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Performance evaluation of embedded acoustic emission sensors in a glass fibre composite under mechanical loading
Get PDFFully embedding acoustic emission (AE) sensors in a composite is postulated to increase the sensor’s sensitivity. The increased sensitivity will enable the sensor to detect subtle structural changes and lower the number of sensors required for monitoring. However, researchers have differed on whether the sensitivity increases or not. To robustly investigate the fully embedded AE sensor’s sensitivity, the surface and fully embedded AE sensors are placed on the same specimen, away from the high-stress region and compared based on the same hit. Two mechanical testing methods are used: three-point bend and double cantilever beam (DCB) mode I. Three sensors are embedded: lead zirconate titanate (PZT), gold-plated polyvinylidene difluoride (PVDF), silver-ink PVDF. The DCB mode I method showed that the sensitivity of the surface embedded sensor was generally better or equal to the fully embedded sensor. However, the three-point bend method showed similar sensitivity with both surface and fully embedded sensors. The results indicate that the fully embedded sensor’s sensitivity is based on the frequency of the AE event and, therefore, the failure type. The aim of the study is to analyse the sensitivity of the surface-embedded and fully embedded sensors concerning surface-originating and subsurface-originating cracks.Applied Acoustic
Work engagement and the impact of a social identity crafting approach to leadership: a case from Africa’s air transport industry
Get PDFPurpose
Managers of public organizations in liberalized sectors face the dual imperative of retaining skilled employees who might be poached by commercial competitors and improving service performance levels without a free hand to invest resources. While employee work engagement (EWE) has been previously suggested as a solution to such management challenges, limitations in its ability to retain employees have been identified. We therefore examine how a social identity crafting (SIC) approach to public leadership that confers a sense of group identity among team members can enhance and extend beyond EWE in addressing this dual imperative.
Design/methodology/approach
We report findings from a survey of employees (n = 199) at “ATCO,” a state-owned national airline that is facing challenges from commercial rivals within a new, competitive environment.
Findings
We confirm previously identified limitations of EWE and, further, demonstrate that a social identity approach to leadership offers a promising avenue for public managers, not only by enhancing employee engagement but, more importantly, by enhancing retention and service performance.
Originality/value
We contribute to studies of leadership, particularly for managers operating in the public sector and resource-constrained environments, demonstrating how SIC, which does not require costly investment to attain, can deliver improved service performance and reduced employee turnover intention, operating beyond EWE, which reaches a plateau in respect of the latter.Personnel Revie
Physicochemical and nanomechanical behaviour of 3d printed pegda hydrogel structures for tissue engineering applications
Get PDFAria, Adrianus Indrat - Associate Supervisor
Goel, Saurav - Associate SupervisorPoly(ethylene glycol) diacrylate (PEGDA) hydrogels are well established in tissue
engineering and organ-on-chip applications as scaffolds for 3D templates in
aqueous environments due to their high water content, biocompatibility and low
toxicity. The versatility of PEGDA hydrogels as a platform for cell encapsulation
and tissue engineering is attributed to their ability to be modified in various ways,
including concentration, molecular weight, and polymerisation technique. Since
properties of the PEGDA host material will affect the functionality of the cells and
tissues, and vice versa, a key missing feature of the currently developed
screening solutions is the lack of proper understanding of the behaviour of the 3D
printed PEGDA soft support structures holding living tissues in a dynamic human like tissue microenvironment. Thus, the aim of this research is to demonstrate
repeatability and reliability in the measurement of physicochemical and
nanomechanical properties of multilayer 3D printed UV crosslinked PEGDA
hydrogels for use in organ-on-chip devices. The research offers insights into long
term stability of hydrogels through studying how changes in both environmental
and printing parameters can be extrapolated to other biomaterials for benefit of
other tissue engineering applications.
Recent advancements in the use of PEGDA hydrogels for tissue engineering are
reviewed, with a focus on bulk cross-linking and 3D printing synthesis methods.
