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Advanced methods for wind turbine performance analysis based on SCADA data and CFD simulations
Get PDFDeep comprehension of wind farm performance is a complicated task due to the multivariate dependence of wind turbine power on environmental variables and working parameters and to the intrinsic limitations in the quality of SCADA-collected measurements. Given this, the objective of this study is to propose an integrated approach based on SCADA data and Computational Fluid Dynamics simulations, which is aimed at wind farm performance analysis. The selected test case is a wind farm situated in southern Italy, where two wind turbines had an apparent underperformance. The concept of a space–time comparison at the wind farm level is leveraged by analyzing the operation curves of the wind turbines and by comparing the simulated average wind field against the measured one, where each wind turbine is treated like a virtual meteorological mast. The employed formulation for the CFD simulations is Reynolds-Average Navier–Stokes (RANS). In this work, it is shown that, based on the above approach, it has been possible to identify an anemometer bias at a wind turbine, which has subsequently been fixed. The results of this work affirm that a deep comprehension of wind farm performance requires a non-trivial space–time comparison, of which CFD simulations can be a fundamental part
To tweet or not to tweet? the determinants of tweeting activity in initial coin offerings
Get PDFOur research explores the causes of Twitter activity in highly technological start-ups that finance their activities via initial coin offerings (ICOs). By relying on weekly data of 297 ICOs for the period 2015–2020 (35,459 observations), we examine how major exogenous events affect the number of tweets issued by the start-up. Then, we explore how the community of followers reacts to the tweets. We discover that events external to firms reduce ICOs’ tweeting activity. Moreover, our evidence indicates that the followers’ reaction is positively related to the tweets issued by the firm and negatively related to major events unrelated to the firm. Interestingly, followers’ reaction has an inverted U-shaped relation with the firm’s Twitter volume, suggesting that excessive Twitter activity can harm the further dissemination of tweets. Our results, robust to alternative estimation techniques, emphasize the important role of Twitter as an information disseminator, legitimizer, and endorser for highly opaque firms
GNSS/INS/VO fusion using gated recurrent unit in GNSS denied environments
Get PDFUrban air mobility is a growing market, which will bring new ways to travel and to deliver items covering urban and suburban areas, at relatively low altitudes. To guarantee a safe and robust navigation, Unmanned Aerial Vehicles should be able to overcome all the navigational constraints. The paper is analyzing a novel sensor fusion framework with the aim to obtain a stable flight in a degraded GNSS environment. The sensor fusion framework is combining data coming from a GNSS receiver, an IMU and an optical camera under a loosely coupled scheme. A Federated Filter approach is implemented with the integration of two GRUs blocks. The first GRU is used to increase the accuracy in time of the INS, giving as output a more reliable position that it is fused, with the position information coming from, the GNSS receiver, and the developed Visual Odometry algorithm. Further, a master GRU block is used to select the best position information. The data is collected using a hardware in the loop setup, using AirSim, Pixhawk and Spirent GSS7000 hardware. As validation, the framework is tested, on a virtual UAV, performing a delivery mission on Cranfield university campus. Results showed that the developed fusion framework, can be used for short GNSS outages.AIAA SciTech Forum 202
Saving the world? how CSR practitioners live their calling by constructing different types of purpose in three occupational stages
Get PDFMuch attention in the meaningful work literature has been devoted to calling as an orientation toward work characterized by a strong sense of purpose and a prosocial motivation beyond self-gain. Nonetheless, debate remains as to whether individuals change or maintain their calling, and especially whether they live their calling differently in different occupational stages. In this article, we respond to this conundrum through an analysis of the corporate social responsibility (CSR) occupation—substantiated by interviews with 57 CSR practitioners from Swedish international companies who are living their calling. We demonstrate that social/commercial tensions affect these CSR practitioners, fueled by a divide between their social aspirations and the commercial goals, and prompt them to respond in a way that impacts how they construct the purpose of their work. Subsequently, we induce three stages of the CSR occupation—early-, mid- and late-stage—and conceptualize three types of purpose in each stage—activistic, win–win and corporate purpose. By uncovering how and why CSR practitioners respond to social/commercial tensions and construct different types of purpose in each stage of the CSR occupation, we show that individuals can live the same calling in multiple ways. Hence, our article advances the meaningful work literature as well as studies of micro-CSR.Swedish Foundation for Strategic Environmental Research (Mistra) Vetensskabsrådet (project no 2019-03122) Handelsbanken Forskningsstiftelser – Project no P19-0099) European Institute of Japanese Studies, Stockholm School of Economics Mistra Centre for Sustainble Markets, Stockholm School of Economics Sasin School of Management, Chulalongkorn University Centre for Social and Sustainable Innovation, Gustavson School of Business (CSSI receives funding from Newmont Goldcorp Inc.)
