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Cascaded incremental nonlinear dynamic inversion trajectory following for a stratospheric airship in wind
No full textThis paper presents a guidance and control system for controlling the trajectory of a stratospheric unmanned airship using a cascaded Incremental Nonlinear Dynamic Inversion (INDI) method. The control system uses a two-loop cascaded INDI controller with virtual efforts and moments formulation to control both the airship attitude and velocity, while providing perturbation rejection properties. An active-set solver allocates the virtual controls to the airship propellers and aerodynamic surfaces while respecting the actuator bounds and rates saturation. The guidance system uses a Nonlinear Dynamic Inversion controller, where the position error dynamics formulation explicitly considers the lateral velocity of the airship, which enables it to counteract the wind influence. Simulation results demonstrate that the reference trajectory is precisely followed, even in the presence of unknown wind perturbations and both aerodynamic coefficients and mass and inertia parametric uncertainties through Monte-Carlo simulations.Unmanned System
Project-based learning course design for multi-agent autonomy using quadrotors
Get PDFThis paper proposes a project-based learning course utilising multiple quadrotors, aiming to solidify and amplify technical knowledge and develop critical thinking capabilities. An engineering problem is provided as a surveillance mission with multiple quadrotors autonomously searching, detecting, and tracking ground vehicles. The course covers all stages of multi-agent autonomy development, from identifying system requirements, designing software and hardware, to conducting demonstrations in a drone flying arena. During the course, students improve their ability to critically formulate, solve and evaluate engineering problems as well as gain and apply technical knowledge in all aspects of autonomy such as flight dynamics, control, navigation, guidance, task allocation, situational awareness and communication. The paper details the problem design, course timeline, outcomes, and key lessons learnt from the course.2nd IFAC Workshop on Aerospace Control Education - WACE 2024IFAC-PapersOnLin
Exploring the organizational value of international assignments: home versus host
Get PDFInternational assignments (IAs) are a common feature of international business and human resource management, yet evidence of their organizational value is mixed and contradictory. We argue, contrary to extant IA literature, that this is due to the need to investigate the value to each of the home and the host organizations separately. We apply such an approach in a public sector case study using a dynamic capabilities lens, relevant given its theoretical underpinnings in value creation. Extending the IA value literature, we find that the value to the home and host differs both in type and timing, that the value to one may be detrimental to the other, and that the funding of the underlying costs of an IA is a critical feature. Understanding and assessing these factors separately is key to managing the overall combined organizational value of IAs.The International Journal of Human Resource Managemen
Grain refinement and mechanical properties improvement of additively manufactured Al-Cu alloy through pre-deformation in thermo-mechanical treatment
No full textInferior mechanical properties induced by porosity and coarse grains of wire-arc additively manufactured Al-Cu alloy restrict its industrial application. The inter-layer cold rolling, conventional heat treatment (T6) and thermo-mechanical heat treatment (T8) was applied to Al-Cu alloy, and the effect of pre-stretched strain in T8 treatment was investigated. The pre-stretched strain induces equal increments of hardness and YS for both the as-deposited and cold-rolled conditions before aging treatment, while the increments for cold-rolled samples are larger after aging treatment. The cold-rolled sample shows better tensile properties than the as-deposited sample with the same pre-stretched strain in T8 treatment, proving that T8 treatment further increased the strengths compared to the T6 treatment. It shows the best tensile properties with the pre-stretched strain of 5 %, exceeding the properties of 2219-T87 plate. With the increased pre-stretched strain, the density of the θ′ phases significantly increases; while further increase to 10 % pre-stretched strain induces severe coarsening of θ′ phases. Therefore, an optimized pre-stretched strain leads to high-density and tiny dispersed θ′ phases, thus resulting in the best tensile properties. Grain refinement induced by inter-layer cold rolling and uniformly precipitated phases resulted from proper pre-stretched strain both contribute to the strengths enhancement. The strengthening mechanism of hybrid additive manufacturing and inter-layer cold rolling followed by T8 treatment was discussed.The authors wish to acknowledge the financial support from the State Key Laboratory of Precision Manufacturing for Extreme Service Performance, Central South University (ZZYJKT2024-08), Natural Science Foundation of Changsha (kq2402213), and China Scholarship Council (201806835007).Materials Science and Engineering:
