1,354,207 research outputs found
Free and forced vibrations of damped locally-resonant sandwich beams
No full textThis paper addresses the dynamics of locally-resonant sandwich beams, where multi-degree-of-freedom viscously-damped resonators are periodically distributed within the core matrix. On adopting an established model in the literature, which consists of an equivalent single-layer Timoshenko beam coupled with mass-spring-dashpot subsystems representing the resonators, novel and exact analytical expressions are presented for the frequency response and modal response under arbitrary loads. Specifically, the frequency response is built by a direct integration method, while the modal impulse and frequency response functions are derived by a complex modal analysis approach, upon introducing orthogonality conditions pertinent to the complex modes. The expressions obtained for frequency response and modal response hold for any number of resonators and degrees of freedom within the resonators, any number of loads and positions of the loads relative to the resonators. In the proposed complex modal analysis approach, the challenging issue of calculating all complex eigenvalues, without missing anyone, is solved applying a recently-introduced contour-integral algorithm to an exact dynamic stiffness matrix that, here, is built with size depending only on the number of degrees of freedom at the beam ends, regardless of the number of resonators and degrees of freedom within the resonators. Numerical applications prove exactness and robustness of the proposed framework
Novel dynamic-stiffness approaches to the dynamics of metamaterial structures
No full textMetamaterial structures are structural systems that are tailored in such a way to possess periodicity in conjunction with local resonance effects. To the first class belong all the structures that exhibit a structural periodicity whose scale is comparable to the wave length of the propagating wave; these structures go by the name of phononic crystals. In the second class are included all the structural systems, known as locally-resonant acoustic metamaterials, that are endowed with periodic arrays of suitably tuned resonant subsystems. The purpose of this thesis is to propose new exact and analytical methods for the computation of the dynamic response and the wave propagation analysis of metamaterial structures by means of dynamic-stiffness based techniques. The dynamic-stiffness method presents itself as a very powerful method since it allows to exactly relate the response variables of continuous system, i.e. containing an infinite number of degrees of freedom, in the frequency domain through a finite set of degrees of freedom, namely the response variables sampled at the boundary nodes of the system. It is demonstrated that the dynamic-stiffness method is particularly suitable for computing the dynamic response and performing the wave propagation analysis of metamaterial structures very efficiently, as it allows implementing an ad hoc exact dynamic condensation of the degrees of freedom within the resonators with a significant model order reduction, not obtainable by approximate finite element methods. Furthermore, in this thesis it is shown that the dynamic-stiffness method can be profitably employed to compute the dynamic response in the time domain by deriving appropriate orthogonality conditions for the modes of the structure under the assumption of both classical and non-classical damping and by employing the modal superposition principle. This is an important result, because the dynamic-stiffness method is typically implemented in the frequency domain and no study in existing literature has ever demonstrated its applicability in the time domain as well, for any structure including metamaterial ones
A dynamic-stiffness approach for damped locally-resonant Timoshenko beams
No full textA dynamic-stiffness matrix approach is presented for locally-resonant Timoshenko beams with a periodic array of viscously-damped multi-degree-of-freedom resonators. First, an exact dynamic condensation of the resonator degrees of freedom is pursued, expressing the resonator reaction forces in terms of the deflections of the attachment points via pertinent frequency-dependent stiffness terms. On this basis, a direct integration deriving from the theory of generalized functions provides the exact dynamic-stiffness matrix of the beam, whose size is 4 × 4 for any the number of resonators and degrees of freedom within the resonators. The dynamic-stiffness matrix is used to calculate the complex eigenvalues of the beam by a recently introduced contour-integral algorithm, without missing anyone. Further, it provides the transmittance for an insight into the elastic wave attenuation properties of the beam
