1,721,039 research outputs found
Rodaggio e scuffing in contatti alluminio/acciaio
No full textThe possibility of increasing the scuffing resistance of an aluminum/steel contact through running-in as well as the existence of optimal run-in procedures was shown in a previous paper. In this work emphasis is given to whether the two aspects of topographical modifications and surface layer formation may play different roles in scuff prevention depending on the working conditions of the sliding pair, in other words whether the optimal run-in procedure may be a function of the working conditions. Results show that the protection offered by surface films, and therefore the increase in the scuffing resistance, ceases to be effective when the working conditions involve high sliding velocities. In this case, the run-in procedure needs to favor the highest degree possible of surface conformit
Running-in of aluminum/steel contacts under starved lubrication - Part II: Effects on Scuffing
No full textQuasi-unsupervised color constancy
No full textWe present here a method for computational color constancy in which a deep convolutional neural network is trained to detect achromatic pixels in color images after they have been converted to grayscale. The method does not require any information about the illuminant in the scene and relies on the weak assumption, fulfilled by almost all images available on the web, that training images have been approximately balanced. Because of this requirement we define our method as quasi-unsupervised. After training, unbalanced images can be processed thanks to the preliminary conversion to grayscale of the input to the neural network. The results of an extensive experimentation demonstrate that the proposed method is able to outperform the other unsupervised methods in the state of the art being, at the same time, flexible enough to be supervisedly fine-tuned to reach performance comparable with those of the best supervised methods
Select & Enhance: Masked-based image enhancement through tree-search theory and deep reinforcement learning
No full textThe enhancement of low-quality images is both a challenging task and an essential endeavor in many fields including computer vision, computational photography, and image processing. In this paper, we propose a novel and fully explainable method for image enhancement that combines spatial selection and histogram equalization. Our approach leverages tree-search theory and deep reinforcement learning to iteratively select areas to be processed. Extensive experimentation on two datasets demonstrates the quality of our method compared to other state-of-the-art models. We also conducted a multi-user experiment which shows that our method can emulate a variety of enhancement styles. These results highlight the effectiveness and versatility of the proposed method in producing high-quality images through an explainable enhancement process
TreEnhance: A tree search method for low-light image enhancement
No full textIn this paper we present TreEnhance, an automatic method for low-light image enhancement capable of improving the quality of digital images. The method combines tree search theory, and in particular the Monte Carlo Tree Search (MCTS) algorithm, with deep reinforcement learning. Given as input a low-light image, TreEnhance produces as output its enhanced version together with the sequence of image editing operations used to obtain it. During the training phase, the method repeatedly alternates two main phases: a generation phase, where a modified version of MCTS explores the space of image editing operations and selects the most promising sequence, and an optimization phase, where the parameters of a neural network, implementing the enhancement policy, are updated. Two different inference solutions are proposed for the enhancement of new images: one is based on MCTS and is more accurate but more time and memory consuming; the other directly applies the learned policy and is faster but slightly less precise. As a further contribution, we propose a guided search strategy that “reverses” the enhancement procedure that a photo editor applied to a given input image. Unlike other methods from the state of the art, TreEnhance does not pose any constraint on the image resolution and can be used in a variety of scenarios with minimal tuning. We tested the method on two datasets: the Low-Light dataset and the Adobe Five-K dataset obtaining good results from both a qualitative and a quantitative point of view
Role of run-in parameters on the scuffing resistance of aluminum/steel area contacts
No full textThis paper summarises the effects of run-in procedures on the scuffing resistance of 390-T6 aluminium pins sliding on 1018 carburized steel disks. The area contact is lubricated by a base polyalkylene glycol (PAG) lubricant mist carried by a tetrafluoroethane (R134a) refrigerant gas under starved lubrication conditions. These material and lubricant/refrigerant combinations are found in automotive swash plate compressors. Run-in pressure, velocity and time as well as the effect of the friction coefficient during run-in are examined. Surfaces are traced before and after run-in to examine topographical modifications. In addition, SEM and Auger spectroscopy are used to monitor film formation due to run-in.
