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Fatigue life assessment of offshore wind support structures in the presence of corrosion pits
Get PDFOffshore wind turbine support structures, which connect the wind turbine transition piece and/or tower to the seabed, are located below the sea level and are in direct contact with seawater during the entire lifespan; therefore, they are highly susceptible to corrosion damage and cracking. In particular, the pitting corrosion is very crucial in these support structures, as it leads to local stress concentrations and thus affects the fatigue life. Although corrosion protection mechanisms are commonly implemented in offshore wind turbines, they have a finite life and therefore corrosion damage cannot be completely avoided during the entire life cycle, and this can lead to pitting corrosion on the steel surface. This paper aims to investigate the impact of pitting corrosion on fatigue durability of steel structures by performing tests on lab-scale coupons, made of S355 structural steel which is widely employed in fabrication of offshore wind support structures. For this purpose, cross-weld uniaxial samples were initially exposed to seawater for different time durations and then tested under cyclic loading condition. Furthermore, the durability analysis of corroded samples was carried out using a modified NASGRO equation. The results show that the pitting corrosion significantly reduces the fatigue life, and its level of life reduction is strongly dependent on the seawater exposure time. Moreover, the results show that employment of a linear trend for lower stress ranges would result in significant underprediction of the fatigue life, hence over-conservatism in the design life, at longer seawater exposure times.Engineering and Physical Sciences Research Council (EPSRC): EP/S000747/1Marine Structure
Automation for digital forensics: towards a definition for the community
Get PDFWith the increasing amount of digital evidence per case, the automation of investigative tasks is of utmost importance to the digital forensics community. Consequently, tools are published, frameworks are released, and artificial intelligence is explored. However, as the foundation, i.e., a definition, classification, and common terminology, is missing, this resembles the wild west: some consider keyword searches or file carving as automation while others do not. We, therefore, reviewed automation literature (in the domain of digital forensics as well as other domains), performed three practitioner interviews, and discussed the topic with domain experts from academia. On this basis, we propose a definition and then showcase several considerations with respect to automation for digital forensics, e.g., what we classify as no/basic automation as well as full automation (autonomous). We conclude that it requires these foundational discussions to promote and progress the discipline through a common understanding.Forensic Science Internationa
Inhibitory mechanisms on dry anaerobic digestion: Ammonia, hydrogen and propionic acid relationship
Get PDFInhibitory pathways in dry anaerobic digestion are still understudied and current knowledge on wet processes cannot be easily transferred. This study forced instability in pilot-scale digesters by operating at short retention times (40 and 33 days) in order to understand inhibition pathways over long term operation (145 days). The first sign of inhibition at elevated total ammonia concentrations (8 g/l) was a headspace hydrogen level over the thermodynamic limit for propionic degradation, causing propionic accumulation. The combined inhibitory effect of propionic and ammonia accumulation resulted in further increased hydrogen partial pressures and n-butyric accumulation. The relative abundance of Methanosarcina increased while that of Methanoculleus decreased as digestion deteriorated. It was hypothesized that high ammonia, total solids and organic loading rate inhibited syntrophic acetate oxidisers, increasing their doubling time and resulting in its wash out, which in turn inhibited hydrogenotrophic methanogenesis and shifted the predominant methanogenic pathway towards acetoclastic methanogenesis at free ammonia over 1.5 g/l. C/N increases to 25 and 29 reduced inhibitors accumulation but did not avoid inhibition or the washout of syntrophic acetate oxidising bacteria.Waste Managemen
When does a light sphere break ice plate most by using its net buoyance?