Numerical simulation of plasticity in double lap metallic bolted joints
Get PDFThis article aims to compare three plasticity models, namely Bai-Wierzbicki (BW), von Mises and Drucker Prager, to predict the failure modes in double-lap metallic bolted joints under shear loading. The double-lap bolted joint finite element model has been validated against literature data, which demonstrated the application of BW ductile fracture model to bolt joint failure prediction. Taguchi Design is used to investigate the effects of geometrical parameters, preload and stress triaxiality on the failure modes. Force–displacement response amongst the three models differs up to 20% when failing in shear and a different prediction of the failure mode (shear out vs. net section) under the same loading and geometry conditions is observed.Mechanics Based Design of Structures and Machine
Changes in soil surface properties under simulated rainfall and the effect of surface roughness on runoff, infiltration and soil loss
Get PDFSoil erosion by water is a result of detachment of particles or small aggregates from the soil surface followed by transport of the detached material. One of the elements that affects surface runoff and soil erosion is the soil surface roughness (SSR). Prior research reports that increasing SSR reduces generation of runoff and soil loss. In addition to that, it is widely reported that across-slope oriented roughness is better at controlling soil and water losses. However, to date there have been few studies into the effect of both magnitude and orientation of SSR on runoff, infiltration and soil erosion at the sub process level (i.e. by raindrop splash and overland flow), occurring simultaneously. In this study, the effects of up-down-slope oriented SSR (Treatment A), across-slope oriented SSR (Treatment B) and random SSR (Treatment C) were compared, along with a smooth surface (Treatment D). A moderate slope gradient of 10 %, a simulated rainfall intensity of 90 mm hr−1 and storm durations of 15 or 30 min were considered. The SSR was measured using the chain method, before and after the rainfall event. Images of the soil surface were taken using a hand-held laser scanner to monitor the effect of rainfall on the surface morphology. The outcome of this study shows that rainfall erosivity increases the SSR of the initially smooth surface, but decreases that of the initially rough surface, particularly in the random SSR treatment, where the decrease in SSR was 64 % of the pre-rainfall condition. This was due to the effects of raindrop impacts and overland flow. The random SSR treatment generated significantly more runoff and soil loss, and less infiltration than all other treatments (p < 0.001), but for raindrop splash erosion, there was no significant difference between random SSR and the other treatments. Contrary to expectations, the across-slope oriented SSR did not always reduce runoff and soil erosion compared to the up-down-slope orientation. This can be explained by degradation of surface microtopography by rainfall and runoff, as confirmed by the post-rainfall SSR measurements.Geoderm
Touchscreen controls for future flight deck design: investigating visual parameters on human-computer interactions between pilot flying and pilot monitoring
Get PDFThis study is concentrated on investigating the different visual behaviors and HCI patterns between pilot flying and pilot monitoring while interacting with touchscreen controls on the flight deck. Twelve participants with flight experiences (M=1150, SD=4019.9) attended this research. The apparatus included Future Systems Simulator (FSS), eye tracker, and system usability scale (SUS). The designated scenario in the experiment was an instrument landing. All participants were required to perform two instrument landings in two different roles, pilot flying (PF) and pilot monitoring (PM). The order of role of randomized to eliminate practice effects. The results revealed that fixation counts of pilot flying were different among four AOIs, F (3, 9) = 10.58, p = .003, η_p^2 = .78. On the other hand, the FC of pilot monitoring demonstrated a significant difference among four AOIs, F (3, 8) = 8.69, p = .007, η_p^2 = .77. There was a significant difference between PF and PM on the subjective assessment of SUS total score, t (11) =3.85, p = 0.003, Cohen's d= 1.11. The application of a touchscreen can integrate input and output in the same area for visual feedback. There is a rising need to simplify the future flight deck design based on the principle of human-centered design. Conclusion: The application of touchscreen flight controls may have the potential to facilitate single-pilot operations flight deck design in the future. TSCs considerations must be consistent with human information processing and pilots' operational characteristics on the future flight deck.Journal of Aeronautics, Astronautics and Aviatio
