Politecnio die Bari - Catalogo di prodotti della Ricerca
Not a member yet
36616 research outputs found
Sort by
Novel structural health monitoring strategies and procedures based on thermal methods for the damage characterization of 3D printed composite materials
No full textA novel methodology for affecting the strain paths during hydraulic bulge tests by means of laser heat treatments
No full textNowadays, the design of manufacturing processes is supported by numerical simulations, that require an understanding of the material forming limits under the process conditions. The hydraulic bulge test represents an effective and well-established experimental procedure to evaluate critical strains of a material. However, it relies on using different elliptical die geometries to vary strain paths, introducing limitations in experimental flexibility. This work aims to evaluate the feasibility of achieving different strain paths during hydraulic bulge tests only using a circular die, by pre-softening certain zones of the testing blank using laser heating. The laser heat treatments (LHTs) were designed using a numerical/experimental approach. Two LHT strategies using different laser power values were performed to locally modify the material properties. Then, hydraulic bulge tests were conducted on the LHTed specimens and the resulting strain paths were analysed. The strain paths acquired during hydraulic bulge tests confirmed the possibility to affect the slope of the strain path at the dome by changing the LHT strategy, designed with the proposed methodology
When Sediments Meet Shells: A Promising Geotechnical Story
No full textThis article reports some of the results of an experimental research dealing with the reuse of two highly impacting wastes of marine origin, i.e., dredged sediments and mussel shells. Traditionally, commercial cement has been for long used for the mechanical improvement in ex-situ management options of dredged sediments. However, the environmental impact of cement production pushes toward more sustainable binder materials. This study contributes to such a general objective by investigating the effectiveness of shell powder as a partial replacement of cement for the stabilization of dredged sediments. Specifically, the experimental programme involved both traditional cement-based sediment stabilization solutions and original ones where different sediment-shell powder-cement mixtures where prepared and tested. The results of multiscale investigations, including physicochemical and geomechanical tests, indicate a promising potential for mussel shells to reduce compressibility and increase strength properties of sediments, thus contributing to more sustainable waste management practices
MARIO BACCIOCCHI E L’IMMAGINE DELLO SVILUPPO
No full textWith the book Mario Bacciocchi,
Stazioni di Servizio AGIP, 1952-1954,
written by Antonio Labalestra and
Tiziano De Venuto, the “letture di architettura”
series entrusts an architectural
historian and an architect with a
different theme than those dealt with
so far. Not a project narrated according
to the series’ typical scheme, but a
cornerstone of Italian infrastructural
expansion. The experiment, fully successful,
designs a prototype capable of
supporting multiple variations without
losing its character. The medium
is an invariant: the cross-section.
Each typological variation keeps it intact
without affecting its charm and
function. As a consequence, objects,
touches, and light flowing between
planes become actions that originate
from the composition and experience
that the architects of “modern
Italian” had accumulated in previous
decades. A nationwide message had
to be launched, regardless of the degree
of industrialisation. Enrico Mattei’s
approach has always been naive.
I still remember his interventions to lay the methane distribution network
in historic centres using unauthorised
night raids. By entrusting Bacciocchi,
Mattei seeks a new approach to
the emerging car industry branch. He
does so through architecture, with a
small object capable of reawakening,
in the memory of most, the emotions,
smells and noises of a semi-rural Italy
that, thanks precisely to architecture,
is changing. This book deals with this
change by investigating the compositional
interpretation of a small architectural
miracle
EU Regulatory Framework and Funding to Combat Desertification
No full textDue to the lack of a univocal organic approach to the desertification within the EU regulatory framework, this latter is critically examined in this paper by illustrating the strategies that guide the Member States towards an integrated solution as well as to environmental, agricultural, climatic and financial policies contributing to the management of the phenomenon. The legal implications of the regulatory gap at European level are also investigated, evaluating the effectiveness of the existing discipline, the limits and the prospects for improvement, aiming at an integrated regulatory strategy that can respond in a coordinated and sustainable way to combat the desertification
Bayesian Signal Processing for Robust IoT: Classical vs. Graph Based Methods for Joint Estimation and Anomaly Detection
No full textInternet of Things (IoT) is recognized as a key enabler of an increasing number of applications, including monitoring of parameters such as temperature, pH, particulate matter, etc. Unfortunately, IoT devices are vulnerable to sudden anomalies caused by accidental faults or malicious behaviors (e.g., byzantine attacks), underscoring the need for robust methods. While anomaly detection has been widely employed to identify and discard unreliable measurements or outliers, further improvements in the sensing processes can be obtained by adopting signal processing algorithms that take full advantage of all the collected information without rejecting any of the measurements. In this contribution, we focus on Bayesian approaches that perform joint estimation of a parameter of interest and anomaly detection, i.e., classification of each IoT node as regular or anomalous. More specifically, we illustrate the joint maximum-likelihood and maximum a posteriori (ML-MAP) approach for both the classical paradigm, where a common (average) parameter is estimated, and the graph signal processing (GSP) paradigm that leverages the graph structure to capture data correlations. We present results on synthetic and experimental data, highlighting the strengths and limitations of the two paradigms
A chemical kinetics-based approach to predict uncontrolled self-ignitions in Hydrogen Internal Combustion Engines
Get PDFThe primary objective of the present work is to correlate the hydrogen explosive characteristics with internal combustion engine design parameters, particularly the engine compression ratio. An approach that couples the knowledge about H2 chemical behaviour, and the in-cylinder charge thermodynamic state, has been conceptualized in the form of a unified plot to visually inspect the likelihood of an auto-ignition event. The plot cautions the possible occurrence of autoignition if the state of the charge inside the engine cylinder reaches thermodynamic conditions beyond the explosion limit curve. Having at hand such a tool enables one to cautiously design future experiments to prevent possible damage because of extreme stresses due to an undesired autoignition event.
