Inconsistent frequency and mode coupling are primary concerns of ultrasonic motors. These modal properties are influenced by motor features, including piezoelectric ceramics, stator teeth, or other supports attached on a stator. While this influence is understood intuitively and has been studied numerically, they have not been clarified analytically. This work develops the analytical model of the example cylindrical stator and uses it to study the influence of the features on the modal properties. In this model, the stator is considered as a thin ring with equally spaced features. The analytical solution of the model is obtained by using the direct perturbation analysis, which connects the feature number and the wave number with the modal properties, and naturally provides an effective means to achieve the coincident frequency and suppress or even eliminate the predominant mode coupling only by optimizing the combination of the two numbers. Simulation results are well consistent with the analytical conclusions. The main feature of this work is that a quick and quantitative understanding of the effects of deviation from the perfect cylindrical stator is obtained. In addition, the derived analytical results contribute to the applications of common ultrasonic motor design choices. Furthermore, while the terminology of a cylindrical stator is used in this work, the analysis method applies for other stators, such as the disc-like or linear stator.

Liquefaction can be considered to occur in saturated sand widely under seismic load, which will cause serious disaster, including road damage, ground subsidence, cracking of houses. Thus, it is quite necessary to study the liquefaction characteristics of saturated sand. For this aim, the undrained simple shear test on saturated sand under cyclic loading were simulated by three-dimensional distinct element method (DEM), where the stress-strain relationship, excess pore pressure ratio, mechanical coordination number and contact normal direction were analyzed. The results show that the liquefaction of saturated sand is manifested by the accumulation of excess pore pressure ratio. In addition, the mechanical coordination number gradually reduces and the sample anisotropy slightly fluctuates before the saturated sand reaches initial liquefaction. When the specimen approaches initial liquefaction, the mechanical coordination number drops abruptly and the sample anisotropy obviously increases.

As one of the basic industries in the manufacturing industry, the modeling and evaluation of resource utilization efficiency in the machining process is the premise of energy conservation and consumption reduction in the manufacturing industry. Mechanical processing is the process of using resources to change the shape and performance of the blank to form the workpiece and generate emissions. However, the current research on the utilization of machining process resources, whether focusing on energy efficiency or emissions, cannot provide a comprehensive solution to this problem. Therefore, this paper proposes a Data Envelopment Analysis (DEA) model with a slacks-based measure (SBM) to evaluate the resource utilization efficiency of a machining process with non-expected output. Through the relative effectiveness of DEA, the resource utilization efficiency of each processing process can be compared, which can provide a feasible and specific method for enterprises to evaluate their existing processing processes from the perspective of reducing unexpected output. In this case, the input-output model of the machining process is used to analyze the processed resource list. Then the mathematical model of each process in the processing process is established, and the dynamic resources are determined quantitatively. Finally, the accuracy of the method is verified by combining the resource utilization efficiency of each working procedure in the shaft gear machining process of an enterprise.

The development and utilization of renewable energy is an important part of national strategy. In this study, Cite Space was used to analyze the Knowledge Graph of relevant research literature and define the research hotspots and the key technologies in the field of renewable energy. Then, the domestic and foreign related patent data in the field of renewable energy were retrieved through the database of Wanfang, and Logistic model was used to make a comparative analysis of the life cycle of relevant technologies in this field, so as to predict the current development stage and future development trend of China's renewable energy technology.

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