371 research outputs found
A model for a flywheel automatic assistedmanual transmission
This paper is focused on the model and dynamical analysis of a flywheel assisted transmis- sion aiming at reducing the torque gap during gear shift manoeuvres. A completely passive device, consisting of a planetary gear set mounting a flywheel on the sun gear shaft, allows to continuously connect the engine to the load shaft. Depending on the operating condi- tions, it can either absorb energy from the engine or deliver the previously stored kinetic energy to the wheels when the clutch is disengaged, thus allowing better vehicle performances and/or ride comfort through a suitable coordinated control of engine and clutc
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Dynamic unbinding transitions and deposition patterns in dragged meniscus problems
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.We sketch main results of our recent work on the transfer of a thin liquid film onto a flat plate
that is extracted from a bath of pure non-volatile liquid. Employing a long-wave hydrodynamic model, that
incorporates wettability via a Derjaguin (disjoining) pressure, we analyse steady-state meniscus profiles as the
plate velocity is changed. We identify four qualitatively different dynamic transitions between microscopic
and macroscopic coatings that are out-of-equilibrium equivalents of equilibrium unbinding transitions. The
conclusion briefly discusses how the gradient dynamics formulation of the problem allows one to systematically
extend the employed one-component model into thermodynamically consistent two-component models as used
to describe, e.g., the formation of line patterns during the Langmuir-Blodgett transfer of a surfactant layer
Experimental device to identify friction levels for airport applications
This paper presents an experimental device aimed at
identifying different road friction levels; it has been designed
at the Politecnico di Torino as part of the research
program AWIS (Airport Weather Information
System: study and realisation of a system for the prediction,
monitoring and management of meteorological
winter emergencies in airports) funded by Regione
Piemonte
On the Power-Weighted Efficiency of Multimode Powertrains: A Case Study on a Two-Mode Hybrid System
Multimode powertrains represent one of the most versatile solutions for hybrid electric vehicles where multiple power sources are integrated with aim of improving fuel economy and reducing pollutants emission in every operating condition. Some hybrid powertrain designs feature multiple planetary gear sets whose components can be directly driven by the powertrain actuators (electric motor or thermal engine) or can be connected through clutches and brakes. The advantages due to the availability of multiple modes are mitigated by the increase of production costs and complexity because of the higher number of components required if compared with the single mode solutions. A numerical methodology is adapted from the literature to analyze, categorize, and compare each distinct working configuration. The energy consumption of each powertrain configuration is then evaluated through the power-weighted efficiency concept whose formulation normalize the contribution from each power source. This paper aims at extending the methodology to investigate the operating range for each powertrain configuration to always achieve the maximum efficiency. The methodology is then applied to the realistic case study of the EVT 2-Mode Hybrid System
Integrated correlators with a Wilson line in SYM
In the context of integrated correlators in SYM, we study the
2-point functions of local operators with a superconformal line defect.
Starting from the mass-deformed theory in presence of a
-BPS Wilson line, we exploit the residual superconformal symmetry
after the defect insertion, and show that the massive deformation corresponds
to integrated insertions of the superconformal primaries belonging to the
stress tensor multiplet with a specific integration measure which is explicitly
derived after enforcing the superconformal Ward identities. Finally, we show
how the Wilson line integrated correlator can be computed by the
Wilson loop vacuum expectation value on a 4-sphere in terms
of a matrix model using supersymmetric localization. In particular, we
reformulate previous matrix model computations by making use of recursion
relations and Bessel kernels, providing a direct link with more general
localization computations in theories.Comment: 34 pages, 1 figur
Integrated correlators with a Wilson line in N= 4 SYM
In the context of integrated correlators in N= 4 SYM, we study the 2-point functions of local operators with a superconformal line defect. Starting from the mass-deformed N= 2* theory in presence of a 1/2-BPS Wilson line, we exploit the residual superconformal symmetry after the defect insertion, and show that the massive deformation corresponds to integrated insertions of the superconformal primaries belonging to the stress tensor multiplet with a specific integration measure which is explicitly derived after enforcing the superconformal Ward identities. Finally, we show how the Wilson line integrated correlator can be computed by the N= 2* Wilson loop vacuum expectation value on a 4-sphere in terms of a matrix model using supersymmetric localization. In particular, we reformulate previous matrix model computations by making use of recursion relations and Bessel kernels, providing a direct link with more general localization computations in N= 2 theories
BPS wilson loops in generic conformal N = 2 SU(N) SYM theories
We consider the 1/2 BPS circular Wilson loop in a generic N = 2 SU(N) SYM theory with conformal matter content. We study its vacuum expectation value, both at finite N and in the large-N limit, using the interacting matrix model provided by localization results. We single out some families of theories for which the Wilson loop vacuum expectation values approaches the N = 4 result in the large-N limit, in agreement with the fact that they possess a simple holographic dual. At finite N and in the generic case, we explicitly compare the matrix model result with the field-theory perturbative expansion up to order g^8 for the terms proportional to the Riemann value zeta(5), finding perfect agreement. Organizing the Feynman diagrams as suggested by the structure of the matrix model turns out to be very convenient for this computation
Emitted radiation and geometry
In conformal N = 2 Super Yang-Mills theory, the energy emitted by an accelerated heavy particle is computed by the one-point function of the stress tensor operator in the presence of a Wilson line. In this paper, we consider the theory on the ellipsoid and we prove a conjectured relation between the stress tensor one-point function and the firrst order expansion of the Wilson loop expectation value in the squashing parameter. To do this, we analyze the behavior of the Wilson loop for a small deformation of the background geometry and, at firrst order in the deformation, we fix the kinematics using defect CFT constraints. In the final part of the paper, we analyze the consequences of our results for the weak coupling perturbative expansion. In particular, comparing the weakly coupled matrix model with the ordinary Feynman diagram expansion, we find a natural transcendentality driven organization for the latter
Correlators between Wilson loop and chiral operators in N=2 conformal gauge theories
We consider conformal N=2 super Yang-Mills theories with gauge group SU(N)
and Nf=2N fundamental hypermultiplets in presence of a circular 1/2-BPS Wilson
loop. It is natural to conjecture that the matrix model which describes the
expectation value of this system also encodes the one-point functions of chiral
scalar operators in presence of the Wilson loop. We obtain evidence of this
conjecture by successfully comparing, at finite N and at the two-loop order,
the one-point functions computed in field theory with the vacuum expectation
values of the corresponding normal-ordered operators in the matrix model. For
the part of these expressions with transcendentality zeta(3), we also obtain
results in the large-N limit that are exact in the 't Hooft coupling lambda.Comment: 37 pages, 10 figures. v2: typo corrected, 3 references added. Version
to appear on JHE
A Methodology for Parameter Estimation of Nonlinear Single Track Models from Multibody Full Vehicle Simulation
In vehicle dynamics, simple and fast vehicle models are required, especially in the framework of real-time simulations and autonomous driving software. Therefore, a trade-off between accuracy and simulation speed must be pursued by selecting the appropriate level of detail and the corresponding simplifying assumptions based on the specific purpose of the simulation. The aim of this study is to develop a methodology for map and parameter estimation from multibody simulation results, to be used for simplified vehicle modelling focused on handling performance. In this paper, maneuvers, algorithms and results of the parameter estimation are reported, together with their integration in single track models with increasing complexity and fidelity. The agreement between the multibody model, used as reference, and four single track models is analyzed and discussed through the evaluation of the correlation index. The good match between the models validates the adopted simulation methodology both during steady-state and during transient maneuvers. In a similar way, this method could be applied to experimental data gathered from a real instrumented car rather than from a multibody model
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