5-point Likert scale, by survey respondents. Based on this investigation, a suite of research directions were proposed to promote the operational adoption of RGB-D devices for forest inventory tasks; (a) integration of RGB-D sensors into handheld or wearable devices for forestry professionals, (b) development of bespoke Simultaneous Localisation and Mapping (SLAM) algorithms for forestry environments, (c) development of a framework for RGB-D sensor operation and assessment in different forest environments, and (d) the exploration of plot-scale inventory capture that utilise low-cost devices from both terrestrial and airborne perspectives to overcome limitations associated with each approach.
RQ2 and RQ3 were then designed to address point RQ1.c. The second research question assessed the accuracy and application of the Microsoft Azure Kinect, a Time of Flight (ToF) RGB-D device, for measuring individual stem Diameter at Breast Height (DBH) within urban parkland. This study also assessed the effect of ambient light and measurement distance when estimating DBH. Individual urban trees (n=51) were captured from one viewing angle at 1 m distance intervals, up to 5 m away, using the various capture settings available to the RGB-D sensor. DBH values were estimated and compared to measurements acquired with diameter tape. Optimal capture parameters with the Azure Kinect were observed to be at a distance of 2 m from the target stem and using the binned near field-of-view capture setting. Root Mean Square Error (RMSE) of DBH estimates when using this approach was 8.4 cm; however, after removing stems with obvious irregularities or non-circular deformation, RMSE was reduced to 3.5 cm (n=38). Ambient light was observed to have little effect on the accuracy of DBH estimates, however, strong ambient light was observed to reduce the effective range of the sensor.
SLAM algorithms are commonly used by RGB-D devices to register depth images. However, SLAM may be influenced by spatial drift, resulting in point-cloud misalignment error. RQ3 aimed to evaluate the impact of environmental features on RGB-D SLAM when representing stem structure. Plots were established in urban parkland (S1) to assess the effect of stem proximity, and native woodland (S2), to assess the effect of surrounding vegetation (≤1.3 m), on the performance of three RGB-D devices. RGB-D measurements were then compared to those acquired using Terrestrial Laser Scanning (TLS). Depth-frame misalignment, as a result of accidental repeat stem observations, was visible in point clouds from all RGB-D devices. However, there was no significant difference in DBH error when comparing stem representations that were influenced by, and absent of, repeat observation errors at S1 (Kinect p = .16; iPad p = .27; Zed p = .79). When using a plot-scale capture approach, the iPad was the only RGB-D device to maintain SLAM position in all plots at S2. When assessing the effect of surrounding under-story vegetation on DBH measurement error, there was significant correlation with the Kinect RGB-D device (p = .04). Conversely, no significant relationship was observed for representations captured with the iPad (p = .55) and Zed (p = .86) devices. Of the assessed RGB-D devices, the iPad had the lowest DBH RMSE estimates across both individual-stem (DBH RMSE = 2.2 cm) and continuous-plot (DBH RMSE = 3.2 cm) capture approaches.
With evidence that RGB-D devices can provide representations of the lower area of stems (≤4 m) in complex native forest environments, RQ4 was formulated to address point RQ1.d. RQ4 aimed to determine the benefits acquired through the alignment and fusion of low-cost iPad RGB-D and drone Structure from Motion (SfM) point-clouds when representing forest structure. A 0.15 ha plot, established in native eucalypt forest, was captured using the low-cost devices. Registration marks, distributed beneath canopy gaps, were used to align the low-cost point clouds. Estimates of stem location, DBH, height and crown area were extracted from both the fused and standalone low-cost point clouds and compared with TLS measurements. The iPad was able to represent the majority of stems with DBH ≥ 5 cm (n=131/159), providing estimates of stem DBH (RMSE = 2.7 cm) and location (RMSE = 1.21 m). Conversely, drone SfM point clouds represented 21 stems at DBH height (DBH RMSE = 6.5 cm}, location RMSE = 0.33 m), however, did provide estimates of height to canopy (RMSE = 2.79 m) and crown area (RMSE = 12.09 m2). The fused Low-Cost 3D (LC3D) point cloud provided improvement when estimating stem location (RMSE = 0.37 m) and segmented crown area (RMSE = 7.6 m2). Whilst slight improvement was observed in estimates of stem DBH (RMSE = 2.5 cm), it was not significant (p = .98). Incomplete representation of structure between 2 m and 7 m meant that the fused LC3D approach struggled with estimates of stem height due to poor representation of forest mid-story (RMSE = 3.18 m).
