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A combined experimental and DEM investigation of grain interlocking in sheared granular assemblies

particuology 2024年第7期90卷 436-451页

作者： Rui Lu Qiang Luo Tengfei Wang David p.Connolly Tao xie School of Civil Engineering Southwest Jiaotong UniversityChengdu 610031China Key Laboratory of High-Speed Railway Engineering(Southwest Jiaotong University) Ministry of EducationChengdu 610031China School of Civil Engineering University of LeedsLeeds LS29JTUK Department of Civil Engineering McMaster UniversityHamiltonONCanada

Compacted granular material,integral to geotechnical engineering,undergoes translation,rotation,and interlocking when subject to shear displacements or external *** present study focuses on the interlocking of heterogeneous granular materials,a complex behavior influenced by gradation,compaction,and varying particle geometry,and has consequently received limited attention in existing *** address this research gap,we conducted an analysis on the effect of grain interlocking on the shear resistance of granular assemblies,using a combination of laboratory testing and the discrete element method(DEM).Initially,large-scale direct shear tests were conducted on gravel−sand mixes with varying degrees of compaction and normal *** of the mixes also underwent subsequent shear reversal to explore the differences in grain interlocking between the two shearing processes on the shear *** analyzing the laboratory results,a mesoscopic scale investigation was performed by replicating the test using discrete element *** facilitate this,granular particle geometries were measured using 3D laser scanning based on the physical lab ***,based on these scans,discrete element R-block and ball models were utilized to construct both the coarse and fine particles within the *** vibro-compaction was employed to regulate the degree of *** results indicate that an increase in vertical pressure,coupled with a zero dilatancy angle,results in a rising stress ratio,indicative of grain *** interlocking exhibits a positive correlation with both the coarse content and the degree of compaction,and varies depending on the shear *** interlocking progresses,the shear band,induced by particle movement,expands and is associated with reduced particle rotation near the shear *** study further reveals a consistent positive correlation between interlocking and the principal orientation angle of strong normal c

关键词： Granular material Interlocking Shear resistance Direct shear Discrete element method Vibro-compaction

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Mass extinctions, their causes and consequences: an interview with Douglas *** and Shuzhong Shen

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National Science Review 2024年第1期11卷 66-70页

作者： Shucheng xie State Key Laboratory of Biogeology and Environmental Geology China University of Geosciences at Wuhan

‘Mass extinctions’ have been a hot topic for several decades. What triggers a mass extinction? How does a mass extinction impact the evolution of life? How does our ecosystem recover after a mass extinction? These questions attracted the interest of both scientists and the public *** spoke to two renowned researchers in the field of mass extinctions: prof. Douglas H. Erwin from the National Museum of Natural History of the USA, and prof. Shuzhong Shen from Nanjing University, China.

关键词： Stratigraphy

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Turbulence Statistics of Thermo-Buoyancy Supercritical Fuel Flow in a Regenerative Cooling Channel

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Journal of Thermal Science 2024年第1期33卷 126-137页

作者： SUN Feng xie Gongnan School of Marine Science and Technology Northwestern Polytechnical UniversityXi'an 710072China Department of Thermal Engineering Tsinghua UniversityBeijing 100084China

Active regenerative cooling with supercritical hydrocarbon fuel is considered as the most promising thermal protection *** existence of buoyancy force would lead to strongly anisotropic flow and thermal transport *** is closely related to the cooling performance of the *** elucidate the mechanisms of turbulent transport,the large eddy simulation(LES) was performed to assess turbulence statistics within different turbulence *** results indicated that the buoyancy and inertial force together dominated the change of turbulent ***,the spatial thermal buoyancy effect significantly suppressed the vertical velocity *** is due to the laminar motion caused by the buoyancy force,thereby weakening the thermal *** the statistics of velocity fluctuation,it was found that the buoyancy force and inertial force greatly weaken the vertical and streamwise velocity fluctuation,*** the statistics of thermal transport,the results pointed out that the near-wall heat transport characteristics need to be paid more *** thickness of the temperature mixing boundary layer led to the attenuation of vertical heat flux,which inhibited vertical temperature diffusion and predisposed to extreme conditions of heat transfer *** results can enhance the academic understanding of the heat transfer mechanism of supercritical fluids,and give guidance for further applications of thermal protection.