Characterisation methods for 3D printed PEGDA hydrogels are also discussed.
The current state of development of biomedical applications, particularly in organ on-chip devices, is highlighted. The thermal response of multilayer PEGDA
hydrogels made using in-house projection lithography was compared to
monolithic hydrogels created through bulk photo-cross-linking. The results
indicated that the volume of multilayer PEGDA hydrogels changes in response to
the temperature with dimensional change between +10% and -11.5%, and also
displaying an anisotropic characteristic where the axial dimensional change was
higher than the lateral dimension. The results also confirmed the swelling
behaviour to be reversible between 8 and 45 °C. The nanomechanical properties
of monolithic and multilayer PEGDA hydrogels fabricated through bulk cross linking and layer-by-layer projection lithography were studied. The findings
showed that an increase in the number of layers results variation in axial elastic
modulus between 1.69 and 0.67 MPa. Additionally, the research examines the
structural heterogeneity of 3D printed hydrogels which is linked to the degree of
cross-linking of the printed layers and showed variations in lateral elastic modulus
between 2.8 and 11.9 kPa. The results suggest that by controlling the cross linking throughout the 3D printed structure, the surface nanomechanical
properties of the hydrogels can be manipulated to direct cell attachment and
adhesion in specific regions within the structure, offering potential for future
improvement in the reproducibility and reliability of 3D printed hydrogels for tissue
engineering and organ-on-chip applications.Engineering and Physical Sciences Research Council (EPSRC)PhD in Manufacturin
Examination of prolonged dry cold storage and hydration lengths during the process stage on cut roses vase life
Get PDFCut flowers have found an important role in human life, so market demand and
cultivation are increasing. As cut flowers are highly perishable, it is important to
extend their vase life to address sustainability challenges, avoid waste of natural
resources, reduce carbon footprint and gain customer satisfaction.
In the UK approximately 90% of cut flowers are imported (ca. 30% represent cut
roses) and kept under dry cold conditions. During periods of high consumer
demand, flowers may experience prolonged dry storage time compared to the
rest of the year; this can affect vase life negatively. There are few studies
mimicking real supply chain scenarios and, therefore, we simulate it for cut roses
in the UK to examine the impacts of prolonged dry cold storage and hydration
lengths on rose vase life in two separate experiments.
The first study investigated drying lengths (24, 48, 72, and 96 hours at 5ºC) on
vase life of two varieties: ‘Revival Sweet’ and ‘Golden Smile’. Interaction between
drying (96 and 168 hours) and hydration solution usage time (0, 12, 24 and 48
hours) on ‘Revival Sweet’ was examined in the second experiment. In general,
shorter drying times resulted in the longest vase life with fewer signs of physical
damage (bent neck and damaged flower). In colour examination, no clear
relationship between L*, C* h°, drying and hydration lengths was seen which may
be because of the pink colour of ‘Revival Sweet’. Expanding hydration length
improved solution uptake, reduced the pH, eliminated bacterial growth in vase
water, preserved the sugar source and postponed senescence. When flowers
were kept dry for 168 hours, hydration for 48 hours helped them show less than
50% damaged flowers and just approximately 30% bent necks after 18 days. In
conclusion, during peak period, hydration for more than 24 hours is suggested to
eliminate the negative impacts of prolonged dry storage.MSc by Research in Environment and Agrifoo
Reliability as a metric for structural health monitoring systems performance: application on fixed jacket offshore structures
Get PDFShafiee, Mahmood - Associate SupervisorThis research work addresses the need for reliability performance metrics for
Structural Health Monitoring (SMH) systems on a fixed offshore jacket platform.
The most common metric used to quantify SHM performance is the probability of
detection (POD), it only quantifies the probability of detecting damage of a
specific size. While POD is of high importance, it does not fully quantify the total
performance of SHM systems. SHM systems can produce outcomes on the
detection of damage, its predicted location of damage on the monitored structure
and severity of damage detected at the predicted location. These outcomes are
of interest for maintenance of the monitored structure. It is paramount to quantify
the quality of information attained from all three SHM outcomes.