The research conducted as a part of this thesis has provided insight into the feasibility of contemporary RGB-D devices for the measurement of tree structures in both urban and native forests. The principal outcomes of the research presented within this thesis are: (i) modern Time of Flight (ToF) RGB-D sensors are more resilient to ambient light, making them appropriate for outdoor application; (ii) SLAM registration error does not significantly affect the accuracy of stem structural measurements; (iii) the first investigation and intercomparison of RGB-D devices in complex native forest environments; and (iv) the novel fusion of handheld RGB-D and consumer drone SfM point cloud products, presenting the benefits of aligning the two data sets. RGB-D sensors, integrated into consumer devices, offer the opportunity to improve access to 3D representations of forest structure. Future research should focus on how these sensors fit within the greater constellation of remote sensing approaches for representing forests. Recognising that with the decreasing price of hardware, cost-effective and sustainable forest management relies on efficient sampling and leveraging remotely sensed data captured from different platforms and across multiple scales
Plasmonic modulation of spatially confined reactions on a silver nanoprism
No full textLight-induced nanoparticle photochemistry and photobiology continue to draw significant interest due to their vast potential across industrial catalyses to therapeutics applications. Plasmons are collective electron oscillations that occur when an incident electromagnetic field interacts with free electrons on a metal surface. These plasmons are prominently exhibited by noble metals such as silver (Ag), gold (Au), and copper (Cu) at nanoscale dimensions. The size, shape, and composition of the nanoparticles can radically alter plasmonic characteristics. The localised surface plasmon resonances (LSPRs) resulting from light-matter interactions lead to interesting optoelectronic effects such as optical near-field enhancement close to the nanoparticle surface, generation of hot carriers, and photo-thermal effects. These phenomena have been of significant research interest, particularly to harness them for chemical and biology applications.
Anisotropic nanoparticles such as silver nanoprisms (AgPRs) exhibit multiple LSPR modes, like the in-plane and out-of-plane dipolar and quadrupolar modes. These modes can be selectively photoexcited using narrow bandwidth light sources, which leads to localised hot spots within the nanoparticle depending on the mode excited. These plasmonic hotspots can also act as chemical hotspots that can be used to drive and control chemical reactions on nanoparticle surfaces. An LSPR-driven spatially controlled chemical reaction offers unique prospects in the field of single atom and single particle catalysis, as it may allow light to be used as an external trigger to promote chemical reactions at specific locations within a nanoparticle.
The aim of this thesis is to control the chemical reaction sites within a plasmonic nanoparticle through selective optical excitations of plasmon eigenmodes and while doing so, develop unique hybrid materials that have different components precisely positioned at specific sub-sites within a single nanoparticle. The thesis employed AgPRs as the representative anisotropic plasmonic nanoparticle to study the outlined aims. Further, to achieve the core objective, as a proof of concept, the plasmon-induced processes were coupled with a well-established reaction system, the galvanic replacement reaction (GRR) that involves a spontaneous redox reaction between two metallic components. The thesis initially investigated the influence of plasmons on a thermodynamically feasible GRR between AgPRs and tetrachloroaurate ([AuCl4]-) ions. Subsequently, the learnings from this study were implemented to study the influence of plasmonic chemistry in advancing a thermodynamically-unfavourable reaction between AgPRs and tetrachloroplatinate ([PtCl4]2-) ions. Thus, the thesis dived into exploring the possibility of “turning impossible into possible via plasmonics”.
The unique anisotropic feature of an AgPR allow selective excitation of its LSPR modes through optical illumination. The excitation of the in-plane and out-of-plane dipole plasmons selectively produces the optical hot spots at the tips and edges of the AgPR, respectively. Thus, the thesis investigated the possibility of selectively driving the GRR processes at these specific sub-sites in the AgPR where corresponding LSPR modes were excited. The overall outcomes revealed that metallic Au0 and Pt0 can in fact be successfully deposited on the tips and edges of an AgPR through selective excitation of the LSPR modes.
