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Highlights • The collision mechanism based on the material is developed. • A coupled multi-group-continuous method in incident-neutron energy is investigated. • Continuous model is used to resonance range the multi-group is used to other energy. • The coupled method has precision of continuous model and speedup exceeds two. Abstract It is well known that Monte Carlo neutron transport calculation based on the continuous cross section is with high precision, but the computing time is too long and memory consumption is large relative to the multi-group calculation. In contrast, the multi-group calculation is good both in terms of speed and memory relative the continuous calculation, but the short appears on S(α,β) and resonance energy region. For combining the advantages of these two models, we firstly develop the collision mechanism based on material. Then the coupled model is investigated based on the multi-group and continuous. The continuous model was employed to treat the thermal and resonance energy ranges, the multi-group model uses in the other energy ranges. Different energy ranges are coupled through the neutron scattering and fission contributions between each other. We chose the ITER 1-D sphere model for test example. This example contains a great amount of hydrogen, deep-subcritical and involves thermal scattering and resonance. The result of continuous model is as standard. The cases of criticality fission source and fixed source are considered. The comparison shows good agreement between coupled and continuous model. The speedup of coupled model increases about two times relative continuous model. The validity of coupled model has been proved by numerical simulation. [ABSTRACT FROM AUTHOR]

Highlights • Formulation of loaded transmission error (LTE) considering the tooth flank contact deformation, shear deformation especially shaft deformation under different bearing support. • Synthesis and analysis of single-stage spiral bevel gear transmission system by simulated loaded tooth contact analysis (SLTCA). • Comparison and analysis between the numerical formulation and SLTCA method. Abstract Collaborative manufacturing requiring both geometric and physical evaluations has been an increasingly important trend in the industrial applications of spiral bevel gears. It is an innovative attempt that design for six sigma (DFSS) is introduced to establish a model of above collaborative manufacturing system. In the DFSS-based modeling, in addition to establishing the basic framework, the related data-driven decision and optimization are proposed, respectively. The house of quality (HOQ) is firstly established to convert the voice of customer (VOC) into the critical to qualities (CTQs) and determine the geometric and physical evaluations. Then, the conventional machine setting modification is extended to the multi-objective optimization (MOO) modification considering both geometric and physical evaluations. The whole system is divided into the three data-driven sub-problems for their respective decision and optimization. First, the accurate measurement and compensation is used to operate the noise factors in the actual manufacturing. Second, a prescribed ease-off topography is identified as the target flank by MOO of the physical evaluations. An improved high-order modification of the optimal machine setting is performed to optimize the geometric performance. A case of study on measurement-modification-machining (3 M) collaborative manufacturing system is provided to verify the proposed model. [ABSTRACT FROM AUTHOR]

Highlights • An improved computation model to determine tooth contact analysis (TCA) in consideration of the different misalignment items. • Numerical determination of the loaded tooth contact mechanical performances considering misalignments for spiral bevel gears. • Implementation of the proposed method in collaborative consideration of the different loaded tooth contact mechanical performance evaluations. Abstract In order to meet demands of low noise and strong strength from their transmission of spiral bevel gears, loaded tooth contact analysis (LTCA) technique has become an increasingly access to determining the loaded tooth contact performances directly affecting the above demands. Moreover, the misalignment always is a main noise factor in the actual manufacturing and can directly affect the loaded tooth contact performances. Distinguish with the conventional simulated loaded tooth contact analysis (SLTCA) based on finite element simulation software package, a numerical loaded tooth contact analysis (NLTCA) method in consideration of the misalignments is presented for the spiral bevel gears. First, an improved computation model is established to perform the tooth contact analysis (TCA) considering the misalignments. Moreover, the principal curvature of contact points is also determined as the input for the proposed numerical LTCA. In the consideration of influences of the different misalignment, the loaded tooth contact performance items such as loaded contact force, loaded contact pattern, elastic contact deformation and loaded transmission error are calculated, respectively. Finally, the numerical instance including the results from SLTCA is given to verify the proposed method. [ABSTRACT FROM AUTHOR]