This work proposes the use of Reliability as a metric to quantify outcomes from
SHM systems. Furthermore, it also proposes the use of conditional reliability to
quantity the interdependence of the predicted damage severity, given damage
was localized, and damage was detected. The dependency of the Monitored
structured reliability on the reliability of the SHM system was also proposed a
metric of overall SHM performance.
Probability performance metrics were also proposed in this work to extend the
widely used POD, to other outcomes of SHM systems. The Probability of accurate
localization and probability of accurate assessment were presented. Additionally,
conditional probabilities were also proposed to address the interdependencies
between SHM outcomes.
Methods used in this work to estimate reliability include the First order reliability
method (FORM), and Monte Carlo simulation. Finite element models of Fixed
offshore platform were created, the modal response under specific loading
conditions, and simulated damage events were used as inputs for Vibration
based SHM methods. Hit/Miss techniques were implemented to calculate the
probability-based parameters for each SHM outcome. A framework was
developed to capture the uncertainties associated with the SHM process, with a
limit state function generated for each SHM outcome. Fatigue reliability was
implemented using Paris Law to estimate the reliability of structure members in
the Fixed offshore platform. Bayes method was implemented to calculate
conditional reliabilities.
The outcomes from the proposed approach presented in this thesis, present a
pathway to quantify SHM system performance beyond damage assessment.
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Presented in this work is a comparison between two SHM systems, where their
performance outcomes are quantified for damage detection, localization, and
severity assessment. The contribution of the overall SHM systems reliability on
the predicted monitored structure members predicted fatigue reliability was
presented. Furthermore, a comparison between different vibration based SHM
systems at all levels of SHM performance was also presented. In addition, the
fusion of multiple SHM systems and their potential contribution to the
improvement in predictions of the monitored structure’s reliability was also
described. This methodology can stand as a generic approach that can be
applied to non-vibration based SHM systems or structures that are not fixed
offshore platforms.PhD in Energy and Powe
Single-use vape batteries: investigating their potential as ignition sources in waste and recycling streams
Get PDFThis study investigates the potential link between the increasing prevalence of single-use vapes (SUVs) and the rising frequency of waste and recycling fires in the UK. Incorrectly discarded Li-ion cells from SUVs can suffer mechanical damage, potentially leading to thermal runaway (TR) depending on the cells’ state of charge (SOC). Industry-standard abuse tests (short-circuit and nail test) and novel impact and crush tests, simulating damage during waste management processes, were conducted on Li-ion cells from two market-leading SUVs. The novel tests created internal short circuits, generating higher temperatures than the short-circuit test required for product safety. The cells in used SUVs had an average SOC ≤ 50% and reached a maximum temperature of 131 °C, below the minimum ignition temperature of common waste materials. The high temperatures were short-lived and had limited heat transfer to adjacent materials. The study concludes that Li-ion cells in used SUVs at ≤50% SOC cannot generate sufficient heat and temperature to ignite common waste and recycling materials. These findings have implications for understanding the fire risk associated with discarded SUVs in waste management facilities.Batterie
Can we increase the granularity in understanding global value chains? an integration of academic and practice perspectives to enhance future developments
No full textValue chains are increasingly fragmented globally, and companies and governments struggle with understanding where value is added. Both scholars and practitioners developed models, but recent challenges are calling for original approaches to develop instruments to map and evaluate global value chains (GVCs) footprint. We carried out a structured literature review (SLR) to summarise the existing academic knowledge about GVCs mapping and also examined the related practitioners’ materials. We then investigated what data sources are currently available to collect data about global trade flows, and involved practitioners in the discussion to collect insights that could improve the current understanding. We aim at offering guidance in this process, highlighting what future directions should be pursued to increase the models’ descriptive and explanatory power. For example, customs data is largely available. Original models could be developed, and GVCs could be studied leveraging rich and granular customs data rather than traditional macro-economic data.Global Business and Economics Revie
