Detecting the tunneling rates for strongly interacting fermions on optical lattices

Strongly interacting fermionic atoms on optical lattices are studied through a Hubbard-like model Hamiltonian, in which tunneling rates of atoms and molecules between neighboring sites are assumed to be different. In the limit of large onsite repulsion U, the model is shown to reproduce the t-J Hamiltonian, in which the J coefficient of the Heisenberg term depends on the particle-assisted tunneling rate g: explicitly, $J=4 g^2/U$. At half-filling, g drives a crossover from a Brinkman-Rice paramagnetic insulator of fully localized atoms (g=0) to the antiferromagnetic Mott insulator of the standard Hubbard case (g=t). This is observed already at the intermediate coupling regime in the number of doubly occupied sites, thus providing a criterion to extract from measurements the effective value of g.Comment: 5 pages, 3 figure

Low energy quantum regimes of 1D dipolar Hubbard model with correlated hopping

We apply the bosonization technique to derive the phase diagram of a balanced unit density two-component dipolar Fermi gas in a one dimensional lattice geometry. The considered interaction processes are of the usual contact and dipolar long-range density-density type together with peculiar correlated hopping terms which can be generated dynamically. Rigorous bounds for the transition lines are obtained in the weak coupling regime. In addition to the standard bosonization description, we derive the low energy phase diagram taking place when part of the interaction is embodied non-perturbatively in the single component Hamiltonians. In this case the Luttinger liquid regime is shown to become unstable with respect to the opening of further gapped phases, among which insulating bond ordered wave and Haldane phases, the latter with degenerate edge modes.Comment: 6 pages, 1 figur

Energy recovery of the biomass from livestock farms in italy: The case of Modena province

The overall energy conversion efficiency of the waste-to-energy technologies is strongly affected by the distance of the biomass supply and the rate available during the year. Therefore, a simulation tool for the evaluation of the main outputs of a power plant for the wastes exploitation is a useful instrument for investigating the best trade-off between the plant size and the biomass supply. Nevertheless, it usually involves a large number of data and an extensive training and expertise. This paper focuses on the development of a numerical tool for the comparison of different waste-to-energy technologies and thus supporting the selection of the best exploitation strategy based on the data usually accessible to administrations. The numerical approach employs validated numerical models for the considered biomass exploitation technologies and its capabilities are demonstrated by simulating a reference case: the energy recovery from manure of different livestock farms in the province of Modena (Italy). The electric and thermal power production from the manure available in the considered territory is estimated and the produced electric energy is balanced with the energy requirements of the local animal farms. The remaining amount of wastes that has to be disposed is also calculated and compared with the initial input to the systems. Finally, different strategies for distributed and centralized exploitation of the manure are investigated and the related plant size and production of electric and thermal energy are evaluated. The proposed approach and the developed numerical tool prove to be useful instruments for decision makers and can help the efficient exploitation of the biomasses available in a region

An Innovative Approach to Kinematic Analysis of Multibody Hydraulic Actuation Systems

The paper focuses on the development of an innovative methodology for the direct measurement of the main kinematic variables in multi-body hydraulic actuation systems. The analysis investigates how the motion capture technique has been applied to the experimental determination of position, velocity and acceleration of hydraulically controlled actuation systems for off-highway machineries. A number of earth-moving machines has been taken into account, in particular a mini-excavator articulated harm has been equipped with both a standard mechanical system for position and acceleration measurement (including different accelerometers, linear and angular transducers), and a set of IR markers for motion capture application. First, the hydraulically controlled boom-arm-bucket system has been operated using a control routine reproducing a reference operating condition, in order to define the accuracy of the motion capture system in detecting the kinematic quantities\u2019 variations. At the same time, the hydraulic variables have been also acquired to monitor the behavior during the machine working routine. Thus, the results obtained by the different experimental techniques have been compared, in order to state the reliability of the motion capture technique to predict the fast dynamics of pressure variations through the accurate measurement of mechanical devices\u2019 oscillation. Finally, the paper reports the main results obtained using the data from the motion capture characterization of the dynamic performance of the mini-excavator, with particular attention devoted to the dynamic analysis through lumped and distributed parameter numerical co-simulation

