Accurate Multilayered Shell Buckling Analysis via the Implicit-Mesh Discontinuous Galerkin Method

A novel formulation for the linear buckling analysis of multilayered shells is presented. High-order equivalent single-layer shell theories based on the through-the-thickness expansion of the covariant components of the displace ment field are employed. The novelty of the formulation regards the governing equations solution via implicit-mesh discontinuous Galerkin method. It is a high-order accurate numerical technique based on a discontinuous representation of the solution among the mesh elements and on the use of suitably defined boundary integrals to enforce the continuity of the solution at the inter-element interfaces as well as the boundary conditions. Owing to its discontinuous nature, it can be naturally employed with nonconventional meshes. In this work, it is combined with the implicitly defined mesh technique, whereby the mesh of the shell modeling domain is constructed by intersecting an easy-to-generate background grid and a level set function implicitly representing the cutouts. Several numerical examples are considered for the buckling loads of plates and shells modeled by different theories and characterized by various materials, geometry, boundary conditions, and cutouts. The obtained results are compared with literature and finite-element solutions, and they demonstrate the accuracy and the robustness of the proposed approac

Experimental calibration and validation of a simulation model for fault detection of HVAC systems and application to a case study

Automated fault detection and diagnostics (FDD) could provide a cornerstone for predictive maintenance of heating, ventilation and air-conditioning (HVAC) systems based on the development of simulation models able to accurately compare the faulty operation with respect to nominal conditions. In this paper, several experiments have been carried out for assessing the performance of the HVAC unit (nominal cooling/heating capacity of 5.0/5.0 kW) controlling the thermo-hygrometric comfort inside a 4.0 × 4.0 × 3.6 m test room at the Department of Architecture and Industrial Design of the University of Campania Luigi Vanvitelli (Italy); then, a detailed dynamic simulation model has been developed and validated by contrasting the predictions with the measured data. The model has also been used to analyze the dynamic variations of key parameters associated to faulty operation in comparison to normal performance, in order to identify simplified rules for detection of any non-optimal states of HVAC devices. Finally, the simulated performance of the HVAC unit has also been investigated while serving a typical Italian building office with and without the occurrence of typical faults with the main aim of assessing the impact of the faults on thermo-hygrometric comfort conditions as well as electric energy consumption

Omental infarction in children misdiagnosed as acute appendicitis

Omental infarction (OI) is a rare cause of acute abdomen in children. It is found in  0.1–0.5% of pediatric patients undergoing abdominal exploration for the suspect of  acute appendicitis. OI is considered a self-limited entity, and conservative management should be considered. This approach implicates computer tomography scan radiation exposure, prolonged hospitalization, and prolonged analgesic and anti-inflammatory therapy. In contrast, surgery allows immediate pain resolution with low complication rate. We present our experience with two cases of pediatric acute abdomen due to OI, misdiagnosed as acute appendicitis, which were successfully treated surgically.Keywords: acute abdomen, acute appendicitis, omental infarction, pediatri

Contribution to a Taxonomic Revision of the Sicilian Helichrysum Taxa by PCA Analysis of Their Essential-Oil Compositions

The chemical profile of the essential oils in ten populations of the genus Helichrysum Mill. (Asteraceae), collected in the loci classici of the nomenclatural types of the taxa endemic to Sicily, were analyzed. Our results confirm that the analysis of secondary metabolites can be used to fingerprint wild populations of Helichrysum, the chemical profiles being coherent with the systematic arrangement of the investigated populations in three main clusters, referring to the aggregates of H. stoechas, H. rupestre, and H. italicum, all belonging to the section Stoechadina. The correct nomenclatural designation of the investigated populations is discussed and the following two new combinations are proposed: Helichrysum preslianum subsp. compactum (Guss.) Maggio, Bruno, Guarino, Senatore & Ilardi and Helichrysum panormitanum subsp. latifolium Maggio, Bruno, Guarino, Senatore & Ilardi

Image-based system and artificial neural network to automate a quality control system for cherries pitting process

Abstract This work proposes a non-destructive quality control for a pitting process of cherries. A system composed of a video camera and a light source records pictures of backlit cherries. The images processing in MATLAB environment provides the dynamic histograms of the pictures, which are analysed to state the presence of the pit. A feedforward artificial neural network was implemented and trained with the histograms obtained. The network developed allows a fast detection of stone fractions not visible by human inspection and the reduction of the accidental reject of properly manufactured products

Polydopamine-Coated Poly-Lactic Acid Aerogels as Scaffolds for Tissue Engineering Applications

