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Propulsion aerodynamics for a novel high-speed exhaust system
Get PDFA key requirement to achieve sustainable high-speed flight and efficiency improvements in space access, lies in the advanced performance of future propulsive architectures. Such concepts often feature high-speed nozzles, similar to rocket engines, but employ different configurations tailored to their mission. This paper presents a numerical investigation on the aerodynamic performance of a representative novel exhaust system, which employs a high-speed, truncated, ideal contoured nozzle and a complex-shaped cavity region at the base. Reynolds-Averaged Navier-Stokes computations are performed for a number of Nozzle Pressure Ratios (NPRs) and free stream Mach numbers in the range of 2.7 < NPR < 24 and 0.7 < M∞ < 1.2 respectively. The corresponding Reynolds number lies within the range of 1.06 · 106 < Red < 1.28 · 106 based on the maximum diameter of the configuration. The impact of the cavity on the aerodynamic characteristics is revealed by direct comparison to an identical non-cavity configuration. Results show a consistent trend of increasing base drag with increasing NPR for all examined M∞ for both configurations, owing to the jet entrainment effect. Cavity is found to have no impact on the incipient separation location of the nozzle flow. At conditions of M∞ = 1.2 and high NPRs, the cavity has a significant effect on the aerodynamic performance, transitioning nozzle operation to under-expanded conditions. This results in approximately 12% higher drag coefficient compared to the non-cavity case and shifts the minimum NPR for which the system produces positive gross propulsive force to higher values.Journal of Engineering for Gas Turbines and Powe
Tensor robust principal component analysis based on Bayesian Tucker decomposition for thermographic inspection
Get PDFThermographic inspection is considered an effective and promising nondestructive testing tool because of its intuitiveness, wide range and noncontact property. Despite this, the detection of weak defects and the recovery of their shape remain difficult, particularly when the surface being inspected is the opposite of the surface being drilled. This study proposes a new tensor robust principal component analysis method based on Bayesian Tucker decomposition to improve the spatial resolution of thermography. A hierarchical form of a generalized Student-t prior is imposed on the model parameters in the Bayesian framework so as to approximate the low-rank component related to the defect feature. Through variational Bayesian inference, all model parameters are adaptively estimated. Based on two experimental data, it appears that the proposed method is capable of improving the spatial resolution and detection accuracy of the thermographic inspection system.Mechanical Systems and Signal Processin
Actinobacteria: an underestimated source of potential microbial biocontrol agents against fusarium-related diseases in cultivated crops
Get PDFCrop infections with Fusarium spp. and associated mycotoxins have devastating economic implications and are a significant limitation to fifteen of the seventeen United Nations Sustainable Development Goals. Therefore, it is necessary to develop innovative strategies to reduce or eliminate diseases caused by Fusarium spp. in cultivated crops. Management of Fusarium-related diseases using beneficial microorganisms is a promising and eco-friendly solution. In this context, actinobacteria are considered one of the best candidates because of their multifunctional properties, which consist in the reduction of Fusarium spp. diseases and the promotion of plant growth. Actinobacteria represent a large Gram-positive bacterial phylum that is widespread in different environments, especially in soil. They are principally known for their versatile capacity to produce biologically active molecules with potential applications in different fields, including agriculture. As Fusarium species threaten diverse crops worldwide and cause global yield and quality losses that can negatively impact food security, the use of actinobacteria for plant diseases management is gaining interest as a safer and more potent alternative to ineffective synthetic-based pesticides. Thus, this work aims to review and highlight the importance of actinobacteria as microbial biocontrol agents and discuss the current research on Fusarium spp. diseases with a focus on species that threaten economically important crops, such as F. graminearum, F. oxysporum, F. solani, and F. culmorum. This review also presents actinobacteria-based products that have been patented for Fusarium disease control. We aim to provide valuable data, guidance and advancements for future research on microbial biocontrol against Fusarium-related diseases. In addition, this review emphasizes the need for further research about the impact of actinobacteria-Fusarium interactions on mycotoxin production. It also highlights the need of in-depth understanding microbial biocontrol mechanisms to ensure safe and sustainable crop production worldwide.European Journal of Plant Patholog