On the Free Vibrations of Non-Classically Damped Locally Resonant Metamaterial Plates
No full textIn this paper, the focus is on the free vibrations of locally resonant metamaterial plates with viscously damped resonators. Upon formulating a dynamic-stiffness model where the resonators are represented via pertinent reaction forces depending on the deflections of the attachment points, the complex eigenvalues are calculated by a contour-integral algorithm introduced in the literature for general nonlinear eigenvalue problems. The interest in the proposed approach is twofold. The dynamic-stiffness model involves a limited number of generalised coordinates compared to the nodal degrees of freedom of a standard finite-element model, and the contour-integral algorithm proves successful in evaluating all complex eigenvalues, without missing any one, with remarkable computational efficiency. Numerical results are presented for Lévy plates, but are readily extendible to other plate theories. Finally, an ad hoc dynamic-stiffness approach is formulated to calculate the frequency response of the plate under arbitrarily placed loads, which is of particular interest to investigate its elastic wave attenuation properties
Arthroscopic Management of TMJ Dislocation
No full textDislocation of the temporomandibular joint and repositioning of the dislocated mandible are important topics in oral and maxillofacial surgery. The first surgical techniques for preventing and treating recurrent mandibular dislocation were described in the late 1800s and the early 1900s [1, 2]
Elogio della mitezza. Un ricordo del Prof . Beppe Russillo, in Giuseppe Russillo. La vocazione politica della pedagogia. A cura di Marina De Nicolò
No full textHo accettato con grande piacere e con non poche emozioni, il cortese e dolce invito della collega Prof. Marina De Nicolò, moglie del Prof. Giuseppe Russillo, di fornire un mio contributo, al volume che intende ricordarlo.
Ho conosciuto il Prof Russillo, mentre ero ancora studente, negli anni ottanta e viaggiavo su e giù da Roma per formarmi come psicoterapeuta e contestualmente lavoravo, nel settore della riabilitazione psichiatrica e della deistituzionalizzazione dei malati di mente, per un ente del privato sociale. Successivamente, dopo essermi licenziato per contrasti, nella gestione delle strutture intermedie in psichiatria, con la dirigenza dell’ente del privato sociale, da cui ero stato assunto, iniziai a lavorare come “ esperto e consulente ex. Art. 80, presso alcuni Istituti Penitenziari della Regione Puglia.
Siamo nel periodo immediatamente successivo alla promulgazione della Legge 180 del 1978 e la nostra conoscenza e poi amicizia fu favorita da un altro importante intellettuale della nostra città e della nostra università, amico e collega di Beppe Russilo, e suo conterraneo, ( entrambi lucani), con cui ho avuto l’onore ed il piacere di collaborare negli anni,e con cui in quegli anni in particolare, collaboravo per alcune ricerche sul campo, e che è scomparso di recente, il Prof. Vincenzo Persichella, docente di sociologia all’Università di Bari.
Con entrambi, nonostante la differenza di età e di interessi scientifico-culturali, sono diventato ben presto amico, oltre che collega più giovane. Ho un debito enorme di riconoscenza, verso Beppe ed Enzo, mi hanno dato tanto dal punto di vista formativo e culturale, li ho frequentati spesso a cavallo degli anni 80 e 90, del secolo scorso. Di Beppe Russillo ricordo bene il senso mite, pacato, colto, raffinato, dello stare nel mondo ed in particolare nel difficile e complesso mondo universitario, la capacità di leggere e trasferire agli interlocutori il senso critico del reale, i bisogni sociali, educativi e formativi della gente, la difesa accanita e tenace dei diritti
Cone-morse implant connection system significantly reduces bacterial leakage between implant and abutment : an in vitro study
No full textOsseointegrated implants are very popular dental treatments today in the world. In osseointegrated implants, the occlusal forces are transmitted from prosthesis through an abutment to a dental implant. The abutment is connected to the implant by mean of a screw. A screw is the most used mean for connecting an implant to an abutment. Frequently the screws break and are lost. There is an alternative to screw retained abutment systems: the cone-morse connection (CMC). The CMC, thanks to the absence of the abutment screw, guarantees no micro-gaps, no micro-movements, and a reduction of bacterial leakage between implant and abutment. As P. gingivalis and T. forsythia penetration might have clinical relevance, it was the purpose of this investigation to evaluate molecular leakage of these two bacteria in a new CMC implants systems (Leone Spa®, Florence, Italy). To identify the capability of the implant to protect the internal space from the external environment, the passage of genetically modified Escherichia coli across implant-abutment interface was evaluated. Four cone-morse Leone implants (Leone® Spa, Florence, Italy) were immerged in a bacterial culture for 24 h and bacteria amount was then measured inside implant-abutment interface with Real-time PCR. Bacteria were detected inside all studied implants, with a median percentage of 3% for P. gingivalis and 4% for T. forsythia. Cone-morse connection implant system has very low bacterial leakage percentage and is similar to one-piece implants