The research also saw a careful deployment of a range of analysis techniques to obtain deep mechanistic insights into the underlying plasmonic chemistry. These include high resolution transmission electron microscopy and x-ray diffraction studies to carefully study the crystal structure and defect states in the AgPR; low-loss electron energy loss spectroscopy to map the plasmons across the AgPR surface as well as to quantify the relative changes in the thickness of the nanoprism across the AgPR; chemical mapping of AgPRs via energy dispersive x-ray mapping to study the elemental distribution profiles; x-ray photoemission spectroscopy to validate the formation of reaction products as well as to study the fate of capping agents during plasmonic catalysis; atomic emission spectroscopy to quantify the degree of GRR; absorption spectroscopy to study the changes in the optical properties of AgPRs during GRR; as well as electrochemical analysis of reactions to understand why theoretically-prohibited GRR between AgPRs and tetrachloroplatinate ions takes place.
These investigations generated enriched knowledge about the underlying mechanisms of chemical reactions that can be influenced by the excitation of the specific LSPR modes of an AgPR. The role of both short-lived non-thermalised and long-lived thermalised ‘hot’ charge carriers in influencing different aspects of the GRR was established. Both photonic energy and excitation of specific LSPR modes were observed to influence the GRR under photoillumination conditions. While photonic energy was found to increase the efficiency of GRR, the plasmonic excitation allowed spatial biasing of the GRR at the tips and edges of the AgPR. While it remained challenging to completely disentangle the effects of photonic and plasmonic chemistry, the investigations suggested that the reaction thermodynamics is controlled by the photonic energy, whereas plasmons control the kinetics of the reaction. The study also revealed that often overlooked reaction parameters, such as the crystal defects, capping agents, and the stability of the reactant molecules can play a non-trivial role during plasmon-enhanced chemical reactions. In particular, citrate molecules bound onto AgPRs played a key role in completely changing the mechanism of GRR under photoillumination. This allowed overcoming the thermodynamic barrier of the reaction between Ag and tetrachloroplatinate ions, and “turning impossible into possible via plasmonics”.
Overall, this thesis is an attempt to advance our understanding of plasmonic chemistry and plasmonic catalysis. The methodologies, tools and techniques developed during the course of this thesis, the key observations made, and the future directions proposed, could benefit those seeking to further advance this important area of research
Digital transformation in warehousing: a case of Saudi Arabia
No full textSaudi Vision 2030 focuses on achieving a diversified technology-enabled economy. This can be done by accelerating the development of digitalisation. Although Saudi Arabia supports its implementation it is still in the early stages of digitalisation. The Saudi government is seriously investigating digitalisation in various sectors, including the logistics sector. This study examined the digitalisation of warehousing in Saudi Arabia and investigated its effect on warehouse performance. Digitalisation of warehousing systems has become crucial for logistics firms in Saudi Arabia to develop and remain competitive. This helps to streamline the supply chain and improve warehouse performance; which, in turn, will enable Saudi Arabia to position itself as a global logistics hub. Based on an extensive review of the digitalisation literature a conceptual framework was developed with the structuring, bundling, and leveraging constructs of the resource orchestration theory (ROT) as the drivers of warehouse digitalisation that creates value and improves warehouse performance.
This study adopted a quantitative methodology to examine the relationships between constructs and validate the research model. A simple random sampling technique was used to obtain a highly representative sample of 323 responses. These responses were collected from participants who work in Saudi Arabian firms of different sizes and within different industry sectors, and who are involved in IT deployment in Saudi Arabia. Structural equation modeling (SEM) was employed to evaluate the conceptual model and test the hypotheses. Furthermore, a fuzzy set qualitative comparative analysis (fsQCA) method was applied to identify different configurations of digitalisation. Identifying alternative ways of promoting digitalisation in a warehouse through fsQCA complements the SEM results.