Understanding and controlling the growth of the vital Li 2 O 2 product, which is associated with intrinsic property of cathode surface, is essential to design effective cathode catalysts in Li-O 2 batteries. Herein we establish the correlation between the Li 2 O 2 growth model and the O 2 adsorbability on cathode surface that determines the pathway of the first electron transfer to O 2 . The weak O 2 adsorbability drives the solution growth model to form Li 2 O 2 toroid, while the strong one drives the surface growth model to thin film. Based on this mechanism, we select the N-doped carbon nanocages as cathode to realize a simultaneous large discharge capacity and low charge overpotential by forming copious thin-film Li 2 O 2 , deriving from its high specific surface area and enhanced O 2 adsorbability due to N-doping. Our study demonstrates an effective strategy to design advanced cathode catalysts in Li–O 2 batteries and potentially other metal-air batteries. [ABSTRACT FROM AUTHOR]

A dynamic model of spur gear pair combined with elastic shaft–disc–ring rotor is proposed to study the effect of web thickness on the dynamic characteristics. The shaft, disc and ring structures are simulated based on Timoshenko straight beam theory, Mindlin plate theory and Timoshenko curved beam theory, respectively. A universal method to derive the kinetic energy of rotating gear rotor is proposed based on multi-body dynamics theory and small deformation assumption. The elastic deformations of thin-web are included in the potential energy of time-varying mesh process. The equations of motion are established based on differential quadrature finite element method (DQFEM). The dynamic model of gear rotor is validated numerically by comparing to finite element (FE) model. The effects of web thickness on dynamic responses are studied by analyzing the dynamic deformations and stresses within web, which reveals that elasticity of web and shaft can reduce the vibration energy transferred to support structures, which contributes to vibration reduction of gear transmission system. [Display omitted] • A dynamic model of thin-webbed gear pair with fully elastic shaft–disc–ring​ rotor. • A universal modeling method for rotating structures. • Dynamic responses of displacements and stresses in gear web are discussed. • Effects of web thickness on dynamic behaviors are discussed. [ABSTRACT FROM AUTHOR]

A finite element node dynamic model of gear-rotor-bearing system with different lengths of crack by taking the time-varying mesh stiffness, backlash, transmission error excitation, flexible shaft and supporting bearing into account is proposed. The time-varying mesh stiffness of gear-pair with cracked tooth is obtained by applying the improved potential energy method. Due to the periodic features of the dynamic responses of the system when the tooth is cracked, the short term component (tooth profile error and tooth pitch error) and long term component (accumulative pitch error) transmission error excitations are introduced, the RMS values, kurtosis values, and frequency spectrum diagrams of the dynamic response with respect to input speed considering different forms of transmission error excitation are gained. The influences of transmission error excitation and crack length on the dynamic responses are investigated. The effectiveness of the RMS value, kurtosis value and frequency spectrum in the judgment of the crack length is analyzed. [ABSTRACT FROM AUTHOR]

A numerical simulation by using a computational fluid dynamics (CFD) code is carried out to predict heat and mass transfer during vacuum cooling of porous foods on the basis of mathematical models of unsteady heat and mass transfer. The simulations allow the simultaneous prediction of temperature distribution, weight loss and moisture content of the meats at low saturation pressure throughout the chilling process. The simulations are also capable of accounting for the effects of the dependent variables such as pressure, temperature, density and water content, thermal shrinkage, and anisotropy of the food. The model is verified by vacuum cooling of cooked meats with cylindrical shape within an experimental vacuum cooler. A data file for pressure history was created from the experimental pressure values, which were applied in the simulations as the boundary condition of the surface temperature. [Copyright &y& Elsevier]

A numerical investigation using a computational fluid dynamics (CFD) code is carried out to examine the influence of airflow on the thermocouple-measured temperature during air-blast chilling. A CFD model is developed to predict the temperature distribution and weight loss of the foods with and without the presence of thermocouples; the simulated temperature data are compared with experimental results. The comparison shows significant differences in the temperature results, especially near the surface of the foods being chilled. The study demonstrates that the temperature error depends not only on the length of the thermocouple remaining outside the product, but also the depth of the thermocouple inserted into the product. This study reveals a hidden source of experimental error and may help process engineers to better understand the phenomenon, and to correctly evaluate and examine their experimental and/or simulated temperature results for the air-blast chilling process. [Copyright &y& Elsevier]

