Damage evolution of rock-encased-backfill structure under stepwise cyclic triaxial loading

Rock-encased-backfill(RB)structures are common in underground mining,for example in the cut-andfill and stoping methods.To understand the effects of cyclic excavation and blasting activities on the damage of these RB structures,a series of triaxial stepwise-increasing-amplitude cyclic loading experiments was conducted with cylindrical RB specimens(rock on outside,backfill on inside)with different volume fractions of rock(VF=0.48,0.61,0.73,and 0.84),confining pressures(0,6,9,and 12 MPa),and cyclic loading rates(200,300,400,and 500 N/s).The damage evolution and meso-crack formation during the cyclic tests were analyzed with results from stress-strain hysteresis loops,acoustic emission events,and post-failure X-ray 3D fracture morphology.The results showed significant differences between cyclic and monotonic loadings of RB specimens,particularly with regard to the generation of shear microcracks,the development of stress memory and strain hardening,and the contact forces and associated friction that develops along the rock-backfill interface.One important finding is that as a function of the number of cycles,the elastic strain increases linearly and the dissipated energy increases exponentially.Also,compared with monotonic loading,the cyclic strain hardening characteristics are more sensitive to rising confining pressures during the initial compaction stage.Another finding is that compared with monotonic loading,more shear microcracks are generated during every reloading stage,but these microcracks tend to be dispersed and lessen the likelihood of large shear fracture formation.The transition from elastic to plastic behavior varies depending on the parameters of each test(confinement,volume fraction,and cyclic rate),and an interesting finding was that the transformation to plastic behavior is significantly lower under the conditions of 0.73 rock volume fraction,400 N/s cyclic loading rate,and 9 MPa confinement.All the findings have important practical implications on the ability of backfill to support underground excavations.

Shear mechanical properties and fracturing responses of layered rough jointed rock-like materials

This study aims to investigate mechanical properties and failure mechanisms of layered rock with rough joint surfaces under direct shear loading.Cubic layered samples with dimensions of 100 mm×100 mm×100 mm were casted using rock-like materials,with anisotropic angle(α)and joint roughness coefficient(JRC)ranging from 15°to 75°and 2-20,respectively.The direct shear tests were conducted under the application of initial normal stress(σ_(n)) ranging from 1-4 MPa.The test results indicate significant differences in mechanical properties,acoustic emission(AE)responses,maximum principal strain fields,and ultimate failure modes of layered samples under different test conditions.The peak stress increases with the increasingαand achieves a maximum value atα=60°or 75°.As σ_(n) increases,the peak stress shows an increasing trend,with correlation coefficients R² ranging from 0.918 to 0.995 for the linear least squares fitting.As JRC increases from 2-4 to 18-20,the cohesion increases by 86.32%whenα=15°,while the cohesion decreases by 27.93%whenα=75°.The differences in roughness characteristics of shear failure surface induced byαresult in anisotropic post-peak AE responses,which is characterized by active AE signals whenαis small and quiet AE signals for a largeα.For a given JRC=6-8 andσ_(n)=1 MPa,asαincreases,the accumulative AE counts increase by 224.31%(αincreased from 15°to 60°),and then decrease by 14.68%(αincreased from 60°to 75°).The shear failure surface is formed along the weak interlayer whenα=15°and penetrates the layered matrix whenα=60°.Whenα=15°,as σ_(n) increases,the adjacent weak interlayer induces a change in the direction of tensile cracks propagation,resulting in a stepped pattern of cracks distribution.The increase in JRC intensifies roughness characteristics of shear failure surface for a smallα,however,it is not pronounced for a largeα.The findings will contribute to a better understanding of the mechanical responses and failure mechanisms of the layered rocks subjected to shear loads.

Blade-Coated Porous 3D Carbon Composite Electrodes Coupled with Multiscale Interfaces for Highly Sensitive All-Paper Pressure Sensors

Flexible and wearable pressure sensors hold immense promise for health monitoring,covering disease detection and postoperative rehabilitation.Developing pressure sensors with high sensitivity,wide detection range,and cost-effectiveness is paramount.By leveraging paper for its sustainability,biocompatibility,and inherent porous structure,herein,a solution-processed all-paper resistive pressure sensor is designed with outstanding performance.A ternary composite paste,comprising a compressible 3D carbon skeleton,conductive polymer poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate),and cohesive carbon nanotubes,is blade-coated on paper and naturally dried to form the porous composite electrode with hierachical micro-and nano-structured surface.Combined with screen-printed Cu electrodes in submillimeter finger widths on rough paper,this creates a multiscale hierarchical contact interface between electrodes,significantly enhancing sensitivity(1014 kPa-1)and expanding the detection range(up to 300 kPa)of as-resulted all-paper pressure sensor with low detection limit and power consumption.Its versatility ranges from subtle wrist pulses,robust finger taps,to large-area spatial force detection,highlighting its intricate submillimetermicrometer-nanometer hierarchical interface and nanometer porosity in the composite electrode.Ultimately,this all-paper resistive pressure sensor,with its superior sensing capabilities,large-scale fabrication potential,and cost-effectiveness,paves the way for next-generation wearable electronics,ushering in an era of advanced,sustainable technological solutions.

