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A finite group is called a [Formula: see text]-group if all its minimal subgroups are normal. In this paper, [Formula: see text]-groups were characterized by investigating on the generalized norm of minimal subgroups.

This study aims to make approximate motion generation that has multiple solutions to facilitate the selection of the best mechanism parameters. Therefore, an approximate synthesis method for an epicyclic gear train (EGT) with noncircular gears based on optimization–homotopy algorithm is proposed in this paper. First, the multipose synthesis objective function of a simplified model of EGT (planar RR dyad) is established. The approximate motion generation is transformed into the extremum problem of multivariate function, and a variable is introduced to expand the solution space. A homotopy algorithm is used to solve the gradient equation of the objective function to obtain the finite range solution domain. Second, the feasible solution domain of EGT is obtained by identifying the total rotation of revolute joints of the RR dyad, and a mechanism error evaluation index is established. In accordance with actual constraints, the most suitable solution is selected in the feasible solution domain, and the relative angular displacement relationship of the selected RR dyad is used to determine the transmission ratio and pitch curve of noncircular gears to realize the design of an EGT. Lastly, a design example is provided to illustrate the feasibility of the method.

The phase transformation of catalysts has been extensively observed in heterogeneous catalytic reactions that hinder the long cycling catalysis, and it remains a big challenge to precisely control the active phase during the complex conditions in electrochemical catalysis. Here, we theoretically predict that carbon-based support could achieve the phase engineering regulation of catalysts by suppressing specific phase transformation. Taken single-walled carbon nanotube (SWCNT) as typical support, combined with calculated E-pH (Pourbaix) diagram and advanced synchrotron-based characterizations technologies prove there are two different active phases source from cobalt selenide which demonstrate that the feasibility of using support effect regulating the potential advantageous catalysts. Moreover, it is worth noting that the phase engineering derived Co3O4-SWCNT exhibits a low overpotential of 201 mV for delivering the current density of 10 mA/cm2 in electrocatalytic oxygen evolution reaction (OER). Also, it reaches a record current density of 529 mA/cm2 at 1.63 V (vs. RHE) in the electrocatalytic urea oxidation reaction (UOR), overwhelming most previously reported catalysts.

Enhancing activity and stability of iridium- (Ir-) based oxygen evolution reaction (OER) catalysts is of great significance in practice. Here, we report a vacancy-rich nickel hydroxide stabilized Ir single-atom catalyst (Ir

A planar three-revolute (3R) serial chain is an important part of many mechanisms. The classical approach in motion generation of a planar 3R serial chain is to construct closed-loop equations based on complex numbers, which yields a large-scale polynomial system. In this study, a new approach of planar 3R serial chain motion generation by establishing the relative kinematics model based on conformal geometric algebra (CGA) is proposed. The simpler design equations are obtained, which can be used to design a planar 3R serial chain that can accurately achieve the N poses. In the numerical examples, the number of different poses is used to verify the correctness and efficiency of the proposed method by using polyhedral homotopy continuation. The results indicate that the design equations obtained via CGA are more concise for improving the solving efficiency compared with the previous method. Finally, a geared five-bar mechanism with a seven-pose motion generation example is considered.

HighlightsA method for solving a spatial transplanting mechanism with noncircular gears is proposed.A new mechanism for transplanting rice pot seedlings is proposed.A trajectory with a small lateral displacement at the preparation phase is obtained.The working performance is validated by simulations and field tests.Abstract. This study proposes a method of solving the parameters of a spatial planetary gear train with noncircular gears to meet the requirements of wide-narrow row pot seedling transplanting (WPST). First, the planetary gear train was simplified to a spatial open-chain 2R mechanism (planetary carrier). A kinematic model of the 2R mechanism was derived from the three given homogeneous matrices describing the spatial position and attitude information of grasping, extracting, and planting seedlings. Second, the length of each link, attitude of each rotation axis, and relative initial angles were calculated. The model for solving the transmission ratio was deduced. A spatial planetary gear train configuration with a single planet carrier and two-stage driving was derived, in which the middle axis could be determined by combining the selected configuration, represented trajectory, and transmission ratio of each gear pair. Finally, a planetary gear train combining a noncircular gear pair and a helical gear pair was used in the WPST mechanism design. Simulations and tests conducted on a prototype confirmed the correctness of the theoretical model and the practicality of the design. Keywords: Noncircular gear, Planetary gear train, Spatial trajectory, Transmission ratio, Transplanting mechanism.

Electrochemical water splitting is a promising strategy to generate highly purified molecular hydrogen (H2) without any pollutants, but several challenges have impeded its large-scale application b...