The results of hypotheses testing indicated that all the ROT constructs were positively associated with digitalisation. In addition, it was found that digitalisation had a positive effect on value creation, financial performance, and operational performance. The results of this study showed that firm size, industry type and ownership structure did not have an impact on digitalisation. The results of SEM and fsQCA regarding the impact of digitalisation on performance aspects were compared. The fsQCA results confirmed that achieving high warehouse performance in Saudi Arabia depends on the configurational effects of all the model variables, as opposed to individual effects. The fsQCA results for high outcome revealed that the combination of structuring, digitalisation, operational performance and financial performance led to high value creation. In addition, the combination of structuring, bundling, leveraging and digitalisation led to a high level of operational performance. Furthermore, the combination of structuring, digitalisation and value creation, with the absence of leveraging, led to a high level of financial performance. In summary, it was found that digitalisation had a significant impact on performance, and this is consistent with the findings of previous studies.
This study has significant theoretical, methodological, and practical implications with regard to developing a theoretical model that conceptualises the digitalisation of warehouses and the impact on performance in the context of Saudi Arabia. The study’s contribution to the theory is the assessment of the dimensions and the configuration design of the dimensions to gain a theoretical understanding of the digitalisation process. Methodologically, this study is the first of its kind to use SEM combined with fsQCA to examine the impact of digitalisation on warehouse performance. From a practical perspective, the study findings can guide managers to develop a step-by-step procedure for implementing the digitalisation process in their warehouses. It will also assist managers to assess the type and level of the resources required for the digitalisation of their warehouses. In addition, the study will help managers to clearly identify the various roles of digitalisation in improving performance.
Although this study has some limitations, they serve as opportunities for further research. Data were collected from only one country, namely Saudi Arabia and the results may vary in other countries that have different warehousing systems. This study also used cross-sectional data rather than longitudinal data, which may not fully reflect a phenomenon such as digitalisation, which develops over time. In addition, this study focused on several industry sectors to assess the impact of digitalisation. Future research could examine the validity of applying the proposed model to other developing countries with contexts that are similar to Saudi Arabia, such as Gulf Cooperation Council countries. Furthermore, a longitudinal study could better capture the development of digitalisation over time. Moreover, it is recommended that a comparative analysis of various sub-types of sectors in Saudi Arabia, as well as the different warehouses within each sector should be performed
Lightweight and post-quantum safe security solutions for IoT systems
No full textThe recent emergence and expansion of the Internet of Things (IoT) and its applications have dramatically changed the IT services supporting domains such as manufacturing, energy management, intelligent transportation, smart cities and defence. These IT services interconnect Internet-based cloud systems with IoT or smart devices, such as cars, fridges, light bulbs, TVs and home security devices, to transform the physical world into the cyber world. As a result, IoT has applications in a broad spectrum of areas such as smart homes, smart cities, healthcare, water and sanitation, transportation, defence, environment and agriculture.
The integration of IoT with emerging technologies, such as Edge, Fog, and Cloud computing, opens up endless opportunities and benefits for its users but also poses numerous security challenges. These security challenges are mainly due to the resource-constrained nature of IoT devices. Several computationally lightweight cryptographic protocols exist for these resource-constrained IoT devices. However, due to the asymmetric computational nature of end-to-end IoT-based systems with resource-limited and resource-rich devices, lightweight cryptographic protocols could become security soft-spots and cause
critical vulnerabilities over resource-rich devices like Edge, Fog or Cloud computing. These vulnerabilities are due to the availability of computational resources at these platforms (Edge, Fog and Cloud) for multi-tenancy/-programming and their operations in relatively more malicious environments.
This research is motivated by the lack of cryptographic schemes that take into account the asymmetric and heterogeneous nature of IoT systems. Most cryptographic protocols do not address the asymmetric computational nature of devices across IoT-based systems. The resource-rich components (e.g., Edge, Fog and Cloud), possibly operating in highly contaminated environments (e.g., Internet), need stronger security protocols than their resource-limited counterparts in an IoT-based system. With the addition of vulnerabilities due to evolving quantum computing (i.e., cryptographic primitives that can be broken by quantum computers), the attack surface of the IoT-based systems also increases. Hence, there is a need for asymmetric cryptographic protocols that can adapt to the asymmetric computational nature of devices across IoT architecture and protect
against quantum attacks.
