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

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

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

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

Comparative turbulent three-dimensional Navier-Stokes hydrodynamic analysis and performance assessment of oscillating wings for renewable energy applications

Oscillating wings can extract energy from an oncoming water or air stream, and first large-scale marine demonstrators are being tested. Oscillating wing hydrodynamics is highly unsteady, may feature dynamic stall and leading edge vortex shedding, and is significantly three-dimensional due to finite-wing effects. Understanding the interaction of these phenomena is essential for maximizing power generation efficiency. Much of the knowledge on oscillating wing hydrodynamics stemmed from two-dimensional low-Reynolds number computational fluid dynamics studies and laboratory testing; real installations, however, will feature Reynolds numbers higher than 1 million and unavoidable finite-wing-induced losses. This study investigates the impact of flow three-dimensionality on the hydrodynamics and the efficiency of a realistic aspect ratio 10 device in a stream with Reynolds number of 1.5 million. The improvements achievable by using endplates to reduce finite-wing-induced losses are also analyzed. Three-dimensional time-dependent Navier-Stokes simulations using the shear stress transport turbulence model and a 30 million-cell grid are performed. Detailed comparative hydrodynamic analyses of the finite and the infinite wings reveal that flow three-dimensionality reduces the power generation efficiency of the finite wing with sharp tips and that with endplates by about 17% and 12% respectively. Presented analyses suggest approaches to further reducing these power losses

Comparative assessment of the harmonic balance Navier Stokes technology for horizontal and vertical axis wind turbine aerodynamics

Several important wind turbine unsteady flow regimes, such as those associated with the yawed wind condition of horizontal axis machines, and most operating conditions of all vertical axis machines, are predominantly periodic. The harmonic balance Reynolds-averaged Navier-Stokes technology for the rapid calculation of nonlinear periodic flow fields has been successfully used to greatly reduce runtimes of turbomachinery periodic flow analyses in the past fifteen years. This paper presents an objective comparative study of the performance and solution accuracy of this technology for aerodynamic analysis and design applications of horizontal and vertical axis wind turbines. The considered use cases are the periodic flow past the blade section of a utility-scale horizontal axis wind turbine rotor in yawed wind, and the periodic flow of a H-Darrieus rotor section working at a tip-speed ratio close to that of maximum power. The aforementioned comparative assessment is based on thorough parametric time-domain and harmonic balance analyses of both use cases. The paper also reports the main mathematical and numerical features of a new turbulent harmonic balance Navier-Stokes solver using Menter’s shear stress transport model for the turbulence closure. Presented results indicate that a) typical multi-megawatt horizontal axis wind turbine periodic flows can be computed by the harmonic balance solver about ten times more rapidly than by the conventional time-domain analysis, achieving the same temporal accuracy of the latter method, and b) the harmonic balance acceleration for Darrieus rotor unsteady flow analysis is lower than for horizontal axis machines, and the harmonic balance solutions feature undesired oscillations caused by the wide harmonic content and the high-level of stall predisposition of this flow field type

Robust aerodynamic design optimization of variable speed wind turbine rotors

Background: Manufacturing and assembly tolerances may cause wind turbine (WT) energy production to differ significantly from nominal design targets. Issue can be alleviated in two ways: A. Reducing tolerances. This may be expensive. B. Developing reliable and computationally affordable robust analysis and design optimization technologies. Robust WT rotor is one yielding minimal variations of aerodynamic performance arising due to errors affecting rotor geometry. Objectives: To develop/demonstrate computational framework for the robust design optimization of WT rotors. Main aim is to 1) maximize expectation and 2) minimize standard deviation of yearly energy production. Highlight computational effectiveness of the Univariate Reduced Quadrature approach to ‘deterministic’ uncertainty propagation. Highlight capabilities of a recently developed multi-level evolution-based optimizer

Marian Cult-sites along the Venetian sea-routes to Holy Land in the Late Middle Ages

The present paper discusses materials collected and analysed in the frame of a research project coordinated by Michele Bacci at Fribourg University and supported by the Swiss National Found. It focuses on the spread of Marian cultic phenomena along the maritime routes between Venice and the Holy Land, which corresponded to the major commercial itineraries among territories mainly belonging to the Venetian Stato da Mar. Relying on evidence provided by 14th to mid-16th century pilgrims’ travelogues, this study lays emphasis on the dissemination of new holy sites and cultic attractions which took place in this intermediary space between Venice and Palestine, namely on the coasts of Istria, Dalmatia, Albania, Corfu, the Morea, Candia, Rhodes and Cyprus, during the Late Middle Ages. In this respect, a number of holy objects found in such sites were regarded as especially attractive on account of their more or less direct association with the Gospel narratives. A key-role was played, in this context, by Marian mementoes, and more specifically by the images attributed to Saint Luke and perceived as authentic portraits of the Mother of God. An almost uninterrupted sequence of the Evangelist’s autograph icons dotted the navigation routes. The famous Nicopea icon in San Marco was the first of such objects encountered by pilgrims during their trip, but more were to be found in many different places, including the Franciscan church in Korčula, the Dubrovnik Cathedral, a small chapel at Kassiopi, St. Dominic in Modone, the convents of St. Francis and St. Saviour in Candia, the shrine of Monte Filerimo in Rhodes, the orthodox cathedral in Nicosia and finally the monastery of Saint Sabas in Alexandria. All those shrines participated in shaping a holy topography of the eastern coasts connected to the maritime pilgrimage phenomena in which outstanding is the particular Marian devotion. Such places gave shape to a topographic network which was perceived by pilgrims as an anticipation of the religious experience they expected to have in the Holy Land

Wind turbine design optimization under environmental uncertainty

Wind turbine design optimization is typically performed considering a given wind distribution. However, turbines so designed often end up being used at sites characterized by different wind distributions, and this results in significant performance penalties. This paper presents a probabilistic integrated multidisciplinary approach to the design optimization of multimegawatt wind turbines accounting for the stochastic variability of the mean wind speed. The presented technology is applied to the design of a 5 MW rotor for use at sites of wind power class from 3 to 7, where the mean wind speed at 50 m above the ground ranges from 6.4 to 11.9 m/s. Assuming the mean wind speed to vary stochastically in such range, the rotor design is optimized by minimizing mean and standard deviation of the levelized cost of energy. Airfoil shapes, spanwise distributions of blade chord and twist, blade internal structural layup and rotor speed are optimized concurrently, subject to structural and aeroelastic constraints. The probabilistically designed turbine achieves a more favourable probabilistic performance than the initial baseline turbine. The presented probabilistic design framework is portable and modular in that any of its analysis modules can be replaced with counterparts of user-selected fidelity

Numerical and experimental investigation of a vortical flow-inducing jet pump

Experimental analyses and CFD simulations are performed on a vortical flow-inducing jet pump. The device is a multi-nozzle annular jet pump, in which a high-pressure fluid is injected into a bore through circumferentially distributed nozzles. The nozzles are angled axially and radially so that the injected primary fluid produces both suction and a vortical flow pattern. Analysis of the pump is considered as single phase, using compressed air to pump atmospheric air. Experiments are carried out on two jet pump designs, working at different conditions with results used to validate CFD simulations. CFD turbulence model analyses is used to determine the optimal numerical method, with hybrid turbulence models shown to be effective in predicting the pressure produced by the swirling flow phenomena. Suction pressure induced by the jets is shown to be highly dependent on the axial angle of the nozzles, which has considerable impact on the radial and tangential components of the resulting flow field, consequently affecting the pump performance