Enhanced biofuel production by co-pyrolysis of distiller's grains and waste plastics: a quantitative appraisal of kinetic behaviors and product characteristics
Get PDFPyrolysis of biomass feedstocks can produce valuable biofuel, however, the final products may present excessive corrosion and poor stability due to the lack of hydrogen content. Co-pyrolysis with hydrogen-rich substances such as waste plastics may compensate for these shortcomings. In this study, the co-pyrolysis of a common biomass, i.e. distiller's grains (DG), and waste polypropylene plastic (PP) were investigated towards increasing the quantity and quality of the production of biofuel. Results from the thermogravimetric analyses showed that the reaction interval of individual pyrolysis of DG and PP was 124–471 °C and 260–461 °C, respectively. Conversely, an interaction effect between DG and PP was observed during co-pyrolysis, resulting in a slower rate of weight loss, a longer temperature range for the pyrolysis reaction, and an increase in the temperature difference between the evolution of products. Likewise, the Coats-Redfern model showed that the activation energies of DG, PP and an equal mixture of both were 42.90, 130.27 and 47.74 kJ mol−1, respectively. It thus follows that co-pyrolysis of DG and PP can effectively reduce the activation energy of the reaction system and promote the degree of pyrolysis. Synergistic effects essentially promoted the free radical reaction of the PP during co-pyrolysis, thereby reducing the activation energy of the process. Moreover, due to this synergistic effect in the co-pyrolysis of DG and PP, the ratio of elements was effectively optimized, especially the content of oxygen-containing species was reduced, and the hydrocarbon content of products was increased. These results will not only advance our understanding of the characteristics of co-pyrolysis of DG and PP, but will also support further research toward improving an efficient co-pyrolysis reactor system and the pyrolysis process itself.Chemospher
Effective transfer of safety interventions within and between organizations: Leveraging translation theory to achieve improved outcomes
Get PDFSafety interventions are often ‘borrowed’ from one organizational setting, where they have worked successfully, to another organizational setting but not necessarily with the same positive outcomes. Translation theory could offer potential insights into the processes through which managers translate safety practices either from one organization to another or from one part to another part of the same organization. To examine this possibility, this study used the framework method of analysis, underpinned by a conceptual framework developed from translation theory, to analyse qualitative data from interviews with experienced managers having responsibility for safety in their organization who shared narratives of eight different safety interventions deployed in a variety of industry sectors ranging from oil and gas to retail from around the world. By inference from the data, analysis shows that interventions of low complexity, low embeddedness and high explicitness which theory characterises as more translatable, were also in practice more successfully translated. Furthermore, interventions with senior management support had higher levels of interpretive viability, thus making them more transformable and ensuring translation success. Also, translations were more successful when the safety interventions received adequate resourcing, were targeted at a narrow rather than a broad organizational scope and where they were integrated into existing work practices. The conceptual elements of the framework adopted in this study have the potential to support the development of translation competence among safety professionals, thus permitting the future deployment of more effective safety interventions in the workplace to reduce accidents and injuries.Safety Scienc
Active stall flutter suppression for a revised Leishman/Beddoes model
Get PDFThis paper proposes a nonlinear disturbance observer (NDO) based sliding mode control (SMC) method to the problem of stall flutter suppression for a revised Leishman/Beddoes (L/B) model. To capture accurate aerodynamic characteristics whilst reducing the plant model mismatch, the dynamics of the separation point and the shift of the aerodynamic centre are analysed to improve the structure of the L/B model. Based on this revised L/B model, an active flutter suppression problem which includes aerodynamic disturbances and actuator dynamics is addressed. The inclusion of the actuator dynamics means that the aerodynamic disturbance from the flow separation, induced by the revised L/B model, is considered as an ‘unmatched’ disturbance. To counteract the effect of unmatched disturbances, an NDO-based sliding mode control scheme is applied to suppress stall flutter and to ensure rapid reference tracking performance in both steady and unsteady flow conditions. Simulation results show the improvements of the proposed revised L/B model via a comparative analysis. In addition, the efficacy of the proposed stall flutter suppression scheme is demonstratedJournal of Aerospace Engineerin
On the relationship between fiscal consolidation (austerity) and income inequality. Novel empirical evidence.