The dynamic responses and load sharing features of a two-path split torque gear transmission system are investigated in this study. The possible combinations of shaft angles to ensure the gear pairs work properly are determined considering the adjacency relationship, concentric relationship, geometrical conditions and installation conditions. A dynamic model of the system considering time-varying mesh stiffness, backlash, static transmission error, stagger angle excitations and gyroscopic effects of gear body and flexible shaft is proposed. The natural characteristics of the system including natural frequencies and critical speeds are obtained. The influences of the shaft angle, asymmetric transmission error excitations and right-to-left stagger angle of double-helical gear teeth on the dynamic transmission error responses and load sharing features of the two-path split torque gear transmission system are investigated. Several references to determine the system parameters to improve the transmission property and load sharing performance of the system are provided based on the numerical simulation results. [ABSTRACT FROM AUTHOR]

• A novel wear prediction method is proposed considering friction and multi-parameter updates. • An iterative calculation model for TVMS is developed considering friction-wear coupling. • Dynamic responses influenced by tooth wear are revealed based on tribo-dynamic analysis. Gear wear becomes one of the important reasons for the fault of gear systems by causing tooth surface geometric deviations, changing time-varying mesh stiffness (TVMS), and increasing unloaded static transmission error (USTE). However, existing wear prediction models ignore the effects of friction and tooth profile parameter updates, which inevitably leads to unclear research on dynamic analysis. Based on the Archard equation, this work proposes a real-time iterative update model to calculate the wear evolution process with equivalent curvature radius updates. Subsequently, an improved friction-wear coupling model is developed to calculate the wear depth, TVMS, and USTE, with an iterative solution process based on the updating of friction and wear coefficients, and the load sharing factor (LSF). The effectiveness of the improved model is verified by wear experiments and finite element analysis. Based on the tribo-dynamic model of the gear-rotor-bearing systems, the dynamic characteristics considering friction-wear coupling are studied. The results indicate that the effect of friction intensifies as the speed decreases, while increased wear amplifies vibrations at most speeds, exacerbates meshing shocks, and initially expands then contracts the chaotic speed range. This work provides strong theoretical support for predicting wear depth and understanding gear wear behavior. [Display omitted] [ABSTRACT FROM AUTHOR]

• The proposed model can retain the intrinsic properties of bevel gears intact. • The effect of bevel gear body flexibility on modal and dynamic characteristics is analyzed. • The vibration patterns at the resonant speed of a bevel gear system are revealed. • The proposed model can quickly calculate the complete dynamic response of the system. Bevel gears, a crucial part of aircraft transmission systems, are more susceptible to wheel body vibration issues as lightweight requirements rise. In the past, the gear wheel body was often considered rigid while assessing the dynamic properties of gear systems. Constructing a bevel gear model with a thin-walled structure might not be appropriate for this modeling technique; this research suggests a dynamic model that considers the flexibility of bevel gears. The web and teeth structure of the gear are preserved by realistic modeling using three-dimensional hexahedral components. The component mode synthesis (CMS) approach reduces the model order for increased computational efficiency. To confirm the accuracy of the modeling method, the modal frequencies and vibration shapes of the proposed model single-gear shaft are compared with results from experiments and ABAQUS. By contrasting ABAQUS system-level meshing modal frequencies and vibration shapes, the accuracy of the system model assembly is further confirmed. The model examines the impact of bevel gear flexibility on the modal frequencies, modal vibration shapes, and system dynamic properties. The mode shape diagram at dangerous modal frequencies found using the modal strain energy technique and the vibration displacement cloud maps at resonance speeds computed using the Newmark- β method are mutually verified, and this demonstrates that lightweight bevel gears are more susceptible to excitation due to nodal diameter type vibrations. Proposed and traditional models anticipate substantially different resonance speeds since the traditional model assumes that the gear, being a rigid disk, can only excite the shaft's bending mode of vibration. The proposed model provides a more comprehensive description of the dynamic characteristics of bevel gear systems, providing a theoretical basis and optimization tool for the high-performance design, vibration reduction, and noise control of high-speed lightweight gear transmission systems. [ABSTRACT FROM AUTHOR]