The impact of Blockchain adoption on supply chain performance: evidence from food industry
Get PDFThe food supply chain (FSC) constantly needs to address persistent challenges such as information asymmetry, low transparency, food quality and authenticity, and unnecessary waste. Blockchain is perceived as a promising solution to overcome these FSC challenges. Existing literature captures a conceptual understanding of various aspects of Blockchain for FSC, such as how the technology can enhance transparency, efficiency, and food authenticity. However, a quantitative assessment of the overall impact of Blockchain adoption on the FSC operational performance is still missing. This study combines empirical and analytical approaches to investigate the evident research gap. Under the lens of systems thinking and System Dynamics (SD) modelling perspective, the study collected questionnaire and interview data to develop different FSC models for evaluating the impact of Blockchain on key operational performance metrics. The findings indicated that Blockchain positively affects inventory level and lead time in the immediate term, and cost in the long term. The results also warn that forgoing inventory buffers can come with the cost-of-service level. This study provides quantitative evidence of the positive influence of Blockchain on the FSC. This research contributes by extending the understanding of Blockchain's implications on broader supply chain performance from a systems perspective.International Journal of Production Researc
Enhancing the natural absorbing capacity of rivers to restore their resilience
Get PDFResilience, which can also be described as absorbing capacity, describes the amount of change that a system can undergo in response to disturbance and maintain a characteristic, self-sustaining regime of functions, processes, or sets of feedback loops. Rivers exhibit varying levels of resilience, but the net effect of industrialized anthropogenic alteration has been to suppress river resilience. As changing climate alters the inputs to rivers and human modification alters the morphology and connectivity of rivers, restoration increasingly considers how to enhance resilience. Characteristics that underpin river absorbing capacity include natural regimes, connectivity, physical and ecological integrity, and heterogeneity. River management emphasizing channel stabilization and homogenization has reduced river absorbing capacity. We propose that the paths to restoring rivers include defining relevant measures of absorbing capacity and understanding the scales of restoration and the sociopolitical elements of river restoration. We provide a conceptual framing for choosing measures that could be used to assess river absorbing capacity.BioScienc
Effectiveness of H₂O₂/UV and O₃/H₂O₂/UV for metaldehyde removal in drinking water and full-scale costing analysis
No full textMetaldehyde is a widely used pesticide in the UK and has been reported to
produce drinking water quality failures across the national water utilities.
Advanced Oxidation Processes (AOPs) are effective in the removal of recalcitrant
organic constituents but pose (i) high energy and chemical costs and (ii) by-
products formation upon disinfection stage. In this context, UV/H₂O₂ and O₃/H₂O₂
+ H₂O₂/UV were tested at pilot-scale concurrently at Draycote water treatment
work (WTW) (UK) for metaldehyde degradation and disinfection by products
formation potential (DBPFP) at different energy demands (Eᴅ), H₂O₂ and O₃
doses; and pesticide concentrations. Whole-life costing analysis (WLCA) was
undertaken to assess which AOP was most economic for metaldehyde removal
at a Draycote sized WTW. Sensitivity analysis considered potential costs of each
AOP. Metaldehyde was removed up to 98% (UV/H2O2) and 97% (O₃/H₂O₂ +
H₂O₂/UV) successfully fulfilling European Directive 98/83/EC below both 1.0
kWh m⁻³ and 2.14 µg L⁻¹ pesticide inlet water level. Net DBPFP contribution
ranged -283 µg L⁻¹ to +255 µg L⁻¹ for trihalomethanes formation potential
(THMFP), which are UK regulated. DBPFP was related to organic background
characteristics rather than the operating conditions tested in both AOPs. Cost
estimating the AOPs for a 0.72-log metaldehyde removal enabled the total
expenditures to be determined indicating that energy consumption accounted for
50% (UV/H₂O₂), 49 % (O₃/H₂O₂+ H₂O₂/UV) and 31% (O₃/H₂O₂) of their operating
costs. Similar £14.7 million capital costs were appraised for O₃/H₂O₂ and
UV/H₂O₂. Overall, O₃/H₂O₂ sub process outperformed the rest of AOPs when
considering both metaldehyde degradation (≤96%) and net DBPFP contribution
(≤51 µg L⁻¹ THMFP) at the most economically operating costs for 5-month yearly
treatment (£0.07 m⁻³). Sensitivity analysis showed the O₃/H₂O₂ more efficient
process requiring less inputs than UV/H₂O₂ for the same metaldehyde removal.
