20505 research outputs found
Sort by
Computational aeroacoustic study of co-rotating rotors in hover
Get PDFThis paper aims to investigate, by means of Lattice-Boltzmann simulations, the flow-field and far-field noise of two co-axial co-rotating rotors operating at 3000 rpm in hover conditions. The two co-rotating configurations are made by 2 × 2-bladed rotors with a fixed axial separation and two different azimuthal separations Δ equal to 84◦ and 12◦. Isolated 2- and 4-bladed rotors, are also simulated at the same operating conditions and used as aerodynamic and aeroacoustic reference. For both Δ = 84◦ and 12◦, the upper rotor tip vortices are accelerated downstream due to the induction from the lower rotor, avoiding blade vortex interaction (BVI). The lower rotor tip vortices convect into the wake with a lower velocity, causing BVI for Δ = 12◦. The lower rotor shows a reduction of thrust, relative to the upper rotor, of 36% and 66% for Δ = 84◦ and 12◦, respectively. For Δ = 12◦, the lower blades act as a wing flap for the upper ones, increasing their thrust. The tonal noise emission for the co-rotating rotors is driven by the interference between the acoustic waves from upper and lower rotors. Because of destructive interference, the configuration Δ = 84◦ shows a first harmonic up to 15 dB lower than Δ = 12◦, but still 4.5 dB higher than the isolated 4-bladed rotor.Aerospace Science and Technolog
Simulation of a Cyber-Physical Lifecycle System based on a blockchain platform
Get PDFProduct lifecycle management plays a crucial role in establishing resource circulation systems based on artifact stocks accumulated in society. However, given the involvement of diverse stakeholders, managing the complex circular systems of a product lifecycle requires advanced digital technologies. The concept of a cyber-physical lifecycle system (CPLS) is proposed in this paper. CPLS constructs the digital twin of a product lifecycle to be managed. The digital model in the cyberspace is used for analysis, simulation, and reconfiguration of the lifecycle based on real data acquired from the physical space of the CPLS. In this research, we introduce blockchain technology in the CPLS to aggregate information on target products and processes from each stakeholder involved in the lifecycle. To support decision-making in lifecycle management, a life cycle simulation (LCS) is conducted in the cyberspace of the CPLS based on the acquired data through blockchain. Subsequently, decisions are made based on the simulation results to increase the profit of each stakeholder and minimize the environmental loads of the entire lifecycle. In a case study focusing on the life cycle management of electric motors, we conducted a simulation-based analysis on the prototype of CPLS. A twin-experiment for the case showed the effectiveness of production management using the CPLS from economic and environmental perspectives.12th International Conference on Through-life Engineering Services – TESConf202
β-Grain refinement in WAAM Ti-6Al-4 V processed with inter-pass ultrasonic impact peening
Get PDFAs-deposited Wire-Arc Additive Manufactured (WAAM) Ti-6Al-4V parts typically contain large columnar β-grains on a centimetre scale, with a strong 〈001〉 fibre texture, leading to anisotropic mechanical properties and unacceptable scatter in damage tolerance. Inter-pass deformation, introduced by the application of Ultrasonic Impact Peening (UIP) across each added layer, has been shown to be effective in refining the β-grain structure and achieving a weaker texture. The depth of deformation and the grain refinement mechanism induced by UIP have been investigated by combining advanced electron backscatter diffraction (EBSD) characterization with a ‘stop action’ observation technique. UIP facilitates a similar refinement mechanism and nearly the same depth of deformation as conventional machine hammer peening, with the advantages of a much higher strain rate, lower peak force, and two orders of magnitude lower impact energy, making it a faster and more economical process. β recrystallization is seen within the deformation zone during re-heating through the α → β transition. Although new recrystallized β-grains formed in the UIP surface-deformed layer to a shallower depth than that of remelting, recrystallization initiated ahead of the melt pool and the recrystallized grains grew downwards to a greater depth before remelting. These refined grains were thus able to survive and act as nucleation sites at the fusion boundary for epitaxial regrowth during solidification, greatly refining the grain structure.The authors are grateful to the EPSRC programme grants NEWAM (EP/R027218/1) for funding of the research, as well as to LightForm (EP/R001715/1) and facilities provide by the Henry Royce Institute for Advanced Materials, through Royce equipment grant (EP/P025021/1), for supporting aspects of this work. P.B. Prangnell is grateful to the Royal Academy of Engineering, UK, and Airbus for financial support.Materiali
