Flow forming is a promising metal forming technology to manufacture thin-walled tube with helical grid-stiffened ribs (TTHGRs). High quality of grid-stiffened ribs is the primary concern in this ...forming technology. Thus, the rib filling behavior during this process was investigated in this study. It is found that there exist two kinds of asymmetric filling behavior during flow forming of TTHGRs—temporary asymmetric filling behavior of helical rib and permanent asymmetric filling behavior of cross region. The former is caused by the combination of spiral distribution of helical rib and local loading pattern of flow forming. It introduces an asymmetry of rib shape at early stage during rib-filling. The latter is induced by the decreasing of extrusion force of roller on material when the roller rotates across the cross region. It introduces an asymmetry of rib shape in the whole forming process. Moreover, the temporary asymmetric filling behavior of helical rib introduces height difference between the two helical ribs, and the permanent asymmetric filling behavior of cross region leads to a dramatic variation of rib height across the cross region. These together introduce an uneven distribution of rib height. Therefore, the rib height and its distribution inhomogeneity were quantitatively evaluated to analyze the rib forming qualities at different processing parameters. Furthermore, an integrated quality index evaluating rib height and inhomogeneity was proposed and correlated with these parameters using the response surface method. On these bases, the rib forming quality was improved by optimizing the processing parameters in flow forming.
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•The Zhenyuan quartz porphyries were derived from an Au-rich lower crust.•The gold was precipitated with the crystallization of Ti–Fe oxides.•Lithosphere-scale processes for gold ...accumulation and precipitation are proposed.
Numerous Au-rich deposits in the western South China Block, SW China, provide insights into the gold enrichment process at a lithospheric scale. Zhenyuan is a giant gold deposit in the western South China Block, but its genesis remains controversial with competing hypotheses of magmatic–hydrothermal and metamorphic–hydrothermal development. Here, we present new petrographic, major and trace element, and zircon U–Pb age data for quartz porphyry from the Zhenyuan deposit to evaluate the specific gold enrichment process. Zircon SHRIMP and LA–ICP–MS results demonstrate that the Zhenyuan quartz porphyries crystallized at ca. 255–247 Ma. This age is broadly consistent with the Re–Os age of gold-bearing pyrite measured in previous studies. The porphyries are characterized by high-K calc-alkaline compositions and exhibit significant enrichment in LILEs and LREEs, and strong depletion in HFSEs. They share the same source (Au-rich lower crust) with Cenozoic Au-bearing intrusions. The initial melts had a weak oxidation state (ΔFMQ = –0.15–0.55), which favored Au accumulation and migration. However, the gold was precipitated with the crystallization of Ti–Fe oxides in the middle crust, resulting in the emplacement of Au-poor magma in the upper crust. The gold orebodies in the Zhenyuan deposit formed due to Cenozoic hydrothermal processes, as evidenced by our observations of ore-bearing pyrite and Ar–Ar ages of phlogopite measured in previous studies. Combined with regional mineralization data, we propose lithosphere-scale processes for gold accumulation, migration, and precipitation from the Neoproterozoic to Cenozoic. Specifically, we predict an Au-rich middle crust beneath the western South China Block.
Hydroxylated isoprenoid glycerol dialkyl glycerol tetraethers (OH‐GDGTs) preserved in marine sediments are thought to be controlled by sea surface temperature (SST). However, water depth may also ...exert a significant influence on OH‐GDGTs. Here, we investigated sedimentary OH‐GDGTs in the Kermadec and Atacama trench regions (2,560–9,560 m water depth). Sedimentary OH‐GDGTs in hadal trenches were dominated by OH‐GDGT‐0 (72 ± 8%), potentially reflecting an adaption of source organisms to ambient cold deep water. This result, combined with global data set, revealed that the predominance of OH‐GDGT‐0 is a ubiquitous phenomenon in deep‐sea sediments, leading to a considerable underestimation of RI‐OH′‐derived SSTs. By considering both SST and water depth effects, we developed more accurate OH‐GDGT‐based paleothermometers for both shallow regions and the global ocean, encompassing the full‐ocean‐depth range. Our findings highlight the importance of accounting for the effect of water depth on OH‐GDGTs and provide improved tools for reconstructing paleo‐SSTs.
Plain Language Summary
Building quantitative proxies that can accurately estimate SSTs is one of the most common themes in paleoceanography. Archeal‐derived hydroxylated isoprenoid glycerol dialkyl glycerol tetraethers (OH‐GDGTs) preserved in marine sediments have a potential to reflect past sea surface temperatures (SSTs). However, the source organisms of OH‐GDGTs can live throughout the water column, implying that sedimentary OH‐GDGTs record an integrated water column signal rather than only SST. Currently, the effect of water depth on sedimentary OH‐GDGTs remains vague. We investigated the distribution of OH‐GDGTs in 13 sediment cores in the hadal zone, which represents the deepest and least explored habitats on Earth's surface. The data from this study and literature revealed that the deep‐sea (including hadal trench) sediments are characterized by a predominance of OH‐GDGT‐0, which causes a considerable underestimation of OH‐GDGT‐derived SSTs. We evaluated the effects of both SST and water depth on OH‐GDGTs and established new calibrations that more accurately reconstruct paleotemperatures at a global scale.
