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In this work, a dynamic model considering time-varying mesh stiffness and backlash was proposed and a test rig was built to investigate the vibration behavior of the idle gear set in a gerotor pump. The effects of input shaft speed, torque fluctuation, and gear tooth backlash on the dynamic performance of gerotor pump were analyzed according to the numerical and experimental results. Results demonstrate that when the torque fluctuation is neglected, the dynamic transmission error of drive gear is dominated by the first three mesh harmonic components; however, the RMS values of vibration acceleration have high frequency characteristics. When the torque fluctuation is considered, the dynamic responses of gerotor pump are modulated by the torque fluctuation. The effect of tooth backlash on the dynamic performance of gerotor pump is limited and mostly depended on the torque fluctuation condition. The gerotor pump noise is dominated by the low frequency component around the mesh frequency. The vibration energy can be divided into two parts in the frequency domain. In the low frequency band, the vibration energy is caused by the mechanical vibration. However, in the high frequency band, the cavitation phenomena may cause the concentration of the vibration energy and resonant of pump structure. [ABSTRACT FROM AUTHOR]

Energy transfer is a ubiquitous phenomenon that delivers energy from a blue-shifted emitter to a red-shifted absorber, facilitating wide photonic applications. Two-dimensional (2D) semiconductors provide unique opportunities for exploring novel energy transfer mechanisms in the atomic-scale limit. Herein, we have designed a planar optical microcavity-confined MoS2/hBN/WS2 heterojunction, which realizes the strong coupling among donor exciton, acceptor exciton, and cavity photon mode. This configuration demonstrates an unconventional energy transfer via polariton relaxation, brightening MoS2 with a record-high enhancement factor of ~440, i.e., two-order-of-magnitude higher than the data reported to date. The polariton relaxation features a short characteristic time of ~1.3 ps, resulting from the significantly enhanced intra- and inter-branch exciton-exciton scattering. The polariton relaxation dynamics is associated with Rabi energies in a phase diagram by combining experimental and theoretical results. This study opens a new direction of microcavity 2D semiconductor heterojunctions for high-brightness polaritonic light sources and ultrafast polariton carrier dynamics. Here, the authors design a microcavity-confined 2D heterojunction to realize the strong coupling among donor exciton, acceptor exciton, and cavity photon mode, leading to an unconventional energy transfer via polariton relaxation with an enhancement factor of ~440. [ABSTRACT FROM AUTHOR]

The study of the bearing fatigue life in high-speed gearboxes is an integral part of high-speed gear transmission research. There is still a lack of research on the analysis and calculating the bearing internal dynamic load and fatigue life considering gear engagement and centrifugal force simultaneously. Therefore, the paper proposes a new approach to acquire the internal load and fatigue life of the deep groove ball bearing in a high-speed gearbox system. Firstly, the modeling method of the gear mesh, flexible shaft, high-speed deep groove ball bearing, and housing is established, constructing the gearbox system dynamic model, which has the ability to calculate the bearing internal load. Then, the calculation method for analyzing the fatigue life of bearings is given based on the linear damage theory. The results show that the gear engagement and centrifugal force have meaningful effects on bearing internal loads and fatigue life, especially at high speeds. Both of them should be considered when evaluating the bearing life. The calculation method and model proposed in this paper provide a new technical approach for service performance evaluation and reliability design of high-speed deep groove ball bearing. [ABSTRACT FROM AUTHOR]

The dynamic transmission error of a straight bevel gear pair is tested and the relationship between the dynamic transmission error and the gear vibration is analyzed,with a straight bevel gear transmission system as the research object. The dynamic transmission error test system for the high speed straight bevel gear pair is developed and the transmission error curves are obtained. The dynamic property parameters of the gear pair are researched by the analysis of the experiment data with the signal processing approach. According to the comparison of the dynamic transmission error and the vibration behavior tested near the corresponding area of the gearbox,the results show,for the straight bevel gear pair,the shaft frequency components are the main frequency components of the dynamic transmission error,the low frequency components of the dynamic transmission error vary obviously with the rotation speed,the effect of the dynamic transmission error and the vibration acceleration near the supporting bearings on describing the dynamic responses are consistent.