Laser ignition of energetic crystals of cyclotrimethylenetrinitramine (RDX) optically sensitized with gold nanoparticles and light-absorbing dye
Get PDFLaser ignition of energetic materials has shown promise in eliminating sensitive primary explosives to initiate a main explosive charge. To enhance the laser ignitibility of energetic material cyclotrimethylenetrinitramine (RDX) with a near-infrared diode laser, the RDX was re-crystallized with three optical sensitizers: COOH-PEGylated gold nanorods (both solution and dry gold nanoparticle) and laser absorbing dye. Optical microscopy was undertaken on the crystals to investigate the uniformity of doping of the optical sensitizers. High-speed video was used to experimentally observe the enhanced laser ignitability of these RDX crystals. The solution gold nanoparticles enhanced doping uniformity resulting in it being an effective optical sensitizer. Compared to the other two optical sensitizers, the solution gold nanoparticles optical sensitizer significantly enhanced the laser ignitibility of RDX by reducing the required power density to as little as 79 Wcm−2 to achieve ignition. At this laser power density, the ignition delay was approximately 68 ms.Optics and Laser Technolog
Exploring deepfake technology: creation, consequences and countermeasures
Get PDFThis paper presents a comprehensive examination of deepfakes, exploring their creation, production and identification. Deepfakes are videos, images or audio that are remarkably realistic and generated using artificial intelligence algorithms. While they were initially intended for entertainment and commercial use, their harmful social consequences have become more evident over time. These technologies are now being misapplied for the creation of explicit content, coercing individuals and disseminating false information, resulting in an erosion of and potentially negative societal consequences. The paper also highlights the significance of legal regulations in controlling the utilization of deepfakes and investigates methods for their identification through machine learning. In the modern digital world, comprehending the ethical and legal implications of deepfakes necessitates a thorough understanding of the phenomenon.Human-Intelligent Systems Integratio
Potential impact of current agricultural practices on mycotoxin occurrence and mycotoxin knowledge along the cassava value chain in Uganda
Get PDFCassava is the second most important staple food crop for Uganda and is prone to contamination with mycotoxins. This study aimed at understanding the current agricultural practices, their potential influence on mycotoxin occurrence, as well as assessing mycotoxin knowledge among key cassava value chain actors, including farmers, wholesalers, and processors. Data were collected through individual interviews (210), key informant interviews (34), and 4 focus group discussions. The findings revealed that 51% of farmers peeled cassava directly on bare ground, resulting in direct contact with soil that potentially harbors mycotoxin-producing fungi, such as Aspergillus section Flavi. During postharvest handling, 51.6% of farmers dried cassava chips directly on bare ground. Nearly, all (95.2%) of wholesalers packed cassava chips in local gunny bags and placed them on ground instead of pallets. In the processing of cassava chips into flour, only one of the 14 processing machines was certified by the Uganda National Bureau of Standards. Additionally, there was only one processing machine available for every 180 (1:180) consumers bringing their cassava for processing. 50.8% of cassava consumers interviewed admitted to consuming cassava flour regardless of quality, while 73% blended cassava flour with flour from mycotoxin-susceptible crops mainly maize, millet, and sorghum. Most (96.2%) of the people along the cassava value chain did not understand what the term mycotoxins meant. However, 56% of interviewed respondents were familiar with the term aflatoxins. Of the cassava value chain actors aware of mycotoxins, 82.9% knew of methods for reducing aflatoxin contamination, but only 40.9% were putting such methods into practice. More farmers (47.9%) managed aflatoxins compared to wholesalers (33.3%) and processors (21.4%). Knowledge on aflatoxins was significantly associated with value chain actor (P = 0.026), head of household (P = 0.004), region (P = 0.033), age (P = 0.001), and experience (P = 0.001). This study highlights the critical areas of mycotoxin contamination within the cassava value chain in Uganda and underscores the need to improve the knowledge among value chain actors especially farmers.Commonwealth Scientific and Industrial Research OrganisationJournal of Food Protectio