In the aerospace transmission system, thin web gears are appreciated for reducing weight. Due to the force excitation from the helical gear, except the in-plane vibrations, gears are also vulnerable to out-of-plane vibrations which may cause system instability. However, few papers investigated how the out-of-plane vibrations influence the system in current years. This study analyzes both the in-plane and out-of-plane vibration modes of thin web gear based on the Timoshenko theory. The governing equations of three-dimensional displacements are derived from Hamilton's principles. The results show that instability will likely happen in out-of-plane vibration and the existence of discrete springs will deteriorate the instability. Additionally, frequency veering is a common phenomenon in a non-axisymmetry gear system. A comparison between the Timoshenko and Euler–Bernoulli models indicates little differences are founded at zero speed, but a significate gap comes up at high rotation speed. Lastly, a Timoshenko gear pair model with a coupling mesh stiffness matrix is presented. The natural frequencies divers from those with independent discrete springs fixed to the ground. The results indicate the importance of the coupling mesh stiffness matrix in system vibration analysis. This work is introductive in the thin web gear transmission system design. • A three-dimensional vibration model of the thin web gear is developed to obtain the in-plane and out-of-plane eigenvalues. • Natural frequencies comparison between the Timoshenko and Euler–Bernoulli model varying with rotation speed. • The coupling effect of the mesh stiffness in the gear pair is included for system vibration analysis. [ABSTRACT FROM AUTHOR]

• A gear dynamic model considering thin-walled gear and shaft. • The shortcomings of the traditional dynamic model are investigated. • The influences of the thin-walled hollow shaft are analyzed. This paper proposes a gear dynamic model considering the thin-walled gear and hollow shaft. The shell element is adopted to establish the gear-shaft finite element model instead of using the beam element and lumped mass element. The shortcomings of the traditional dynamic model and the influences of thin-walled hollow shafts are analyzed. Numerical results show that the simplification strategy of the traditional dynamic model will lose several vital modal information and evaluate excessive critical speeds. The proposed model obtains the extra resonant frequency in the high-speed region. However, the traditional model loses this phenomenon due to the simplified thin-walled structural features. The equivalence of the hollow shaft to a beam model requires the condition of a small radius-thickness ratio. Otherwise, it will lead to deviations in the predicted vibration characteristics. The proposed model helps to provide a theoretical basis for high-performance design and vibration and noise reduction of high-speed and lightweight gear transmission systems. [ABSTRACT FROM AUTHOR]

Hyperlipidemia as a major health issue has attracted much public attention. As a geographical indication product of China, Liupao tea (LPT) is a typical representative of traditional Chinese dark tea that has shown good potential in regulating glucose and lipid metabolism. LPT has important medicinal value in hyperlipidemia prevention. However, the active ingredients and metabolic mechanisms by which LPT alleviates hyperlipidemia remain unclear. This study aimed to systematically investigate the metabolic mechanisms and active ingredients of LPT extract in alleviating hyperlipidemia. Firstly, we developed a mouse model of hyperlipidemia to study the pharmacodynamics of LPT. Subsequently, network pharmacology and molecular docking were performed to predict the potential key active ingredients and core targets of LPT against hyperlipidemia. LC-MS/MS was used to validate the identity of key active ingredients in LPT with chemical standards. Finally, the effect and metabolic mechanisms of LPT extract in alleviating hyperlipidemia were investigated by integrating metabolomic, lipidomic, and gut microbiome analyses. Results showed that LPT extract effectively improved hyperlipidemia by suppressing weight gain, remedying dysregulation of glucose and lipid metabolism, and reducing hepatic damage. Network pharmacology analysis and molecular docking suggested that four potential active ingredients and seven potential core targets were closely associated with roles for hyperlipidemia treatment. Ellagic acid, catechin, and naringenin were considered to be the key active ingredients of LPT alleviating hyperlipidemia. Additionally, LPT extract modulated the mRNA expression levels of Fxr , Cyp7a1 , Cyp8b1 , and Cyp27a1 associated with bile acid (BA) metabolism, mitigated the disturbances of BA and glycerophospholipid (GP) metabolism in hyperlipidemia mice. Combining fecal microbiota transplantation and correlation analysis, LPT extract effectively improved species diversity and abundance of gut microbiota, particularly the BA and GP metabolism-related gut microbiota, in the hyperlipidemia mice. LPT extract ameliorated hyperlipidemia by modulating GP and BA metabolism by regulating Lactobacillus and Dubosiella , thereby alleviating hyperlipidemia. Three active ingredients of LPT served as the key factors in exerting an improvement on hyperlipidemia. These findings provide new insights into the active ingredients and metabolic mechanisms of LPT in improving hyperlipidemia, suggesting that LPT can be used to prevent and therapeutic hyperlipidemia. [Display omitted] • An integrated strategy to assess the amelioration of LPT in hyperlipidemia. • Obvious alleviation of hyperlipidemia observed in mice intervened with LPT. • Key microbiota and active ingredients of LPT improving hyperlipidemia. • LPT with great potential for the prevention and treatment of hyperlipidemia. [ABSTRACT FROM AUTHOR]