Homogeneous and domain-wall topological Haldane conductors with dressed Rydberg atoms

The interplay between antiferromagnetic interaction and hole motion is capable of inducing conducting Haldane phases with topological features described by a finite nonlocal string order parameter. Here we show that these states of matter are captured by the one-dimensional t − J z model, which can be experimentally realized with dressed Rydberg atoms trapped onto a one-dimensional optical lattice. In the sector with vanishing total magnetization, exact calculations associated with the bosonization technique allow us to predict that both metallic and superconducting topological Haldane states can be achieved. With the addition of an appropriate magnetic field, the system enters a domain-wall structure with finite total magnetization. In this regime, the conducting Haldane states are confined in domains separated by regions where a fully polarized Luttinger liquid occurs. A procedure to dynamically stabilize such topological phases starting from a confined Ising state is also described

Multidimensional Design of Hydraulic Components and Systems

In this chapter, the above mentioned critical aspects in the application of multidimensional numerical analysis for the design of mechanical devices and components for hydraulic systems are addressed. The objective of the chapter is to provide a roadmap for the multidimensional numerical analysis of the hydraulic components to be used effectively in the design process. In particular, two examples of hydraulic systems are accounted for in the application of the CFD analysis: a proportional control valve and a fuel accumulator for multi-fuel injection systems. These test cases have been selected due to their representativeness in the field of hydraulic applications and to the complexity and variety ofthe physical phenomena involved

Numerical Evaluation of a New Strategy of Emissions Reduction by Urea Direct Injection for Heavy Duty Diesel Engines

The effect of ammoniac deoxidizing agent (Urea) on the reduction of NOx produced in the Diesel engine was investigated numerically. Urea dissolved in water was directly injected into the engine cylinder during the expansion stroke. The NOx deoxidizing process was described using a simplified chemical kinetic model coupled with the comprehensive kinetics of Diesel oil surrogate combustion. If the technology of DWI (Direct Water Injection) with the later injection timing was used, the deoxidizing reactants could be delivered in a controlled amount directly into the flame plume zones, where NOx formed. Numerical simulations for the Isotta Fraschini DI Diesel engine were carried out using the KIVA-3V code, modified to account for the “co-fuel” injection and reaction with combustion products. The results showed that the amount of NOx could be substantially reduced up to 80% with the injection timing and the fraction of Urea in the solution optimized

Hidden magnetism in periodically modulated one dimensional dipolar fermions

The experimental realization of time-dependent ultracold lattice systems has paved the way towards the implementation of new Hubbard-like Hamiltonians. We show that in a one-dimensional two-components lattice dipolar Fermi gas the competition between long range repulsion and correlated hopping induced by periodically modulated on-site interaction allows for the formation of hidden magnetic phases, with degenerate protected edge modes. The magnetism, characterized solely by string-like nonlocal order parameters, manifests in the charge and/or in the spin degrees of freedom. Such behavior is enlighten by employing Luttinger liquid theory and numerical methods. The range of parameters for which hidden magnetism is present can be reached by means of the currently available experimental setups and probes

Dynamic Analysis of the Lubrication in a Wet Clutch of a Hydromechanical Variable Transmission

The paper investigates the oil flow through a multi plate clutch for a hydro-mechanical variable transmission under actual operating conditions. The analysis focuses on the numerical approach for the accurate prediction of the transient behavior of the lubrication in the gear region: the trade-off between prediction capabilities of the numerical model and computational effort is addressed. The numerical simulation includes the full 3D geometry of the clutch and the VOF multi-phase approach is used to calculate the oil distribution in the clutch region under different relative rotating velocities. Furthermore, the lubrication of the friction disks is calculated for different clutch actuation conditions, i.e. not-engaged and engaged positions. The influence of different geometrical features of the clutch lubricating circuit on the oil distribution is also determined. The results show the areas where poor lubrication occurs and extend the experiments where measurements are difficult to carry out. The simulation highlights the regions where high thermal stresses are observed during tests