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Modeling of Oil Film Thickness in Piston Ring/Liner Interface
No full textThe correct understanding of piston ring/liner lubrication condition has a primary importance in order to improve internal combustion engine efficiency in terms of oil consumption and friction losses. Analytical and numerical investigation of piston ring-pack becomes then a reliable tool for evaluating piston ring/liner interface lubrication mechanism. Main aim of this paper is to examine the effects of technical aspects, such as ring geometry and operating condition on modeling of piston ring/liner lubrication. An analytical model based on lubrication theory under hydrodynamic regime is here presented and discussed. The model can represent a useful tool for designing low friction engine components and it can be applied to develop reliable friction models to predict actual engine output
Pietra artificiale. Progetto e restauro. Il Palazzo delle Aquile a Torino. Conversazione con Marco Zerbinatti
No full textA 4-W Doherty Power Amplifier in GaN MMIC Technology for 15-GHz Applications
No full textThis letter presents an integrated Doherty power amplifier (PA) in 0.25- μm GaN on SiC process. Designed for 15-GHz point-to-point radios, the PA exhibits an output power of 36 ± 0.5 dBm between 13.7 and 15.3 GHz, while at 14.6 GHz, it shows a 6-dB output back-off efficiency higher than 28%. Modulated signal measurements applying digital predistortion demonstrate the compatibility of the amplifier with point-to-point radio requirements. To the best of our knowledge, this PA has the highest back-off efficiency for the 15-GHz band, and is the first GaN Doherty in the Ku-band
Comparison of the Shielding Properties of Superconducting and Superconducting/Ferromagnetic Bi- and Multi-layer Systems
No full textThis paper compares the shielding properties of superconducting (SC) and superimposed superconducting/ferromagnetic (SC/FM) systems, consisting of cylindrical cups with an aspect ratio of height/radius close to unity. Both bilayer structures, with the SC cup placed inside the FM one, and multilayer structures, made up of two SC and two FM alternating cups, have been considered. Induction magnetic field values have been calculated by means of a finite element model based on the vector potential formulation, simultaneously taking into account the non-linear properties of both the SC and FM materials. The analysis highlights that at low applied fields, the presence of a height difference between the edges of the SC/FM cups, as well as a suitable choice of the lateral gap between the cups, is a key factor in obtaining hybrid structures with a shielding potential comparable to, or even higher than, that of the single SC cup. In contrast, at high applied fields, all the hybrid arrangements investigated always provide much greater shielding factors than the SC cup alone. The computation results show that at both low and high applied fields, the multilayer solutions are the hybrid shields with the highest efficiency
Design of a Graphene-Loaded Slotted Ring Resonator for Sensor Applications
No full textGraphene is a monolayer of carbon atoms with remarkable electronic and mechanical properties amenable to sensor applications. While the plasmonic nature of graphene at terahertz frequency has been widely reported, investigations on the practical utility of graphene at the microwave frequencies used in wireless sensor nodes are sparse. In this paper, a printed RF slot ring resonator is configured with a graphene thin-film for sensor application. The conductive losses in the graphene film are characterized by dielectric spectroscopy and considered in the design. The graphene sensing element comprising the slot ring can be integrated with control electronics as a passive wireless sensor node, but the sensor aspect is not addressed in this paper. The novelty of the paper is that RF losses are minimized by capacitively loading the ring at selective locations along its periphery. Dielectric spectroscopy is used to study variation in surface impedance of the film for various graphene loadings, and RF simulations are corroborated with measurements on graphene loaded slot ring resonators
Application of refined beam elements to the coupled-field analysis of magnetostrictive microbeams
No full textBending of magnetostrictive unimorph microbeams is investigated using a one-dimensional refined finite element model based on the Carrera Unified Formulation. Since these type of smart devices are usually being used in low magnetic fields, the linear coupled magnetomechanical constitutive relations are used to characterize their coupling behavior. With the use of the principle of virtual displacement, components of the fundamental nucleus matrix are obtained and the governing equations are discretized. 2, 3 and 4-node beam elements are used for modelling the beam major axis while linear 4-node and quadratic 9-node Lagrange elements are used as expansion functions over the cross-section. Two examples of unimorph micro-devices are considered and the results of present work are compared with those of experimental and conventional finite element works existing in the literature. It is shown that the one-dimensional refined finite element model, which is capable of generating three-dimensional results, can accurately catch the experimental data with a lower computational cost than the classical models
A Layered Methodology for the Simulation of Extra-Functional Properties in Smart Systems
No full textSmart Systems represent a broad class of intelligent, miniaturized devices incorporating functionality like sensing, actuation, and control. In order to support these functions, they must include sophisticated and heterogeneous components, such as sensors and actuators, multiple power sources and storage devices, digital signal processing, and wireless connectivity. The high degree of heterogeneity typical of smart systems has a heavy impact on their design: the challenges are not in fact restricted to their functionality, but are also related to a number of extra-functional properties, including power consumption, temperature and aging. Current simulation- or model-based design approaches do not target a smart system as a whole, but rather single domains (digital, analog, power devices, etc.) or properties. This paper tries to overcome this limitation by proposing a framework for the concurrent simulation of both functionality and such extra-functional properties. The latter are modeled as different information flows, managed by dedicated "virtual buses" and formalized through the adoption of IPXACT. SystemC, through the support of physical and continuous time modeling provided by its Analog and Mixed Signal (AMS) extension, is used to implement both functional and extrafunctional models. Experimental results show the efficiency, accuracy and modularity of the proposed approach on an example case study, in which substantial speedups with respect to standard model-based design tools go along with a very high degree of accuracy (< 10−5%). Furthermore, the case study highlights that the proposed framework allows to easily capture at run time the mutual impact of properties, e.g., in case of power and temperature
On the detection of board delay faults through the execution of functional programs
No full textIn the last years, the phenomenon of electronic products passing all tests by the manufacturer but failing in the field (No Fault Found, or NFF) attracted the attention of industries and researchers. Delay faults are supposed to be among the contributors to this phenomenon. Hence, companies are increasingly adopting functional test as a final step, which is expected to detect this kind of defects. This paper investigates the capabilities of detecting delay faults by several types of functional test, and proposes a method to write functional test programs able to detect most of the delay faults on the connections between the CPU and the memory