• Numerical prediction methods for elastic behavior of anisotropic and quasi-isotropic webs are proposed. • The iterative calculation methods of meshing behavior for two hybrid metal-composite gears are unified. • The calculation accuracy and efficiency of the proposed method are verified. • Detailed discussion on effects of hybrid gears replacing full metal gears. • Multi-parameter design to reduce mesh stiffness fluctuations. Thin-web structures are the primary strategy for lightweight gears in the aerospace and automotive fields, but current research mainly focuses on metal thin web, lacking understanding of the application of anisotropic and quasi-isotropic composite thin-web gears. Focusing on accurate and efficient calculations of mesh stiffness and load sharing ratio, this work develops a unified numerical analysis method to assess the meshing behavior of the two hybrid metal-composite gears. Multi-scale numerical prediction methods for elastic properties of anisotropic composite and homogeneous laminated webs are established, and two tooth-loading deformation calculation methods for metal-composite-metal gear bodies with different web widths are developed separately. A numerical analysis method is proposed by unifying the iterative calculation process of the two hybrid gears through deformation coordination relationships, which is also applicable to full metal gears. Finally, extensive comparisons with the finite element method (FEM) and existing numerical method verify the proposed analytical method (PAM). The investigation results reveal the impact of replacing full metal gears with these two hybrid gears on the meshing behavior and further elucidate the advantages of using composite webs for micro and macro parameters design in adjusting the mass and stiffness and reducing mesh stiffness fluctuations. This work provides a new analytical method for the structural design and performance assessment of lightweight hybrid metal-composite gear systems. [ABSTRACT FROM AUTHOR]

• A light-weight SGTS model considering the elasticity of shaft and gear body. • A meshing model considering the movements of the mesh points along the ring. • The analysis on vibrations within the gear body is achievable. • The gear's elasticity decreases the transmission accuracy and reduces the vibration intensity. A dynamic model of light-weight spur gear transmission system (SGTS) considering the elasticity of shaft and gear body is established to study the influences of the elasticity of the gear body on the dynamic characteristics. The spur gear is simplified as elastic ring and support springs stemming from the elasticity of the gear web. The shaft and ring are modelled based on Timoshenko beam theory. The kinetic energy of the elastic shaft-ring gear rotor is obtained based on multibody dynamic theory. A time-varying meshing model is proposed considering the movements of the meshing points along the base circles of gears. The differential equations of the SGTS are formulated by differential quadrature finite element method (DQFEM). The present model is validated by compared to lumped-mass model (LMM) by setting the elasticity of the gear body to be infinitely small. The influences of the elasticity of the gear web are studied. The results show that the elasticity of the gear web can reduce the intensity of the vibration. [ABSTRACT FROM AUTHOR]