Metallic glasses–novel materials for applications in nuclear fusion
Get PDFNovel alloys like metallic glasses (MGs) hold the potential to revolutionize many scientific and industrial sectors including nuclear fusion (NF). These metallic materials with amorphous atomic structure possess outstanding mechanical properties in combination with high corrosion resistance and high radiation tolerance. They can be made and shaped in unique ways impossible for conventional crystalline materials. MGs also offer high compositional flexibility and can be tailored to various specific applications. Here, we give a brief overview on how the fusion sector can benefit from MGs and, as examples, highlight some specific use cases. We also outline a pathway for the future development of MGs specifically designed for the extreme environments occurring in NF.IEEE Transactions on Plasma Scienc
Assessment Model for facilitating digital retrofitting in manufacturing: key factors and practical insights
Get PDFIn an era where factories are required to evolve or face obsolescence, digital retrofitting offers a lifeline to manufacturing companies striving to stay competitive. Digital retrofitting, the process of integrating cutting-edge technologies such as IoT components into legacy manufacturing systems, is emerging as a crucial strategy. However, due to the diversity of these legacy systems, a one-size-fits-all solution is ineffective. Despite the transformative potential of digital retrofitting, there is a noticeable gap in the tools that enable decision-makers to accurately assess their readiness for this process. To bridge this gap, it is essential to identify and evaluate critical factors that determine a system’s preparedness for integration with advanced technologies. This study proposes 21 key factors that must be considered to ensure readiness for digitalisation. These factors are grouped under four critical dimensions: strategy and organisation, workforce enhancement, smart factory, and smart process. Engagement with 18 industry practitioners was undertaken to validate these factors, ensuring their practical relevance. The findings provide valuable insights into the critical factors that need to be evaluated before embarking on the journey of digitalisation, ensuring that companies are fully prepared to integrate new technologies and optimise their manufacturing processes.34th CIRP Design Conference 2024Procedia CIR
Supporting flight dynamics, parameter identification and simulation teaching with a flying classroom
Get PDFCranfield University recently commissioned a modified Saab 340B airliner as a new flying laboratory classroom. The modifications are briefly described before the use of the flying classroom for flight test teaching is described. A flight dynamic model of the aircraft has been developed, and that, along with the data from the flight test programme are extensively used to support masters-level teaching in flight dynamics, flight simulation and flight parameter identification. Some examples of student results are also briefly presented.2nd IFAC Workshop on Aerospace Control Education - WACE 2024IFAC-PapersOnLin
Towards a better framework for estimative intelligence – addressing quality through a systematic approach to uncertainty handling
Get PDFThe analytic standards governing the production of intelligence are outlined in a number of Intelligence Community Directives (ICDs). In this paper, we are concerned with ICDs 203, 206 and 208 and, in particular, how these relate to the handling of uncertainty in estimative intelligence. An inductive thematic analysis is employed which identifies several recurring themes. In addition, a conceptual map is developed which highlights relationships and the level of inter-connectedness between the standards. Requirements for improved operationalization of uncertainty handling are also discussed. The question of analytic feasibility is then examined in relation to the five themes extracted from the earlier analysis. The paper concludes that a new framework for uncertainty handling is required and suggests that such a framework should contain a process to assess analytic feasibility from the outset of a study.Intelligence and National Securit