Get PDFA free-rising buoyant sphere can break an ice plate floating above it. The problem is when the light sphere breaks the ice plate most, or the optimal relative density of the sphere which can break the ice plate the most severely. This experimental study was done to answer this problem. A set of experimental devices were designed, and a high-speed camera system was adopted to record the whole dynamic process, including the free-rising of the sphere, the collision between the sphere and the ice plate, the crack initiation and propagation, as well as the breakup of the ice plate. The failure mode of the ice plate under impact load was analyzed. It was found that conical cracks were formed under the reflected tensile wave at the top surface of the ice plate. On this basis, the influences of ice thickness, the initial submergence depth, and the relative density of the sphere on icebreaking were further investigated. An optimal relative density of the sphere was found when the sphere was released at a certain initial submergence depth, at which point the ice was damaged the most severely. For example, when the dimensionless initial submergence depth of the sphere was 2.31, the optimal relative density of the sphere was close to 0.4, with the probability of the ice plate breakup as high as 91.7%. It was also found from the experiments that the degree of damage to the ice plate correlated well with the kinetic energy of the sphere just before collision. Results showed that the optimal relative density can be estimated by theoretical analysis of the kinetic energy of the sphere, which will provide a reference for potential icebreaking applications in the future.Journal of Marine Science and Engineerin
The influence of micro-expressions on deception detection
Get PDFFacial micro-expressions are universal symbols of emotions that provide cohesion to interpersonal communication. At the same time, the changes in micro-expressions are considered to be the most important hints in the psychology of emotion. Furthermore, analysis and recognition of these micro-expressions have pervaded in various areas such as security and psychology. In security-related matters, micro-expressions are widely used to detect deception. In this research, a deep learning model that interprets the changes in the face into meaningful information has been trained using The Facial Expression Recognition 2013 dataset. Necessary data is also obtained through live stream or video stream by detecting via computer vision and evaluating with the trained model. Finally, the data obtained is transformed into graphic and interpreted to determine whether the people are trying to deceive or not. The deception classification accuracy of the custom trained model is 74.17% and the detection of the face with high precision using the computer vision methods increased the accuracy of the obtained data and provided it to be interpreted correctly. In this respect, the study differs from other studies using the same dataset. In addition, it is aimed to facilitate the deception detection which is performed in a complex and expensive way, by making it simple and understandable.Multimedia Tools and Application
From total quality management to Quality 4.0: a systematic literature review and future research agenda
Get PDFQuality 4.0 is an emerging concept that has been increasingly appreciated because of the intensification of competition, continually changing customer requirements and technological evolution. It deals with aligning quality management practices with the emergent capabilities of Industry 4.0 to improve cost, time, and efficiency and increase product quality. This article aims to comprehensively review extant studies related to Quality 4.0 to uncover current research trends, distil key research topics, and identify areas for future research. Thus, 46 journal articles extracted from the Scopus database from 2017 to 2022 were collected and reviewed. A descriptive analysis was first performed according to the year-wise publication, sources of publication, and research methods. Then, the selected articles were analyzed and classified according to four research themes: Quality 4.0 concept, Quality 4.0 implementation, quality management in Quality 4.0, and Quality 4.0 model and application. By extracting the literature review findings, we identify the Quality 4.0 definitions and features, develop the quality curve theory, and highlight future research opportunities. This study supports practitioners, managers, and academicians in effectively recognizing and applying Quality 4.0 to enhance customer satisfaction, achieve innovation enterprise efficiency, and increase organizational competitiveness in the era of Industry 4.0.National Social Science Fund of China: Grant No. 21ZDA02
The effect of Cu content on the microstructure and properties of the wire arc additive manufacturing Al-Cu alloy