• A thermal expansion model of tooth profile under the steady bulk temperature field is established. • An analytical method for calculating mesh stiffness of spur gear considering thermal effect is proposed. • The proposed models are verified by the finite element method. • The effects of temperature on mesh stiffness, load sharing ratio and loaded static transmission error are analyzed. • The difference between uniform and non-uniform temperature field on mesh stiffness are discussed. Thermal effect is an important cause of engineering failure of gear system. However, the lack of accurate model limits the research on the thermal behavior of gear transmission system. Here, based on the linear thermal expansion theory, involute profile theory and energy method, the thermal expansion model, the mesh stiffness model, the load sharing ratio model and the loaded static transmission error model of spur gears are proposed which comprehensively consider the thermal changes of material properties, theoretical involute, thermal profile error and actual contact positions. The corresponding finite element models are established to verify the accuracy of the proposed model and published models. The results indicate that the proposed model is accurate enough. The increase of temperature leads to the decrease of mesh stiffness, the unevenness of load sharing ratio and the increase of loaded static transmission error, accompanied by the phenomenon of earlier meshing. The hub bore radius has obvious influences on the thermal profile error and mesh stiffness, and the load torque also has apparent influences on mesh stiffness. The research provides supports for gear thermal effect analysis and gear system design. [ABSTRACT FROM AUTHOR]

• Two kinds of comprehensive modification methods are deduced. • An improved analytical method for mesh stiffness with modification is established based on the slicing theory. • The ratio of double-teeth engagement changes with comprehensive modification. • Higher computational efficiency and accuracy compared with the published model. • The bearing capacity of gears obtained by the two methods is different. Comprehensive modification refers to a modification method that simultaneously performs lead crown modification and tooth profile modification, which is widely used in precision gear manufacturing. However, there are few time-varying meshing stiffness (TVMS) models of spur gears with comprehensive modification. Based on the actual manufacturing methods and slice theory, an improved analytical model (IAM) for calculating the TVMS considering the coupling modification is established. The model does not require to use the finite element method (FEM) to determine the correlation coefficients. The IAM is compared with the published models and verified by the FEM. The results show that the IAM has higher accuracy and efficiency in the calculation of lead crown modification, tooth profile modification and comprehensive modification. The gear bearing capacity of machining method 2 is better than that of method 1. It is useful to improve the calculation accuracy to choose the number of slices reasonably according to the modification amount. [ABSTRACT FROM AUTHOR]

A multi-node dynamic model is proposed for the gear system composed of face gear meshing, rigid gear rotors, flexible shafts and deformable bearings, and the model is applied to investigate the characteristics of the system. Firstly, as the existing vector formula of angular velocity ignores the torsional deformation, a new formula including torsion, bending and translation is derived, and accordingly the motion equations of rotors and beam elements are formulated. The gyroscopic effect is considered in the gear rotors and shaft beams. Then, the node equation of face gear meshing is derived according to the characteristics of face gear drives, in which the gear backlash, meshing damping, time-varying mesh stiffness and transmission error excitation is involved. Finally, the dynamic model of the face geared rotor-shaft-bearing system is established with nodes assembled. The natural characteristics and the dynamic responses are investigated. Moreover, the proposed model is compared with the lumped parameter model and applied to explore the dynamic responses to variable support stiffness and support spans. Results indicate that the parameters of input shaft have enormous influence on dynamic responses rather than that of output shaft, and the influence mainly comes from the support close to meshing. • A rotor-shaft-bearing dynamic model with multiple nodes of the face gear transmission system is established and verified. • A new formula of angular velocity vector with 6 DOFs including torsion, bending and translation is derived. • The natural characteristics and dynamic responses are investigated. • The influence of support stiffness and support span on dynamic responses is explored. [ABSTRACT FROM AUTHOR]