Pancreaticojejuno anastomosis after pancreaticoduodenectomy: Brief pathophysiological considerations for a rational surgical choice
No full textIntroduction. The best pancreatic anastomosis technique after pancreaticoduodenectomy (PD) is still debated. Pancreatic fistula (PF) is the most important complication but is also related to postoperative bleedings and pancreatic remnant involution. We support pancreaticojejuno anastomosis (PJ) advantages describing our technique with brief technical considerations. Materials and Methods. 89 consecutive patients underwent PD with suprapyloric gastric resection and double loop reconstruction. Pancreaticojejunal end-to-end anastomosis was done by simple invagination with a single layer of interrupted pledget-supported Ticron stitches. Results. Pancreatic fistula occurred in seven patients (7.8%): six cases of grade A fistula resolved spontaneously, and in only one case of grade B fistula percutaneous drainage was necessary. Postoperative hemorrhage occurred in only two (2.2%) of 89 patients. Conclusion. Pancreaticojejunostomy with minor changes in anastomotic techniques can contribute to improvement of the outcome of Roux-en-Y reconstruction regarding PF and other related complications. The particular reconstruction reported seems also to preserve the pancreatic exocrine function. © 2012 Roberto Caronna et al
Microsurgical endodontic treatment of the upper molar teeth and their relationship with the maxillary sinus: a retrospective multicentric clinical study
No full textPurpose: To assess the clinical and radiographic success rate of microsurgical endodontic treatment of upper molar teeth in relationship with the maxillary sinus, with 12 months follow-up. Methods: Patients treated with microsurgical endodontic treatment of upper molar teeth in the period between 2017 and 2019 were recruited from two dental clinics according to specific selection criteria. The outcomes were determined based on clinical and radiographic results taken three, six and 12 months post-operatively, compared with those taken immediately before and after surgery. Clinical and radiographic outcomes were recorded. The distance between the most apical part of the root and of the lesion to the maxillary sinus was measured on CBCT images before the surgery. Patient-related outcomes were recorded. Results: Out of 35 patients evaluated, 21 were selected according with the selection criteria for a total of 27 roots and 29 canals treated. After 12 months, 18 patients showed a complete healing whereas three demonstrated incomplete healing. Consequently, the success rate in this study was 85.7% after one year. In 28.5% (6 patients) there was a perforation of the Schneiderian membrane that didn’t seem to affect the outcome. All patients kept the molar one year later. The pain level decreased significantly over the time during the first week after surgery. Conclusion: Microsurgical Endodontic treatment of the upper molar teeth should be considered a valid and predictable treatment option even in case of Schneiderian membrane perforation. Future clinical studies with a larger sample size are needed to compare the results obtained
ODArC – Opend Digital Archive of Catalogues. Centocinquant’anni di esposizioni e collezionismo a Napoli dal 1826 al 1970
No full textIl portale Open Digital ARchive of Catalogues (ODArC), creato dall'autrice, nasce per soddisfare le esigenze della ricerca scientifica nel settore degli studi dedicati all'arte dei secoli XIX e XX. Offre, infatti, agli studiosi la possibilità di consultare i cataloghi delle esposizioni d'arte dell'epoca e quelli delle grandi collezioni disperse. Il portale, già attivo, mette a disposizione del pubblico in maniera libera una prima catalogazione delle mostre sviluppatesi a Napoli in tutto l'Ottocento e nel primo Novecento. Lo scopo ultimo sarà quello d'immettere l'intero patrimonio di cataloghi di mostre pubbliche nazionali e internazionali e delle collezioni d'arte italiane dei secoli XIX e XX
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