1,721,171 research outputs found
Shear strengthening of wall panels through jacketing with cement mortar reinforced by GFRP grids
No full textThis paper gives the results of a series of shear tests carried out on historic wall panels reinforced with an innovative technique by means of jacketing with GFRP (Glass Fiber Reinforced Plastics) mesh inserted into an inorganic matrix. Tests were carried out in situ on panels cut from three different historic buildings in Italy: two in double-leaf rough hewn rubble stone masonry in Umbria and L'Aquila and another with solid brick masonry in Emilia. Two widely-known test methods: the diagonal compression test and the shear-compression test with existing confinement stress. The test results enabled the determination of the shear strength of the masonry before and after the application of the reinforcement. The panels strengthened with the GFRP exhibited a significant improvement in lateral load-carrying capacity of up to 1060% when compared to the control panels. A numerical study assessed the global behavior and the stress evolution in the unreinforced and strengthened panels using a finite element code
Masonry wall panels retrofitted with thermal-insulating GFRP-reinforced jacketing
No full textToday there is a need to provide thermally efficient walls, while at the same time to increase the mechanical properties of old unreinforced masonry walls that will not require large amounts of energy in the retrofitting or deconstruction processes. To address this problem, this paper gives the results of shear tests carried out on masonry panels made of solid bricks retrofitted with a new technique based on the use of glass fiber-reinforced polymers (GFRP) grids inserted into a thermal insulating jacketing. This was made of different low-strength lime-based mortars. Tests were carried out in laboratory and results were used for the determination of the shear modulus and strength of the wall panels before and after the application of the GFRP reinforcement. Retrofitted panels exhibited a significant enhancement in the lateral capacity when compared to the control panels. The thermal performance of the proposed mortars was also investigated both with and without GFRP. Low values of thermal conductivity were found, especially for the samples with GFRP; a reduction of the thermal transmittance value in the 34–45 % range was also obtained by applying 45 mm layer of coating in conventional masonry walls
F. Veronese, Un franco (anzi, due) in Brianza. Gli ultimi anni di Ugo di Tours e sua moglie Ava (834-39), in I. Barbiera – F. Borri – A. Pazienza (a cura di), I Longobardi a Venezia. Scritti per Stefano Gasparri, Turnhout 2020 (Haut Moyen Âge, 40), p. 155-163.
No full textSpectroscopic measurement of volatile organic compounds as biomarkers for human breath analysis
Full text linkI composti BTEX - benzene, toluene, etilbenzene e xileni - sono tra i composti organici volatili (COV) più pericolosi, pertanto il loro rilevamento altamente sensibile e selettivo può fornire informazioni chiave in molte applicazioni, dal monitoraggio ambientale all'analisi dell'espirato. I sensori ottici basati su tecniche di spettroscopia di assorbimento laser (LAS) possono rappresentare una soluzione per il rilevamento di BTEX poiché questi composti mostrano caratteristiche di assorbimento forti e distinte nella regione spettrale 13 - 15 μm. Tra queste tecniche, la spettroscopia fotoacustica a diapason di quarzo (QEPAS) e la spettroscopia termoelastica indotta dalla luce (LITES) rappresentano due tecniche efficaci. L'attività di ricerca svolta durante il mio dottorato di ricerca in Industria 4.0 presso il Politecnico di Bari si è concentrato sullo sviluppo di sensori ottici basati su tecniche QEPAS e LITES per il rilevamento di benzene, mirando la banda di assorbimento target centrata a 14,85 μm utilizzando un Laser a cascata quantica (QCL) non commerciale. I sensori QEPAS e LITES sviluppati hanno mostrato un'eccellente risposta lineare e sono stati ottenuti limiti di rilevamento minimi stimati (MDL), rispettivamente di 13 ppb e 105 ppb, con una costante di tempo del lock-in amplifier di 100 ms.BTEX compounds - benzene, toluene, ethylbenzene, and xylenes - are among the most hazardous Volatile Organic Compounds (VOCs), thus their highly sensitive and selective detection can provide key information in many applications, ranging from environmental monitoring to breath analysis. Optical sensors based on laser absorption spectroscopy (LAS) techniques can represent a viable solution for BTEX detection since these compounds show strong and distinct absorption features in the spectral region 13 - 15 μm. Among these techniques, Quartz-Enhanced Photoacoustic Spectroscopy (QEPAS) and Light-Induced Thermoelastic Spectroscopy (LITES) represent two effective techniques. The research activity carried out during my Ph.D. program in Industry 4.0 at the Polytechnique University of Bari was focused on the development of optical sensors based on QEPAS and LITES techniques for benzene detection, targeting the absorption band centred at 14.85 μm using a non-commercial Quantum Cascade Laser (QCL) source. The developed QEPAS and LITES sensors showed an excellent linear response and estimated minimum detection limits (MDL) of 13 ppb and 105 ppb, respectively, were obtained with a lock-in time constant of 100 ms
Integrated design of symbolic controllers for nonlinear systems
No full textSymbolic models of continuous and hybrid systems have been studied for a long time, because they provide a formal approach to solve control problems where software and hardware interact with the physical world. While being powerful, this approach often encounters some limitations in concrete applications, because of the large size of the symbolic models needed to be constructed. Inspired by on-the-fly techniques for verification and control of finite state machines, in this note we propose an algorithm that integrates the construction of the symbolic models with the design of the symbolic controllers. Computational complexity of the proposed algorithm is discussed and an illustrative example is included
On Practical Stability Preservation under Fast Sampling and Accurate Quantization of Feedbacks for Nonlinear Time-Delay Systems
No full textIn this article, we deal with the problem of stabilizing a nonlinear system with state-delays by means of quantized sampled-data state feedback control laws. Quantization in the state measurements and in the input signal are simultaneously considered. Fully nonlinear (i.e., possibly nonaffine in the control) time-delay systems are studied. Sufficient conditions are provided such that suitably fast sampling and accurate quantization of the state feedback at hand yield semiglobal practical stability, with arbitrarily small final target ball of the origin. Nonlinear delay-free systems are addressed as a special case: it is shown that the above sufficient conditions, ensuring the semiglobal practical stability, are satisfied if the continuous-time static state feedback controller is a global stabilizer. The theory of stabilization in the sample-and-hold sense is used. The theoretical results are validated through an example
Reinforcement Learning for Non-Deterministic Transition Systems With an Application to Symbolic Control
No full textReinforcement learning (RL) is a well-established framework for the computation of optimal control policies maximizing the expected reward collected along the evolution of Markov decision processes. In this letter, we extend the RL framework to non-deterministic finite transition systems (FTSs), whose solutions are non-unique but not endowed with a probability measure. We show how to dynamically build RL controllers (possibly learning the FTS model just from experience) maximizing the best-case and worst-case return obtained from a trajectory (run) of the model, assuming full-state information. The framework is successfully applied to the case in which the considered transition system is obtained as a finite approximation of a continuous system, also called a symbolic model. Numerical results on the classical mountain car benchmark highlight the potential of the proposed approach
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