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With the intention of man-made radioactive aerosol separating and monitoring in a high radon environment, in this paper, a novel submicron virtual impactor was developed, and a numerical simulation model was established. Then, the rationality of the numerical method was validated by comparison to experimental data. Afterward, the variations of separation characteristics under different operating conditions of sample flow rate, minor flow ratio and clean air velocity ratio were discussed and analyzed in detail. In view of the different inertia between man-made and natural radioactive aerosol, the proposed novel submicron virtual impactor could provide a quicker approach to separate and detect the man-made radioactive aerosol particles. After that, the collection nozzle structure of the virtual impactor was improved based on the computational fluid dynamics analysis results. The results show that the proposed impactor has a higher separation efficiency and lower wall loss for fine particles compared to the conventional structures.

Lithium-ion capacitors (LICs) combine the advantages of both batteries and supercapacitors; they have attracted intensive attention among energy conversion and storage fields, and one of the key points of their research is the exploration of suitable battery-type electrode materials. Herein, a simple and low-cost strategy is proposed, in which SnO2 particles are anchored on the conductive porous carbon nano-sheets (PCN) derived from coffee grounds. This method can inhibit the grain coarsening of Sn and the volume change of SnO2 effectively, thus improving the electrochemical reversibility of the materials. In the lithium half cell (0–3.0 V vs. Li/Li+), the as-prepared SnO2/PCN electrode yields a reversible capacity of 799 mA h g−1 at 0.1 A g−1 and decent long-term cyclability of 313 mA h g−1 at 1 A g−1 after 500 cycles. The excellent Li+ storage performance of SnO2/PCN is beneficial from the hierarchical structure as well as the robust carbonaceous buffer layer. Besides, a LIC hybrid device with the as-prepared SnO2/PCN anode exhibits outstanding energy and power density of 138 W h kg−1 and 53 kW kg−1 at a voltage window of 1.0–4.0 V. These promising results open up a new way to develop advanced anode materials with high rate and long life.

General CuCo

Li-ion capacitors (LICs) are assembled from a lithium-ion battery (LIB)-type anode and a capacitor-type cathode, but their power density is limited by the battery anode. Looking for high electrochemical performance anode materials is an available approach to improve the properties of LICs. Herein, we report a porous Nb2O5@C hollow nanosphere composite material (3D Nb2O5@C), in which the hollow structure plays a role in buffering the volume expansion during the Li+ insertion and the outer carbon layer enhances the electrical conductivity. In a lithium half-cell, the composite electrode delivers a high capacity of about 134 mA h g−1 at 0.1 A g−1 and exhibits a capacity retention of 72% after 500 cycles. A lithium-ion capacitor fabricated with 3D Nb2O5@C as the anode displays a high energy density of 96.8 W h kg−1 and a high power density of 41 kW kg−1. Moreover, the capacity retention of the LIC is 75% at 2 A g−1 after 3000 cycles. This work shows that 3D Nb2O5@C has the potential to be a superior electrode material in energy storage devices.

Lithium-ion capacitors (LICs) combine the advantages of both batteries and supercapacitors; they have attracted intensive attention among energy conversion and storage fields, and one of the key points of their research is the exploration of suitable battery-type electrode materials. Herein, a simple and low-cost strategy is proposed, in which SnO

The paper proposes a novel inductive angular displacement sensor to measure large-diameter hollow rotating mechanical components in large science facilities. The sensor design includes a stator, a rotor with two layers of windings. The stator is fabricated according to the dimension of the rotor, which is the large-diameter hollow rotary mechanical components. Based on the principle of electromagnetic induction, the theoretical model of the proposed sensor is acquired by mathematical equations in detail. The proposed sensor design ensures integration of the large-diameter hollow rotating mechanical components with the stator, and solves the problem that the sensors cannot be coaxially installed in the closed-loop control process of large mechanical rotating parts. The performance of the sensor is evaluated by tests of the prototype sensor fabricated by printed circuit board technology, which manifests the effectiveness of the proposed sensor. The results demonstrate the value of original dynamic relative error is ±97.6″ over 0°–360° range, and the measurement error mainly includes first-order and second-order harmonic components. Therefore, the original errors are reduced by optimizing the angular displacement algorithm of the sensor, optimized results demonstrate the final relative accuracy of the sensor is ±3.5″ over the 0°–360° measurement range.

