1,720,988 research outputs found
Using Old Schröder-Reuleaux Models in Modern Kinematics Lectures
Full text linkThe paper deals with the use for educational purposes of kinematic models of the Schroder/Reuleax collection preserved at the Department of Mechanical and Aerospace Engineering of Politecnico di Torino. The article first traces a brief history of the models, which were acquired at the end of the 19th C. by the Regio Museo Industriale of Turin. Four straight-line mechanisms of the collection, employed in modern kinematics lectures, are presented in detail. The didactic method adopted starts from the analysis of the models of the collection and leads the students to develop schemes and software models, in a process of transition from real to virtual. The simulation results are then interpreted and correlated with the functioning of the real model
Numerical Stability Analysis of a Distributed Thermal Model for Pouch Cell Assemblies via Gershgorin Circle Theorem
No full textThermal simulation plays a key role in battery pack design, supporting cooling system sizing, temperature control and thermal failure prevention. However, accurate thermal models involving the numerical solution of a large number of partial differential equations (PDEs) can exhibit numerical instabilities that are difficult to diagnose and resolve. This letter applies the Gershgorin Circle Theory to evaluate the numerical stability of a distributed-parameter thermal model (DTM), which simulates the temperature distribution evolution of a multi-body assembly composed of a Li-ion pouch cell, its tabs, and a compression aluminum plate. A discrete state-space representation of the system is developed before calculating the Gershgorin circles. This method identifies the stability boundaries of the DTM as a function of the physical parameters of the system, e.g., thermal conductivities and thermal resistances, and simulation parameters, e.g., mesh size and sampling step. The proposed approach provides an efficient tool for optimizing simulation settings, ensuring convergence and reliability in thermal simulations of complex multi-element Li-ion pouch cell assembly
Aspetti normativi, tecnici ed economici connessi alla penetrazione di sistemi di trigenerazione
No full textLa memoria analizza gli aspetti tecnologici e normativi relativi alla realizzazione di impianti di cogenerazione e di trigenerazione.
Attraverso anche l’esemplificazione dell’applicazione ad un caso studio, si evidenzia come il beneficio energetico ottenibile non venga sufficientemente remunerato nella situazione attuale, sia in termini economici che di semplificazione delle procedure autorizzative.
Anche in ottemperanza alla volontà europea di perseguire la cogenerazione come mezzo per migliorare lo sfruttamento delle risorse primarie, è necessario definire strumenti di incentivazione e di semplificazione che potrebbero trovare una prima concretizzazione nella definizione dei titoli di efficienza energetica
Da cogenerazione a trigenerazione: migliorare l'efficienza energetica
No full textAll'indubbio beneficio energetico ottenibile dagli impianti di cogenerazione e di trigenerazione non corrispondono attualmente sufficienti opportunità dal punto di vista economico, fiscale e normativo
Air Pad Controlled by Means of a Diaphragm-Valve: Static and Dynamic Behaviour
Full text linkThis paper presents the analysis of the static and dynamic performance of a passively compensated air pad. The proposed method consists in the integration of a custom-built diaphragm valve and a commercial aerostatic pad. A lumped model is used to simulate the static and dynamic performance of the pad. Results demonstrate that the proposed method is very effective when the system works with excitation frequencies below 10 Hz
Dynamic Characterisation of Rectangular Aerostatic Pads with Multiple Inherent Orifices
Full text linkLumped parameters models for the stability analysis of rotors supported on gas bearings
Full text linkIn this paper different lumped parameters models are presented for the stability analysis of rotors supported on gas bearings. The analysis is carried out taking into account the damping and stiffness coefficients of journal bearings, calculated with the perturbation method. Lumped parameters models of different complexity are discussed for the description of the main rigid modes of the spindle. In case of symmetric systems, it is shown that the complexity of the model can be reduced by halving the number of the degrees of freedom. The analogy with the single mass approach is demonstrated. The considerations discussed in the paper are preliminary for the stability analysis of more complex systems, such as the ones with non-fixed bushes
An optimization approach for a complex real-life container loading problem
No full textWe consider a real-world packing problem faced by a logistics company that loads and ships hundreds of trucks every day. For each shipment, the cargo has to be selected from a set of heterogeneous boxes. The goal of the resulting container loading problem (CLP) is to maximize the value of the cargo while satisfying a number of practical constraints to ensure safety and facilitate cargo handling, including customer priorities, load balancing, cargo stability, stacking constraints, positioning constraints, and limiting the number of unnecessary cargo move operations during multi-shipment deliveries. Although some of these constraints have been considered in the literature, this is the first time a problem tackles all of them jointly on real instances. Moreover, differently from the literature, we treat the unnecessary move operations as soft constraints and analyze their trade-off with the value maximization. As a result, the problem is inherently multi-objective and extremely challenging. We tackle it by proposing a randomized constructive heuristic that iteratively combines items in a preprocessing procedure, sorts them based on multiple criteria, uses randomization to partially perturb the sorting, and finally constructs the packing while complying with all the side constraints. We also propose dual bounds based on CLP relaxations. On large-scale industry instances, our algorithm runs in a few seconds and outperforms (in terms of value and constraints handling) both the solutions constructed manually by the company and those provided by a commercial software. The algorithm is currently used by the company generating significant economic and CO2 savings
Joint non-invasive identification of an electrochemical and thermal model for an ultra high-power Li-ion pouch cell
Full text linkAccurate physical models of battery cells are required to design safe and reliable Battery Management Systems (BMSs). Due to the safety-critical nature of cell voltage and temperature, both the electrical and thermal behavior of the cell need to be precisely predicted. In this work, an electrochemical – the Single Particle Model (SPM) – and a lumped thermal model are experimentally identified and validated for an ultra high-power pouch cell. To ease its application, the proposed identification procedure is based exclusively on non-invasive tests, i.e., requiring only voltage, current, and temperature measurements. Specifically, the identification protocol is based on two steps: (1) the equilibrium potentials are identified from quasi-static tests; (2) the kinetics and thermal parameters are jointly optimized from a highly dynamic current profile. Due to the high power requirements, the considered pouch cell is always kept pressed by an external fixture, which is properly considered in the modeling and identification. The SPM is compared with a first-order Equivalent Circuit Model (ECM) and the validation is finally performed on two different dynamic tests, showing the good capability of the identified electrochemical and thermal model to match the measured outputs (voltage and temperature) while giving an insight on the internal cell states
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