Influence of High-Pressure Induced Lattice Dislocations and Distortions on Thermoelectric Performance of Pristine SnTe

As a sister compound of PbTe, SnTe possesses the environmentally friendly elements. However, the pristine SnTe compounds suffer from the high carrier concentration, the large valence band offset between the L and Σpositions and high thermal conductivity. Using high-pressure and high-temperature technology, we synthesized the pristine SnTe samples at different pressures and systemically investigated their thermoelectric properties.High pressure induces rich microstructures, including the high-density dislocations and lattice distortions, which serve as the strong phonon scattering centers, thereby reducing the lattice thermal conductivity. For the electrical properties, pressure reduces the harmful high carrier concentration, due to the depression of Sn vacancies.Moreover, pressure induces the valence band convergence, reducing the energy separation between the L and Σpositions. The band convergence and suppressed carrier concentration increase the Seebeck coefficient. Thus, the power factors of pressure-sintered compounds do not deteriorate significantly under the condition of decreasing electrical conductivity. Ultimately, for a pristine SnTe compound synthesized at 5 GPa, a higher ZT value of 0.51 is achieved at 750 K, representing a 140% improvement compared to the value of 0.21 obtained using SPS. Therefore, the high-pressure and high-temperature technology is demonstrated as an effectively approach to optimize thermoelectric performance.

Machine Learning‑Based Detection of Graphene Defects with Atomic Precision

Defects in graphene can profoundly impact its extraordinary properties,ultimately influencing the performances of graphene-based nanodevices.Methods to detect defects with atomic resolution in graphene can be technically demanding and involve complex sample preparations.An alternative approach is to observe the thermal vibration properties of the graphene sheet,which reflects defect information but in an implicit fashion.Machine learning,an emerging data-driven approach that offers solutions to learning hidden patterns from complex data,has been extensively applied in material design and discovery problems.In this paper,we propose a machine learning-based approach to detect graphene defects by discovering the hidden correlation between defect locations and thermal vibration features.Two prediction strategies are developed:an atom-based method which constructs data by atom indices,and a domain-based method which constructs data by domain discretization.Results show that while the atom-based method is capable of detecting a single-atom vacancy,the domain-based method can detect an unknown number of multiple vacancies up to atomic precision.Both methods can achieve approximately a 90%prediction accuracy on the reserved data for testing,indicating a promising extrapolation into unseen future graphene configurations.The proposed strategy offers promising solutions for the non-destructive evaluation of nanomaterials and accelerates new material discoveries.

Development of a fast electron bremsstrahlung diagnostic system based on LYSO and silicon photomultipliers during lower hybrid current drive for tokamak

A novel real time fast electron bremsstrahlung (FEB) diagnostic system based on the lutetium yttrium oxyorthosilicate scintillators (LYSO) and silicon photomultipliers (SiPM) has been developed for tokamak.The diagnostic system is dedicated to study the FEB emission in the hard x-ray (HXR) energy range between 10 and 200 keV during the lower hybrid current drive.The system consists of a detection module and three data acquisition and processing (DAP)boards.The detection module consists of annulus LYSO-SiPM detector array and a 12-channel preamplifier module.The DAP boards upload the data to the host computer for displaying and storing through PXI bus.The time and space resolutions of the system are 10 ms and 4 cm,respectively.The experimental results can show the evolution over time and the spatial distribution of FEB.This paper presents the system performance and typical discharge results.

Shear mechanical properties and energy evolution of rock-like samples containing multiple combinations of non-persistent joints

Discontinuities are often considered as important factors responsible for the instability caused by shear failure in engineering rock mass,and energy-driven instability is the root cause of rock failure.However,few studies focus on the energy evolution during the failure process using a three-dimensional(3D)numerical model.In this study,a series of laboratory direct shear tests on rock-like samples is numer-ically simulated using bonded particle models(BPMs)with multiple combinations of discontinuous in the particle flow code(PFC3D),in which the location and size of the particles conform to the uniform distribution.The effects of joint row number and inclination on the stress-strain characteristics and failure mode of rock were studied from the perspective of microcrack growth and energy evolution.The results showed that,when the number of joint rows Nr>1,the shear failure region does not change with the increase of Nr for the type B(2-columnn multiple-row at center)and the type C(2-column multiple-row at edge)as compared to the type A(1-column multiple-row at center)joint models.Notably,joints significantly increase the post-peak energy dissipation but have little effect on the proportion of energy before the peak.Friction consumes most of the energy while kinetic energy accounts for less than 1%of total energy during the shear process.Peak elastic strain energy follows the variation trend of peak shear displacement.The development and accumulation of microcracks directly affect the energy dissipation,and there is a significant linear relationship between the cumulative number of critical microcracks and the critical dissipated energy at the failure,when the dip direction of joints is opposite to the shear direction,more microcracks will be accumulated at the peak time,resulting in more energy dissipation.The results contribute to deeply understanding the shear failure process of non-persistent jointed mass.