Get PDFAl-Cu alloy has broad application prospects in the field of aerospace due to its excellent performance. In this paper, deposits with different Cu contents were prepared by the wire arc additive manufacturing (WAAM) process, and the effects of Cu content on the microstructure and mechanical properties were investigated. The microstructure of Al-Cu alloy was investigated by metallography, scanning electron microscope (SEM), energy-dispersive spectrometer (EDS), and transmission electron microscope (TEM). The results show that both the number and size of the precipitated θ phases (Al2Cu) in the as-deposited material increase with the increase of Cu content. After the T4 treatment, the solid solution amount of Cu in the matrix showed a trend of first increasing and then remaining stable. When the content of Cu was greater than 5.65%, as the Cu content increased, the number and size of the remaining θ phases both increased. In the peak ageing state, the amount of precipitated θ’ phase showed a trend of increasing and then remaining stable. After the T6 treatment, the mechanical properties showed a trend of first increasing and then decreasing with the increase of the content of Cu. When the Cu content was 5.65%, the deposit achieved the best mechanical properties, and the anisotropy of the mechanical properties disappeared. The tensile strength, yield strength, and elongation reached 538 MPa, 478 MPa, and 10.5%, respectively. When the content of Cu was greater than 5.65%, the anisotropy of mechanical properties was obvious, and the fracture mode of the vertical specimen changed from ductile fracture to brittle fracture.Material
Digital twin concept of a force measuring device based on the finite element method
Get PDFIn the framework of EMPIR project ComTraForce, the Digital Twin (DT) concept of force measurement device is developed. DT aims to shade static, continuous as well as dynamic calibration processes, preserving data quality and collecting calibration data for improved Decision-making. To illustrate the developed DT concept, a prototype realisation for static and continuous force calibration processes is developed, involving simulation with ANSYS engineering software. The focus of the current work is placed on the data connection between the physical device and the DT. The DT model is validated using traceable measurements.Acta IMEK
Wind preview-based model predictive control of multi-rotor UAVs using LiDAR
Get PDFAutonomous outdoor operations of Unmanned Aerial Vehicles (UAVs), such as quadrotors, expose the aircraft to wind gusts causing a significant reduction in their position-holding performance. This vulnerability becomes more critical during the automated docking of these vehicles to outdoor charging stations. Utilising real-time wind preview information for the gust rejection control of UAVs has become more feasible due to the advancement of remote wind sensing technology such as LiDAR. This work proposes the use of a wind-preview-based Model Predictive Controller (MPC) to utilise remote wind measurements from a LiDAR for disturbance rejection. Here a ground-based LiDAR unit is used to predict the incoming wind disturbance at the takeoff and landing site of an autonomous quadrotor UAV. This preview information is then utilised by an MPC to provide the optimal compensation over the defined horizon. Simulations were conducted with LiDAR data gathered from field tests to verify the efficacy of the proposed system and to test the robustness of the wind-preview-based control. The results show a favourable improvement in the aircraft response to wind gusts with the addition of wind preview to the MPC; An 80% improvement in its position-holding performance combined with reduced rotational rates and peak rotational angles signifying a less aggressive approach to increased performance when compared with only feedback based MPC disturbance rejection. System robustness tests demonstrated a 1.75
s or 120% margin in the gust preview’s timing or strength respectively before adverse performance impact. The addition of wind-preview to an MPC has been shown to increase the gust rejection of UAVs over standard feedback-based MPC thus enabling their precision landing onto docking stations in the presence of wind gusts.Sensor
Chapter 1: Collapse, cataclysm, and eruption: Alien archaeologies for the Anthropocene
No full textOur shared planet is becoming increasingly alien in the Anthropocene, and increasingly
inundated. These radical changes to our home call for critical considerations of collapse – when
destruction comes from above and rains downward – and cataclysm – as in flood or deluge,
when destruction surges up from below – alongside eruption – or hyperbolic destruction spewing
forth from a container as small as a split atom. The authors propose that a theoretical framework
of object orientation offers a way for archaeologists, especially those whose work brings them
into the sea, to contribute more meaningfully to contemporary research about our planet’s pastpresent-
future. We have two primary aims: 1) to help usher the alienated subdiscipline of
maritime archaeology into the broader discourse of the humanities; and 2) to issue a call to action
for fellow maritime archaeologists to respond to ecocide more urgently, more crossdisciplinarily,
and more responsibly with new interventions into old research questions. After
defending the unique relevance of object orientation to the humanities and social sciences –
archaeology specifically and maritime or nautical archaeology most of all – it will pose some
relevant questions on how to use our research expertise to move forward, while establishing
effective methodologies for thinking and communicating the nonhuman to students and the
general public. Ultimately, this paper advocates for mobilizing a radical shift in how humans
think and care for all the objects sharing our lives, and our destinies, which are increasingly
impacted from above, below, and within