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Copyright of Hydrogeology & Engineering Geology / Shuiwendizhi Gongchengdizhi is the property of Hydrogeology & Engineering Geology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aiming at the phenomenon of frequency coupling in the dynamic response of double planetary gears system，this paper uses MSC.Adams software to establish a dynamic simulation models for two typical connection forms of double planetary gears system. The meshing force is Fourier-decomposed and combined according to the two-row tooth frequency and its multiplication. The influence of joint stiffness，rotational speed and load on frequency coupling of double planetary gears is studied by the ratio of the amplitude of the two-part meshing force. The results show that when the joint stiffness of the connection shaft reaches 108 N·mm/（°） or more，the proportion of frequency coupling is stable，and the current gear tooth frequency influence ratio is always higher than the coupling gear frequency influence ratio. As the speed increases，the current gear tooth frequency influence ratio increases，and the load increases，the current gear tooth frequency influence ratio decrease，the coupling frequency influence ratio is opposite. For the parallel tooth row load and speed combination analysis，in the working range，the frequency coupling influence ratios in the two rows are similarly expressed，∑fh minus∑fb is proportional to the load ratio minus the speed ratio. In multi-row planetary gear system，the frequency influence ratio distribution conforms to the above-mentioned frequency coupling law of series and parallel row，and the frequency coupling of parallel row is more serious than that of series row.

[Objectives] The purpose of this paper is to study the way to establish finite element models with real geometric defects,and to predict and analyze the bearing capacity of a scale down pressureresisting cylindrical shell structure based on different types of defects.[Methods] Therefore,a geometric defect extraction method based on quadratic transformation is proposed,then the method of introducing the measured initial geometric defect,which is expressed by double Fourier series,is established. Finally, the buckling capacity of scale down pressure-resisting cylindrical shell under external pressure is analyzed and obtained based on eigenvalue modal defect and measured defect.[Results] The results indicate that Fourier series method only involves traversing of grid nodes and calculation of a few function values and can significantly improve the calculation efficiency of defect introduction without reducing the accuracy of calculation.[Conclusions] Fourier series method can provide guidance for accurate analysis of ultimate bearing capacity of cylindrical shell structure and structural optimization design.

[Objectives] In this paper, the harmonic characteristics of output voltage for a matrix converter (MC)in marine electric propulsion system are studied.[Methods] Based on triple Fourier Series,an analytical calculation method to determine harmonic components of MC is proposed. Firstly,combined with the triple Fourier Series,the analytical results of the harmonic components of output voltage for a matrix converter under the direct transfer function modulation strategy are derived. Then according to the results,the harmonic distribution characteristics as well as main harmonic components are analyzed. Finally,the feasibility of the method and the accuracy of the analysis conclusions are verified by comparative analysis against the Fast Fourier Transform(FFT) results of the output voltage waveform obtained from the test.[Results] It is found that the amplitude of common mode components with high frequency of fc ±fin and 2fc ±fin are higher.[Conclusions] This method can determine the amplitudes and frequency of different harmonic components precisely,which provides a theoretical basis for the study of harmonic suppression,and also improves the theory of harmonic analysis of matrix converter.

Aiming at the problem that the numerical atlas method can’t be used to synthesize the finitely separated positions design requirements for the planar four-bar mechanism,based on the complex function least square method,a method for realizing the feature extraction of finitely separated positions discrete points is proposed by using the Fourier series approximation fitting finitely separated position. The relationship of feature parameters between the finitely separated positions and their transformations,including translation,rotation,and scaling is found. Combining with numerical atlas method,the finitely separated positions design requirements path generation of the planar four-bar mechanism is realized. Examples are presented to illustrate the applicability and effectiveness of the proposed method.

A high-speed cam design method is proposed based on the Fourier series and principle of Minimum Gaussian square difference. The design principle for the cam of the Fourier series follower motion law（ referred to as the Fourier series cam） and the construction of its displacement function are analyzed. Taking the flat-bottom centering setting push rod-cam mechanism as an example,the cam profile of the Fourier series cam is designed. A valve train including the cam mechanism is established,the natural vibration modes and motion features of the valve are analyzed to validate the work property of the cam. The results show that the displacement curve of the valve is determined by the profile of the cam within a certain range of rotation speeds.The maximum value of velocity of the valve will increase with the increase of the rotation speed of shaft and the increase of the valve clearance. The acceleration of valve will increase first and then decrease in the rise process and will have a symmetric trend in the return period.

The study of the lower limb movement model of the human body is one of the core contents of the exoskeleton robot driving and control system. Aiming at the shortcomings of complicated fitting process,discontinuity after high order derivation of the model and so on in the fitting process of ankle joint motion model by using piecewise function,the Fourier series method is used to establish the model of the horizontal movement of the ankle joint in the sagittal plane,and the motion model of the ankle joint in the sagittal plane is established by using the polynomial fitting process,it has a simple,accurate,non-impact characteristics by the ankle articulation model obtained by the method,and the model is continuity and the conductivity. Finally,the model can be used to demonstrate the characteristics of the ankle movement in healthy people,at the same time,motion simulation is performed by ADAMAS to verify the correctness of the ankle driver used in exoskeleton robots. The study of the lower limb ankle movement model of the human body provides an important theoretical basis for studying the characteristics of the ankle movement in healthy subjects during normal walking,and provides a reference model for the driving and control of the ankle joint of the exoskeleton.

According to studying Angle cutting conditions of shearer drum cutting teeth distribution on the influence law of load spectrum,which provides reference for the design of the cutter tooth,in which equivalent test tooth holder to roll the same spiral blades cut line cut tooth load the real-time online monitoring,synchronous export analysis after storage.Experimental results show that the system is reliable,stable performance,can real-time dynamic testing of cutter tooth cutting force changes,through different cut line cut tooth time-cutting force change curves available:cutting force curve variation rule has the similarity,oblique cutting coal and rock,drum cutting tooth load whole curve peaks and troughs alternating form,cutting teeth with different cutting depth change of cutting force changing process;Same cutting resistance of greater than its feeding resistance,but its fluctuations are similar,have many irregular fluctuations;Single pick on the cutting resistance and traction resistance of instantaneous value obey the symmetry good Gamma distribution,the distribution parameters with pick in the cutting line spacing end plate distance relationship is a Fourier series,for the research on the rules of cutter tooth load spectrum provides a new method.