8,494 research outputs found
Experimental campaign tests on ultra micro gas turbines, fuel supply comparison and optimization
The increasing demand for miniaturized radio-controlled vehicles inspired the following research. The uses of these unmanned miniaturized/micro vehicles range from aero-modeling to drones for urban control and military applications too. The common characteristic of these vehicles is the need for a light and compact propulsion system. The radio-controlled (RC) turbines for modeling are ideally suited for this purpose, guaranteeing the necessary thrust with compactness and lightness. This device is a miniaturized turbojet, and it is generally composed of three basic elements: compressor, combustion chamber and turbine. The main goal of the paper is to evaluate the turbojet performance for considering the possibility of its use as a range extender in a hybrid vehicle. Considering the total volume constraints, it will be important to evaluate the specific fuel consumption. Also from the environmental point of view, the possibility of feeding the device with gas has been considered and, consequently, the needed device modifications performed. The test bench has been realized and assembled at the University Department Laboratory. Several different
experimental configurations are reproduced and reported here, to obtain performance maps. The experiments results have been compared to previous tests results, as well as numerical simulations. Therefore, it has been possible to make a comparison between the two different fuels. The results show that this device can be used as a range extender for a hybrid vehicle. Moreover, the various tests have shown that, acting on the control unit, it is possible to feed the device with gas (mixture of propane and butane), obtaining a further benefit from the economic point of view. Surely, an in-depth study of the turbine management logic would produce a further advantage in terms of fuel consumption
Generalized Connectives for Multiplicative Linear Logic
In this paper we investigate the notion of generalized connective for multiplicative linear logic. We introduce a notion of orthogonality for partitions of a finite set and we study the family of connectives which can be described by two orthogonal sets of partitions.
We prove that there is a special class of connectives that can never be decomposed by means of the multiplicative conjunction ? and disjunction ?, providing an infinite family of non-decomposable connectives, called Girard connectives. We show that each Girard connective can be naturally described by a type (a set of partitions equal to its double-orthogonal) and its orthogonal type. In addition, one of these two types is the union of the types associated to a family of MLL-formulas in disjunctive normal form, and these formulas only differ for the cyclic permutations of their atoms
Dispersion Relations for Electroweak Observables in Composite Higgs Models
We derive dispersion relations for the electroweak oblique observables
measured at LEP in the context of composite Higgs models. It is
shown how these relations can be used and must be modified when modeling the
spectral functions through a low-energy effective description of the strong
dynamics. The dispersion relation for the parameter is then used
to estimate the contribution from spin-1 resonances at the 1-loop level.
Finally, it is shown that the sign of the contribution to the
parameter from the lowest-lying spin-1 states is not necessarily positive
definite, but depends on the energy scale at which the asymptotic behavior of
current correlators is attained.Comment: 34 pages, 4 figures. v2: a few minor changes, typos corrected, list
of references revise
One-loop effects from spin-1 resonances in Composite Higgs models
We compute the 1-loop correction to the electroweak observables from spin-1
resonances in SO(5)/SO(4) composite Higgs models. The strong dynamics is
modeled with an effective description comprising the Nambu-Goldstone bosons and
the lowest-lying spin-1 resonances. A classification is performed of the
relevant operators including custodially-breaking effects from the gauging of
hypercharge. The 1-loop contribution of the resonances is extracted in a
diagrammatic approach by matching to the low-energy theory of Nambu-Goldstone
bosons. We find that the correction is numerically important in a significant
fraction of the parameter space and tends to weaken the bounds providing a
negative shift to the S parameter.Comment: 45 pages, 13 figures. v2: minor corrections, conclusions unchanged.
v3: two diagrams in Fig.13 correctly redraw
Two-Loop Master Integrals for the Planar QCD Massive Corrections to Di-photon and Di-jet Hadro-production
We present the analytic calculation of the Master Integrals necessary to
compute the planar massive QCD corrections to Di-photon (and Di-jet) production
at hadron colliders. The masters are evaluated by means of the differential
equations method and expressed in terms of multiple polylogarithms and one- or
two-fold integrals of polylogarithms and irrational functions, up to
transcendentality four.Comment: 20 pages, ancillary file
A physically-based approach for evaluating the hydraulic invariance in urban transformations
Transformation of urban areas satisfies hydraulic invariance (HI) if the maximum flow rate outgoing
the area stays unchanged. The HI can be respected by dimensioning appropriate water storage
volumes or low impact developments (LID) to balance the soil sealing and ground levelling effects.