Key Points
Sedimentary hydroxylated isoprenoid glycerol dialkyl glycerol tetraethers (OH‐GDGTs) were first investigated in the Kermadec and Atacama trenches with water depth ranging from 2,560 to 9,560 m
Water depth has large impact on OH‐GDGT distributions with higher OH‐GDGT‐0% and lower RI‐OH′ values of deep‐sea sediments
More accurate global sea surface temperature calibrations based on OH‐GDGTs were established
The waste red brick aggregate substituted with natural coarse aggregate can effectively alleviate environmental pollution in engineering concrete constructions. However, its mechanical performance ...lags far behind natural coarse aggregate due to micro-pore voids and micro-cracks. Three types of steel fiber contents (0, 1%, and 2%) are selected to improve the mechanical behavior of recycled concrete in this study. Cubic compression test, splitting tensile test, prism compression test, and static compressive elastic modulus test are carried out to study the influence of steel fiber content and replacement rate of recycled coarse aggregate. In addition, the stress-strain behavior and failure mechanism of steel fiber recycled brick aggregate concrete are discussed, and microscopic crack development is also analyzed. Test results show that the specimens without steel fiber are prone to aggregate destruction under loading. The cubic and prismatic compressive strength decreased by 48% and 34%, while the splitting tensile strength reduced by 40%. The mechanical properties substantially improve when the steel fiber content is 1%. The finite element model of steel fiber recycled brick aggregate concrete under uniaxial compression is established. The constitutive model for predicting uniaxial compression of steel fiber recycled brick aggregate concrete is also proposed.
Moving object detection (MOD) is a crucial research topic in the field of computer vision, but it faces some challenges such as shadows, illumination, and dynamic background in practical application. ...In the past few years, the rise of deep learning (DL) has provided fresh ideas to conquer these issues. Inspired by the existing successful deep learning framework, we design a novel pyramid attention-based architecture for MOD. On the one hand, we propose a pyramid attention module to get pivotal target information, and link different layers of knowledge through skip connections. On the other hand, the dilated convolution block (DCB) is dedicated to obtain multi-scale features, which provides sufficient semantic information and geometric details for the network. In this way, contextual resources are closely linked and get more valuable clues. It helps to obtain a precise foreground in the end. Compared with the existing conventional techniques and DL approaches on the benchmark dataset (CDnet2014), the experiments indicate that the performance of our algorithm is better than previous methods.
Abstract Bismuth ferrite (BiFeO 3 ) is a multiferroic material that exhibits both ferroelectricity and canted antiferromagnetism at room temperature, making it a unique candidate in the development ...of electric-field controllable magnetic devices. The magnetic moments in BiFeO 3 are arranged into a spin cycloid, resulting in unique magnetic properties which are tied to the ferroelectric order. Previous understanding of this coupling has relied on average, mesoscale measurements. Using nitrogen vacancy-based diamond magnetometry, we observe the magnetic spin cycloid structure of BiFeO 3 in real space. This structure is magnetoelectrically coupled through symmetry to the ferroelectric polarization and this relationship is maintained through electric field switching. Through a combination of in-plane and out-of-plane electrical switching, coupled with ab initio studies, we have discovered that the epitaxy from the substrate imposes a magnetoelastic anisotropy on the spin cycloid, which establishes preferred cycloid propagation directions. The energy landscape of the cycloid is shaped by both the ferroelectric degree of freedom and strain-induced anisotropy, restricting the spin spiral propagation vector to changes to specific switching events.
A six degree-of-freedom (DOF) motion control system for docking with a deep submergence rescue vehicle (DSRV) test platform was the focus of this study. The existing control methods can meet the ...general requirements of underwater operations, but the complex structures or multiple parameters of some methods have prevented them from widespread use. The majority of the existing methods assume the heeling effect to be negligible and ignore it, achieving motion control in only four or five DOFs. In view of the demanding requirements regarding positions and inclinations in six DOFs during the docking process, the software and hardware architectures of the DSRV platform were constructed, and then sparse filtering technology was introduced for data smoothing. Based on the adaptive control strategy and with a consideration of residual static loads, an improved S-plane control method was developed. By converting the force (moment) calculated by the controller to the body coordinate system, the complexity of thrust allocation was effectively reduced, and the challenge of thrust allocation in the case of a high inclination during dynamic positioning was solved accordingly. The automatic control of the trimming angle and heeling angle was realized with the linkage system of the ballast tank and pump valve. A PID method based on an intelligent integral was proposed, which not only dealt with the integral "saturation" problem, but also reduced the steady-state error and overshooting. Water pool experiments and sea trials were carried out in the presence of water currents for six-DOF motion control. The responsiveness and precision of the control system were verified by the pool experiment and sea trial results and could meet the control requirements in engineering practice. The reliability and operational stability of the proposed control system were also verified in a long-distance cruise.
