The (alpha) version of the Fermi-Pasta-Ulam is revisited through direct numerical simulations and an application of weak turbulence theory. The energy spectrum, initializedwith a large scale excitation, is traced through a series of distinct qualitative phases en route to eventual equipartition. Weak turbulence theory is applied in an attempt to provide an effective quantitative description of ...

Stefano Lepri, 2, 3, ∗ Roberto Livi, 3 and Antonio Politi 2, 3 Istituto Nazionale di Ottica Applicata, largo E. Fermi 6 I-50125 Firenze, Italy Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, Sez. Territoriale di Firenze, largo E. Fermi 6 I-50125 Firenze, Italy Istituto Nazionale per la Fisica della Materia-UdR Firenze, via G. Sansone 1 I-50019 Sesto Fiorentino, Italy Diparti...

IBM is currently developing the new line of BlueGene/L supercomputers. The top-of-the-line installation is planned to be a 65,536 processors system featuring a peak performance of 360 Tflop/s. This system is supposed to lead the Top 500 list when being installed in 2005 at the Lawrence Livermore National Laboratory. This paper presents one of the first numerical kernels run on a prototype BlueG...

Peristalsis by actively generated waves of muscle contraction is one the most fundamental ways producing motion in living systems. We show that peristalsis can be modeled a train rectangular-shaped solitary localized activity propagating through otherwise passive matter. Our analysis based on Fermi-Pasta-Ulam (FPU) type discrete model accounting for active stresses and we reveal existence this ...

BACKGROUND Lignocellulosic biomass such as wood is an attractive material for fuel ethanol production. Pretreatment technologies that increase the digestibility of cellulose and hemicellulose in the lignocellulosic biomass have a major influence on the cost of the subsequent enzymatic hydrolysis and ethanol fermentation processes. Pretreatments without chemicals such as acids, bases or organic ...

Brewer’s spent grain components (cellulose, hemicellulose and lignin) were fractionated in a two-step chemical pretreatment process using dilute sulfuric acid and sodium hydroxide solutions. The cellulose pulp produced was hydrolyzed with a cellulolytic complex, Celluclast 1.5 L, at 45 C to convert the cellulose into glucose. Several conditions were examined: agitation speed (100, 150 and 200 r...

We study the original α-Fermi-Pasta-Ulam (FPU) system with N = 16, 32, and 64 masses connected by a nonlinear quadratic spring. Our approach is based on resonant wave-wave interaction theory; i.e., we assume that, in the weakly nonlinear regime (the one in which Fermi was originally interested), the large time dynamics is ruled by exact resonances. After a detailed analysis of the α-FPU equatio...

The dispersive interacting waves in Fermi-Pasta-Ulam (FPU) chains of particles in thermal equilibrium are studied from both statistical and wave resonance perspectives. It is shown that, even in a strongly nonlinear regime, the chain in thermal equilibrium can be effectively described by a system of weakly interacting renormalized nonlinear waves that possess (i) the Rayleigh-Jeans distribution...

This paper presents the formal veriication of all sub-circuits in a oating-point arithmetic unit (FPU) from an Intel microprocessor using a word-level model checker. This work represents the rst large-scale application of word-level model checking techniques. The FPU can perform addition, subtraction, multiplication, square root, division, remainder, and rounding operations; verifying such a br...

We study the dynamics of quasilinear mappings in Hilbert spaces in the neighbourhood of a fixed point. The linearized map is a closed unbounded operator and thus the initial value problem is ill-posed. Under suitable spectral assumptions, we show that all solutions staying in some neighbourhood of the fixed point lie on an invariant centre manifold. We apply this result to the study of time-per...