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The working conditions (i.e., gas content, working pressure, and working temperature) of oil in the actual hydraulic system are always in a dynamic process, which will cause the basic properties of oil (i.e., density, absolute viscosity, and effective bulk modulus) to change and further generate changes of the flow characteristics in the straight conjugate crescent gear pump (SCCGP). However, no clear explanation has been given for the variation of the flow characteristics of the SCCGP with the working conditions in previous studies. This paper first expounds the gear pair profile equations used to draw the tooth profile curves and the equation applicable to the calculation of the geometric displacement at the given geometric parameters. Subsequently, the mathematical models of the oil's basic properties are analyzed, and it is explained how the changing working conditions affect the changes in oil properties. After that, the paper designs an orthogonal test scheme and applies it to the study of the flow characteristics of the SCCGP for the first time to optimize its working conditions. Then, the paper performs simulations in commercial CFD numerical software, and the change laws of the internal flow field, flow pulsation, pressure pulsation, volumetric efficiency, and total efficiency of the SCCGP at different working conditions are analyzed in detail. The working conditions for decreasing pulse rate and improving total efficiency are summarized. Finally, for model validation purposes, the paper elucidates the construction process of a high-pressure positive displacement pump test system and carried out experimental research. The simulation and actual measurement results are compared under the same working conditions. The results validate the accuracy of the simulation model and the potential for future analytical studies. [ABSTRACT FROM AUTHOR]

Exceptional precision and excellent resolution reconstruction of sea surface currents are beneficial for exploring complex oceanic dynamic processes. Normally, this required physical inversion models for global or regional oceans are constructed to reconstruct oceanic currents. These models are based on the analysis of sea surface geostrophic and Ekman currents derived from satellite observations of sea level and wind stress fields. Nevertheless, the presence of various typical dynamic processes in marine environments, such as mesoscale eddies and small-scale waves, continues to pose challenges in accurately reconstructing oceanic currents. Meanwhile, any product of surface current that neglects the contribution of wave motion would, at best, be incomplete. Therefore, in this paper, we introduce an accurate sea surface current product at a depth of 15 m, named GEST (Geostrophic-Ekman-Stokes-Tide). This product is produced by a multi-scale dynamics-informed neural network that learns the intricate representation of concealed characteristics in Ekman, geostrophic currents, wave-induced Stokes drift, and TPXO9 tidal currents. Its structure design is predicated upon the intricate coupling relationships between various ocean surface components and the veritable currents discerned by the deployment of drift buoys, with each ocean surface component correlating to discrete physical processes. Compared with the prevailing product, the GEST confers an elevation in precision by approximately 9.2 cm/s over the traditional multinomial fitting method, 10.4 cm/s beyond the OSCAR, and 8.81 cm/s surpassing GlobCurrent. [ABSTRACT FROM AUTHOR]

It is well understood that isolated eddies are presumed to propagate westward intrinsically at the speed of the annual baroclinic Rossby wave. This classic description, however, is known to be frequently violated in both propagation speed and its direction in the real ocean. Here, we present a systematic analysis on the divergence of eddy propagation direction (i.e., global pattern of departure from due west) and dispersion of eddy propagation speed (i.e., zonal pattern of departure from Rossby wave phase speed). Our main findings include the following: 1) A global climatological phase map (the first of its kind to our knowledge) indicating localized direction of most likely eddy propagation has been derived from 28 years (1993–2020) of satellite altimetry, leading to a leaf-like full-angle pattern in its overall divergence. 2) A meridional deflection map of eddy motion is created with prominent equatorward/poleward deflecting zones identified, revealing that it is more geographically correlated rather than polarity determined as previously thought (i.e., poleward for cyclonic eddies and equatorward for anticyclonic ones). 3) The eddy–Rossby wave relationship has a duality nature (waves riding by eddies) in five subtropical bands centered around 27°N and 26°S in the two hemispheres, outside which their relationship has a dispersive nature with dominant waves (eddies) propagating faster in the tropical (extratropical) oceans. Current, wind, and topographic effects are major external forcings responsible for the observed divergence and dispersion of eddy propagations. These results are expected to make a significant contribution to eddy trajectory prediction using physically based and/or data-driven models. [ABSTRACT FROM AUTHOR]

Systematic eddy propagation with a westward dominance is a well-documented feature in the global ocean, thanks to the availability of constellated altimeter measurement of sea level anomaly with a centimeter-level accuracy. According to their zonal speed relative to the phase speed of the first baroclinic Rossby wave, we propose that eddies can be divided into two modes: "eddy trains" and "eddy jets". The former refers to isolated eddies intrinsically guided by the long Rossby wave theory in zonal propagation, meanwhile significantly advected by energetic extratropical currents (via Doppler-like effect) and equatorial planetary waves (basically Kelvin waves). The latter refers mostly to "geared" eddy dipoles (also known as "modons" governed by the equivalent barotropic vorticity equation) that propagate with a "super" speed escaping from the Rossby wave guide. In this study, departure and reversal of eddy trains from the Rossby theory are analyzed and compensated, meanwhile the signature and mechanism of eddy jets are identified and revealed. As a result, three distinct regimes are observed in oceanic eddy propagation: A primary Rossby regime (∼66%, westward), a secondary anti-Rossby regime (∼33%, eastward, modulated by Doppler-like and Kelvin wave effects), and a third minor non-Rossby regime (∼1%, zonally neutral, of dipolar nature with gear effect). The first two regimes combine to form the eddy trains, while the third regime belongs to the eddy jets. A clear understanding of the mechanism and pattern of the complex eddy propagations is critical to marine science in general, and to eddy science in particular. • Eddies can be intrinsically divided into two regimes: "eddy trains" and "eddy jets". • "Eddy trains" refer to isolated eddies guided by the long Rossby wave theory. • "Eddy jets" refer to "geared" dipolar eddies propagating with a super speed. [ABSTRACT FROM AUTHOR]

