Modelling of a Free-Piston Generator Based on Spark-Ignition Engine, Linear Electric Machine and Active Rectifier

The Free-Piston Linear Generator (FPLG) technology is meant to serve as a link between the period of fossil fuels and the next green power generation. It consists of a Free-Piston Internal Combustion Engine (ICE) mechanically coupled with a Linear Electric Machine (LEM). No constraints on the piston movement and the inherently variable Compression Ratio (CR) result in a low vibrations, low friction, low maintenance costs, multifuel and high efficiency ICE, with a significant reduction of fuel consumption and greenhouse-gas emissions. In this paper the modelling of this new electricity generation system is investigated. The models of a gasoline single-piston Spark Ignition (SI) Free-Piston ICE and of the electric conversion system based on a three-phase LEM and a Space Vector Pulse Width Modulation (SVPWM) controlled active rectifier are developed in the CFD open-source OpenFOAM and Matlab Simulink environments, respectively

Fault diagnosis of wind turbine gearboxes through on-site measurements and vibrational signal processing

Condition monitoring of wind turbine gearboxes has attracted an impressive amount of attention in the wind energy literature. This happens for practical issues, as gearbox damages account for at least the 20% of wind turbines operational unavailability, and for scientific issues as well, because the condition monitoring of gear-based mechanical systems undergoing non-stationary operation is particularly challenging. The present work is devoted to the diagnosis of gearbox damages through a novel approach, designed exclusively for this study, based on on-site measurements and data post-processing. The main point of this method is the relatively easy repeatability, also for wind turbine practitioners, and its low impact on wind turbine operation: actually, the measuring site is not the gearbox itself, but the tower, further from the gearbox but in an easily accessible place. A real test case has been considered: a multi mega-watt wind turbine sited in Italy and owned by the Renvico company. The vibration measurements at the wind turbine suspected to be damaged and at a reference wind turbine are processed through a multivariate Novelty Detection algorithm in the feature space. The application of this algorithm is justified by univariate statistical tests on the time-domain features selected and by a visual inspection of the dataset via Principal Component Analysis. Finally, the novelty indices based on such time-domain features, computed from the accelerometric signals acquired inside the turbine tower, prove to be suitable to highlight a damaged condition in the wind-turbine gearbox, which can be then successfully monitored

Malte e conglomerati a vista: verso un atlante dinamico

The report sets out the main objectives and presents the first specific results of an experimental research on the general theme of mortars and conglomerates for historic and traditional buildings; the work is developed by a research group of the Polytechnic of Turin, and grafted on the results of an experimental research on local aggregates based mortars for historical buildings. The ongoing study will coordinate in particular in-depth studies aimed at the mechanical and performance characterization of innovative materials. One of the main objectives of this line of research is the following: - to define a reference ‘atlas’, compared to many mixtures of mortars and conglomerates, for restoration, recovery, and maintenance of historic buildings, - to encourage (in particular for small yard sites) the use of local materials with a 'short supply chain', compatible and installed with traditional techniques and methods, - to enhance methods of choice oriented towards the circular economy (respecting their values of historical and technological testimony and significant stratifications). The research is also based on experimental data by laboratory tests and by some sites of historic buildings, also with the support of the Superintendence for the architectural heritage of Piedmont and companies producing material

A Mechanism for Chronic Filarial Hydrocele with Implications for Its Surgical Repair

Chronic hydrocele is the accumulation of fluid around the testis leading to an increase in the volume of the scrotal contents. Depending on the volume of fluid, hydrocele can be disfiguring and even incapacitating. Chronic hydrocele has multiple etiologies, but irrespective of the cause, surgery is the standard form of treatment and this can be done using different surgical techniques. The prevalence of chronic hydrocele in bancroftian filariasis endemic areas—a parasitic disease transmitted by mosquito—is very high and represents the most common clinical manifestation of bancroftosis, following by swollen legs of lower limbs or lymphedema among women. In Greater Recife, northeastern, Brazil, a bancroftian filariasis endemic area, a pioneering, prospective surgical study proposes a new mechanism for filarial-induced hydrocele and presents evidence that the filarial hydrocele fluid may damage the testis. Thus, based on the findings presented, the authors propose that in bancroftian filariasis endemic areas hydrocele patients should be operated on using a specific surgical technique in order to avoid recurrence of the disease, and consequently, additional damage to the testicle

Weakly Supervised Object Detection for Remote Sensing Images: A Survey

The rapid development of remote sensing technologies and the availability of many satellite and aerial sensors have boosted the collection of large volumes of high-resolution images, promoting progress in a wide range of applications. As a consequence, Object detection (OD) in aerial images has gained much interest in the last few years. However, the development of object detectors requires a massive amount of carefully labeled data. Since annotating datasets is very time-consuming and may require expert knowledge, a consistent number of weakly supervised object localization (WSOL) and detection (WSOD) methods have been developed. These approaches exploit only coarse-grained metadata, typically whole image labels, to train object detectors. However, many challenges remain open due to the missing location information in the training process of WSOD approaches and to the complexity of remote sensing images. Furthermore, methods studied for natural images may not be directly applicable to remote sensing images (RSI) and may require carefully designed adaptations. This work provides a comprehensive survey of the recent achievements of remote sensing weakly supervised object detection (RSWSOD). An analysis of the challenges related to RSWSOD is presented, the advanced techniques developed to improve WSOD are summarized, the available benchmarking datasets are described and a discussion of future directions of RSWSOD research is provided

A simplified vibration compensation through magnetostrictive actuators

This paper addresses the vibration reduction of a simple structure, simulating a workpiece carrier plate, through a cancellation technique based on the use of smart compensation actuators. The proposed compensation strategy is implemented resorting to magnetostrictive actuators acting far from their resonant frequencies. Specifically, the procedure has been tested on two test rigs designed with particular reference to machine tools applications: they require the use of one and three magnetostrictive actuators for 1D and 3D vibrations compensation. The parameters of the compensation strategy are identified from the direct characterization of the actuators embedded in the structure. The resulting reduction of the lateral vibrations of 1D and 3D plates in the frequency range up to 400 Hz proves to be very satisfactor

A simplified vibration compensation through magnetostrictive actuators

This paper addresses the vibration reduction of a simple structure, simulating a workpiece carrier plate, through a cancellation technique based on the use of smart compensation actuators. The proposed compensation strategy is implemented resorting to magnetostrictive actuators acting far from their resonant frequencies. Specifically, the pro- cedure has been tested on two test rigs designed with particular reference to machine tools applications: they require the use of one and three magnetostrictive actuators for one-dimensional (1D) and three-dimensional (3D) vibrations compensation. The parameters of the compensation strategy are identified from the direct characterization of the actuators embedded in the structure. The resulting reduction of the lateral vibrations of 1D and 3D plates in the frequency range up to 400 Hz proves to be very satisfactory