We are interested in both theoretical and technical aspects of the asymmetric computational nature of devices across IoT. We begin with critically analyzing the resource constraints of the range of devices at Cloud, Fog, Edge and smart nodes and the feasibility of existing lightweight cryptographic protocols on these devices. First, we conduct a comparative analysis and classify the existing lightweight cryptographic protocols against security requirements, including confidentiality, privacy, authentication, access control, resource asymmetry, etc. After analyzing these cryptographic protocols, we identify that the major portion of the literature is related to IoT communication protocols, authentication, vulnerability and attacks on IoT systems, while a few recent works partially address the asymmetric capabilities of devices in IoT systems. Second, we highlight the need for a cryptographic protocol with elasticity that can adapt to the asymmetric capabilities of different devices across the IoT structure.
The development of elastic cryptographic protocols that can adapt according to the resources of the devices in IoT systems is a crucial task. One way to achieve this is by taking advantage of the resourceful parties involved in the communication to perform
computations on ciphertext without leaking any information or compromising the privacy of the communicating parties. Proxy re-encryption schemes are widely used to outsource ciphertext to edge nodes (proxy) and can perform computations on that
outsourced data. We propose a proxy re-encryption scheme that transforms the ciphertext to make it suitable and secure on smart and resource-rich devices. For this, we design an efficient ABE-IBE proxy re-encryption scheme that converts the ciphertext encrypted under ABE with classical encryption to IBE with post-quantum safe encryption and then converts ciphertext re-encrypted under IBE with post-quantum safe encryption to IBE with classical encryption. In this proposed scheme, we use bilinear pairing (classical cryptography) for ABE and IBE schemes at sender and receiver ends, while re-encryption and re-decryption use lattice-based cryptography (post-quantum safe) at proxy (fog/edge) nodes. We conduct the experimental and security analysis of our proposed proxy re-encryption scheme and compare the results with the existing classical ABE-IBE proxy re-encryption scheme.
Post-Quantum construction of various algorithms is an interesting field of research. We use the post-quantum safe learning with error (LWE) problem from lattice-based cryptography to improve the results of our proposed ABE-IBE proxy re-encryption scheme. In this part of our research, we explicitly demonstrate the structures of post-quantum secure ABE and IBE schemes (using lattice-based LWE) to design the first-of-its-kind Post-Quantum secure ABE-IBE proxy encryption scheme without using the classical encryption schemes. This lattice-based proxy re-encryption scheme improves the security of proxy nodes and smart end devices (sender and receiver) from quantum adversaries
Investigation of ultra-thin gallium compound layers fabricated by liquid metal chemistry for hybrid integrated photonics
No full textIn today's digital age, the demand for internet connectivity is growing at an unprecedented rate. Conventional optical transceivers, although effective, are often bulky, costly and energy consuming, limiting their widespread implementation. It is imperative to seek out innovative technologies that can address this demand for high-speed data transmission while overcoming the limitations of traditional solutions. In the span of the past two decades, the landscape of photonic technology has undergone a dramatic transformation, with silicon photonics emerging as a mature technological platform. By integrating various optical components on a silicon substrate, it can provide advanced functionality while harnessing the advantages of silicon's well-established manufacturing processes. With its ability to transfer optical data at very high speeds, across a wide bandwidth, with its power efficiency and scalability, silicon photonics has created an effective and compact technology for telecommunications, data centers, and sensing systems. Nowadays, multiple optical functions can be integrated onto a single chip, resulting in the availability of optical systems including electro-optic modulators, Silicon germanium (SiGe) photodetectors, and low-loss silicon waveguides.
However, silicon encounters intrinsic limitations regarding light emission or nonlinear functions, calling for the use of complementary materials. The heterogeneous integration of III-V materials onto silicon has offered one route to overcome these limitations . Concurrently, several material candidates are being investigated for their nonlinear properties with an aim to integrate them onto the mature silicon photonic platform. However, despite the high application potential of nonlinear optics, no clear nonlinear material candidate has clearly emerged to complement silicon photonics. Hence, scientists continue to search for materials with strong nonlinearities even at a reduced scale, which could be readily integrated with silicon photonics.Enter two-dimensional (2D) materials, a promising contender in the quest for the ideal nonlinear material. These materials, compatible with planar photonic devices through post-processing techniques, bring new properties to the table that can potentially complement silicon photonics.