As a precision mechanical component to reduce friction between components, the rolling bearing is widely used in many fields because of its slight friction loss, strong bearing capacity, high precision, low power consumption, and high mechanical efficiency. This paper reviews several excellent kinds of study and their relevance to the fault detection of rolling bearings. We summarize the fault location, sensor types, bearing fault types, and fault signal analysis of rolling bearings. The fault signal types are divided into one-dimensional and two-dimensional images, which account for 40.14% and 31.69%, respectively, and their classification is clarified and discussed. We counted the proportions of various methods in the references cited in this paper. Among them, the method of one-dimensional signal detection with external sensors accounted for 3.52%, the method of one-dimensional signal detection with internal sensors accounted for 36.62%, and the method of two-dimensional signal detection with external sensors accounted for 19.72%. The method of two-dimensional signal detection with internal sensors accounted for 11.97%. Among these methods, the highest detection rate is 100%, and the lowest detection rate is more than 70%. The similarities between the different methods are compared. The research results summarized in this paper show that with the progress of the times, a variety of new and better research methods have emerged, which have sped up the detection and diagnosis of rolling bearing faults. For example, the technology using artificial intelligence is still developing rapidly, such as artificial neural networks, convolutional neural networks, and machine learning. Although there are still defects, such methods can quickly discover a fault and its cause, enrich the database, and accumulate experience. More and more advanced techniques are applied in this field, and the detection method has better robustness and superiority. [ABSTRACT FROM AUTHOR]

As a medium and low pressure gear machine without automatic compensation structure for axial and radial clearances, the friction pairs in the straight conjugate internal gear pumps (SCIGPs) depend on the fixed small clearances to seal, lubricate and transfer the force. The oil film design of the friction pairs has become an important part of gear pump design. However, there has never been a publicly published research on the oil film design of the SCIGP in past literature. This paper applies orthogonal test to the oil film design of the SCIGP for the first time to determine the best working clearances. With this goal, the paper first provides the mathematical models for analyzing the internal leakage flow and the viscous friction loss, which elucidate the relationships between the leakage and the friction loss with working conditions. After that, the orthogonal test scheme for numerical simulation was designed on the basis of determining the range of oil film thickness. The paper also propounds the viewpoints of using the range-method to estimate the primary and secondary relationship of factors and determining the optimal combination according to the test target. Based on this concept, the main factors affecting the target are procured and the optimal working clearances of the friction pairs are determined. For the purpose of verifying the model, the redesigned prototype was tested and compared with the simulation results. The results validate the applicability of the simulation model and the correctness of the simulation method. Finally, the paper summarizes the ways to improve the total efficiency and the working conditions at the highest efficiency. [ABSTRACT FROM AUTHOR]

Mesoscale eddies exist throughout the global ocean and significantly impact local vertical marine stratification through the physical processes of stirring and pumping. While the vertical transportation dynamics of eddies are known, the contribution to the displacement of pycnocline depth from eddies has not been comprehensively investigated. In this study, the 17-year Argo dataset and satellite altimetry data are used to estimate the deepening and uplifting of the pycnocline depth induced by anticyclonic eddies (AE) and cyclonic eddies (CE), respectively. Pycnocline displacements exhibit multiple geographic and seasonal trends, with the largest magnitude occurring in spring. More pronounced displacements are concentrated in mid-latitudes, particularly along the western boundary currents, with peak displacements reaching more than 90 m. Furthermore, these displacements are positively correlated with eddy properties (particularly eddy amplitude), suggesting that higher intensity eddies may induce larger pycnocline displacements. In the eddy coordinate system, the pycnocline displacement reveals a monopole structure with a marked extremum in the eddy centre. At the eddy core, maximum deepening in AE reaches ~54 m in spring, but only ~25 m in autumn. In contrast, uplifting in CE reaches ~66 m (~18 m) in spring (autumn). The eddy-induced pycnocline displacements reported here emphasize the intrinsic vertical dynamics of eddies during oceanic observations and provide a pathway to reproduce the effects of eddies on variations of the pycnocline in ocean models. • The role of eddy on the pycnocline depth variation is quantitatively estimated. • Anticyclonic and cyclonic eddy are observed to deepen and uplift the pycnocline. • Larger pycnocline displacement is found in areas with energetic eddies in spring. • The displacement is symmetrically distributed in the eddy coordinate system. [ABSTRACT FROM AUTHOR]