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The Hamburg meteorite fell on January 16, 2018, near Hamburg, Michigan, after a fireball event widely observed in the U.S. Midwest and in Ontario, Canada. Several fragments fell onto frozen surfaces of lakes and, thanks to weather radar data, were recovered days after the fall. The studied rock fragments show no or little signs of terrestrial weathering. Here, we present the initial results from an international consortium study to describe the fall, characterize the meteorite, and probe the collision history of Hamburg. About 1 kg of recovered meteorites was initially reported. Petrology, mineral chemistry, trace element and organic chemistry, and O and Cr isotopic compositions are characteristic of H4 chondrites. Cosmic ray exposure ages based on cosmogenic 3He, 21Ne, and 38Ar are ~12 Ma, and roughly agree with each other. Noble gas data as well as the cosmogenic 10Be concentration point to a small 40-60 cm diameter meteoroid. An 40Ar-39Ar age of 4532 ± 24 Ma indicates no major impact event occurring later in its evolutionary history, consistent with data of other H4 chondrites. Microanalyses of phosphates with LA-ICPMS give an average Pb-Pb age of 4549 ± 36 Ma. This is in good agreement with the average SIMS Pb-Pb phosphate age of 4535.3 ± 9.5 Ma and U-Pb Concordia age of 4535 ± 10 Ma. The weighted average age of 4541.6 ± 9.5 Ma reflects the metamorphic phosphate crystallization age after parent body formation in the early solar system.

The effect of curing temperature on hardening, thermal, and mechanical characteristics of adhesive for retard‐bonded prestressed systems is investigated in detail. To evaluate the degree of hardening of the adhesive, the cone penetration and Shore hardness of two samples are tested throughout the curing process under conditions of 25, 35, 45, 55, and 65°C. The thermal performance and curing reaction are characterized using differential scanning calorimetry and Fourier transform infrared spectroscopy, respectively. The mechanical properties with respect to the cure temperatures are characterized by compression strength tests. Experimental results present that after curing under conditions ranging from 25 to 65°C, the hardness of the samples reached its maximum values (85–90 D). As the temperature increased from 25 to 65°C, there was a greater degree of curing cross‐linking, resulting in an increase in compressive strength from 55 to 72 MPa. Based on Shore hardness–time experimental data, a logarithmic model is proposed for predicting the hardness of adhesives at any given time for engineering applications. Additionally, the time–temperature superposition principle is utilized to extrapolate the curing time of the adhesive under low‐temperature conditions. The research findings are of significant importance for the assessment of adhesive hardening. [ABSTRACT FROM AUTHOR]

Knowledge regarding the abundance and distribution of solar wind (SW)‐sourced water (OH/H2O) on the Moon in the shallow subsurface remains limited. Here, we report the NanoSIMS measurements of H abundances and D/H ratios on soil grains from three deepest sections of the Chang'E‐5 drill core sampled at depths of 0.45–0.8 m. High water contents of 0.13–1.3 wt.% are present on approximately half of the grain surfaces (topmost ∼100 nm), comparable to the values of Chang'E‐5 scooped soils. The extremely low δD values (as low as −995‰) and negative correlations between δD and water contents indicate that SW implantation is an important source of water beneath the lunar surface. The results are indicative of homogeneous distribution of SW‐derived water in the vertical direction, providing compelling evidence for the well‐mixed nature of the lunar regolith. Moreover, the findings demonstrate that the shallow subsurface regolith of the Moon contains a considerable amount of water. Plain Language Summary: Recently, China's Chang'E‐5 mission targeted a higher latitude on the Moon than previous Apollo and Luna missions, and brought back scooped and drilled samples to the Earth. These new soil samples provide an opportunity to investigate the distribution, abundance, and origin(s) of water in Moon's middle latitude. Here, we focus on using the NanoSIMS technique to analyze water content on soil near‐surface regions to understand whether the solar wind (SW)‐derived water could be preserved after burial at depth. Our results show that more than half of the core soils have high water contents on the rims of grains, similar to those of the Chang'E‐5 scooped soils. This finding suggests that the SW remains an important source of water in the Moon's subsurface. Our work provides direct evidence that the lunar regolith below the surface contains considerable water from SW implantation. This type of water could be a promising water resource in future exploration. Key Points: More than half of the soils from the single drill core have high water contents and low D/H ratios below the surfaceThe solar wind (SW)‐derived water could be preserved for hundreds of millions of years if buried at depthLunar regolith from the drill core contains considerable water from SW implantation, which is much more accessible [ABSTRACT FROM AUTHOR]

Chitosan (CS) was selected as the carbon source, and the Chitosan/dicyandiamide (CS/DCDA) precursors with hydrogen bonding interactions were prepared by freeze-drying and normal drying, and the carbon-Chitosan/graphite carbon nitride (C-CS/g-C3N4) composites were obtained after calcination. The results show that the freeze-drying process can produce more hydrogen bonding interaction between chitosan and dicyandiamide (DCDA) and more pores through recrystallization. More composite carbon is formed in the C-CS/g-C3N4-2 composite obtained after calcination. More hydrogen bonds are broken, releasing more N lone pairs of electrons, which not only facilitates the n−π* electron leap, but also facilitates the separation and photogenerated electron-hole, and provides a large number of reactive sites for photocatalytic degradation of pollutants. This results in better photocatalytic performance of C-CS/g-C3N4-2. [ABSTRACT FROM AUTHOR]

Because the physical properties of carbon fiber and glass fiber are very different, the fiber volume fraction in carbon/glass hybrid fiber composites cannot be tested by burning method or digestion method, respectively. Furthermore, these methods partially consume the fiber, especially for carbon fibers. To investigate the fiber volume fraction in carbon/glass hybrid fiber composites correctly, the test method is put forward. The burning method and the digestion method were combined to calculate the volume fraction of carbon fiber and glass fiber, respectively. The results show that the relative error between the measured value and the theoretical value is very small. The result of the present work implies that the feasibility and accuracy of this method through experimental verification. [ABSTRACT FROM AUTHOR]

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]

The mechanism parameters of the manipulator not only have a great influence on the size of the working space but also affect flexible performance distribution. Aimed at obtaining a 6 DOF modular manipulator, mechanism parameters were optimized in order to explore the effect of upper arm and forearm dimensions on the end dexterity of the manipulator. First, forward kinematic equations were derived using the DH method, and the Jacobian matrix of the manipulator was solved. Second, three indicators, including the condition number index, structural length index, and global conditioning index, were employed as optimization indicators for the mechanism parameters of the manipulator, and an orthogonal experiment was designed based on the Grey–Taguchi method and robot toolbox. Third, the grey relational analysis method was used to process the experimental results, and the grey relational grade for each group was solved. Last, the variation curve between the grey relational grade and the parameter level of each mechanism was drawn, and optimized mechanical arm mechanism parameters were derived. It was found that although the overall dimension of the manipulator was slightly decreased, as determined via comparing the original and optimized manipulator length, the performance indexes were improved. The results not only verified the correctness of the proposed optimization method but also laid a foundation for subsequent research on the dynamic performance of modular robot systems. [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]