A permanent magnet synchronous motor (PMSM) driven system is a typical electromechanically coupled system. In this paper, to improve the operational performance and stability of the PMSM system, torsional vibrations due to the electromechanical coupling effects are studied. An electromagnetic excitation model was first established to consider the effect of torsional angle on magnetomotive force. Then, nonlinear torsional vibration equations of the driven system were obtained. In addition, an electromechanically-coupled torsional vibration mechanism based on natural frequency modulation of the system was revealed. Finally, the torsional vibration equations and coupled mechanism were validated against experimental results describing the actual torsional vibration and a numerical method was used to verify our theoretical analysis. The results provide a theoretical basis for the parameter design of electromechanical transmission systems.

General CuCo2O4 electrodes suffer a very low reversible capacity and poor cycling stability because of easily fading phenomena and volume change during cycling. To optimize the electrode, a facile method is conducted to fabricate a novel electrode of Cu@CuCo2O4@polypyrrole nanoflowers. Due to larger specific surface area and more electrochemical reactive areas of CuCo2O4@polypyrrole nanoflowers, the pseudocapacitance of the in situ grown CuCo2O4@polypyrrole (912 F g−1 at 2 A g−1) is much higher than the pristine CuCo2O4 (618 F g−1 at 2 A g−1). Remarkably, the CuCo2O4@polypyrrole (cathode) and active carbon (anode) are used to assemble an asymmetric supercapacitor, which exhibits a relatively high energy density of 90 Wh kg−1 at a power density of 2519 W kg−1 and 35 Wh kg−1 at a high-power density of 9109 W kg−1, and excellent cycling stability (about 90.4% capacitance retention over 10 000 cycles). The prominent performance of CuCo2O4@polypyrrole makes it as a potential electrode for supercapacitor.

This paper presents a novel calculation method for dynamic excitation of the 3-D modified double-helical gear pair in consideration of actual contact state. The 3-D modification method combines tip, root, and axial modification. Firstly, the tooth surface equation of double-helical gear with 3-D modification is derived and the calculation method for time-varying mesh stiffness (TVMS) of the modified double-helical gear pair is proposed and the effects of modification parameters on TVMS are studied. Secondly, the tooth surface load distribution is analyzed on the basis of TVMS for the double-helical gear pair. Accounting the influence of modification parameters on tooth surface friction coefficient, the time-varying friction excitation (TVFE) of the modified double-helical gear pair is researched. Besides, combining approach mesh stiffness of the modified double-helical gear pair and impact dynamic model, the calculation formula of meshing impact force (MIF) is proposed, and the effects of helix angle and modification parameters on MIF are discussed. The calculation methods of TVMS, TVFE and MIF proposed in this paper will be useful for accurate prediction about vibration and noise of the double-helical gear system.

We present a method for analyzing the transmission error of helical gear system with errors. First a finite element method is used for modeling gear transmission system with machining errors, assembly errors, modifications and the static transmission error is obtained. Then the bending-torsional-axial coupling dynamic model of the transmission system based on the lumped mass method is established and the dynamic transmission error of gear transmission system is calculated, which provides error excitation data for the analysis and control of vibration and noise of gear system.

The dynamical characteristics research of planetary gear system with tooth pitting is useful for early fault diagnosis and monitor. However, it is an unsolved puzzle to establish the relationship between tooth pitting and dynamical characteristics. In this study, a pitting fault analytical model is proposed to investigate the effects of tooth pitting on the gear mesh stiffness. Then this mesh stiffness with tooth pitting is incorporated into a dynamical model of planetary gear system, and the effects of the tooth pitting on the vibration characteristics is investigated. The simulated results show that the time-varying mesh stiffness is reduced with tooth pitting propagations along width or depth direction. The mesh frequency and its harmonics are mainly frequencies components in the frequency spectrum of dynamic mesh force, but sidebands caused by the tooth pitting are more sensitive than the mesh frequency and its harmonics. The tooth pitting frequency and its harmonics also increase with the rising rotational speed of the sun gear. In addition, both relative statistical indicators of RMS and Kurtosis increase with the growth of tooth pitting size. But the relative indicators have different sensitivity on the vibration signal type. These results could supply some guidance to the condition monitoring and fault diagnosis of planetary gear system, especially to the gear tooth pitting at early stage.