Followers beat content: social media and the managers in initial coin offerings (ICOs)
Get PDFOur research investigates the role of social media communication in amplifying high-quality information and its impact on the success of ICOs in achieving their soft cap. We analyzed data from 3,644 ICOs and the demographics of 1,987 CEOs, CFOs, and CTOs to compare their quality attributes against their number of social media followers. Our findings reveal that the most significant factors for reaching the soft cap are the number of followers and team size, while the competencies (education and skills) of the management team have a very marginal effect, even when enhanced through social media. This indicates that widespread social media signals can positively influence investor behavior without necessarily reducing information asymmetries regarding the quality of the team. We propose that this effect arises from the combination of minimal investment amounts and stimulated herding behavior among investors.Review of Managerial Scienc
Exploring agroforestry limiting factors and digitalization perspectives: insights from a european multi-actor appraisal
Get PDFDespite its potential for fostering farm sustainability, the adoption of agroforestry faces context-dependent challenges, among which the (perceived) shortage of decision-supporting tools and barriers hindering the assessment of economic, environmental, and social benefits. The process of digitalization offers significant opportunities to enhance sustainability, but it remains crucial to foster a human-centric, fair, and sustainable approach. In the context of the DigitAF Horizon Europe project, we present the results of a multi-stakeholder questionnaire aimed at understanding the perceptions of stakeholders regarding agroforestry and digitalization, as well as the needs of these stakeholders for a successful implementation of this agricultural practice. In the questionnaire, there was a specific focus on the need for and the conditions for the use of digital tools and models, such as generalized digital tools, applications and mapping, climate and weather forecasting and recording, farm management and decision support, and agroforestry and environmental tools. The purpose of this survey was to provide insights to inform agroforestry actors and to foster collaborative initiatives that enhance the potential of digital tools to support the design, implementation, and maintenance of effective and sustainable agroforestry in the European context. Our questionnaire was completed by stakeholders from seven European countries, including farmers, academics, policy actors, farm advisors, and actors in the value chain with an interest in agroforestry. Stakeholders from six living labs, representing Czechia, Finland, Germany, Italy, the Netherlands, and the UK, were involved in the appraisal, along with a multi-stakeholder group from Belgium. Respondents used data and digital tools for various purposes in farming systems and were interested in their potential to improve agroforestry including animal, tree, and crop performance, management guidance, system design, and tree species selection. Our survey revealed that the perceived usefulness of digital tools for agroforestry was substantially higher than stakeholders' awareness of existing tools, indicating a need for better promotion and development of user-friendly, accessible solutions. Additionally, significant obstacles to agroforestry adoption, such as large up-front investments, administrative burdens, and fear of reduced CAP support, were identified, emphasizing the necessity for targeted support and policy improvements. Moving forward, efforts should focus on developing targeted solutions to promote agroforestry according to stakeholder perception, and user-friendly digital tools tailored to the needs and preferences expressed by stakeholders, while also increasing knowledge sharing and capacity building among practitioners and researchers.This study was funded by the DigitAF Horizon Europe project (GA N°101059794).Agroforestry System
Academic libraries and estates strategy: a library leadership perspective
Get PDFThis chapter draws and reflects on the author’s academic library leadership experiences at five different institutions. Valuable insight is shared for the emerging generation of library leaders on the pros and cons of various leadership styles, influencing and negotiating skills when decisions are being made by senior institutional management on investment in their library estate. The author adopts a matrix approach to identify the key surface and/or latent institutional and external variables that will determine the impact of an Estates Strategy on a refurbishment or new build library project – these include formal customer feedback, senior management perceptions, institutional space constraints, structural surveys etc.Privileged Spaces: Academic Libraries in University Estates Strateg