• Development of a general mathematical model of finite length squeeze film dampers (FLSFD). • Development of modeling in the field of bevel gear systems supported on FLSFD. • The vibration reduction characteristics of bevel gears equipped with FLSFD is studied. • The response sensitivity to the length and radial clearance of FLSFD is discussed. • The proposed model is verified by comparing with the conventional model. Though finite length squeeze film dampers (FLSFD) are practically and effectively applied to vibration attenuation, they have not been popularly used in bevel gear systems (BGS) due to the limitations of the existing models of FLSFD. The present work proposes a general approach for modeling and calculating the nonlinear oil-film force of FLSFD, which is introduced into system motion equations to model the BGS supported on FLSFD mathematically. Comparisons with conventional methods show the superiorities of the proposed model in terms of computational accuracy and versatility. The damping characteristics of FLSFD are examined by comparing the dynamic behaviors of the BGS with and without FLSFD. Besides, the response sensitivity of the system to different parameters, including the length and radial clearance of FLSFD, is also discussed. The results show that FLSFD can significantly reduce the vibration amplitude passing through the critical speeds and suppress the nonlinear characteristics of the system, such as bistable state responses and jump phenomena. The results also reveal a dependence of the damping performance on the choice of the FLSFD design parameters. [ABSTRACT FROM AUTHOR]

The large Schottky barriers formed at metal–semiconductor junctions severely limit the development of transition metal dichalcogenide (TMDC)-based ultrathin electronics and optoelectronics. Various approaches to create Ohmic contacts at TMDC and metal interface have been developed, including contact phase engineering, contact doping, buffer layer engineering, and contact integration engineering. Here, we report degenerate electron doping of mono- and bi-layer tungsten diselenide (WSe 2) by a molecular organometallic donor, [RuCp*(mes)] 2. In-situ evaporation of [RuCp*(mes)] 2 molecules onto WSe 2 field-effect transistors in vacuum leads to a remarkably diminished gate dependence of the transport property and a large enhancement of electrical conductance by five orders of magnitude, implying the great potential of this doping approach in tuning the Schottky barrier for TMDC devices. The interfacial electronic structure at the WSe 2 –dopant interface was revealed through the combination of in-situ photoelectron spectroscopy investigations and theoretical calculations. Moreover, the doped device is found to be robust in oxygen and nitrogen atmosphere and also moderately stable in humid air, which is favorable in device applications. [ABSTRACT FROM AUTHOR]

Hybrid metal-composite gears are designed for weight optimization and vibration/noise control in gear transmission systems. However, it is time-consuming and expensive to analyze the meshing characteristics of hybrid gears based on the finite element method (FEM) and experiment. Therefore, this work presents an efficient analytical method (AM) for calculating gear body-induced tooth deflections of hybrid gears. Based on the multi-scale modeling method, mechanical properties of the two-dimensional triaxial braided composite (2DTBC) web are predicted by integrating micro yarn properties, meso braiding structures, and macro configuration. Subsequently, boundary problems of isotropic and anisotropic planar elastic rings are investigated to deduce analytical formulas for gear body-induced tooth deflections of hybrid gears considering structure coupling effect. The comparison with the FEM demonstrates that the proposed AM can accurately and effectively estimate gear body-induced tooth deflections. More results show that periodic variation exists in gear body-induced tooth deflections within one rotation cycle, while the rim thickness contributes more to weight reduction and the amplitude and fluctuation of tooth deflections than the braiding angle. This work provides beneficial guidance for the meshing behavior and weight reduction design of hybrid gears. [Display omitted] [ABSTRACT FROM AUTHOR]

• Quantitative extraction of 3D spalling characteristics by surface measurement technology. • Development of mesh stiffness model for lightweight spalling gear pair. • The coupling modulation phenomenon between spalling and holes are investigated. • Identification of spalling by time and frequency domain characteristics. Focusing on gear transmission systems having thin web and hole structures for energy saving and weight reduction, this work aims to propose an effective method for dynamical modeling and characteristics identification of spalling in lightweight gear systems. A novel three-dimensional (3D) spalling morphology modeling method is developed by the optical scanner. Subsequently, an analytical-finite element (AFE) model is established to calculate the mesh stiffness with weight reduction structures and spalled teeth. Additionally, the discrete tooth surfaces from coordinate measuring machines (CMMs) are used to calculate the no-load static transmission error (NLSTE). A rigid-flexible coupling dynamic model is introduced into the gear-rotor-bearing system considering the lightweight rotor and friction characteristics. The effects of spalling fault levels, the number and distribution form of spalled teeth on dynamic characteristics of the lightweight gear system are investigated. The numerical and experimental results demonstrate the existence of coupling modulation between spalling and holes, but it can still be identified by time and frequency domain characteristics. The proposed model and analysis results provide important references for identifying spalling in lightweight gear systems. [ABSTRACT FROM AUTHOR]