Therefore, our research endeavors began with the aim of identifying new 2D materials that have the potential to complement silicon photonics for applications at around 1,55um wavelength. Among the candidates, gallium oxide (Ga2O3) and gallium nitride (GaN) have gained significant attention due to their impressive optoelectronic. However, it is worth noting that the existing research primarily focuses on the properties of Ga2O3 and GaN in bulk or thick layers, leaving a significant knowledge gap regarding their behavior in the 2D or ultrathin dimensions. Recognizing this gap, we aim to shed light on the unique properties of these materials in the 2D realm.
My PhD research project was centred on three main focal points:
- the synthesis of ultrathin Ga2O3 and GaN through an inventive method known as liquid metal chemistry
- the structural and optical characterization of these ultrathin Ga-based materials
- the integration of these materials into photonic devices.
This project is part of an international cotutelle between Ecole Centrale de Lyon (ECL) and Royal Melbourne Institute of Technology (RMIT) under the umbrella of European Union and Marie Curie framework. The investigative endeavor this project presented unfolded across two state-of-the-art laboratories:
(i) Institute of Nanotechnologies of Lyon (INL) and NANOLYON nanotechnology platform
(ii) RMIT Micro Nano Research Facility (MNRF) and the assistance of RMIT Microscopy and Microanalysis Facility (RMMF).
In Chapter 1: 'State of the Art', we provide a thorough overview of research literature related to 2D materials, particularly emphasizing Ga2O3 and GaN.This chapter explores the ongoing journey to find a method that is affordable, scalable, and efficient in producing high-quality Ga2O3 and GaN. Moreover, we are looking for a technique that allows for easy integration of these materials into photonic devices. We also discussed the structure and characteristics of liquid metal as a method for synthesizing these materials. This discussion highlights the importance of finding new techniques to overcome current obstacles that prevent us from fully harnessing the potential of 2D materials and their integration on photonic devices.
Chapter 2: expands upon our exploration by tackling a central issue: large-area, ultra-thin layer fabrication. Here, we introduce an inventive approach in the form of liquid metal chemistry has been recently developed at RMIT university and mainly relies on a two-step process . This method has exhibited encouraging outcomes in the scalable synthesis of exceedingly thin layers of Ga2O3 and GaN. Next, the chapter delves into intricate details, elaborating on the various characterization methods utilized to investigate the topography, spectroscopy, and optical traits of the synthesized ultra-thin Ga2O3 and GaN.
Chapter 3: presents the experimental results of the Ga-based ultra-thin layers synthesized by the method developed in chapter 2. It also turns our attention to a pivotal element of our research – exploring Gallium OxyNitride (GaOxNy) compounds, an intermediate stage between Ga2O3 and GaN. Additionally, this chapter exhibits the results from the characterization methods previously introduced in Chapter 2. It proffers an in-depth examination of the structural and optical attributes of these intermediate compounds and Ga2O3 and GaN. We combined sophisticated characterization methods, Raman measurement, and Density functional theory (DFT) calculations to achieve this.