Poly-L-lactic acid (PLLA) aerogel-based scaffolds were obtained from physical PLLA gels containing cyclopentanone (CPO) or methyl benzoate (BzOMe) molecules. An innovative single step method of solvent extraction, using supercritical CO2, was used to achieve cylindrical monolithic aerogels. The pore distribution and size, analyzed by SEM microscopy, were found to be related to the crystalline forms present in the physical nodes that hold the gels together, the stable alpha'-form and the metastable co-crystalline epsilon-form, detected in the PLLA/BzOMe and PLLA/CPO aerogels, respectively. A higher mechanical compressive strength was found for the PLLA/CPO aerogels, which exhibit a more homogenous porosity. In vitro biocompatibility tests also indicated that monolithic PLLA/CPO aerogels exhibited greater cell viability than PLLA/BzOMe aerogels. An improved biocompatibility of PLLA/CPO monolithic aerogels was finally observed by coating the surface of the aerogels with polydopamine (PDA) obtained by the in situ polymerization of dopamine (DA). The synergistic effect of biodegradable polyester (PLLA) and the biomimetic interface (PDA) makes this new 3D porous scaffold, with porosity and mechanical properties that are tunable based on the solvent used in the preparation process, attractive for tissue engineering applications

Magnetic Response of Nano/Microparticles into Elastomeric Electrospun Fibers

Combining magnetic nanoparticles (MNPs) with high-voltage processes to produce ultrathin magnetic nanofibers (MNFs) fosters the development of next-generation technologies. In this study, polycarbonate urethane nanofibers incorporating magnetic particles were produced via the electrospinning technique. Two distinct types of magnetic payload were used: (a) iron oxide nanoparticles (IONPs) with an average size and polydispersity index of 7.2 nm and 3.3%, respectively; (b) nickel particles (NiPs) exhibiting a bimodal size distribution with average sizes of 129 nanometers and 600 nanometers, respectively, and corresponding polydispersity indexes of 27.8% and 3.9%. Due to varying particle sizes, significant differences were observed in their aggregation and distribution within the nanofibers. Further, the magnetic response of the IONP and/or NiP-loaded fiber mats was consistent with their morphology and polydispersity index. In the case of IONPs, the remanence ratio (Mr/Ms) and the coercive field (Hc) were found to be zero, which agrees with their superparamagnetic behavior when the average size is smaller than 20–30 nm. However, the NiPs show Mr/Ms = 22% with a coercive field of 0.2 kOeas expected for particles in a single or pseudo-single domain state interacting with each other via dipolar interaction. We conclude that magnetic properties can be modulated by controlling the average size and polydispersity index of the magnetic particles embedded in fiber mats to design magneto-active systems suitable for different applications (i.e., wound healing and drug delivery)

Caratterizzazione degli edifici non residenziali ad uso scolastico della PA siciliana