• Macro tooth flank modeling, discretization and discrete point interpolation. • Determination of autocorrelation function from the actual measurement. • Fast Fourier transformation (FFT) based micro flank topography reconstruction. • Comprehensive effect considering both macro and micro flank. • Micro flank geometric topography reconstruction for spiral bevel and hypoid gears. Focusing on comprehensive effect of both macro and micro geometries, accurate flank geometric topography design in a micro scale is developed for spiral bevel and hypoid gears showing a complex flexural behaviors. Firstly, macro flank modeling is performed for determining sparse tooth surface by using the discrete point interpolation. For micro-scale and smooth flank points, the vector between the current point and the adjacent tooth surface point are used as the tangent vector, and the vector in normal direction is obtained by calculating vector product of tangent vector. Then, fast Fourier transform (FFT) method is employed for the micro flank geometric topography reconstruction considering comprehensive effect. While determining the height distribution parameters from the actual measurement, autocorrelation function (ACF) is established to obtain the reconstructed roughness height matrix, and these microscopic height data are added to the corresponding macroscopic smooth tooth surface points in the normal direction for accurate micro flank geometric topography generation. The proposed method is exercised with an example double helical grinding spiral bevel gear from an aerospace application to demonstrate the impact of reconstruction design on flank performance. [ABSTRACT FROM AUTHOR]

To establish a bridge between grinding tool parameters and loaded tooth fatigue life, an innovative data-driven root flank bending fatigue life forecasting and optimization via Top-Rem tool parameters was proposed for grinding spiral bevel gears. The recent machine settings modification is extended into grinding Top-Rem tool parameters modification in case that geometric accuracy and root bending fatigue life are integrated into a collaborative optimization. The proposed Top-Rem modification includes three key steps: (I) arc-shaped blade, (II) top part, and (III) top fillet part. Then, while root bending stress is determined by using finite element method (FEM)-based simulated loaded tooth contact analysis (SLTCA), data-driven fatigue life forecasting is developed by correlating with the multiaxial fatigue damage model based assessment. Moreover, data-driven bending fatigue life optimization model is established by using Top-Rem tool parameters modification, where the important constraints in target flank determination includes: (i) root overcutting, (ii) geometric accuracy, and, (iii) fatigue life. For high accuracy and efficiency, two different strategies are proposed: (i) the different parameters modification types; and, (ii) sensitivity analysis of grinding Top-Rem tool parameters. Finally, proposed method can verify that bending fatigue life can be significantly improved by modifying the key Top-Rem tool parameters in early stage of the whole life product development for spiral bevel gears. [ABSTRACT FROM AUTHOR]

This research paper presents a unified Fourier series solution to solve the vibration problem of functionally graded carbon nanotube-reinforcement composite (FG-CNTRC) cylindrical shells, conical shells and annular plates subjected to general boundary conditions, so as to enrich the existing research results on FG-CNTRC structures. Utilizing a micro-mechanical model based on the developed rule of mixtures, the effective material properties of the FG-CNTRC structures which is strengthened by single-walled carbon nanotubes (SWCNTs) are scrutinized. The first-order shear deformation theory (FSDT) and the virtual boundary method are applied to achieve the energy expressions of FG-CNTRC structures. On the basis of that, the unified Fourier series solution in conjugation with the modified Fourier series and Ritz method, is utilized to receive characteristic equation of the structural vibration. The correctness, convergence and several advantages of the present methodology are verified by numerous numerical examples. Furthermore, some novel numerical results, including the vibration results of FG-CNTRC cylindrical shells, conical shells and annular plates accompanied with classical boundary, elastic boundary, classical-elastic mixed boundary and parameterized results of structure and material parameters, will be presented for future researchers. [ABSTRACT FROM AUTHOR]