In the final chapter (Chapter 4:) we develop an approach to integrate 2D Ga2O3 and GaN materials into photonic devices. We exploit here Mach-Zehnder Interferometers (MZIs) and selective patterning to study the optical properties of hybrid SiN waveguides covered with ultra-thin Ga-based compounds. This step is crucial, for it paves the way towards realizing hybrid integrated photonics with these 2D materials. We discuss the integration process in detail, the challenges faced, and the ways to overcome these challenges. We undertook precise linear measurements on the MZIs to characterize the properties of Ga2O3 and GaN in detail. The initial choice of these materials was driven by our aim to develop nonlinear 2D materials for chip-based devices. However, it's important to acknowledge that in this phase of our research, we focused on their linear properties and have not yet studied their nonlinear characteristics. Nonetheless, this investigation underscores the significant potential of these 2D materials in advancing the field of integrated photonics and paves the way for further studies into their nonlinear properties
Light-assisted amperometric based hydrogen gas sensing at low concentrations
No full textHydrogen (H2) is widely used in large-scale fuel-cells and chemical refineries. However, its greatest impact may end up being as a clean energy source. From a safety aspect, detecting low concentrations of H2 gas at low temperatures is now gaining more attention as the use of H2 in consumer-based energy banks is gaining popularity. Additionally, due to its inflammable and explosive nature, safety issues during its production, transportation, and usage must be addressed. Thus, detection well below the lower explosive level (4%) down to ppm levels is imperative in enhancing end-user confidence for future uptake of H2-based fuel technologies. Furthermore, such sensors could also be used for other applications including in medical industry where it can replace the conventional yet expensive and labour-intensive breath analysers that can detect trace amounts of hydrogen gas to diagnose many gastrointestinal diseases (GIDs). Several attempts to develop semiconductor-based hydrogen sensors which can operate at low temperatures have typically resulted in trade-offs on critical performance aspects such as selectivity and sensitivity. Achieving an operating temperature close to room temperature is an important requirement when considering safety, reduced energy consumption, and compatibility etc. Consequently, the major aim of this research has been to develop a light assisted amperometric gas sensor (AGS) that is highly selective toward low concentrations (ppm levels) of H2 gas using transducer platforms that requires little to no external heating sources and operate at close to room temperatures.
A critical literature review revealed that there were several major research questions, and thus knowledge gaps, that needed to be addressed prior to successfully developing an AGS for H2. Various material nanostructure designs were systematically developed to enhance sensor performance while operating at low temperatures. The materials that were developed in progressive sequence included TiO2/MoS2 core shell heterostructure, Pd NPs decorated on TiO2 based colloidal crystals (CCs), and soot templated TiO2 decorated with Pd NPs. Each AGS design and material type addressed a specific research question on H2 sensing performance. The feasibility of the developed sensors was tested under simulated industrial conditions which include carbon dioxide, methyl ethyl ketone, acetone, acetaldehyde, nitric oxide, and humidity. The AGS based hydrogen sensors were tested toward H2 gas concentrations of 50, 75, 100, 200, 300, 400 and 500 ppm with/without the presence of several foreign gas species. The tests involved applying different biases (0.1, 3, 6 and 9 V) with and without light excitation at an operating temperature of 33 ºC. These tests enabled detection of low concentrations at low operating temperatures with various degrees of freedom to control sensor performance, thus enabling tailor designed sensors for different applications. The data from each developed sensor was analysed to determine the effect of fabricated material on each sensor's performance in terms of response magnitudes, limits of detection, response time, recovery time, calibration curve trends, memory tests, sensitivity, and selectivity, all of which are critically relevant when using such devices in real-world industrial conditions.
The analysis of the H2 sensing data revealed that material properties play an important role in sensing performance. For instance, replacing the MoS2 component of the composite with Pd resulted in excellent results with lower LoD, as low as 3.5 ppm under the highest applied potential of 9 V and under a light illumination of 365 nm with an intensity of 2024 micro watts per cm2. This was due to Pd nanoparticles being good H2 sorbents and catalysts for hydrogen sensing while the MoS2 photoactive semiconductor forms heterojunctions with the Pd NPs. This combination resulted in low detection limits and superior operation at low temperatures. By replacing the MoS2 CCs with TiO2 CCs, a significant improvement in selectivity as well as sensitivity was observed. Furthermore, it was postulated that an increase in the surface area of the TiO2-Pd composite, while controlling the uniformity of Pd NPs decoration, should enhance H2 gas sensitivity. This was achieved by using soot templated TiO2 decorated with Pd NPs which resulted in better detection limits while maintaining near room temperature (33 °C) operation.
The success of the data presented in this thesis has resulted in a PCT patent (PCT/AU2021/051274) of the developed AGS-based H2 sensor and is due to undergo preliminary testing for potential aerospace applications at Infinity Fuels (contractors to NASA). Furthermore, the low detection limit and high selectivity at room temperature is a significant technological breakthrough with potential applications in many sectors (aviation, transport, medical, manufacturing etc.) involving hydrogen gas sensing