With the development of industry, the concentration of lead (Pb) in water bodies is gradually increasing, the forms of Pb pollution in water are becoming increasingly diversified, and the environmental and human health hazards caused by Pb pollution are receiving increasing attention. A HCO–(Fe3O4)x composite adsorbent prepared by the coprecipitation method of Fe3O4 mixed in cerium-rich grinding and polishing sludge was used to remove Pb from water. The effects of Ce/Fe molar ratio, pH, dosing amount, and time on the adsorption of HCO–(Fe3O4)x for Pb removal were investigated and the adsorption isotherm model, adsorption kinetics, and adsorption mechanism were studied. The results showed that the maximum adsorption capacity of HCO–(Fe3O4)x on Pb(II) was 35.93 mg·g−1 at a Ce/Fe molar ratio of 1.5:1, pH 4–5, and temperature of 25 °C, and the removal rate could reach 96.05%; the process of Pb(II) adsorption by HCO–(Fe3O4)x was in accordance with the Langmuir isothermal adsorption model and the pseudo-second-order reaction kinetic model; chemisorption was dominant. Characterization results, such as EDS, XRD, and XPS, showed that the composite preparation of HCO with Fe3O4 increased the specific surface area of HCO–(Fe3O4)x and generated amorphous iron oxides, such as FeCe2O4, FeOOH, Fe3O4, and Fe2O3, which provided conditions for the formation of Fe-O-Pb and Ce-O-Pb complexes during the adsorption process, thus facilitating the adsorption removal of Pb(II). [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) transition metal dichalcogenides (TMDs) are considered to be promising building blocks for the next generation electronic and optoelectronic devices. Various doping schemes and work function engineering techniques have been explored to overcome the intrinsic performance limits of 2D TMDs. However, a reliable and long-time air stable doping scheme is still lacking in this field. In this work, we utilize keV ion beams of H2+ to irradiate layered WSe2 crystals and obtain efficient n-type doping effect for all irradiated crystals within a fluence of 1 × 1014 protons·cm−2 (1e14). Moreover, the irradiated WSe2 remains an n-type semiconductor even after it is exposed to ambient conditions for a year. Localized ion irradiation with a focused beam can directly pattern on the sample to make high performance homogenous p-n junction diodes. Raman and photoluminescence (PL) spectra demonstrate that the WSe2 crystal lattice stays intact after irradiation within 1e14. We attribute the reliable electron-doping to the significant increase in Se vacancies after the proton irradiation, which is confirmed by our scanning transmission electron microscope (STEM) results. Our work demonstrates a reliable and long-term air stable n-type doping scheme to realize high-performance electronic TMD devices, which is also suitable for further integration with other 2D devices. [ABSTRACT FROM AUTHOR]

Based on the coherent elastic, incoherent elastic, coherent inelastic and incoherent inelastic scattering processes, a code named SIRIUS is developed to produce thermal neutron scattering data for crystals in ENDF-6 format. The phonon band structures and projected phonon densities of states of 7LiF and BeF2 crystals were calculated by Hellman-Feynman Theorem combined with a lattice dynamics direct method. Finally the thermal neutron scattering data for 7LiF and BeF2 crystals are given.

The bearing internal load distribution and fatigue life estimation are accomplished based on the bearing static model at present, ignoring the gear engagement. Besides, bearings are modeled as a linear spring in gear dynamic models, failing to analyze bearing internal load. This article aims to study the bearing internal load fluctuation and corresponding bearing life in gear systems. A nonlinear dynamic model of the gear-bearing system is built, considering the time-varying mesh stiffness, the static transmission error, backlash, bearing clearance, and the nonlinear bearing force. The dynamic model is capable of calculating the bearing internal load. Based on the internal load, fatigue life is acquired using the linear damage theory. The numerical results show that the gear engagement has a significant influence on the bearing internal load analysis, in which periodic fluctuation is related to the mesh frequency and shaft frequency, resulting in the bearing life affected by gear meshing. Compared with the fatigue life predicted under the bearing static model, evident deviations are observed, pointing to the significant role of the gear engagement in the analysis of fatigue life estimation. [ABSTRACT FROM AUTHOR]

Under high-speed and heavy-load conditions, the influence of temperature on the gear system is extremely important. Basically, the current work on the effect of temperature mostly considers the flash temperature or the overall temperature field to cause expansion at the meshing point and then affects nonlinear factors such as time-varying meshing stiffness, which lead to the deterioration of the dynamic transmission. This work considers the effect of temperature on the material's elastic modulus and Poisson's ratio and relates the temperature to the time-varying meshing stiffness. The effects of temperature on the elastic modulus and Poisson's ratio are expressed as functions and brought into the improved energy method stiffness calculation formula. Then, the dynamic characteristics of the gear system are analyzed. With the bifurcation diagram, phase, Poincaré, and fast Fourier transform plots of the gear system, the influence of temperature on the nonlinear dynamics of the gear system is discussed. The numerical analysis results show that as the temperature increases, the dynamic response of the system in the middle-speed region gradually changes from periodic motion to chaos. [ABSTRACT FROM AUTHOR]