1,721,153 research outputs found
On the accurate computation of the deflection of sandwich beams
No full textMemoria di 3 pagine pubblicata nel cdrom allegato agli atti
Thermodynamic model for gas solubility in glassy polymers: Prediction of dual mode sorption parameters
No full textAcero: specie e varieta' della latifoglia ornamentale per eccellenza
No full textCon un'indagine condotta nell'arco di tre anni sono stati descritti i più importanti caratteri morfologici distintivi di 17 specie e varietà di acero, ai fini di fornire un ausilio sia al vivaista sia al tecnico del verde per l'identificazione, la scelta e l'utilizzazione
A Torque Controlled Approach for Virtual Remote Centre of Motion Implementation
No full textIn this paper, we propose a novel torque controller for the implementation virtual remote center of motion. The controller allows the system to implement the required behavior and guarantees the satisfaction of the remote center of motion constraint. Exploiting the Udwadia-Kalaba equation for constrained dynamic systems, the controller is synthesized considering the dynamic effect the constraint produces on the manipulator, achieving more effective control with respect to kinematic strategies, and allowing the implementation of compliance behaviors. Simulations and experimental validation with a KUKA LWR 4+ with 7 degrees of freedom has been performed to check the performances of the proposed controller. Results show the effectiveness of the proposed controller with different control action, and the capability to interact with the environment by implementing compliant motion control
Dynamic-based RCM Torque Controller for Robotic-Assisted Minimally Invasive Surgery
No full textIn this paper we propose a novel flexible and optimization-free controller for standard torque-controlled manipulator for Robotic-Assisted Minimally Invasive Surgery. A novel method has been developed to model the constraint introduced by the laparoscopic tool, i.e. the remote center of motion, exploiting closed chain manipulators theory, and the final controller was synthesized considering the effects the constraint produces at a dynamic level. A set of simulations has been performed in a trajectory tracking task to validate the performances of the proposed controller. Performances have been also tested in a real experimental scenario with a KUKA LWR 4+ with 7 degrees of freedom endowed with a laparoscopic-like tool. Results show the effectiveness of the proposed controller and its capability of modifying the trajectory in order to preserve the RCM constraint
Analysis Tool for Gas and Vapor Solubility in Glassy Polymers: The Dual Nonequilibrium Lattice Fluid (d-NELF)
No full textIn view of the physically sounding ideas it is founded on, as well of its simplicity and stand-alone character, the dual-mode sorption model (DMS) has been almost universally used in past decades to analyze and compare gas sorption data in polymeric matrixes below the glass transition temperature. The elements the DMS analysis is based on are here revised with the help of results developed within the nonequilibrium lattice fluid (NELF) model to derive meaningful relations between DMS model parameters and equilibrium and nonequilibrium structure property characteristics of the NELF approach. The result is a stand-alone and simple-to-use new tool for the analysis of solubility data in glassy polymers which allows for the use of a limited amount of data to retrieve the nonequilibrium structure property characteristic of the polymer matrix. The model can then be used to compare the solubility of different gases in the same glassy polymer, based just on equilibrium binary interaction parameters, or to distinguish the gas or vapor solubility properties of different nonequilibrium structures in the same polymer species, based on pertinent values of excess-free volume and compressibility
Relaxational behavior of glassy polymers: Experimental sorption and nonequilibrium thermodynamic model
No full textThermodynamic analysis of the solubility of gases and vapors in swelling glassy polymers: A predictive modeling approach
No full text110th Anniversary: Gas and Vapor Sorption in Glassy Polymeric Membranes - Critical Review of Different Physical and Mathematical Models
No full textThe analysis and modeling of the sorption behaviors in glassy polymers, of gases and vapors in particular, is of crucial relevance for a variety of different applications. Due to the peculiar behaviors associated with the nonequilibrium character of polymer glasses, different approaches have been used so far to describe gas solubility, whose dependence on penetrant pressure or activity shows a broad spectrum of experimental behaviors. In this work, three commonly used and completely different approaches (the Dual Mode Sorption (DMS), based on simultaneous adsorption and solubility; the Guggenheim-Anderson-de Boer (GAB) model, considering only adsorption; and the Nonequilibrium Thermodynamic model for glassy polymers (NET-GP), considering only solubility) have been critically reviewed and compared. The screening inspects the model ability to represent the different features shown by solubility isotherms in glassy systems, as well as their ability to provide reliable predictions with parameter values consistent with the underlying physical models. Finally, physical consistency issues have been also considered whenever appropriate. The analysis reveals that DMS and GAB describe well various experimental sorption behaviors, while they fail in representing other cases, such as those shown by the S-shaped isotherms of alcohols or those due to penetrants in supercritical conditions. More remarkably, both models reveal serious physical inconsistencies in the application to sorption-desorption hysteresis. Conversely, the NET-GP approach, combined with a Lattice Fluid model (NELF) shows a better predictive power, as it can naturally account for the S-shaped isotherms, and it is also physically consistent with the behavior observed in sorption-desorption hysteresis cycles
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