In order to comply with HI, some Italian regional legislation and river basin authority provide for
the creation of storage tanks whose volume must be estimated through simple conceptual rainfallrunoff
models. In this work a physically based approach for evaluating HI is proposed. It is based on
interpolating the results from a large number of hydraulic simulations conducted using FullSWOF,
which is an open source code developed by the University of Orléans. In this software the shallow
water equations are solved using a finite volume scheme and friction laws and infiltration models
are included. Simulations have been carried out considering the effect of three properties of the
area, that is: the saturated hydraulic conductivity of soil, the slope of ground surface and the standard
deviation of ground elevation around the mean level. Using the results, interpolating laws for
the peak discharge and the critical rainfall duration as function of the three basin parameters have
been derived. A parametric hydrograph as a function of the basin parameters and rainfall duration
is defined and a HI evaluation method based on routing the parametric hydrograph is proposed.
The results from this approach have been compared with those from non-physically based methods
currently used, such as the direct rainfall approach and the linear reservoir approach. The comparison
shows that the difference between these conceptual methods with that one proposed here
is strongly dependent on the runoff coefficient value. It is also not possible to predict whether they
are conservative or not
LABORsim: an Agent-Based Microsimulation of Labour Supply. An Application to Italy
Most Oecd Countries are experiencing a rapid population ageing. Italy adds to this picture a very low labour market participation of the elders, so that most projections of the impact of ageing on the labour market are rather pessimistic. However, there are other long run modifications currently underway that will presumably have a sizeable impact on the labour market, above all changes in the retirement legislation, in educational choices and participation behaviour. In this paper we present LABORsim, an agent based microsimulation model of labour supply, which offers new insights on the likely evolution of the labour force in the next decades in Italy. LABORsim integrates the current demographic projections with simulation modules modelling retirement rules, retirement behaviours, migrations, education and participation choices, plus a consolle to implement various policy scenario analyses. When all these factors are taken into account, projections for next decades are not that pessimistic. In most scenarios, the overall participation rate is expected to increase steadily for the next two decades, while shortages in the labour force supply and an unfavourable dynamics for the economic dependency rate are expected to show up only after 2020, when the baby boom generations will arrive at their retirement ages. This is not enough, however, to allow Italy to meet the EU Stockolm and Lisbon targets for male and female employment rates for many decades to come. The sharp increase in the participation rates for the elderly (aged 55-64), mainly driven by the recent changes in the retirement eligibility criteria, will make it possible to meet the Stockholm target of 50% employment rate in this age group by 2015, i.e. with only 5 years of delay.microsimulation, participation, employment, retirement, education, policy evaluation.
Estimating hyperbolicity of chaotic bidimensional maps
We apply to bidimensional chaotic maps the numerical method proposed by
Ginelli et al. to approximate the associated Oseledets splitting, i.e. the set
of linear subspaces spanned by the so called covariant Lyapunov vectors (CLV)
and corresponding to the Lyapunov spectrum. These subspaces are the analog of
linearized invariant manifolds for non-periodic points, so the angles between
them can be used to quantify the degree of hyperbolicity of generic orbits;
however, being such splitting non invariant under smooth transformations of
phase space, it is interesting to investigate the properties of transversality
when coordinates change, e.g. to study it in distinct dynamical systems. To
illustrate this issue on the Chirikov-Taylor standard map we compare the
probability densities of transversality for two different coordinate systems;
these are connected by a linear transformation that deforms splitting angles
through phase space, changing also the probability density of almost-zero
angles although complete tangencies are in fact invariant. This is completely
due to the PDF transformation law and strongly suggests that any statistical
inference from such distributions must be generally taken with care.Comment: 14 pages, 23 figures (This paper is for the IJBC Special Issue edited
by Prof. Gregoire Nicolis, Prof. Marko Robnik, Dr. Vassilis Rothos and Dr.
Haris Skokos
On the apparent failure of the topological theory of phase transitions
The topological theory of phase transitions has its strong point in two
theorems proving that, for a wide class of physical systems, phase transitions
necessarily stem from topological changes of some submanifolds of configuration
space. It has been recently argued that the lattice -model
provides a counterexample that falsifies this theory. It is here shown that
this is not the case: the phase transition of this model stems from an
asymptotic () change of topology of the energy level sets, in spite
of the absence of critical points of the potential in correspondence of the
transition energy.Comment: 5 pages, 4 figure
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