IRIS - UNIRSM (Univ. degli Studi della Repubblica di San Marino)
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Refined 2D and Exact 3D Shell Models for the Free Vibration Analysis of Single- and Double-Walled Carbon Nanotubes
No full textThe present paper talks about the free vibration analysis of simply supported Single- and Double-Walled Carbon Nanotubes (SWCNTs and DWCNTs). Refined 2D Generalized Differential Quadrature (GDQ) shell methods and an exact 3D shell model are compared. A continuum approach (based on an elastic three-dimensional shell model) is used for natural frequency investigation of SWCNTs and DWCNTs. SWCNTs are defined as isotropic cylinders with an equivalent thickness and Young modulus. DWCNTs are defined as two concentric isotropic cylinders (with an equivalent thickness and Young modulus) which can be linked by means of the interlaminar continuity conditions or by means of van der Waals interactions. Layer wise approaches are mandatory for the analysis of van der Waals forces in DWCNTs. The effect of van der Waals interaction between the two cylinders is shown for different DWCNT lengths, diameters and vibration modes. The accuracy of beam models and classical 2D shell models in the free vibration analysis of SWCNTs and DWCNTs is also investigated
I “sistemi” di vigilanza e di controllo nel diritto della salute e sicurezza sul lavoro
No full textUna seria riflessione sul ruolo delle politiche per la legalità del lavoro in materia di salute e sicurezza sui lavoratori esige di indagare in via prioritaria i "sistemi" di vigilanza e di controllo. Essi rappresentano uno dei principali strumenti di prevenzione, da declinarsi "al plurale", comprendente sia le attività riservate agli Enti pubblici, sia le azioni definite dal datore di lavoro rispetto alla sua specifica organizzazione aziendale. Si tratta di dimensioni legate da un rapporto dinamico-funzionale, secondo il quale, ancora prima dell'attivazione degli strumenti esterni, è il modello di prevenzione aziendale ex d.lgs. n. 81/2008 che dovrebbe mettere in atto adeguati meccanismi di tutela. Lo scopo del saggio è quello di affrontare alcuni dei temi chiave dei sistemi di vigilanza e controllo in tema di salute e sicurezza dei lavoratori al fine di verificarne il grado di efficacia come strategia di prevenzione
Dynamic Analysis of Thick and Thin Elliptic Shell Structures Made of Laminated Composite Materials
No full textElliptic geometries appear to be important components in engineering practices. The purpose of the present study is to examine the free vibration nature of laminated composite thick and moderately thick elliptic cones, cylinders and plates. A strong form approach, such as the generalized differential quadrature (GDQ) method is employed to carry out the numerical analyses. The geometric description of the structures under consideration is performed through the differential geometry which is a convenient and general mathematical tool to have parametric description of curved structures. Reference solutions are presented for laminated composite thick elliptic shells. 3D finite element models are used for proving the validity and the advantages of the present methodology. Since laminated composite structures are investigated, higher-order theories are considered to capture the nonlinear behavior of the material fibers through the shell thickness. In particular, a hierarchical expansion order of the kinematic displacements is adopted. The expansion order is a function of a free parameter. The numerical solution is found discretizing the dynamic equilibrium equations, written as functions of the displacement parameters, with GDQ method. This technique proved to have several advantages such as stability, accuracy and easy implementation as also demonstrated by the authors in the provided literature
La nostra esperienza presso l’ambulatorio “complicanze da fillers” della Sapienza Università di Roma
No full textCon il termine “filler”, (dall’inglese “to fill”=riempire) si definisce una sostanza, di varia natura, che può essere iniettata nei tessuti molli al fine di migliorare i volumi e gli effetti dell’invecchiamento L’utilizzo di tali materiali è aumentato notevolmente negli anni.
L’incremento del numero di utilizzatori, del numero e varietà di sostanze, l’assenza di protocolli di uso standardizzati e l’aumento dei casi di effetti avversi e complicanze legato all’uso dei filler ci ha spinto all’apertura, presso il nostro ambulatorio di Chirurgia Plastica Sapienza Università di Roma di un centro di riferimento dedicato al trattamento delle complicanze da filler. Nei 15 anni di attività di questo ambulatorio abbiamo potuto fare alcune considerazioni. Spesso i pazienti si avvicinano a questi trattamenti con estrema superficialità, non considerandoli procedure mediche associate a possibili complicanze. In molti casi, i pazienti non sono a conoscenza del materiale iniettato e non sono in grado di contattare il professionista che ha eseguito il trattamento. Inoltre alcuni pazienti hanno riferito l’utilizzo di materiali e/o ambienti non idonei, arrivando addirittura all’auto-inoculazione. Vengono riportati alcuni dei casi giunti alla nostra osservazione
Design and simulation of CONWIP in the complex flexible job shop of a Make-To-Order manufacturing firm
No full textThis paper presents a methodology for the design and integration of CONWIP in a make-to-order firm. The approach proposed was applied directly to the flexible job shop of a real manufacturing firm in order to assess the validity of the methodology. After the description of the whole plant layout, attention was focused on a section of the shop floor (21 workstations). The CONWIP system deals with multiple-product families and is characterized by path-type cards and a pull-from-the-bottleneck scheme. The cards release strategy and a customized dispatching rule were created to meet the firm’s specific needs. After the simulation model of the present state was built and validated, the future state to be implemented was created and simulated (i.e. the CONWIP system). The comparison between the two systems achieved excellent results, and showed that CONWIP is a very interesting tool for planning and controlling a complex flexible job shop
The impact of RFID technologies on inventory accuracy in the apparel retailing: Evidence from the field
No full textIn this paper, we assess the level of inventory accuracy that can be reached by adopting radio frequency identification (RFID) technology for inventory count operations in the fashion retailing. Thanks to an in-field implementation, we carried out two series of RFID inventory counts and compared the resulting accuracy level with that obtained exploiting the traditional barcode (BC) technology, so as to highlight the main pros and cons of the RFID adoption.
As a general conclusion, the findings from the experimental campaigns and the analyses carried out suggest that RFID inventory counts are more reliable thanBCones. Moreover, under several circumstances, RFID allows detecting out-of-stock situations that are not evident when using either the BC technology or the inventory data stored in the company’ information system. From those findings, a trend of the inventory accuracy as a function of the time required for RFID inventory counts is empirically derived. Such a trend can be exploited in practical cases to estimate the accuracy level achievable with inventory counts depending on the time dedicated to those activities
On supporting e-learning in the field of resilience management with an open source authoring tool
No full textAmong all the pedagogical and technological features that could be used with the aim of improving and making more effective online education, we have identified virtual and augmented reality-based technologies and the creation and sharing of digital open resources as interesting issues not yet adequately covered. Both of them can be exploited in the current and trendy Massive Online Open Courses (MOOCs) scenario, so as to make their content and activities more interactive and effective. Furthermore, a key role is played by all the online tools (authoring tools / pedagogical planners) that support, on one side, authors in creating contents and, on the other, learners in exploiting them while they are acquiring skills and competencies. We have designed, developed and customized an e-learning authoring tool, called BEAT (Bologna E-learning Authoring Tool). This paper focuses on main design issues and on the customization of BEAT devoted to meet the needs of the RESINT project, with the aim of supporting authors in creating (designing and editing) and managing interactive and Open Educational Resources. One of the expected results of this project is to create an open source authoring tool to support authors during the creation of open learning objects, accessible (and reusable) through Learning Content Management Systems. A use case in the context of resilience management-related topics is also illustrated in the paper