La presente relazione finale descrive le ricerche svolte, in seno all’accordo di collaborazione tra l’ENEA e il Dipartimento dell’Energia, ingegneria dell’Informazione e modelli Matematici (DEIM) dell’Università di Palermo. L’accordo di collaborazione è titolato “Caratterizzazione degli edifici scolastici nella Regione Sicilia”. La relazione è suddivisa in due sezioni: la prima, Parte A, illustra lo studio condotto per la caratterizzazione degli edifici non residenziali ad uso scolastico della PA siciliana; la seconda, Parte B, descrive lo stato dell’arte del “Ventilative Cooling” con riferimento particolare ad alcuni casi-studio reali, nel contesto della partecipazione del DEIM alle attività dell’IEA EBC ANNEX 62”. Nel corso dell’annualità precedente è stata effettuata un’analisi della consistenza, dello stato, e delle tipologie di involucro più significative del patrimonio edilizio scolastico siciliano, utilizzando dati statistici disponibili in letteratura e indagini di campo. Nel corso di questa annualità si è identificato un ristretto campione di edifici scolastici rappresentativo del patrimonio edilizio siciliano. Si tratta di tre edifici adibiti a strutture scolastiche relative a differenti gradi di istruzione: una scuola elementare, una media ed una superiore. In particolare, l’edificio che ospita la scuola elementare ha subito negli ultimi anni estesi interventi di ristrutturazione e riqualificazione energetica; il confronto tra le prestazioni energetiche dell’edificio riqualificato con quelle relative agli altri due edifici campione ha permesso di valutare i risparmi energetici indotti dall’introduzione di nuove normative di settore sugli edifici scolastici. Gli edifici analizzati sono sufficientemente rappresentativi della eterogeneità del patrimonio edilizio scolastico siciliano poiché si tratta di: - edifici differenti posti nelle zone climatiche B e C, che caratterizzano più del 65% dei Comuni siciliani, - edifici dalle caratteristiche termofisiche differenti: trasmittanze (U) tipiche delle costruzioni degli anni ’70 (Usuperfici_verticali>1 W/(m2 K)) ed edifici recentemente ristrutturati (U conforme al DPR n. 59/2009), - edifici che ospitano scuole di differente ordine e grado. Lo studio è stato sviluppato a partire da un approccio preliminare di raccolta ed analisi dei dati per ciascun edificio. L’analisi sistematica dei casi-studio ha consentito di desumere le caratteristiche fondamentali per la modellizzazione: stratigrafia, spessori e qualità termofisica dell’involucro edilizio, apporti termici interni causati da apparecchiature elettroniche ed illuminanti, livelli di occupazione in ogni zona dell’edificio e relativi apporti termici interni, caratteristiche degli impianti termici e modalità di funzionamento. L’analisi non ha tralasciato di esaminare “abitudini” e “pratiche comuni” utilizzate nella gestione degli immobili, come ad esempio la tendenza degli occupanti ad aprire le finestre o a utilizzare schermature solari in alcune fasce orarie nel corso dell’anno. Il passaggio seguente ha riguardato la suddivisione di ognuno dei tre edifici in opportune zone termiche, secondo logiche di uguale destinazione d’uso, di assimilabilità geometrica e di gestione comune di diversi locali da parte dello stesso impianto termico con le stesse regolazioni. Il software di calcolo prescelto per l’implementazione dei modelli è stato TRNSYS 17.01. La struttura geometrica di ogni edificio è stata dettagliatamente modellizzata in 3D tramite il software Google Sketchup; tali modelli sono successivamente stati importati in ambiente TRNSYS. Ogni modello è stato costruito implementando accuratamente le informazioni raccolte nella fase preliminare, integrandolo con le informazioni relative agli occupanti e alla descrizione dei carichi interni dell’edificio. Le logiche di funzionamento, di regolazione e d’uso degli impianti termici sono state implementate in ognuno dei modelli. L’analisi delle prestazioni energetiche dei tre edifici è stata effettuata tramite un set di indicatori sintetici, al fine di ottenere dei valori di riferimento e di benchmark per il patrimonio edilizio scolastico della Regione Sicilia; tra di essi il fabbisogno energetico per riscaldamento annuo, il fabbisogno energetico per riscaldamento annuo riferito alla superficie in pianta o al numero di studenti. La seconda parte del lavoro illustra lo stato dell’arte del “Ventilative Cooling” (raffrescamento per ventilazione) e tratta le tecniche di controllo passive e attive della movimentazione dei flussi d’aria all’interno degli ambienti confinati. L’importanza dello studio di tali tecniche è generata da un crescente interesse nell’uso della ventilazione quale strategia per garantire anche il comfort ambientale nel periodo estivo e nelle stagioni intermedie, limitando il ricorso ai sistemi di refrigerazione in un’ottica di risparmio energetico. Il lavoro è stato sviluppato nel novero delle attività dell’ “International Energy Agency – Energy in buildings and communities Annex 62, Ventilative Cooling”. Il DEIM partecipa ai lavori della Subtask A dell’Annex 62 suddetto, che focalizza il suo interesse sulla simulazione termofisica e sull’analisi del contesto legislativo a scala internazionale. Il gruppo di lavoro del DEIM ha partecipato al primo meeting dell’Annex 62, svoltosi all’Ecole Polytechnique Federale de Lausanne (EPFL) in Svizzera in qualità di “observer”; i lavori sono stati focalizzati principalmente sul completamento del report interno sullo stato dell’arte nelle pratiche di “Ventilative Cooling”. Il contributo del DEIM ai lavori dell’Annex 62 è relativo: - all’analisi dello stato dell’arte del “Ventilative Cooling” e alle potenziali applicazioni e implementazioni di tali contributi nella legislazione locale italiana; - alla modellizzazione del “Ventilative Cooling”

Coating of submicrometric keratin fibres on titanium substrates: a successful strategy for stimulating adhesion and alignment of fibroblasts and reducing bacterial contamination.

Coatings are a versatile tool for modulation of the biological response of biomaterials; in particular, the use of biopolymers as coating material may improve cell interactions and tissue adhesion. Among others, keratin is a natural protein able to stimulate fibroblast cells effectively and has the ability to bind metal ions. Coatings of keratin fibers onto titanium substrates can improve soft tissue adhesion, eventually coupling topographical (contact guidance) and chemical stimulus through the alignment of the fibers along sub-micrometric grooves of the substrate. Sub-micrometric keratin fibers were obtained by electrospinning both in random and oriented arrangements (though a rotating collector); in addition, antibacterial properties were added by enrichment of the coating with silver ions. This type of coating can be of interest in transmucosal dental implants, where perimplantitis is often due to infection (biofilm formation) and disease worsening is due to inflammation of the surrounding soft tissue, which is guided by fibroblasts. Keratin fibres coatings were prepared and characterized by means of Field Emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), cell (gingival fibroblasts) and bacteria (S. aureus) culture tests. FESEM observations demonstrated the possibility to deposit keratin fibres onto titanium substrates in random or oriented arrangements effectively. Keratin fibres were able to increase fibroblast adhesion and proliferation. On randomly deposited keratin fibres, fibroblast cells were significantly biologically stimulated and showed high adhesion and proliferation, but not orientation ability; on the other hand, aligned keratin fibres on a grooved substrate were able to stimulate cells both from the topographical (orientation) and biological standpoint. Finally, Ag-doped keratin fibres coatings were able to reduce S. aureus adhesion significantly, maintaining high biocompatibility. Considering these results, keratin sub-micrometric fibres coatings are a promising strategy for stimulating fibroblasts and reducing bacterial contamination