Vibration and noise analysis of a gear transmission system

This paper presents a comprehensive procedure to predict both the vibration and noise generated by a gear transmission system under normal operating conditions. The gearbox vibrations were obtained from both numerical simulation and experimental studies using a gear noise test rig. In addition, the noise generated by the gearbox vibrations was recorded during the experimental testing. A numerical method was used to develop linear relationships between the gearbox vibration and the generated noise. The hypercoherence function is introduced to correlate the nonlinear relationship between the fundamental noise frequency and its harmonics. A numerical procedure was developed using both the linear and nonlinear relationships generated from the experimental data to predict noise resulting from the gearbox vibrations. The application of this methodology is demonstrated by comparing the numerical and experimental results from the gear noise test rig

Mixing among the neutral Higgs bosons and rare B decays in the CP violating MSSM

Considering corrections from two-loop Feynman diagrams which involve gluino at large $\tan\beta$, we analyze the effects of possible CP phases on the rare B decays: $\bar{B}_{_{s}} \to l^+l^-$ and $\bar{B}\to Kl^+l^-$ in the CP violating minimal supersymmetric extension of the standard model. It is shown that the results of exact two loop calculations obviously differ from that including one-loop contributions plus threshold radiative corrections. The numerical analysis indicates that the possibly large CP phases strongly affect the theoretical estimation of the branching ratios, and this results coincide with the conclusion of some other works appearing in recent literature.Comment: revtex, 53 pages, including 19 figure

Resonant Conversion of Massless Neutrinos in Supernovae

It has been noted for a long time that, in some circumstances, {\sl massless} neutrinos may be {\sl mixed} in the leptonic charged current. Conventional neutrino oscillation searches in vacuum are insensitive to this mixing. We discuss the effects of resonant massless-neutrino conversions in the dense medium of a supernova. In particular, we show how the detected $\bar\nu_e$ energy spectra from SN1987a and the supernova $r$-process nucleosynthesis may be used to provide very stringent constraints on the mixing of {\sl massless} neutrinos.Comment: latex file, 20 pages, including 3 postscript figure

An H-Theorem for the Lattice Boltzmann Approach to Hydrodynamics

The lattice Boltzmann equation can be viewed as a discretization of the continuous Boltzmann equation. Because of this connection it has long been speculated that lattice Boltzmann algorithms might obey an H-theorem. In this letter we prove that usual nine-velocity models do not obey an H-theorem but models that do obey an H-theorem can be constructed. We consider the general conditions a lattice Boltzmann scheme must satisfy in order to obey an H-theorem and show why on a lattice, unlike the continuous case, dynamics that decrease an H-functional do not necessarily lead to a unique ground state.Comment: 6 pages, latex, no figures, accepted for publication in Europhys. Let

Microstructural evolution of Mn-based maraging steels and their influences on mechanical properties

The microstructural evolution in a set of Mn-based maraging steels (7–12 wt% Mn) when aged at 460–500 ºC for various durations up to 10,080 min and the influences on mechanical properties are systematically investigated. The improved yield strength of peak-aged samples is attributed to the formation of Ni2TiAl precipitates and the precipitation strengthening is governed by Orowan mechanism. Segregation of Mn at grain boundaries in the initial aging stage resulted in severe intergranular brittleness. During further aging, accumulated Mn segregation leading to the formation of ductile lath-like reverted austenite removed the embrittlement and significantly improved the ductility. In the overaged condition, the steady work hardening after yielding compensates the loss of yield strength resulting from the coarsening of precipitates and softening of α′-martensite matrix. There was only limited evidence of the TRIP effect in the reverted austenite, indicating that work hardening was associated with other deformation mechanisms. Increasing the aging temperature or the Mn content of alloy that promotes austenite reversion was demonstrated to accelerate the improvement of ductility

Characterisation of L21-ordered Ni2TiAl precipitates in FeMn maraging steels

The precipitates formed in a new series of Fesingle bondMn maraging steels when aged at 500 °C were identified as the L21-ordered Ni2TiAl phase. The precipitate formed a coherent-coplanar microstructure analogously to γ/γ' Ni-based superalloys and maintained a high number density and homogeneous dispersion within α′-martensite matrix even after aging for 10,080 min. An increase in the Mn content of the alloy led to faster precipitation kinetics and thus rapid hardening kinetics