668 research outputs found
On a class of polynomial Lagrangians
In the framework of finite order variational sequences a new class of
Lagrangians arises, namely, \emph{special} Lagrangians. These Lagrangians are
the horizontalization of forms on a jet space of lower order. We describe their
properties together with properties of related objects, such as
Poincar\'e--Cartan and Euler--Lagrange forms, momenta and momenta of generating
forms, a new geometric object arising in variational sequences. Finally, we
provide a simple but important example of special Lagrangian, namely the
Hilbert--Einstein Lagrangian.Comment: LaTeX2e, amsmath, diagrams, hyperref; 15 page
On the bi-Hamiltonian Geometry of WDVV Equations
We consider the WDVV associativity equations in the four dimensional case.
These nonlinear equations of third order can be written as a pair of six
component commuting two-dimensional non-diagonalizable hydrodynamic type
systems. We prove that these systems possess a compatible pair of local
homogeneous Hamiltonian structures of Dubrovin--Novikov type (of first and
third order, respectively).Comment: 21 pages, revised published version; exposition substantially
improve
Systems of conservation laws with third-order Hamiltonian structures
We investigate -component systems of conservation laws that possess
third-order Hamiltonian structures of differential-geometric type. The
classification of such systems is reduced to the projective classification of
linear congruences of lines in satisfying additional
geometric constraints. Algebraically, the problem can be reformulated as
follows: for a vector space of dimension , classify -tuples of
skew-symmetric 2-forms such that for some non-degenerate symmetric
.Comment: 31 page
Tetrad gravity, electroweak geometry and conformal symmetry
A partly original description of gauge fields and electroweak geometry is
proposed. A discussion of the breaking of conformal symmetry and the nature of
the dilaton in the proposed setting indicates that such questions cannot be
definitely answered in the context of electroweak geometry.Comment: 21 pages - accepted by International Journal of Geometric Methods in
Modern Physics - v2: some minor changes, mostly corrections of misprint
Newly diagnosed and relapsed follicular lymphoma: Esmo clinical practice guidelines for diagnosis, treatment and follow-up
Validation of a small scale woody biomass downdraft gasification plant coupled with gas engine
In recent years, small scale cogeneration systems (< 500 kWe) distributed in different geographical locations
using biomass has received special attention as economically competitive and environmentally friendly ways
of producing energy. These systems can be integrated to industrial and agricultural activities where biomass
residues are generated and can be converted into electricity and thermal energy by combustion or
gasification. The legislations of many European countries such as Italy concerning renewable energy and
energy efficiency along the taxation schemes have raised the incentives for small scale cogeneration plants.
Consequently, there is a clear economic interest of the companies in this sector and there is also a scientific
interest towards demonstration of their energetic efficiency, environmental performance and reliability.
Among the suggested technologies for the biomass conversion into energy, downdraft gasification (using air
as gasification agent), coupled with internal combustion engines, has the advantage of high electric efficiency
(~ 25%) and low tar generation, making easier the gas cleaning process necessary for its use into engines.
In the present work, the results of a measurement campaign performed on a commercial scale 350 kWth
downdraft woodchips gasification plant, coupled with an SI internal combustion engine (ICE), are presented
and discussed. The main goals of this first experimental campaign have been to verify the stability of gasifier
and engine operation, operability of the plant and to determine its energy efficiency. The campaign verified a
stable operation of the gasifier and the plant produced a syngas with a composition suitable for a gas engine.
The energy balance resulted in a potential overall wood fuel to electricity efficiency of about 23 %
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