3,100 research outputs found
Fractional Lindstedt series
The parametric equations of the surfaces on which highly resonant
quasi-periodic motions develop (lower-dimensional tori) cannot be analytically
continued, in general, in the perturbation parameter, i.e. they are not
analytic functions of the perturbation parameter. However rather generally
quasi-periodic motions whose frequencies satisfy only one rational relation
("resonances of order 1") admit formal perturbation expansions in terms of a
fractional power of the perturbation parameter, depending on the degeneration
of the resonance. We find conditions for this to happen, and in such a case we
prove that the formal expansion is convergent after suitable resummation.Comment: 40 pages, 6 figure
Converging Perturbative Solutions of the Schroedinger Equation for a Two-Level System with a Hamiltonian Depending Periodically on Time
We study the Schroedinger equation of a class of two-level systems under the
action of a periodic time-dependent external field in the situation where the
energy difference 2epsilon between the free energy levels is sufficiently small
with respect to the strength of the external interaction. Under suitable
conditions we show that this equation has a solution in terms of converging
power series expansions in epsilon. In contrast to other expansion methods,
like in the Dyson expansion, the method we present is not plagued by the
presence of ``secular terms''. Due to this feature we were able to prove
absolute and uniform convergence of the Fourier series involved in the
computation of the wave functions and to prove absolute convergence of the
epsilon-expansions leading to the ``secular frequency'' and to the coefficients
of the Fourier expansion of the wave function
Bunch Compressor for Beam-Based Alignment
Misalignments in the main linac of future linear colliders can lead to significant emittance growth. Beam-based alignment algorithms, such as Dispersion Free Steering (DFS), are necessary to mitigate these effects. We study how to use the Bunch Compressor to create the off-energy beams necessary for DFS and discuss the effectiveness of this method
Associations between pig leg health and lean meat growth in commercial organic herds
Sustainable development of organic pig production needs to include both animal welfare and productivity aspects. Knowledge about associations between animal welfare and productivity could be a key for constructive, long-term development of organic as well as conventional pig production systems. Poor leg health is considered a central animal welfare issue in organic pig production in Sweden. The preliminary results presented in this paper indicate that pigs in organic herds with more severe leg problems have poorer lean meat growth. However, the majority of the lame pigs had milder forms of leg problems, which were not found to be associated with lean meat growth
Predicting delay factors when chipping wood at forest roadside landings
Chipping of bulky biomass assortments at roadside landings is a common and costly step in the biomass-to-energy supply chain. This operation normally involves one chipping unit and one or several transport trucks working together for simultaneous chipping and chip transport to a terminal or end user. Reducing the delay factors in these operations is a relevant ambition for lowering supply costs. A method to estimate organizational delay based on: (1) the capacity ratio between the transport and the chipper, (2) the use of buffer storage, and (3) the number of transport units involved is suggested here. Other delays will also be present, and some of these may relate to the working conditions at the landing. A method to set a landing functionality index based on characteristics of the forest landing is also suggested. A total of 14 roadside chipping operations were assessed and the operators were interviewed to address the impact of machinery configuration and landing characteristics on machine utilization. At most sites, the chipper was the more productive part, and the chipper utilization was to a large extent limited by organizational delay. Still the utilization of the transport units varied between 37 and 97%, of which some 36% of the variation was explained by the landing functionality index. Knowledge from the work presented here should be a good starting point for improving biomass supply planning and supply chain configuration.acceptedVersio
Ion shock acceleration by large amplitude slow ion acoustic double layers in laser-produced plasmas
A kinetic model for the shock acceleration of ions in laser-produced plasmas is developed. A fraction of the warm ions are accelerated by the large amplitude monotonic potential of the shock created due the plasma compression and electron heating by the laser. The kinetic model for the monotonic shock is based on the slow ion acoustic double layer (SIADL). It is found that the amplitude of the large amplitude SIADL is almost uniquely defined by the electron temperature. Therefore, a balance between electron heating and plasma compression is needed for optimal ion acceleration by this scheme. Typical Mach numbers of the monotonic shocks are close to 1.5. The scheme could potentially produce monoenergetic ions with a relative energy spread of less than 1%. The model is compared with recent simulations and experiments, where efficient shocks acceleration and production of monoenergetic protons have been observed. Similarities and differences with other shock models are pointed out and discussed
Glucaric acid as an indicator of use of enzymeâinducing drugs
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/116979/1/cpt1974154417.pd
Phase-space structures in quantum-plasma wave turbulence
The quasilinear theory of the Wigner-Poisson system in one spatial dimension
is examined. Conservation laws and properties of the stationary solutions are
determined. Quantum effects are shown to manifest themselves in transient
periodic oscillations of the averaged Wigner function in velocity space. The
quantum quasilinear theory is checked against numerical simulations of the
bump-on-tail and the two-stream instabilities. The predicted wavelength of the
oscillations in velocity space agrees well with the numerical results
Relativistic Klein-Gordon-Maxwell multistream model for quantum plasmas
A multistream model for spinless electrons in a relativistic quantum plasma
is introduced by means of a suitable fluid-like version of the
Klein-Gordon-Maxwell system. The one and two-stream cases are treated in
detail. A new linear instability condition for two-stream quantum plasmas is
obtained, generalizing the previously known non-relativistic results. In both
the one and two-stream cases, steady-state solutions reduce the model to a set
of coupled nonlinear ordinary differential equations, which can be numerically
solved, yielding a manifold of nonlinear periodic and soliton structures. The
validity conditions for the applicability of the model are addressed
Energy localization on q-tori, long term stability and the interpretation of FPU recurrences
We focus on two approaches that have been proposed in recent years for the
explanation of the so-called FPU paradox, i.e. the persistence of energy
localization in the `low-q' Fourier modes of Fermi-Pasta-Ulam nonlinear
lattices, preventing equipartition among all modes at low energies. In the
first approach, a low-frequency fraction of the spectrum is initially excited
leading to the formation of `natural packets' exhibiting exponential stability,
while in the second, emphasis is placed on the existence of `q-breathers', i.e
periodic continuations of the linear modes of the lattice, which are
exponentially localized in Fourier space. Following ideas of the latter, we
introduce in this paper the concept of `q-tori' representing exponentially
localized solutions on low-dimensional tori and use their stability properties
to reconcile these two approaches and provide a more complete explanation of
the FPU paradox.Comment: 38 pages, 7 figure
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