Get PDFNellis, Joe - Associate SupervisorEquity concerns regarding increases and persistence of adverse distributional outcomes
tend to rear up during instances of austerity consideration since increasing inequality
levels tend to have material significances on a people’s way of life as well as a nation’s
economic growth by disproportionately affecting economic opportunities for the lower
and median incomes. Motivated by the lack of empirical clarity and conflicting evidence
in the extant austerity-inequality nexus literature this thesis enriches our understanding of
the effect of fiscal consolidation programmes on output and income inequality. More
specifically, by engaging in a systematic literature review, this study explores the
relationship between austerity and income inequality. Furthermore, by employing
different empirical model specifications1 for a panel of 16 OECD countries for the period
1980 to 2019, this research work explores the dynamic distributional effects of fiscal
consolidation programmes as well the role of public debt in determining distributional
outcomes during austerity implementation. The novel evidence obtained suggests that:
adverse distributional effects persist for 15 years following adjustment implementation
through both revenue and expenditure channels; furthermore – point estimates for the
Bottom 40% of the income distribution are higher by the 15th year than previous peak
periods; distributional impacts arising from influences of public debt levels are amplified
during instances of fiscal adjustment with adverse distributional effects on average,
manifesting from medium debt levels.PhD in Economics and Financ
Evidence Project Final Report: Evaluating the productivity, environmental sustainability and wider impacts of agroecological compared to conventional farming systems
No full textReport for DEFRAAgriculture is a major cause of greenhouse gas (GHG) emissions, biodiversity loss, and pollution. Agroecological and regenerative farming have been advocated as alternative approaches that may have fewer negative (or even net positive) environmental impacts than conventional agriculture at farm- and landscape-scales, leading to considerable interest in these approaches (Newton et al. 2020; Bohan et al. 2022; Prost et al. 2023).
This report forms the third part of a Defra-funded project Evaluating the productivity, environmental sustainability and wider impacts of agroecological and regenerative farming systems compared to conventional systems. The first part of this project was a rapid evidence review of agroecological and regenerative farming systems and their impacts (Burgess et al. 2023), and the second reported interview findings to examine farmer and stakeholder perspectives on barriers and enablers in agroecological and regenerative farming (Hurley et al. 2023). This third part of the project characterised the current research capability in agroecology and regenerative farming, and explored the potential role of a new ‘living lab’ trial network
Fractal assessment analysis of China's air-HSR network integration
Get PDFHigh-speed rail (HSR) has emerged as a significant mode for intercity transport in several countries, particularly China, setting an environment that may promote integration between air and HSR networks. To better measure the current level of integration of China's air-HSR intermodal network and identify implementation issues, this paper establishes a novel assessment framework that considers three primary areas: service capability, network connectivity and transfer potential. The framework is based on a comprehensive literature review of network measurement and assessment methodologies. Then, fractal theory is used to establish an assessment model that associates the fractal dimension to the level of intermodal integration, which can serve as an important complement to traditional weighting methods. The model and framework are applied to the 10 cities in China with the potential for air-HSR integration. The results show that international hub airports, together with their closest HSR station, do not necessarily perform at a higher integration level than regional hubs. The paper also proposes policy and practical recommendations to enhance air-HSR network integration levels from service supply, network coordination and transfer design perspectives.Journal of Transport Geograph
What can we learn from severity index on flight data monitoring? analysis of safety resilience in flight operations during COVID-19 disruptions
Get PDFThe unexpected spread of the pandemic raised concerns regarding pilots’ skill decay resulting from the significant drops in the frequency of flights by about 70%. This research retrieved 4761 Flight Data Monitoring (FDM) occurrences based on the FDM programme containing 123,140 flights operated by an international airline between June 2019 and May 2021. The FDM severity index was analysed by event category, aircraft type, and flight phase. The results demonstrate an increase in severity score from the pre-pandemic level to the pandemic onset on events that occurred on different flight phases. This trend is not present in the third stage, which indicates that pilots and the safety management system of the airline demonstrated resilience to cope with the flight disruptions during the pandemic. Through the analysis of event severity, FDM enables safety managers to recommend measures to increase safety resilience and self-monitoring capabilities of both operators and regulators.Higher Education Innovation Fund (HEIF 2021-2022)Ergonomic