A hybrid prognostics approach to estimate the residual useful life of a planetary gearbox with a local defect

A hybrid prognostics approach for the monioring of a planetary gearbox with the local defect is presented. This hybrid method can predict the remaining useful life (RUL) of planetary gearbox with a fatigue crack. The method consists of a dynamical model for simulation data generation, a statistical algorithm for feature selection and weighting, and a modified grey model for RUL prediction. Experimental studies are conducted to validate and demonstrate the feasibility of the proposed method for RUL prediction of a cracked sun gear in planetary gearbox. And the validation has a promising result

Temperature-dependent thermal and electrical conduction in metallic nanostructures

In this work, temperature dependent electrical and thermal conduction in the bio-supported 3.2 nm-thin Ir nanofilm and individual silver nanowire are studied at reduced temperatures. For the Ir film, by studying the temperature-dependent behavior (300 K down to 43 K) of electron thermal conductivity (), we quantify the extremely confined defect-electron scatterings and isolate the intrinsic phonon-electron scattering that is shared by the bulk Ir. At low temperatures below 50 K, of the film has almost two orders of magnitude reduction from that of bulk Ir. The film has ∂/∂T\u3e0 while the bulk Ir has ∂/∂T \u3c0. We introduce a unified thermal resistivity (=T/) to interpret these completely different ~T relations. It is found that the film and the bulk Ir share a very similar ~T trend while they have a different residual part (Θ0) at 0 K limit: 0~0 for the bulk Ir, and 0=5.5 mK2/W for the film. The Ir film and the bulk Ir have very close ∂Θ/∂T (75 to 290 K): 6.33×10-3 mK/W for the film and 7.62×10-3 mK/W for the bulk Ir. This strongly confirms the similar phonon-electron scattering in them. The temperature dependent behavior of the Lorenz number of the Ir film is also reported down to 10 K. Due to the strong defect-electron scattering, a very large residual electrical resistivity (1.2410-7 ·m) is observed for the film that dominates the overall electron transport (1.24~1.5510-7 ·m). The Debye temperature (221 K) of the film is found much smaller than that of bulk (308 K). This phonon softening strongly confirms the extensive surface and grain boundary electron scatterings. We find the Wiedemann-Franz Law still applies to our film even at low temperatures. The overall Lorenz number and that of imperfect structure (~2.25×10-8 W·Ω/K2) are close to the Sommerfeld value and shows little temperature dependence. This is contrast to other studied low dimensional metallic structures that have a much larger Lorenz number (3~7×10-8 W·Ω/K2). Electron tunneling and hopping in the biomaterial substrate are speculated responsible for the observed Lorenz number. Additionally, the thermal and electrical transport in an individual silver nanowire is characterized down to 35 K for in-depth understanding of the strong structural defect induced electron scattering. The results indicate that, at room temperature, the electrical resistivity increases by around 4 folds from that of bulk silver. The Debye temperature (151 K) of the silver nanowire is found 36% lower than that (235 K) of bulk silver, confirming strong phonon softening. At room temperature, the thermal conductivity is reduced by 55% from that of bulk silver. This reduction becomes larger as the temperature goes down. A large residual is observed for silver nanowire while that of the bulk silver is almost zero. The same ~T trend proposes that the silver nanowire and bulk silver share the similar phonon-electron scattering mechanism for thermal transport. Due to phonon-assisted electron energy transfer across grain boundaries, the Lorenz number of the silver nanowire is found much larger than that of bulk silver and decreases with decreasing temperature

Pitting damage levels estimation for planetary gear sets based on model simulation and grey relational analysis

The planetary gearbox is a critical mechanism in helicopter transmission systems. Tooth failures in planetary gear sets will cause great risk to helicopter operations. A gear pitting damage level estimation methodology has been devised in this paper by integrating a physical model for simulation signal generation, a three-step statistic algorithm for feature selection and damage level estimation for grey relational analysis. The proposed method was calibrated firstly with fault seeded test data and then validated with the data of other tests from a planetary gear set. The estimation results of test data coincide with the actual test records, showing the effectiveness and accuracy of the method in providing a novel way to model based methods and feature selection and weighting methods for more accurate health monitoring and condition prediction

Hete-CF : Social-Based Collaborative Filtering Recommendation using Heterogeneous Relations

The work described here was funded by the National Natural Science Foundation of China (NSFC) under Grant No. 61373051; the National Science and Technology Pillar Program (Grant No.2013BAH07F05), the Key Laboratory for Symbolic Computation and Knowledge Engineering, Ministry of Education, China, and the UK Economic & Social Research Council (ESRC); award reference: ES/M001628/1.Preprin