Results show that the higher scuffing resistance after run-in is related primarily to film formation. Low friction conditions during run-in (f 0.1) are necessary to ensure the success of the run-in procedure. The value of the product between the apparent contact pressure and the sliding velocity (PV product) during run-in may be used as a guideline to distinguish between conditions of low and high friction
Intuizioni e strategie antisismiche nelle Masserie Vesuviane: un approccio "strutturale" alle problematiche connesse alla conservazione del patrimonio edilizio storico nelle aree a rischio vulcanico e sismico.
No full textIl presente lavoro si incentra sullo studio di alcune tipologie edilizie appartenenti alla tradizione costruttiva rurale delle aree Vesuviane, le Masserie, con particolare attenzione agli aspetti strutturali connessi alla prevenzione del rischio sismico e vulcanico. Dall’osservazione di molte architetture del passato, si evince chiaramente una strategia di protezione antisismica, realizzata in maniera intuitiva, attraverso espedienti semplici quali la geometria della pianta, le proporzioni delle sezioni e la distribuzione delle aperture, l’uso di materiali e elementi strutturali peculiari, che è stata in grado di conservare nel tempo questi manufatti. Il fine della presente ricerca, dunque, è quello di dimostrare la recuperabilità del sito a dispetto della paura del vulcano in maniera tale da individuare dei metodi da applicare per un corretto restauro antisismico, fondamentale per mitigare il rischi
Running-in of aluminum/steel contacts under starved lubrication - Part I: Surface modifications
No full textHIERARCHICAL PARAMETERS OF PLANNING FOR THE PREVENTION OF ACCIDENTAL DAMAGE IN HIGH STRUCTURES
No full textThis paper focuses mainly on high structures such as towers, skyscrapers, steeples, etc. and analyzes their structural behavior. Through examples of his- tory, as the Bell Tower of San Marco in Venice (1902), the Civic Tower of Pavia (1989) and the Twin Towers in NY (2001), that have undergone ruinous collaps- es, this text attempts to define the good rules to design tower structures with a perspective to prevention from accidental damages such as falls, earthquakes, terrorist attacks, which can invest buildings bringing them to the ground. There- fore, the work highlights new structural concepts that take into account prob- lems related to high dimensions, the robustness as crucial parameter to the security from collapse and the structural hierarchy
The neoclassical dome of san francesco di Paola in Naples. A study on form and stability. (Aimeta 2017)
No full textThe Basilica of San Francesco di Paola, located at the west side of Piazza del Plebiscito, historic center of Naples, was built as a completion of the square in front of the Royal Palace by the will of King Ferdinand IV (1816), designed by the Swiss architect Pietro Bianchi. The "The Bourbon Temple" is mainly characterized by its imposing coverage with hemispherical dome, which protrudes from the complex. It directly refers to the Pantheon for its geometric relations and proportions, its formal and compositive aspects, although it is not completely hemispherical and its interior does not enjoy the spatiality of its model. Furthermore in origin the dome ended with a central oculus in which, even today, the structural forces converge and balance. Subsequently, a lantern was placed on the oculus, which is a conical element completely in glass that allows the passage of light. The aim of this work is the study of the stability of the dome that, firstly, allows to specify the overall safety of the structure in its current state, especially with regard to statics. Secondly, to assess the degree of seismic safety of the structure, identifying the potential conditions of vulnerability in case of earthquake. The static analysis has been performed, by using the graphical method, according with the principles of the limit analysis applied by Heyman to the masonry structures. The methodological innovation consists in the use of the traditional methods of graphical calculation of masonry structures, interconnected with the new antiseismic norms in the territory. The operational aspect of the work is contained in the interdisciplinarity of scientific fields, with the aim of obtaining a complete knowledge of the monument in its current condition without using an elastic analysis, which would not be suitable for the study of historical building
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