Politecnio die Bari - Catalogo di prodotti della Ricerca
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Skyrmions in two dimensional cholesteric liquid crystals
No full textIn this paper we consider a two dimensional cholesteric liquid crystal with an applied external field, whose field configurations u:R2→S2 are constant at infinity, and can be classified by their topological degree. We look for non trivial, topologically stable configurations (chiral skyrmions) by minimizing the Oseen-Frank energy functional over the functions u with deg(u)=-1. The energy functional depends on the splay (K1), twist (K2) and bend (K3) elastic constants, and, assuming that K1=K2, we show the existence of skyrmions provided the cholesteric pitch q0 is small enough; moreover we study the compactness of such skyrmions as q0→0, and their limit. Our results generalize some previous results in the literature obtained under the assumption that K1=K2=K3 (the well known “one-constant approximation” assumption). Moreover, in order to overcome the lack of compactness of the energy functional, we use (instead of the concentration-compactness principle) the fact that the field configurations with energy below a suitable threshold do not cover twice S2 minus a neighborhood of the North Pole, together with a truncation argument at infinity
Documento/Monumento. Il rilievo della chiesa di Santa Maria Maddalena come lettura per immagini dell’opera di Mangini
No full textNumerical Analysis of Human Head Exposure to Electromagnetic Radiation Due to 5G Mobile Phones
No full textThis paper investigates human exposure to electromagnetic fields from 5G mobile phones operating in the 26 GHz frequency band, recently designated for 5G mm-wave communications. Numerical simulations assess near-field exposure generated by a realistic mobile phone model and the thermal effects on a detailed head model, providing valuable insights into the potential impact of this emerging technology on human health
Modeling and Analysis of Dual-Time Petri Nets with Application to Semiconductor Manufacturing Systems
No full textPulsed Laser Deposition and Phosphate Chemical Conversion Coatings for Tailoring the Corrosion Behavior of AZ31 Resorbable Implants Manufactured via Superplastic Forming
No full textMagnesium (Mg) alloys are promising candidates for biodegradable orthopedic implants, thanks to their mechanical properties and biocompatibility. Challenges related to the production of Mg-based prostheses are (i) the choice and the design of flexible manufacturing processes to produce complex shape components (e.g., reproducing human bones) and (ii) the possibility of tailoring magnesium degradation rate in body fluids. Among flexible sheet metal forming processes, superplastic forming (SPF) allows to produce customized and complex parts characterized by a satisfying shape accuracy and surface quality. However, to be defined as a viable process for prostheses manufacturing, investigations about the effect of the processing route on the Mg alloy corrosion behavior as well as viable coatings for tailoring the implant degradation rate are needed. In the present work, electrochemical tests in simulated body environment were carried out on AZ31 samples before and after being subjected to the SPF process. Then, few micrometers thick hydroxyapatite coating obtained by Pulsed Laser Deposition (PLD) or by a phosphate chemical conversion (PCC) were investigated as possible solutions for controlling the degradation rate of the formed components. Chemical-physical characterizations (SEM analysis and Raman spectroscopy) and electrochemical tests (open circuit potential measurement, electrochemical impedances spectroscopy and polarization curves) were performed to assess the possible beneficial effect of the applied coating on the corrosion behavior of the superplastically formed AZ31 Mg components. Phosphate conversion coatings were effective in enhancing the corrosion resistance of AZ31 samples. This is evidenced by a two-order-of-magnitude increase in the overall impedance at low frequencies, from approximately 102Ω·cm2 for the untreated surface to 104Ω·cm2 with the phosphate conversion coating. This significant increase directly indicates a substantial slowdown in the kinetics of magnesium dissolution and water reduction
Impact of Reactive Power Dispatch in a Recursive Two-Stage Optimal Control Algorithm for Isolated Electrical Networks
No full textThe increasing integration of renewable energy sources poses significant challenges for the operation of isolated electrical networks, particularly in ensuring adequate power quality levels. In this regard, this paper explores the role of reactive power dispatch in enhancing the operational performance of isolated networks. To this end, a recursive two-stage optimal control algorithm is adopted to manage the energy resources in the isolated network of a real Italian island. The first stage involves solving an optimal predictive dispatch problem for active power schedule. The second stage refines this dispatch in extended real-time, adapting to changing system conditions and enforcing grid constraints through the formulation of an AC Optimal Power Flow. Through the comparison of two dispatch approaches, the study evaluates the impact of reactive power control under two progressive penetration levels of photovoltaic generation. Specifically, the presented results demonstrate that enabling reactive power support from flexible resources, such as storage systems, improves quality of service levels despite solely active power reserve is considered in the two-stage dispatch
Avatar Design in Virtual Retail Environments: A Scoping Review and Proposed Framework
No full textThe effective use of avatars in 3D virtual stores is a critical component of the success of virtual retail. However, there is a lack of established guidelines on avatar design, an overview of its impact, and its limitations. This work aims to fill these gaps with a scoping review of avatar usage in immersive virtual retail in the last 8 years. Starting with an initial 243 publications, we selected and analysed nine studies to propose the original Virtual Retail Avatar Design (VRAD) framework, as well as investigate the impact avatars have on user’s perceptions, experiences, and behaviors in immersive virtual retail environment. The VRAD framework revealed the key elements of the avatar design to achieve more engaging and effective virtual shopping experiences. We also summarized the avatar’s impact on shopper behaviour, perception, and experience in the iVR retail environment and the future research agenda of avatars in iVR retail. We believe our work can be extended from retail to related areas where avatars play a key role in their further evolution
“Una serie di esercizi ginnastici dell’Immaginazione alle parallele della Memoria...”. Le mostre e l’architettura a Roma nella stagione dell’effimero (1977-1985)
No full textIl saggio analizza l’attività espositiva a Roma nel periodo 1977-1985 in cui la politica culturale dell’Estate Romana,
guidata da Renato Nicolini, inaugura un paradigma effimero e partecipativo superando la dicotomia istituzioni/gallerie private. Si intende così
promuovere una democratizzazione degli spazi urbani attraverso eventi artistici e performativi che coinvolgono centro e periferie. Il testo evidenzia il ruolo di alcune delle mostre più significative nella direzione di risemantizzazione critica del patrimonio e nell’elaborazione di una
“città altra”, riflesso di tensioni sociali, teoriche e ideologiche, un’esperienza che sembra configurarsi, pur nella eterogeneità delle iniziative, come
un laboratorio di contaminazione disciplinare tra architettura, arte e politica, ridefinendo il ruolo dell’intellettuale e del progetto come atti critici
