Robust aerodynamic design of variable speed wind turbine rotors

This study focuses on the robust aerodynamic design of the bladed rotor of small horizontal axis wind turbines. The optimization process also considers the effects of manufacturing and assembly tolerances on the yearly energy production. The aerodynamic performance of the rotors so designed has reduced sensitivity to manufacturing and assembly errors. The geometric uncertainty affecting the rotor shape is represented by normal distributions of the pitch angle of the blades, and the twist angle and chord of their airfoils. The aerodynamic module is a blade element momentum theory code. Both Monte Carlo-based and the Univariate ReducedQuadrature technique, a novel deterministic uncertainty propagationmethod, are used. The performance of the two approaches is assessed both interms of accuracy and computational speed. The adopted optimization method is based on a hybrid multi-objective evolutionary strategy. The presented results highlight that the sensitivity of the yearly production to geometric uncertainties can be reduced by reducing the rotational speed and increasing the aerodynamic blade loads

Introducing CARONTE: a Crawler for Adversarial Resources Over Non Trusted Environments

The monitoring of underground criminal activities is often automated to maximize the data collection and to train ML models to automatically adapt data collection tools to different communities. On the other hand, sophisticated adversaries may adopt crawling-detection capabilities that may significantly jeopardize researchers' opportunities to perform the data collection, for example by putting their accounts under the spotlight and being expelled from the community. This is particularly undesirable in prominent and high-profile criminal communities where entry costs are significant (either monetarily or for example for background checking or other trust-building mechanisms). This work presents CARONTE, a tool to semi-automatically learn virtually any forum structure for parsing and data-extraction, while maintaining a low profile for the data collection and avoiding the requirement of collecting massive datasets to maintain tool scalability. We showcase CARONTE against four underground forum communities, and show that from the adversary's perspective CARONTE maintains a profile similar to humans, whereas state-of-the-art crawling tools show clearly distinct and easy to detect patterns of automated activity

Multi-disciplinary robust design of variable speed wind turbines

This paper addresses the preliminary robust multi-disciplinary design of small wind turbines. The turbine to be designed is assumed to be connected to the grid by means of power electronic converters. The main input parameter is the yearly wind distribution at the selected site, and it is represented by means of a Weibull distribution. The objective function is the electrical energy delivered yearly to the grid. Aerodynamic and electrical characteristics are fully coupled and modelled by means of low- and medium-fidelity models. Uncertainty affecting the blade geometry is considered, and a multi-objective hybrid evolutionary algorithm code is used to maximise the mean value of the yearly energy production and minimise its variance

CFD modelling of wind turbine airfoil aerodynamics

This paper reports the first findings of an ongoing research programme on wind turbine computational aerodynamics at the University of Glasgow. Several modeling aspects of wind turbine airfoil aerodynamics based on the solution of the Reynoldsaveraged Navier-Stokes (RANS) equations are addressed. One of these is the effect of an a priori method for structured grid adaptation aimed at improving the wake resolution. Presented results emphasize that the proposed adaptation strategy greatly improves the wake resolution in the far-field, whereas the wake is completely diffused by the non-adapted grid with the same number and distribution of grid nodes. A grid refinement analysis carried out with the adapted grid shows that the improvements of flow resolution thus achieved are of a smaller magnitude with respect to those accomplished by adapting the grid keeping constant the number of nodes. The proposed adaptation approach can be easily included in the structured generation process of both commercial and in-house structured mesh generators systems. The study also aims at quantifying the solution inaccuracy arising from not modeling the laminar-to-turbulent transition. It is found that the drag forces obtained by considering the flow as transitional or fully turbulent may differ by 50 %. The impact of various turbulence models on the predicted aerodynamic forces is also analyzed. All these issues are investigated using a special-purpose hyperbolic grid generator and a multi-block structured finitevolume RANS code. The numerical experiments consider the flow field past a wind turbine airfoil for which an exhaustive campaign of steady and unsteady experimental measurements was conducted. The predictive capabilities of the CFD solver are validated by comparing experimental data and numerical predictions for selected flow regimes. The incompressible analysis and design code XFOIL is also used to support the findings of the comparative analysis of numerical RANS-based results and experimental data

Leader-Follower Trajectory Generation and Tracking for Quadrotor Swarms

Swarm control is an essential step in the progress of robotic technology. The use of multiple agents to perform tasks more effectively and efficiently than a single agent allows for the expansion of robot use in all aspects of life. One of the foundations of this area of research is the concept of Leader-Follower swarm control. A crucial aspect of this idea is the generation of trajectories with respect to the leader’s path and some desired formation. With these trajectories generated, one can use a tracking controller specific to the swarm vehicle of choice to accomplish the desired swarm formation. In this paper, a Leader-Follower trajectory generator is developed for a planar triangular formation with offset vertical positions. A tracking controller is used to achieve formation flight for the quadrotor application. A well-accepted model for quadrotor vehicles is used, with simulation parameters comparable to those of a small commercial quadrotor. The swarm control objective is achieved in simulation and is proved to be effective theoretically through the Lyapunov analysis

Successful Endoscopic Closure of Pyeloduodenal Fistula Using an Over-the-Scope Clip.

A 62-year-old woman underwent a series of urologic procedures for nephrolithiasis and was diagnosed with a pyeloduodenal fistula (PDF) on computed tomography urography. After the placement of a metallic ureteral stent and nephrostomy tube, an esophagogastroduodenoscopy was performed to evaluate for PDF resolution. Two areas of mucosal defects within the anterior duodenal sweep were closed using the over-the-scope clip system and hemostasis clips. We review the literature and discuss the etiologies, presentation, diagnosis, and treatment of PDF. This is the second documented case of endoscopic PDF closure using the over-the-scope clip system and the third case of endoscopically treated PDF

You Can Tell a Cybercriminal by the Company they Keep: A Framework to Infer the Relevance of Underground Communities to the Threat Landscape

The criminal underground is populated with forum marketplaces where, allegedly, cybercriminals share and trade knowledge, skills, and cybercrime products. However, it is still unclear whether all marketplaces matter the same in the overall threat landscape. To effectively support trade and avoid degenerating into scams-for-scammers places, underground markets must address fundamental economic problems (such as moral hazard, adverse selection) that enable the exchange of actual technology and cybercrime products (as opposed to repackaged malware or years-old password databases). From the relevant literature and manual investigation, we identify several mechanisms that marketplaces implement to mitigate these problems, and we condense them into a market evaluation framework based on the Business Model Canvas. We use this framework to evaluate which mechanisms `successful' marketplaces have in place, and whether these differ from those employed by `unsuccessful' marketplaces. We test the framework on 23 underground forum markets by searching 836 aliases of indicted cybercriminals to identify `successful' marketplaces. We find evidence that marketplaces whose administrators are impartial in trade, verify their sellers, and have the right economic incentives to keep the market functional are more likely to be credible sources of threat.Comment: The 22nd Workshop on the Economics of Information Security (WEIS'23), July 05--08, 2023, Geneva, Switzerlan