Type synthesis is an important step when designing innovations in mechanisms. To overcome the limitation of traditional gear train transplanting mechanisms in realizing a specific trajectory, a swinging linkage mechanism is introduced into the design of the transplanting mechanism. To design a crop-transplanting gear linkage mechanism (GLM), an automatic synthesis method based on graph theory is proposed in this article. First, the numbers of loops, links, joints and other parameters, along with unlabeled graphs, are calculated based on the structural characteristics of the GLM. The labeled graphs that correspond to the kinematic chain (KC) are then obtained by thickening the edges of the unlabeled graphs, and physically reasonable labeled graphs are derived from identification of the structural rationality of the corresponding structures. Based on the relative motion characteristics of the input and output links of the transplanting mechanisms, criteria for screening the gear linkage mechanisms represented by the labeled graphs are formulated, and the labeled graphs that are suitable for transplanting are calculated to enrich the configurations of the transplanting mechanisms. Finally, two examples are tested to verify the effectiveness of the proposed type synthesis method. Keywords: Gear linkage, Screening, Topological graph, Transplanting mechanism, Type synthesis.

Ruthenium (Ru)-based electrocatalysts as platinum (Pt) alternatives in catalyzing hydrogen evolution reaction (HER) are promising. However, achieving efficient reaction processes on Ru catalysts is still a challenge, especially in alkaline media. Here, the well-dispersed Ru nanoparticles with adjacent Ru single atoms on carbon substrate (Ru

Zero Liquid Discharge (ZLD) of high salinity wastewater is always an important subject in the field of energy and environment. In order to improve the evaporation rate, the mass and heat transfer characteristics of the rotary spray evaporation technology in the treatment of high salinity wastewater are explored. The relationship between the evaporation characteristics of wastewater and various parameters such as hot air flow rate, hot air temperature, feed flow rate, atomizing disk rotating speed and feed liquid concentration change is studied by experiment and simulation. It is concluded that the hot air temperature and hot air flow rate are important factors affecting the evaporation effect of the system. The atomizing disk rotating speed and the feed flow rate have a great influence on the atomization effect of the atomizer. A fluid recirculation area is generated around the atomizing disk, which allows droplets to reside longer in the evaporation chamber, thus improving the evaporation efficiency. Compared with other factors, the effect of feed liquid concentration on atomization and evaporation is relatively small. Finally, a better process operation condition is obtained through research: the atomizing disk rotating speed is 24,000 r/min, the feed flow rate is 4.5 kg/h, the hot air temperature is 498 K, and the hot air flow rate is 80 m3/h.

The contracted graph reflects the primary topology of kinematic chains (KCs) and the synthesis of contracted graphs is the foundation for the structural synthesis of KCs. This paper presents an automatic method to synthesize contracted graphs of planar non-fractionated KCs. First, according to the range of the number of vertices in a contracted graph, the vertex degree sequence (VDS) equation of contracted graph is established to derive all possible VDSs. Then, the process of solving the synthesis equation set of contracted graphs is developed, based on which all candidate contracted graphs are generated. Finally, unconnected and fractionated contracted graphs are detected, and a compound topological invariant (CTI) based method is proposed to detect isomorphic contracted graphs. The complete set of non-fractionated contracted graphs with up to seven independent loops are synthesized. All the contracted graphs are classified into planar and non-planar graphs, and similar vertices in each contracted graph are determined, which can improve the efficiency of KC synthesis.

Similarity recognition and isomorphism identification (SRII) of kinematic chains (KCs) are key problems facing their innovative regenerative design and configuration synthesis. Although various detection methods have been proposed, most of them are based on topological characteristics or some codings, which are only suitable for single type KC and error identification is generated in some cases. In this study, a set of SRII methods is proposed based on the graph theory definition of similarity and isomorphism. These are appropriate for planar single and multiple joints KCs, planetary gear trains (PGTs), contracted graphs, and multicolor graphs. The computational complexity and effectiveness of the algorithm are assessed on 10-bar, 15-bar, 21-bar, 28-bar, and 42-bar single-joint KCs, 4-bar tricolor topological graphs, and 8-bar contracted graphs. All the results are in agreement with those in the cited literature, and the advantage in isomorphism identification efficiency of the multibar single-hinged KC is evident. Finally, SRII are performed for all 8-bar one-degree-of-freedom (1-DOF) and 9-bar 2-DOF planar single-hinged KCs, all 8-bar 1-DOF KCs with two multiple joints, and all 6-bar 1-DOF rotation graphs through identification program, with the aim to provide a reference for the application of the algorithm.

Given an image, our proposed model can extract its dominant high-level semantics information through low-level feature extraction and image classification. It contains 3 main parts: image segmentation, feature extraction and classification. To our knowledge, this is the first model that applies Color and Edge Directivity Descriptor (CEDD), a multiple feature extraction algorithm, into the high-level semantics extraction field. Further, we also introduce a new padding strategy for region representation, which is especially suitable for widely-used non-arbitrary over-segmentation. Finally, our experiment shows that CEDD performs equally or better than traditional texture-based Gabor method. Meanwhile, new padding strategy outperforms other relevant methods.