Large eddy simulations of isolated and installed jet noise using the high-order discontinuous Galerkin method
Get PDFA recently developed computational framework for jet noise is used to compute the noise generated by an isolated and installed jet. The framework consists of two parts. In the first part, the spectral/hp element framework Nektar++ is used to compute the near-field flow. Nektar++ solves the unfiltered Navier-Stokes equations on unstructured grids using the high-order discontinuous Galerkin method. The discrete equations are integrated in time using an implicit scheme based on the matrix-free Newton-GMRES method. In the second part, the Antares library is used to compute the far-field noise. Antares solves the Ffowcs Williams - Hawkings equation for a permeable integration surface in the time domain using a source-time dominant algorithm. The simulations are validated against experimental data obtained in the Doak Laboratory Flight Jet Rig, located at the University of Southampton. For the isolated jet, good agreement is achieved, both in terms of the flow statistics and the far-field noise. The discrepancies observed for the isolated jet are believed to be caused by an under-resolved boundary layer in the simulations. For the installed jet, the flow statistics are also well predicted. In the far-field, very good agreement is achieved for downstream observers. For upstream observers, some discrepancies are observed for very high and very low frequencies.AIAA SciTech Forum 202
One-dimensional approximation of heat transfer in flashlamp-assisted automated tape placement
Get PDFA computationally efficient heat transfer simulation of flashlamp-assisted automated tape placement (ATP) is put forward in this work. The simulation combines distinct 1D finite element models representing the tow, the deposited material, and the resulting stack with appropriate transfer of temperature information to ensure field continuity. Direct comparison against a validated 2D model of ATP shows good agreement in the irradiation region, underneath and beyond the roller vicinity with errors up to 14°C. The combined solution of 1D models requires only 1-2% of the computational effort needed for an equivalent 2D analysis without compromising results resolution, whilst it is better suited for providing the full material temperature history throughout consecutive processing cycles. The accuracy and fast computation render this method appealing for studies which require an iterative execution of the model in a practical timeframe such as in optimisation schemes, inverse solutions, training of surrogate models and stochastic simulation.Engineering and Physical Sciences Research Council (EPSRC): EP/L015102/1Journal of Thermoplastic Composite Material
Deep reinforcement learning-based eco-driving control for connected electric vehicles at signalized intersections considering traffic uncertainties
Get PDFEco-driving control poses great energy-saving potential at multiple signalized intersection scenarios. However, traffic uncertainties can often lead to errors in ecological velocity planning and result in increased energy consumption. This study proposes an eco-driving approach with a hierarchical framework to be leveraged at signalized intersections that considers the impact of traffic uncertainty. The proposed approach leverages a queue-based traffic model in the upper level to estimate the impact of traffic uncertainty and generate dynamic modified traffic light information. In the lower level, a deep reinforcement learning-based controller is constructed to optimize velocity subject to the constraints from the traffic lights and traffic uncertainty, thereby reducing energy consumption while ensuring driving safety. The effectiveness of the proposed control strategy is demonstrated through numerous simulation case studies. The simulation results show that the proposed method significantly improves energy economy and prevents unnecessary idling in uncertain traffic scenarios, as compared to other approaches that ignore traffic uncertainty. Furthermore, the proposed method is adaptable to different traffic scenarios and showcases energy efficiency.Energ