Molecular Dynamics of Neutral Polymer Bonding Agent (NPBA) as Revealed by Solid-State NMR Spectroscopy

Neutral polymer bonding agent (NPBA) is one of the most promising polymeric materials, widely used in nitrate ester plasticized polyether (NEPE) propellant as bonding agent. The structure and dynamics of NPBA under different conditions of temperatures and sample processing are comprehensively investigated by solid state NMR (SSNMR). The results indicate that both the main chain and side chain of NPBA are quite rigid below its glass transition temperature (Tg). In contrast, above the Tg, the main chain remains relatively immobilized, while the side chains become highly flexible, which presumably weakens the interaction between bonding agent and the binder or oxidant fillers and in turn destabilizes the high modulus layer formed around the oxidant fillers. In addition, no obvious variation is found for the microstructure of NPBA upon aging treatment or soaking with acetone. These experimental results provide useful insights for understanding the structural properties of NPBA and its interaction with other constituents of solid composite propellants under different processing and working conditions.National Natural Science Foundation (China) (21120102038)National Natural Science Foundation (China) (21373265)National Natural Science Foundation (China) (21003154

Solid-state NMR Investigation of the Host-guest Interactions in Gas Adsorption and Chemical Separation Using MOFs as Adsorbents

Due to its sensitivity to the local geometries and chemical environments, solid-state nuclear magnetic resonance (NMR) is widely applied to investigate the host-guest interactions between metal-organic frameworks (MOFs) and guest molecules in the studies of gas adsorption and chemical separation. Multi-nuclear, multi-dimensional and variable temperature solid-state NMR is employed to investigate the adsorption behavior, primary adsorption sites, dynamic property, and self-diffusion coefficients of light hydrocarbons and carbon dioxide inside the MOFs channels. Moreover, solid-state NMR spectroscopy is utilized to determine the adsorption selectivity, visualize the preferential adsorption and uncover the separation mechanism of light alkane/alkene mixtures inside MOFs. Furthermore, solid-state NMR is used to explore the detailed host-guest interaction mechanism between common chemicals and MOFs adsorbents. All these findings provide insights into deep understanding of the structure-property relationship for the application of functional MOFs in gas adsorption and chemical separation

Design and Locomotion Study of Two-DOF Actuator Driven by Piezoelectric–Electromagnetic Hybrid Mode

A piezoelectric actuator (PEA) has the characteristics of high control precision and no electromagnetic interference. To improve the degree of freedom (DOF) to adapt to more working scenes, a piezoelectric–electromagnetic hybrid-driven two-DOF actuator is proposed. The PEA adopts the composite structure of the lever amplification mechanism and triangular amplification mechanism. The structure effectively amplifies the output displacement of the piezoelectric stack and increases the clamping force between the driving foot and the mover. The electromagnetic actuator (EMA) adopts a multi-stage fractional slot concentrated winding permanent magnet synchronous actuator, which can better match the characteristics of PEA. The structure and working principle of the actuator are introduced, the dynamic analysis is carried out, and the factors affecting the clamping force are obtained. At the same time, the air gap magnetic field is analyzed, and the structural size of the actuator is optimized. The experiment shows that the maximum driving speed can reach 348 mm/s, the load capacity is 3 kg, the optimal initial rotor angle is 49°, the maximum torque is 2.9 N·m and the maximum speed is 9 rad/s, which proves the stability and feasibility of the actuator

Carbon isotope characteristics of the Middle–Upper Cambrian Xixiangchi Group and bottom boundary marks of Furongian Series in the Sichuan Basin and its adjacent areas

The Middle–Upper Cambrian Xixiangchi Group in the Sichuan Basin is mainly a set of dolomites of platform facies. In the past, there was no effective way to determine the bottom boundary mark of the Upper Cambrian strata, so natural gas exploration of this horizon lagged behind. In this paper, it is revealed from the C and O isotopic profile of debris that in the middle of the Xixiangchi Group, there is a positive excursion event of carbon isotopes that can be correlated all over the world, so it can be used as an important mark to identify the Furongian Series (equivalent to the Upper Cambrian strata). Then, based on the characteristics of electric curves, the Furongian Series boundary mark was determined and its classification program was worked out preliminarily. It is shown that during the deposition of the Xixiangchi Group, it is a paleo-geomorphologically gentle-slope carbonate platform which is high in the east and low in the east, and a thin–moderate dolomite layer which is thin in the west and thick in the east is deposited. This layer is vertically divided into 4 intervals. Besides, the bottom boundary mark of the Furongian Series in the Sichuan Basin and its adjacent areas can be determined by combining the SPICE (Steptoean Positive Carbon Isotope Excursion) event of carbon isotopes with the characteristics of electric curves. Finally, the carbon isotope mark of the Furongian Series bottom boundary is the SPICE event corresponding to the positive excursion which is regionally correlated, the corresponding electrical mark is the GR small peak areas in the middle of the Xixiangchi group, and the corresponding lithologic symbol is the argillaceous dolomite. The research results are conducive to the further subdivision of the Xixiangchi Group in the Sichuan Basin and its adjacent areas and promoting the study on sedimentary evolution and reservoir distribution laws so that gas exploration in this series of strata can be speeded up. Keywords: Sichuan Basin, Late Cambrian, Xixiangchi Group, Furongian Series, Stratigraphic mark, Carbon isotope, Positive excursion, GR, Sedimentary environmen

