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The zircon from the pegmatite of the Adui granitic massif displays the unique the rare earth element (REE) distribution spectrum with the tetrad effect in REE fractionation. The tetrad effect often occurs in granitoid rocks, but it is rarely encountered in minerals, e.g., zircon. Fluid saturated with volatiles, water and trace elements is a factor responsible for the tetrad effect in the zircon. The detailed isotopic-geochemical study of the zircon has revealed several zones differing in internal structure (in the back-scattered electron (BSE) image), composition and REE distribution. The zones indicate changes in the crystallization environment provoked by the evolution of the pegmatite-forming melt. They occur as the gradually growing changes in composition from the unaltered zones that are light-colored in BSE to the altered zones that are dark-colored in BSE. The unaltered zones are consistent in composition and geochemical features with magmatic zircons. The high content of trace (U, Th, REE) and volatile elements (F, Cl) in water suggests its crystallization from the fluid-saturated magmatic melt. The altered zircon zones occur as recrystallized zones with high content of non-formula elements (Y, Ca, Sr, Nb, P), a non-differentiated REE distribution spectrum and an absent Ce anomaly. These features are consistent with those of hydrothermal-metasomatic zircon. [ABSTRACT FROM AUTHOR]

Uranium isotope ratios are reported for twenty‐nine geological reference materials (RMs) including igneous, metamorphic and sedimentary rocks, as well as sediments. Measurements were conducted on a multi‐collector inductively coupled plasma‐mass spectrometer (MC‐ICP‐MS) using the 233U‐236U double spike technique. These RMs possess a wide range of matrices with U mass fractions ranging from 0.11 μg g‐1 to 18.7 μg g‐1. The δ234/238U values (relative to the n(234U)/n(238U) ratio at secular equilibrium) show minor fluctuations around the secular equilibrium value except for two Pleistocene speleothem RMs. The δ238/235U values (relative to the value for NBL CRM 112a (NBS SRM 960)) of igneous rocks and metamorphic rocks are within the range of the continental crust value (‐0.29 ± 0.03‰, 95% CI). The δ238/235U value for sedimentary rock and sediment RMs spans a wide range of 0.98‰, suggesting significant 238U/235U isotopic fractionation in low temperature environments. The range of δ238/235U RMs reported in this study (‐0.63‰ to 0.35‰) exceeds that of previous RMs (‐0.61‰ to 0.17‰), allowing inter‐laboratory calibration of wider ranges of geological and environmental samples. [ABSTRACT FROM AUTHOR]

Let G be a finite group and H ≤ G. The authors study the structure of finite groups G having a subgroup H which is maximal in 〈H, Hg〉 for some g ∈ G. Some results on the structure of 〈H, Hg〉 and G are set up. Especially, a generalization of Baer′s theorem is established.

Aiming at the inverse solution problem of the kinematics of dual-arm service robot,a inverse kinematics solution is proposed according to its configuration characteristics. Firstly,according to the structure characteristics of the manipulator,the forward kinematics model of dual-arm is got by using the method of standard DH modeling. A group of completely generalized coordinates is obtained by inverse transformation method of manipulator posture matrix using Euler angles. Then,the inverse kinematics of dual-arm6 R robot is solved by geometrical method and coordinate projection method. After analysis and calculation,the closed solutions of 8 groups can be obtained,and the optimal solution is selected. Finally,a 3 D simulation platform is established to verify the correctness of inverse kinematics based on MATLAB,and it lays the foundation for the trajectory planning and collision avoidance of manipulator.

Aiming at collaborative space problem of the dual arm 6 R service robot,the Monte Carlo and traversal search comparison method are used for analysis according to its configuration characteristics. Firstly,according to the configuration of the manipulator,the standard DH method is used to construct the model,and then the forward kinematics equation of the arms is obtained. Secondly,the work space of each arm is got by using Monte Carlo method. Then,the collaborative space of the arms is obtained by using the traversal search comparison method,and the range of the joint angle of the dual arms is obtained through kinematics inverse method. Finally,the MATLAB toolbox is used to build the simulation platform and the algorithm is written to verify the correctness of the above analysis,and the foundation for the follow-up coordinated operation and trajectory planning is laid.

Surface electromyography (sEMG) is a promising technology that can capture muscle activation signals to control robots through novel human–machine interfaces (HMIs). This technology has already been applied in scenarios such as prosthetic design, assisted robot control, and rehabilitation training. This article provides an overview of sEMG-based robot control, covering two important aspects: (1) sEMG signal processing and classification methods and (2) robot control strategies and methods based on sEMG. First, the article outlines the general steps in sEMG signal processing and summarizes the commonly used methods for data acquisition, pre-processing, and feature extraction. In addition, machine-learning-based pattern recognition methods have been introduced for sEMG signal classification. Subsequently, user intent-based robot control strategies are classified into three categories: full-human continuous control, semi-autonomous continuous control, and discrete control, and their control methods and applicable scenarios are compared. Finally, this article discusses the advantages, disadvantages, and future development prospects of sEMG-based robot control. This review provides a comprehensive overview of sEMG-based robot control, from signal processing and classification methods to robot control strategies and methods, aiming to guide future research on selecting filters, feature sets, and pattern recognition methods and to assist in establishing sEMG-driven robot control frameworks. [ABSTRACT FROM AUTHOR]

This study focuses on using the chemical compositions of plagioclase to further investigate the petrogenesis of Chang'E-5 young mare basalts and constrain its parental melt composition. Together with previously published data, our results show that the plagioclase in mare basalts overall displays large variations in major and trace element concentrations. Inversion of the plagioclase data indicates that the melt compositions parental to Chang'E-5 basalts have high rare earth elements (REE) concentrations similar to the high-K KREEP rocks (potassium, rare earth elements, and phosphorus). Such a signature is unlikely to result from the assimilation of KREEP components, because the estimated melt Sr shows positive correlations with other trace elements (e.g., Ba, La), which are far from the KREEP end-member. Instead, the nearly parallel REE distributions and a high degree of trace element enrichment in plagioclase indicate an extensive fractional crystallization process. Furthermore, the estimated melt REE concentrations from plagioclase are slightly higher than those from clinopyroxene, consistent with its relatively later crystallization. Using the Ti partition coefficient between plagioclase and melt, we estimated the parental melt TiO2 content from the earliest crystallized plagioclase to be ~3.3 ± 0.4 wt%, thus providing robust evidence for a low-Ti and non-KREEP origin for the Chang'E-5 young basalts in the Procellarum KREEP terrane. [ABSTRACT FROM AUTHOR]

We introduce a new subgroup embedding property of finite groups called CSQ-normality of subgroups. Using this subgroup property, we determine the structure of finite groups with some CSQ-normal subgroups of Sylow subgroups. As an application of our results, some recent results are generalized.