关键词： active regenerative cooling large eddy simulation(LES) buoyancy force turbulence statistics

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Output feedback stabilization of stochastic high-order planar nonlinear systems with stochastic inverse dynamics and output-constraint

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Science China(Information Sciences) 2024年第3期67卷 182-196页

作者： Ruiming xie Shengyuan XU Nanjing University of Science and Technology School of Automation

In this paper, we solve the output feedback control problem of stochastic high-order planar nonlinear systems with output constraint and stochastic integral input-to-state stability(SiISS) inverse dynamics. By employing a key coordinate transformation, a stochastic nonlinear system with output constraint and SiISS inverse dynamics is converted into an unconstrained system. By skillfully constructing an observer and adopting SiISS small-gain conditions, we develop a new output feedback control design and analysis method, and prove that all the closed-system signals are bounded almost surely, the output constraint is not violated almost surely, and the equilibrium point of the closed-loop system is stochastically asymptotically stable.

关键词： stochastic high-order planar nonlinear system output constraint stochastic inverse dynamics output feedback stabilization stochastic integral input-to-state stability (SiISS)

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Fixed-time stabilization of output-constrained stochastic high-order nonlinear systems

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Science China(Information Sciences) 2024年第4期67卷 5-20页

作者： Ruiming xie Shengyuan XU Nanjing University of Science and Technology School of Automation

In this study, the fixed-time stabilization problem of stochastic high-order nonlinear systems with output constraint and high-order and low-order nonlinearities is addressed. A new coordinate transformation is employed to directly convert output-constrained stochastic systems into an equivalent unconstrained *** fully extracting the characteristics of system nonlinearities and using the stochastic fixed-time stability theorem, a new design and analysis method is constructed to guarantee that the trivial solution of the closed-loop system is stochastically fixed-time stable while fulfilling the output constraint.

关键词： stochastic high-order nonlinear system output constraint high-order and low-order nonlinearity fixed-time stabilization finite-time stabilization

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Review of the research on the development and utilization of clay-type lithium resources

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particuology 2024年第4期87卷 46-53页

作者： Ruiqi xie Zhihui Zhao Xiong Tong Xian xie Qiang Song peiqiang Fan Faculty of Land Resource Engineering Kunming University of Science and TechnologyKunming650093China Yunnan Engineering Research Center for Metal Tailings Resource Utilization Kunming650093China

Since the demands for lithium have been in explosive growth recently and several great clay lithium resources were founded in China,the development and utilization of clay-type lithium resources become a hot *** order to provide a guidance for the concentration and extracting lithium of clay-type lithium resources,this review systematically summarized the main types and characteristics of clay-type lithium resources and the research status of lithium extraction from clay lithium ***,the flotation research status of the main mineral of clay lithium ore was also ***,we discussed the difficulties in the development and utilization of clay-type lithium ore and put forward the subsequent research *** paper can provide a guidance for the con-centration and extracting lithium of clay-type lithium resources in the future.

关键词： Clay lithium Clay mineral flotation Lithium extraction Leaching

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Conductive and stable polyphenylene/CNT composite membrane for electrically enhanced membrane fouling mitigation

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Frontiers of Environmental Science & Engineering 2024年第1期18卷 35-47页

作者： Huijuan xie Haiguang Zhang Xu Wang Gaoliang Wei Shuo Chen xie Quan Key Laboratory of Industrial Ecology and Environmental Engineering(Ministry of Education) School of Environmental Science and TechnologyDalian University of TechnologyDalian 116024China

Nanocarbon-based conductive membranes, especially carbon nanotube (CNT)-based membranes, have tremendous potential for wastewater treatment and water purification because of their excellent water permeability and selectivity, as well as their electrochemically enhanced performance (e.g., improved antifouling ability). However, it remains challenging to prepare CNT membranes with high structural stability and high electrical conductivity. In this study, a highly electroconductive and structurally stable polyphenylene/CNT (pp/CNT) composite membrane was prepared by electropolymerizing biphenyl on a CNT hollow fiber membrane. The pp/CNT membrane showed 3.4 and 5.0 times higher electrical conductivity than pure CNT and poly(vinyl alcohol)/CNT (pVA/CNT) membranes, respectively. The structural stability of the membrane was superior to that of the pure CNT membrane and comparable to that of the pVA/CNT membrane. The membrane fouling was significantly alleviated under an electrical assistance of −2.0 V, with a flux loss of only 11.7% after 5 h filtration of humic acid, which is significantly lower than those of pp/CNT membranes without electro-assistance (56.8%) and commercial polyvinylidene fluoride (pVDF) membranes (64.1%). Additionally, the rejection of negatively charged pollutants (humic acid and sodium alginate) was improved by the enhanced electrostatic repulsion. After four consecutive filtration-cleaning cycle tests, the flux recovery rate after backwashing reached 97.2%, which was much higher than those of electricity-free pp/CNT membranes (67.0%) and commercial pVDF membranes (61.1%). This study offers insights into the preparation of stable conductive membranes for membrane fouling control in potential water treatment applications.