Short-term prediction of the power of a new wind turbine based on IAO-LSTM

Short-term wind power forecasting is of great significance to the real-time dispatching of power systems, but the short-term forecasting accuracy of wind power is not high. To this end, this paper proposes a hybrid prediction model that combines the Isolated Forest algorithm, the Synchronous Squeeze Wavelet Transform (SWT) method, the Aquila Optimizer (AO) and the Long Short-term Memory network (LSTM). Firstly, the Isolated Forest algorithm is used to detect abnormal data. Secondly, the SWT method is used to denoise the original power signal of the new wind turbine. Then, the wind power prediction model is established through the long short-term memory network algorithm. The OA is used to optimize the LSTM structure parameters to solve the influence of random parameters on the prediction accuracy. Finally, perform example verification. The results show that the proposed model is effective in power prediction of new wind turbine

An Ultra-Micro-Volume Adhesive Transfer Method and Its Application in fL–pL-Level Adhesive Distribution

This study is aimed at addressing the urgent demand for ultra-micro-precision dispensing technology in high-performance micro- and nanometer encapsulation, connection, and assembly manufacturing, considering the great influence of colloid viscosity and surface tension on the dispensing process in micro- and nanometer scale. According to the principle of liquid transfer, a method of adhesive transfer that can realize fL–pL levels is studied in this paper. A mathematical model describing the initial droplet volume and the transfer droplet volume was established, and the factors affecting the transfer process of adhesive were analyzed by the model. The theoretical model of the transfer droplet volume was verified by a 3D scanning method. The relationships between the transfer droplet volume and the initial droplet volume, stay time, initial distance, and stretching speed were systematically analyzed by a single-factor experiment, and the adhesive transfer rate was calculated. Combined with trajectory planning, continuous automatic dispensing experiments with different patterns were developed, and the problems of the transfer droplet size, appearance quality, and position accuracy were analyzed comprehensively. The results show that the average relative deviation of the transfer droplet lattice position obtained by the dispensing method in this paper was 6.2%. The minimum radius of the transfer droplet was 11.7 μm, and the minimum volume of the transfer droplet was 573.3 fL. Furthermore, microporous encapsulation was realized using the method of ultra-micro-dispensing

Structural Design and Analysis of Hybrid Drive Multi-Degree-of-Freedom Motor

Piezoelectric-driven multi-degree-of-freedom motors can turn off self-lock, withstand high and low temperatures, are small in size and compact in structure, and can easily achieve miniaturization. However, they have a short life cycle and limited applications. In addition, high-intensity operation will result in a decrease in their stability. Electromagnetic-driven multi-degree-of-freedom motors, on the other hand, are simple and highly integrated, but they are large in volume and lack positioning accuracy. Therefore, combining the two drive modes can achieve complementary advantages, such as improving the motor’s torque, accuracy, and output performance. Firstly, the structure of the hybrid drive motor is introduced and its working principle is analyzed. The motor can achieve single and hybrid drive control, which is beneficial to improving the performance of the motor. Secondly, the influence of magnetization mode, permanent magnet thickness, slot torque, and stator mode on the motor is analyzed. Thirdly, the structure of the motor is determined to be 6 poles and 15 slots, the thickness of the permanent magnet is 12 mm, and the radial magnetization mode is used. Finally, the mixed torque and speed of the motor in the multi-degree-of-freedom direction are tested by experiments, which indirectly verifies the rationality of the structure design

Fractional Sliding Mode Observer Control Strategy for Three-Phase PWM Rectifier

This research presents a novel current loop control strategy for a three-phase PWM rectifier system aimed at mitigating challenges related to substandard power quality, excessive current harmonics, and insufficient robustness. The suggested approach combines an extended state observer (ESO) with dual-power sliding mode control that is further enhanced by fractional-order micro-integral operators. This amalgamation enhances the adaptability of the controller to system dynamics and augments the flexibility of the current loop control mechanism. The results of this integration include diminished system oscillations, heightened immunity to external disturbances, and improved robustness and dynamics of the overall system. Through MATLAB/Simulink simulations, the effectiveness of the proposed control methodology is validated, demonstrating superior performance in terms of robustness, dynamic response, power quality enhancement, and mitigation of current harmonics when compared to conventional PI control and standard fractional-order dual-power sliding mode control techniques

Molecular Dynamics of Neutral Polymer Bonding Agent (NPBA) as Revealed by Solid-State NMR Spectroscopy

Neutral polymer bonding agent (NPBA) is one of the most promising polymeric materials, widely used in nitrate ester plasticized polyether (NEPE) propellant as bonding agent. The structure and dynamics of NPBA under different conditions of temperatures and sample processing are comprehensively investigated by solid state NMR (SSNMR). The results indicate that both the main chain and side chain of NPBA are quite rigid below its glass transition temperature (Tg). In contrast, above the Tg, the main chain remains relatively immobilized, while the side chains become highly flexible, which presumably weakens the interaction between bonding agent and the binder or oxidant fillers and in turn destabilizes the high modulus layer formed around the oxidant fillers. In addition, no obvious variation is found for the microstructure of NPBA upon aging treatment or soaking with acetone. These experimental results provide useful insights for understanding the structural properties of NPBA and its interaction with other constituents of solid composite propellants under different processing and working conditions