Risk factors for the severity of patellofemoral osteoarthritis (PFOA) are poorly understood. This research aims to evaluate the association between patellofemoral joint (PFJ) morphology and alignment ...with the radiographic severity of PFOA.
A retrospective analysis of CT scan and lateral radiograph data were acquired in patients with PFOA. The radiographic grade of PFOA and tibiofemoral osteoarthritis (TFOA), lateral and medial trochlear inclination angle, sulcus angle, and the Wiberg classification of patella morphology, the congruence angle, patellar tilt angle, and lateral patellar angles, and tibial tubercle trochlear groove distance (TT-TG) and patella height (i.e., Caton-Deschamps index) were assessed using CT scans and sagittal radiographs of the knee. All the PFJ morphology and alignment data were divided into quarters, and the relationships between each of these measures and the severity of PFOA were investigated.
By studying 150 patients with PFOA, we found a U-shaped relationship between the Caton-Deschamps index and the severity of PFOA (P < 0.001). A lower value of sulcus angle and lateral patellar angle, a higher value of congruence angle, and type III patella were associated with more severity of lateral PFOA. Compared with the highest quarter of each measure, the adjusted odds ratios (OR) of the severity of PFOA in the lowest quarter of sulcus angle, lateral patellar angle, and congruence angle; and type I patella was 8.80 (p = 0.043), 16.51 (P < 0.001), 0.04 (P < 0.001), and 0.18 (p = 0.048) respectively.
Extreme value of patella height, a higher value of lateral patellar displacement and lateral patellar tilt, lower value of sulcus angle, and type III patella were associated with more severity of PFOA.
•Coccolith refinement procedures (repeated decanting) separated coccolith fractions dominated by Gephyrocapsa (>80% wt).•The strong links between Gephyrocapsa coccolith isotopic vital effects and ...coccolith size were observed.•Gephyrocapsa coccolith isotopic vital effects covaried with growth rate before MIS 8, showing a glacial–interglacial cyclicality.
Coccolithophores play important roles in marine biochemistry due to the processes of calcification and photosynthesis. Coccoliths are produced intracellularly, and cells produce coccoliths with stable isotopes distinct from theoretically precipitated inorganic calcite due to the influences of coccolithophore physiology, which are the so-called vital effects. The coccolith isotopic vital effects show large variations between species and hamper the use of coccolith isotopes in paleoceanography. In addition, learning the coccolith isotopic vital effects can help to better understand the carbon fractionation in coccolithophore cell, so as to provide a new insight in reconstructing sea water carbonate system (e.g., from alkenone δ13C or directly from coccolith δ13C) in geological past. In the present study, we investigated the morphological parameters, growth rate, and coccolith stable isotope compositions of Gephyrocapsa, the most universal alkenone-producing coccolithophore across the Pleistocene. These data allow us to estimate the influences of Gephyrocapsa morphology as well as the growth rate on coccolith vital effects. The results showed that Gephyrocapsa morphology, as well as coccolith isotopes, varied with species and morphotype changes, which were evolutionarily forced over the past 400 ka. The small Gephyrocapsa morphotypes (G. caribbeanica and Gephyrocapsa <3 μm) produced more robust coccoliths with relatively heavier isotopes for both carbon and oxygen than that of the larger-sized G. oceanica. The carbon and oxygen vital effects were significantly correlated and showed negative values, suggesting a kinetic effect on bicarbonate formation during calcification. The Gephyrocapsa growth rate showed a glacial–interglacial cyclicality, and had close relations with coccolith isotopic vital effects before MIS 8 when G. oceanica dominated. It is suggested that coccolith isotopic fractionation were influenced by coccolithophore growth rate, however these effects were superimposed on an evolutionary forced coccolithophore (coccolith) size changes.
The gearbox is an important component in the mechanical transmission system and plays a key role in aerospace, wind power and other fields. Gear failure is one of the main causes of gearbox failure, ...and therefore it is very important to accurately diagnose the type of gear failure under different operating conditions. Aiming at the problem that it is difficult to effectively identify the fault types of gears using traditional methods under complex and changeable working conditions, a fault diagnosis method based on multi-sensor information fusion and Visual Geometry Group (VGG) is proposed. First, the power spectral density is calculated with the raw frequency domain signal collected by multiple sensors before being transformed into a power spectral density energy map after information fusion. Second, the obtained energy map is combined with VGG to obtain the fault diagnosis model of the gear. Finally, two datasets are used to verify the effectiveness and generalization ability of the method. The experimental results show that the accuracy of the method can reach 100% at most on both datasets.
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