The results of the analyses in the present work have translated into defining a maximum limit on the compression ratio that can be proposed at pre-defined intake thermodynamic state, mixture composition, engine geometry and engine speed. Predictions based on recently developed chemical mechanisms were employed for the analyses, exploiting the well-established knowledge about the chemical kinetics of hydrogen oxidation.
Thus, zero-dimensional numerical simulations were performed. Such an approach avoids also the limitations associated with experimental procedures. To evaluate the maximum safe compression ratio, both a static and a time-based approach have been employed to study the vicinity of a thermodynamic state to the autoignition limit i.e., the explosion limit of hydrogen. Three possible criteria for the definition of a maximum safe geometrical compression ratio were developed and analysed. The present work has then been finally ensembled in the form of an empirical correlation involving intake pressure, intake temperature and equivalence ratio as the variables.
Furthermore lubricant oil as a contaminant seeping through the compression rings of a piston in an internal combustion engine, is modelled to evaluate the distribution of mass and temperature inside a droplet of n-hexadecane using 0D- simulations to evaluate the variation of ignition delay time within the droplet in gas-phase and its effect on the local concentration diluting the pure hydrogen in the vicinity and hence increasing the reactivity causing an early source of self- ignition.
A final study concerning developing detonations from hot spots is carried out to understand the effect of a temperature gradient other than ‘linear’ within the hot spot that could change the detonation response diagrams and subsequently the modes of reacting front propagation. Such detonations with high peak pressures are detrimental to components inside an internal combustion engine and therefore the need to study any possibility of its occurrence is crucial to a better understanding of the design
A collective intelligence model for swarm robotics applications
No full textSwarm intelligence models represent a powerful tool to address complex tasks by multi-agent systems, although they are rarely used in practical applications as decentralized cooperation logic. Modern challenges include the improvement of model reliability with small swarm sizes and enhancing performance with minimal number of free parameters. Available techniques are generally tuned for computational optimization, at the expense of the applicability to real-world scenarios. Merging concepts from meta-heuristic methods and consensus theory we propose a swarm cooperation model which can act both as virtual optimizer and vehicle controller. The model shows a higher or equal success rate with respect to benchmark methods on 22 out of 33 landscapes when dealing with less equal 16 agents and low dimensional problems. Beyond multimodal optimization, a computational proof of concept shows that the method can successfully drive the contaminant localization in a complex marine environment by controlling a group of autonomous underwater vehicles
Elastic or Stiff? Light or Heavy? Pseudo-Haptic Photograph Interaction for Fabric Perception
No full textOnline retail is still mostly limited to the visual channel despite haptic interface technology advances. One potential strategy for overcoming the lack of touch in online retail is using pseudo-haptics: illusory haptic sensations resulting from manipulating the visual feedback of mouse or touchscreen interactions. Previous research used computer-generated graphics for pseudo-haptic experiences, while online retailers rely heavily on accurate photos of their products. Therefore, our study proposes a novel approach to designing pseudo-haptics using interactive photograph series together with mouse cursor gain modulations, called Pseudo-Haptic Photograph Interaction (PHPI). Unlike prior approaches that rely on simulated or stylized imagery, PHPI introduces pseudo-haptic effects through real photographic sequences of fabric motion, bridging the gap between visual realism and interactive haptic simulation. We conducted user studies on the perception of stiffness and weight to validate our approach. In experiment 1, we investigated the relation between the perception of weight and stiffness and increased or decreased gain of mouse movement. The study reveals a strong relation between mouse gain and perception. To test whether this corresponded to pseudo-haptic sensations, we performed experiment 2, in which actual fabrics had to be matched with those displayed through PHPI. We found a correlation between the haptically perceived weight and stiffness of fabrics, and their digital surrogate mediated by visual cues, confirming the potential of PHPI for multimodal experiences in online retail and other photographic presentations
Infrared Thermography for Non-Destructive Testing of Cooling Hole Integrity and Flow Evaluation in Specimens Made with Innovative Technologies
No full textThis study developed a non-destructive testing (NDT) method using infrared thermography to inspect tubes with holes and slots made by electro-erosion and additive manufacturing. CO2 was used as a tracer gas to verify the opening and evaluate the flow shape from the holes and slots. To improve the signal contrast, a controlled hot background was used as a reference, and infrared cameras monitored the thermal response to detect flow variations caused by different geometries. The tests included different diameters, pitches, and aspect ratios, comparing results between additive manufacturing and electro-erosion under various conditions. Moreover, a preliminary setup using compressed air and inductive heating was developed to assess hole openings by cooling the piece, aiming to eliminate CO2 use. The comparison of results, the post-processing analysis of quantitative indices, and specific thermal features enabled a non-destructive evaluation of the holes by using different technologies, providing an assessment of the opening conditions, outlet, geometry, and flow shape