Carbon fiber composite materials have been widely applied in national defense fields, including aviation and aerospace, as well as civilian areas, such as automobile, electronic information, and high-speed machinery. During drilling, the cutting force significantly influences the workpiece machining quality and the insert service life. In this article, a simulation study using a polycrystalline diamond insert to drill carbon fiber composite materials was conducted in order to analyze the features of axial drilling force. Drilling experiments were carried out using various cutting parameters, and experimental results were compared to the simulation results. A regression analysis of the experimental data was made, and a cutting force model was constructed. The research results provide a foundation for the parameters optimization of carbon fiber composite material drilling processes.
To solve the problems of slow convergence speed and low accuracy of the process neural networks, this paper presents the tuning of the structure and parameters of a dynamic wavelet process neural network (DWPNN) using an improved particle swarm optimization (IPSO). A DWPNN with switches introduce to links is proposed. By tuning the structure and improving the connection weights of PNN simultaneously, it eliminates some ill effects introduced by redundant in features of DWPNN. The effectiveness of this method is proved by dynamic optimal design of RV (rot-vector) reducer.
A strain-insensitive wearable temperature sensor based on graphene fibers is proposed to solve the temperature measurement strain interference of wearable temperature sensors. The stress, strain, and conduction characteristics of the sensor are discussed based on finite element simulations and the principle of graphene conduction. The wearable temperature sensor showed excellent negative temperature coefficient characteristics. The responsivity of the sensor is 0.85% °C -1 , and the sensing resolution is 0.1 °C. The sensor shows good antiinterference below a tensile strain of 90% or a curved surface with a curvature of 0.5. When the sensor is attached to the human body, it reliably detects skin temperature changes at different curved surfaces.
The dry sorbent carbon dioxide capture technology is an efficient method to remove CO2 from flue gases. In this work, a multiphase hydrodynamic model with a sorption reaction of CO2 is developed and a two-dimensional computational fluid dynamics (CFD) simulation is carried out. The potassium carbonates are used as dry sorbents. A revised multi-scale interphase drag coefficient model is incorporated into the two-fluid model to consider the influence of clusters. The non-uniform distribution of the solid concentration and CO2 concentration is captured in the reactor. The core-annular regime can be found in the reactor. Predicted results are in good agreement with experimental results. The effects of operating conditions and parameters on the CO2 removal are evaluated. Simulated results indicate that reducing the inlet gas velocity can prolong the residence time of sorbents and enhance the overall CO2 removal. Improving the particle size and solid inventory will lead to an increase of CO2 removal to some extent.
OCR is a complicated process, there are many factors that can influence the recognition rate.Early period people tried to optimize the classifier to obtain high recognition rate, but the premise is that there is only one character no matter print or handwritten.For the performance of classifier has been promoted a lot, recognition rate for single character is high enough for commercial use.With the development of the demand for handwritten text recognition, how to raise the recognition rate of OCR system becomes very important.Unlike OCR system for print which focus on classifier.The research of OCR system for handwritten text is mainly on character segmentation.Statistical analysis showed that the mistake made by missegment is more than the mistake made by classifier.This is decided by the feature of handwritten text.There are more randomness and the lines are not horizontal, besides that, handwritten Chinese characters are more like overlapped and the gaps between characters are smaller.So this is the difficulty of handwritten Chinese characters.In this paper, the mutil-step searching nonlinear line exaction algorithm the paper proposed is easy and the accuracy is high, which can tackle the some weaknesses of direct projection method and indirect projection.
To reveal the nonlinear dynamic behavior of gear rattling vibration caused by gear backlash, a 2-DOF oscillator model with spring and damping elements was established. Based on the theory of discontinuous dynamical systems, the phase plane of gear motion was divided into three parts: the domain of tooth surface meshing motion, the domain of free motion and the domain of tooth back meshing motion. Introducing the global mapping and local mapping dynamics method, the process of gear teeth from impact to meshing and then impact and meshing was accurately described. The influence of different restitution coefficients on gear impact-meshing motion was studied by numerical simulation. The results showed that the grazing bifurcation caused by gear backlash will lead to complex mapping structures of the system and even chaos. The restitution coefficient directly affects the impact-meshing behavior. The introduction of meshing stiffness and restitution coefficient can reasonably characterize the elastic deformation and energy loss during gear meshing, which provides a theoretical model for the application of the theory of discontinuous dynamical systems to a more complex multi-degree of freedom flexible contact gear transmission system.
Taking the large deflection of flexible cables used in spacecrafts into account, a method is proposed to describe the position of any point on the cable using sagittal diameter, pitch angle, and deflection angle.Furthermore, the spatial attitude of the cable is determined using the mutual conversion of four coordinate systems.On the basis of the above, a mechanics model that comprehensively considers physical factors, such as mass, mechanical properties, and space constraints, is proposed in this paper.The forces and spatial attitudes of the equilibrium of the cable are also analyzed.In addition, Simulation analyses of the proposed mechanics model are performed.Results are in reasonable agreement with the actual assembly environment.
Background: The dynamics research of gear transmission systems mainly revolves around "excitation-model-response". The increasing number of dynamic incentive factors considered in the study has brought new problems to selecting modeling and solution methods and analyzing dynamic characteristics. Objective: This study aims to sort out the main research content of gear transmission system dynamics. Moepver, the commonly used analysis models, modeling, and solution methods are compared, and references for method selection and in-depth research are provided. Methods: This paper reviews the representative papers and patents related to the dynamic analysis of the gear system. The main contents of the dynamic excitation, dynamic model and dynamic characteristic analysis of the gear system are discussed, and suggestions for future development directions are given. Results: The dynamic excitations mainly considered in the current research are internal excitations and external excitations; random excitations are rarely considered. This paper analyzes and summarizes the commonly used modeling methods, model classification, solution methods, and dynamic characteristics research content. The advantages and disadvantages of several commonly used analysis models, modeling, and solution methods and their applicable occasions are summarized for the reference of researchers. Conclusion: The dynamics study of the gear system is a systematic work. It requires comprehensively considering the influence of dynamic excitations and selecting appropriate methods to establish and solve the model to obtain the dynamic characteristics that can better reflect the actual working conditions of the gear system. It is of great significance to improve the performance of the gear system.
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