However, the O₃/H₂O₂ was cost effective at an ideal stoichiometric mass ratio of
0.7 H₂O₂:O₃. Therefore, this would require validation at full-scale. The AOPs were
robust for metaldehyde degradation with reasonable costs.MSc by Research in Wate
Probing into hinterland connectivity with a web of transport modes and logistics nodes: a case of Indian container ports
Get PDFThis article investigates the conceptual and empirical aspects of hinterland connectivity, focusing on container ports in India as a case study. It aims to clarify the complex and multidimensional nature of hinterland connectivity within the context of container ports by addressing a key conceptual issue. The study proposes that port-hinterland connectivity goes beyond direct links and emphasises the strategic relationships with key logistics centres in the hinterland. By employing centrality measures from social network analysis, the study evaluates the overall connectivity of Indian container ports, considering both direct and indirect connections from 2009 to 2021, to identify which ports have robust connections to key logistics centres. The results obtain by using eigenvector centrality reveal that an extensive hinterland network does not necessarily guarantee better hinterland connectivity for container ports. Additionally, the quality of connections, particularly to hubs with high betweenness centrality, is crucial for achieving a high degree of hinterland connectivity. These findings provide valuable policy insights, highlighting the importance of ports fostering closer relationships with key logistics hubs to effectively enhance their connectivity. Based on these findings, the paper offers policy recommendations for India aimed at improving connectivity in alignment with corresponding market shares. This research will serve as a foundation for further exploration of the interplay between port-hinterland connectivity and port market shares from a hinterland perspective, especially in a country like India, where hinterlands significantly overlap.Transportation Research Part A: Policy and Practic
The ‘hangar of the future’ for sustainable aviation
Get PDFSustainability is becoming a major strategic driver within the aviation industry, which has moved from providing primarily economic benefits to delivering the ‘triple bottom line’, including social and environmental impact as well as financial performance. Sustainable aviation is also being tracked by the International Civil Aviation Organisation (ICAO) Global Collation for Sustainable Aviation. Operations and Infrastructure is an important near-term opportunity to deliver sustainability benefits. Digital Technologies, Integrated Vehicle Health Management (IVHM) and Maintenance Repair and Overhaul (MRO) play a prominent role in implementing these benefits, with a particular focus on operational efficiencies. As part of this, the sustainable smart hangar of the future is a concept that is becoming more and more important in forming the future of the aviation industry. The Hangar of the Future is an excellent opportunity for innovation, combining the progress in manufacturing, materials, robotics and artificial intelligence technologies. Succeeding in developing a hangar with these characteristics will provide us with potential benefits ranging from reduced downtime and costs to improved safety and environmental impact. This work explores some of the key features related to the sustainable smart hangar of the future by discussing research that takes place in DARTeC’s (Digital Aviation Research and Technology Centre) hangar led by the IVHM Centre in Cranfield. Additionally, the paper touches on some longer-term aspirations.The Hangar of the Future at Cranfield University is part of the Digital Aviation Research and Technology Centre (DARTeC). The DARTeC project received support from the UK Research and Innovation Research Partnership Infrastructure Fund. The DARTeC consortium includes Cranfield University, Heathrow Airport, Cranfield IVHM Centre, Research England, Boeing, BOXARR, the Connected Places Catapult, Etihad Airways, Inmarsat, the International Air Transport Association (IATA), Saab, the Satellite Applications Catapult, Spirent Communications, OSL Technology and ThalesThe Aeronautical Journa
A very simple flexible tandem dye-sensitized solar cell
Get PDFDye-sensitized solar cells (DSSCs) have been proposed as the most important third generation photovoltaic devices owing to their low fabrication cost, design flexibility, having low hazard to the environment and ease of construction. Tandem DSSCs (T-DSSC) were said to possess properties of its sensitized photoanode and sensitized photocathode in terms of the power conversion efficiency (PCE) parameters. With less studies on the fabrication of simple a flexible tandem DSSC, this work aims at filling this gap as well as showing the influence of one of the main factors that affect the performance of such a device. In this paper, TiO2 and NiO layers were prepared by blading method, sensitized separately, then sandwiched together. The fabricated device produced short circuit current, open circuit voltage and power conversion efficiency of 0.138 mA.cm−2, 0.942 V and 0.063%, respectively. This simple T-DSSC produced a high photovoltage and showed that the photocurrent produced by each photoelectrode should be identical. This match is to overcome the possible hump in the device performance.Journal of Umm Al-Qura University for Applied Science