关键词： polyphenylene CNTs Membrane Electro-assistance Membrane fouling mitigation

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Extract lithium from clay-type lithium ore by mixed acid and its mechanism Author links open overlay panel

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particuology 2024年第8期91卷 323-332页

作者： Wuchang Zhou Ruiqi xie Xiong Tong Xian xie Yang Liu Zhihui Zhao Faculty of Land Resource Engineering Kunming University of Science and TechnologyKunming650093China Technology Innovation Center for Comprehensive Utilization of Strategic Mineral Resources Ministry of Natural ResourcesChengdu610041China National&Regional Engineering Research Center for Green comprehensive Utilization of Tailing Resources from Metal Minerals Kunming650093China

A roasting-leaching test was carried out for the efficient utilization of clay-type lithium ore in the central region of Yunnan *** test used the mixed acid of sulfuric acid and phosphoric acid as the leaching *** the conditions of roasting temperature of 600℃,roasting time of 1 h,liquid-solid ratio of 5:1,volume ratio of H_(2)SO_(4)solution to H_(3)pO_(4)solution of 45:5,leaching time of 2 h and leaching temperature of 80℃,the leaching rate of lithium was as high as 97.83%.The leaching mechanism was studied by SEM,pore property analysis,XRD and *** was found that the morphology of the ore changed obviously after roasting and leaching,and a certain degree of collapse and fragmentation occurred,which provided favorable spatial conditions for the leaching of *** porosity,total intrusion volume and total pore area also increased after roasting and leaching,thus promoting the leaching of Li^(+).The results showed that chemical reaction taken placed during the roasting and *** phase of the sample changed from chlorite,kaolinite and diaspore(boehmite)mainly to corundum,hematite,periclase and quartz after ***,after leaching,no new phase was produced in the ore sample,and no S and p elements were found on the surface of the ore sample,indicating that the leaching mechanism of lithium might be the ion exchange between H^(+)and Li^(+).

关键词： Clay-type lithium ore Lithium extraction Roasting Leaching

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Game-theoretic multi-agent motion planning in a mixed environment

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Control Theory and Technology 2024年第3期22卷 379-393页

作者： Xiaoxue Zhang Lihua xie School of Electrical and Electronic Engineering Nanyang Technological UniversitySingapore City 639798Singapore

The motion planning problem for multi-agent systems becomes particularly challenging when humans or human-controlled robots are present in a mixed *** address this challenge,this paper presents an interaction-aware motion planning approach based on game theory in a receding-horizon manner Leveraging the framework provided by dynamic potential games for handling the interactions among agents,this approach formulates the multi-agent motion planning problem as a differential potential game,highlighting the effectiveness of constrained potential games in facilitating interactive motion planning among ***,online learning techniques are incorporated to dynamically learn the unknown preferences and models of humans or human-controlled robots through the analysis of observed *** evaluate the effectiveness of the proposed approach,numerical simulations are conducted,demonstrating its capability to generate interactive trajectories for all agents,including humans and human-controlled agents,operating within the mixed *** simulation results illustrate the effectiveness of the proposed approach in handling the complexities of multi-agent motion planning in real-world scenarios.

关键词： Motion planning Differential potential game Multi-agent systems Constrained potential game

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Transfer learning framework for multi-scale crack type classification with sparse microseismic networks

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International Journal of Mining Science and Technology 2024年第2期34卷 167-178页

作者： Arnold Yuxuan xie Bing QLi Department of Civil and Environmental Engineering Western UniversityLondon N6A 3K7Canada

Rock fracture mechanisms can be inferred from moment tensors(MT)inverted from microseismic ***,MT can only be inverted for events whose waveforms are acquired across a network of *** is limiting for underground mines where the microseismic stations often lack azimuthal ***,there is a need for a method to invert fracture mechanisms using waveforms acquired by a sparse microseismic ***,we present a novel,multi-scale framework to classify whether a rock crack contracts or dilates based on a single *** framework consists of a deep learning model that is initially trained on 2400000+manually labelled field-scale seismic and microseismic waveforms acquired across 692 *** learning is then applied to fine-tune the model on 300000+MT-labelled labscale acoustic emission waveforms from 39 individual experiments instrumented with different sensor layouts,loading,and rock types in *** optimal model achieves over 86%F-score on unseen waveforms at both the lab-and *** model outperforms existing empirical methods in classification of rock fracture mechanisms monitored by a sparse microseismic *** facilitates rapid assessment of,and early warning against,various rock engineering hazard such as induced earthquakes and rock bursts.

关键词： Multi-scale Fracture processes Microseismic Acoustic emission Source mechanism Deep learning

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