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A Comparative Review of the Methodologies to Identify a Global Earthing System
No full textInternational Standards IEC 61936-1 and EN 50522 define a global earthing system (GES) as the earthing network, created by the interconnection of local earthing systems that should guarantee the absence of dangerous touch voltages. Despite that, standards do not provide any official practical guidelines for its identification. The official classification of GES areas would lead to a simplification of the design and verification procedures of medium voltage/low voltage (MV/LV) substations grounding systems with associated economical savings for both distribution system operators and MV users. To overcome this regulatory vacuum, several teams of researchers proposed methods to identify the presence of a GES. In this paper, the main methods developed to identify a GES are presented. The different methodologies are applied to a real urban scenario and compared
Valorisation of alumino-silicate stone muds: From wastes to source materials for innovative alkali-activated materials
No full textImpressive amounts of wastes are produced yearly by extraction and transformation of natural stones. This work addresses the finest fraction of these wastes, named stone muds, and particularly those with a siliceous composition. The disposal in dump of these muds implies high costs, whereas their surface landing poses serious challenges, since they can damage the environment, create necrotic conditions for flora and fauna, and endanger human health. Therefore, the reemployment of these wastes is today an urgent need. In this work, a mud (QM) composed by quartz, feldspars, biotite and dolomite, is used for producing dense and foamed alkali-activated materials through an innovative and simple process, in which a mixture of mud and alkaline solution (plus foaming agent, when needed) is produced, cast in moulds and cured at 80 °C for 48 h. Another mineral powder (SRM), having a similar composition but carbonates-free, was also used, to prove the key role of alumino-silicates in producing dense alkali-activated materials, with excellent mechanical properties. Also, the foamed samples showed good mechanical properties, plus low thermal conductivity. These results demonstrate that alumino-silicate wastes could serve as source materials for producing materials suitable to be used for dense and cellular building elements, providing an effective alternative to mud disposal and related issues
Curiosità, studio e conoscenza... ma l'architettura si deve costruire!
No full textIl saggio indaga la ricerca progettuale di Roberto Gabetti (e Aimaro Isola), in particolare a partire da uno scritto (Appunti per un architetto per un facile avvicinamento a qualche problema di estetica e di architettura: dalle origini a ieri) pubblicato da Gabetti su Atti e Rassegna Tecnica della Società degli Ingegneri e degli Architetti in Torino, nel 1962
Behavior evaluation and effects of different lubricants in ECAP process
No full textThe purpose of equal channel angular pressing (ECAP) is producing ultra-fine grain materials. In practical applications, it is important to understand and predict effect of different process parameters on deformed parts. One of the most important process parameters is friction coefficient. Behavior evaluation of different lubricants in the ECAP process is the aim of this research. Design/methodology/approach The present study concerns the experimental measurements of the effective strain by means of gridded parts for three different lubricants, Graphite, Molybdenum Disulfide, and Zinc Stearate in order to evaluate friction coefficient in ECAP process. Mesh size was 2×2 mm2 and embedded in parts made of AL2024; process was done in ambient temperature and parts were in annealed situation. After the process, strain measured by optical and analytical methods for evaluation of lubricants' behavior with different friction coefficients. Findings This Study shows that Zinc Stearate has better effects rather than other lubricants in ECAP process and ECAPed parts. Originality/value The fatal challenge for researchers and industrial applications of ECAP process is lubrication. This research is a guide for scientists and engineers (in the future applications) to reduce and control bad frictional effects, produce better parts (more strain homogenous parts), prevent die failures, and decrease press tonnage in ECAP process
On-board electromechanical servomechanisms affected by progressive faults: Proposal of a smart GA model-based prognostic approach
No full textThe architecture of the actuation systems implemented in aeronautics in order to actuate the flight controls is changing radically and, in the last years, electromechanical actuators (EMAs) are gradually replacing the older type of actuators based on the hydraulic power. Given that some onboard actuators are safety critical, the practice of monitoring and analyzing the system's response (through electrical acquisition) and, then, to provide an evaluation of the evolution of the fault has gradually become an important task of the system engineering. To this purpose, a new discipline was born, called Prognostics, aiming to predict the moment in which a certain component loses its functionality and is not further able to meet desired performances. Given that many prognostic algorithms rely on model-based approaches (e.g. directly comparing the monitor with the real system or using it to identify the fault parameters by means of optimization processes), the design and development of appropriate monitoring models, able to combine simplicity, reduced computational effort and a suitable level of sensitivity and accuracy, becomes a fundamental step of the prognostic process. To this purpose, authors developed a new EMA Monitor Model able to reproduce the dynamic response of the actual system in terms of position, speed and equivalent current, even with the presence of incipient faults. Starting from this Monitor Model, authors propose a new model-based fault detection and identification (FDI) method, based on Genetic Algorithms optimization approach and parallelized calculations, investigating its ability to timely identify symptoms alerting that a component is degrading. The proposed FDI algorithm has been tested on six different progressive failures (dry friction torques and backlash affecting the mechanical transmission, turn to turn short circuit affecting the coils of the three stator phases and rotor eccentricity), simulating progressive faults and evaluating its accuracy. Results showed an adequate robustness and a suitable ability to early identify EMA malfunctions with low risk of false alarms or missed failures