A rigid-flexible coupling multi-body dynamic model which contains the structure system and transmission system is developed and the bearing dynamic reaction force is calculated. Then a vibro-acoustic coupling model of the gear system is established by taking the frequency histories of bearing reaction force as the boundary condition and the surface sound pressure and airborne noise of gearbox are calculated. Next, the experimental study on the airborne noise is performed on the experimental prototype to verify the calculation method. Afterwards, the airborne noise optimization model is established by taking the sound pressure at multiple field points and frequency bands as objective functions and the structure parameters of gear system as design variables. Finally, the response surface method (RSM) and normal-boundary intersection method (NBIM) are used to analyze and reduce the airborne noise of gearbox.

A rigid-flexible coupling multi-body dynamic model which contains the structure system and transmission system of gear device is developed taking account of the internal excitations such as the time-varying mesh stiffness, tooth backlash and bearing stiffness and the external torque and speed excitation. Then the dynamic meshing forces of gear pairs and bearing reaction forces are calculated based on the dynamic theory of multi-body system. Afterwards, a vibro-acoustic coupling model of the gear system is established by taking the frequency histories of bearing reaction forces as the boundary conditions, and then the surface sound pressure of gearbox and the radiation noise of outer sound field are calculated. In fact, the proposed model would provide a quicker approach to analyze the radiation noise of the gear system during the design phase. Finally, the radiation noise experimental study is performed on the experimental prototype to verify the rationality of the analysis. The comparison analysis shows that computational results are in good agreement with the data of experiment test.

This paper presents a novel calculation method for accurately determining the meshing impact of helical gears. First, a mathematical model of meshing impact is constructed, the position of the impact point and the length of the impact contact line are determined, and the analytical formula of the helical gear pair impact force is deduced. Second, an approach for gear transmission mesh generation at any meshing position is presented, and an automatic modelling program for tooth mesh analysis is developed. The rationality of the analytical mathematical model is validated based on the developed finite element program. In addition, the meshing impact time is determined, and the effects of the input torque, input speed and tooth width on the impact force are analysed. The main conclusion is that the mathematical modelling method proposed in this paper can be used to quickly compute the meshing impact of helical gears.

An approach to calculating vibration modal characteristics of a marine gear system featuring confluence transmission based on the theoretical and the experimental modal analysis is given in view of the fact that it is difficult to accurately determine the modal data of the system because of its complex vibration mechanism. Firstly, a dynamic finite element model of a coupled gear-rotor-bearing-housing system is developed by combining the gearbox transmission model with the gearbox housing model using the modal parameter identification data. Then, the modal frequency and the mode of vibration can be obtained. In fact, the proposed model can provide a faster approach to analysing the mode of the gear system vibration. Finally, experimental testing of the mode of vibration is performed on the experimental prototype to verify the rationality of the theoretical analysis. A comparison of the two sets of results shows that the experimental results are in good agreement with the computational results, with a maximum error of 6.3%.

An approach to synthetically evaluate structure-borne noise and shock resistance of gear system is proposed. Firstly, dynamic finite element mesh model of gear system which includes shafts, bearings, gears and housing is established by using spring element, tetrahedral element and hexahedral element. Then dynamic finite element analysis model of gear system is gotten by loading the dynamic excitation force which can be calculated via the computation program of gear pair stiffness excitation, error excitation and impact excitation onto the tooth meshing line as boundary conditions. And the dynamic response of gear system is analyzed by using modal superposition method, and the vibration response experimental study of gear system is performed on the gearbox test-bed. The comparative analysis shows that computational results of the vibration response are in good agreement with the data of experiment tests and it could verify the rationality of dynamic finite element mesh model of gear system. Finally, taking acceleration shock excitation load into account on the basis of the dynamic finite element mesh model, the impact response of gear system is solved, and the shock resistance is analyzed based on the strength decision criterion.

The vibration characteristics of gear system have a significant influence on mechanical capacity and durable life of vertical mill reducer. In order to improve the performance of reducer, this paper present the research on inherent characteristic and dynamic response of vertical mill reducer. First of all, the finite element model coupled gear-rotor-bearing-housing of reducer is established including internal dynamic excitation. Then, the natural frequencies and natural modes are worked out by mode analysis, which indicates resonance phenomenon will not occur in reducer system. Finally, the vibration displacement, velocity and acceleration of the reducer are obtained through dynamic response analysis, which illustrates the structure vibration energy mainly concentrates in the engage frequencies and their multiples.