Workers' exposure to airborne particulate and crystalline silica (quartz) during the excavation of a geognostic tunnel with a full - face machine
No full textThe underground construction operations require special attention to Occupational Safety and Health - OS&H aspects. In such situations, the presence of some ubiquitous pollutants (e.g. silica) further contributes to the already critical environment due to narrow operating spaces, high concentration of great power machinery, production of airborne particulates from excavation activities. Moreover, the geological variability of rock formations may challenge the design decisions, and affect the exposure of workers to noxious pollutants. In this context an ongoing and continuous monitoring of the workers' exposure conditions and of the working environment quality can provide useful information about the possible correlation between geo-mechanical parameters of the rock formations, erformance parameters of the used technologies and techniques, and production or release of pollutants. The paper summarizes the results of a study carried out at "La Maddalena" pilot tunnel of the Turin-Lyon railway line. The excavation by an open Tunnel Boring Machine -TBM- takes place in a geological environment of rocks with a content of crystalline silica (quartz) ranging from 30 to 80%. Hence, ongoing and continuous measurements (personal and stationary) in compliance with the up to date reference standards were scheduled from the very early stages of the excavation, to monitor the content of airborne particulate (respirable fraction) and crystalline silica. The study discusses factors and parameters possibly affecting the content of airborne silica: • the geological aspects; • the state of fracturing of the rock (in terms of Rock Mass Rate - RMR); • the water seepage; • the TBM's Performance parameters (thrust, head rpm, and daily progress rate); • the micro-climatic conditions in the tunnel. Due to the great variability of activities involved by the tunnel driving macro-phases, the evaluations on workers were conducted by homogeneous groups, divided by work area and with specific indication of the different jobs. The results proved that for almost all the groups the crystalline silica levels exceeded 0,025 mg·m-3, Threshold Limit Value - Time- Weighted Average - TLV-TWA for the pulmonary fibrosis Risk suggested by the American Conference of Governmental Industrial Hygienists - ACGIH (coherently with the ACGIH's approach to provide information on the risk involved by substances with reference only to health impairments other than cancer, and to include clear information on the possible carcinogenic class). The achieved results will be helpful to improve the Chemical Risk Management in the future Base Tunnel construction
UAV PHOTOGRAMMETRIC SOLUTION USING A RASPBERRY PI CAMERA MODULE AND SMART DEVICES: TEST AND RESULTS
No full textNowadays, smart technologies are an important part of our action and life, both in indoor and outdoor environment. There are several smart devices very friendly to be setting, where they can be integrated and embedded with other sensors, having a very low cost. Raspberry allows to install an internal camera called Raspberry Pi Camera Module, both in RGB band and NIR band. The advantage of this system is the limited cost (< 60 euro), their light weight and their simplicity to be used and embedded. This paper will describe a research where a Raspberry Pi with the Camera Module was installed onto a UAV hexacopter based on arducopter system, with purpose to collect pictures for photogrammetry issue. Firstly, the system was tested with aim to verify the performance of RPi camera in terms of frame per second / resolution and the power requirement. Moreover, a GNSS receiver Ublox M8T was installed and connected to the Raspberry platform in order to collect real time position and the raw data, for data processing and to define the time reference. IMU was also tested to see the impact of UAV rotors noise on different sensors like accelerometer, Gyroscope and Magnetometer. A comparison of the achieved results (accuracy) on some control points of the point clouds obtained by the camera will be reported as well in order to analyse in deeper the main discrepancy on the generated point cloud and the potentiality of these proposed approach. In this contribute, the assembling of the system is described, in particular the dataset acquired and the results carried out will be analysed
Towards Optimally Hiding Protected Assets in Software Applications
No full textSoftware applications contain valuable assets that, if compromised, can make the security of users at stake and cause huge monetary losses for software developers. Software protections are applied whenever assets' security is at risk as they delay successful attacks. Unfortunately, protections might have recognizable fingerprints that can expose the location of the assets, thus facilitating the attackers' job. This paper presents a novel approach that uses three main methods to hide the protected assets: protection fingerprint replication, enlargement, and shadowing. The best way to hide assets is determined with a Mixed Integer Linear Program, which is automatically built starting from the code structure, the protected assets, and a model that depicts the dependencies among protection and the fingerprints they generate. Additional constraints, such as overhead limits are also supported to ensure the usability of the protected applications. Our implementation, which uses off-the-shelf solvers, showed promising performance and scalability on large applications