Advances in Research of Components,Pharmacological Activity and Clinical Application of Vicatia thibetica de Boiss

Vicatia thibetica de Boiss is a Tibetan medicinal herb and mainly contains chemical components such as flavonoids,β-sitosterol and ferulic acid.It has good pharmacological effects such as anti-inflammatory,analgesic,anti-fatigue,anti-oxidation,anti-aging and enhancing immunity.Based on relevant domestic and foreign literature,this paper comprehensively reviews the main components,pharmacological activity and clinical prescription application of V.thibetica de Boiss,to provide a reference for the in-depth research and comprehensive development and utilization of V.thibetica de Boiss.

金钱激励和社交激励对运动行为的促进作用:基于一项在线健身项目的实证研究

鉴于员工身体健康对工作的重要性,很多组织广泛开展健身运动鼓励员工锻炼身体。随着可穿戴设备(例如智能手环)和健身应用(手机健身应用)的广泛使用,越来越多的组织使用在线健身项目形式,员工使用可穿戴设备在线跟踪身体活动来完成健身任务。为了鼓励员工的参与性,在线健身项目通常采用金钱激励或社交激励策略。然而,当这两种类型的激励措施共同使用时,其交互作用却鲜有研究。此外,组织者也缺乏相应的科学知识以设置最佳水平的健身挑战。因此,本研究采用实证研究方法验证金钱激励和社交激励对员工锻炼行为的联合效应。基于国内一所大学在线健身项目的面板数据集,包括2578名参与者在100 d内的日常锻炼记录,本研究发现金钱激励和社交激励之间存在挤出效应——当存在未实现的金钱目标时,社交激励(即,社会支持和社会传染)的影响相对较弱;一旦实现了金钱目标,社交激励的影响将会变强。此外,本研究还发现当动态目标设定在最佳水平时,参与者的锻炼行为将最大化。本研究的结论将为组织者更好地设计在线健身项目提供理论指导。

Development of the HL-2M digital pulse analysis system

A digital pulse analysis system is an important diagnostic system in nuclear physics experimental research.In response to the demand for reflecting the particle state in a nuclear physics experiment,we have designed and developed a real-time digital pulse analysis system and applied it to the digital nuclear pulse waveform discrimination of different detectors in the HL-2M tokamak.The system is based on the peripheral component interconnect extensions for instrumentation(PXI)platform,while its software was written in LABVIEW.The key technologies involved in the system implementation include digital pulse analysis technology,digital discrimination technology,pulse height analysis technology,etc.The system has been applied to the plastic scintillator detector at the Neutron Source Lab of the University of Science and Technology of China.And the experimental results indicate that the system can discriminate between neutron(n)particles and gamma(γ)particles well when used to measure the plastic scintillator detector.

Forward-Backward Synergistic Acceleration Pursuit Algorithm Based on Compressed Sensing

We propose the Forward-Backward Synergistic Acceleration Pursuit (FBSAP) algorithm in this paper. The FBSAP algorithm inherits the advantages of the Forward-Backward Pursuit (FBP) algorithm, which has high success rate of reconstruction and does not necessitate the sparsity level as a priori condition. Moreover, it solves the problem of FBP that the atom can be selected only by the fixed step size. By mining the correlation between candidate atoms and residuals, we innovatively propose the forward acceleration strategy to adjust the forward step size adaptively and reduce the computation. Meanwhile, we accelerate the algorithm further in backward step by fusing the strategy proposed in Acceleration Forward-Backward Pursuit (AFBP) algorithm. The experimental simulation results demonstrate that FBSAP can greatly reduce the running time of the algorithm while guaranteeing the success rate in contrast to FBP and AFBP.

Development and preclinical evaluation of multifunctional hydrogel for precise thermal protection during thermal ablation

Image-guided thermal ablation(TA),which is less invasive,has been widely applied for treating various kinds of tumors.However,TA still poses the potential risk of thermal damage to sensitive tissue nearby.Therefore,an adjunctive thermoprotective hydrodissection technique with constant injection of 5%glucose(5%Glu)has currently been adopted for clinical application,but this may be hazardous to humans.In this study,a multifunctional hyaluronic acid-based hydrogel(HA-Dc)was developed for hydrodissection.Compared with 5%Glu(the most clinically used solution)and the previously reported F127 hydrogel,the HA-Dc hydrogel was studied in vitro in a porcine liver model and in vivo in a rabbit model and showed good injectability and better tissue retention,stability,and thermoprotective properties throughout the TA procedure.Furthermore,in the preclinical evaluation in a Macaca fascicularis(M.fascicularis)model,HA-Dc showed excellent performance in terms of stricter neuroprotection compared with 5%Glu.In addition,the HA-Dc hydrogel with good biocompatibility and controllable degradation behavior in vivo could be a promising platform for thermal protection during clinical TA procedures.

Accelerated corrosion of 316L stainless steel in a simulated oral environment via extracellular electron transfer and acid metabolites of subgingival microbiota

316L stainless steel(SS)is widely applied as microimplant anchorage(MIA)due to its excellent mechanical properties.However,the risk that the oral microorganisms can corrode 316L SS is fully neglected.Microbiologically influenced corrosion(MIC)of 316L SS is essential to the health and safety of all patients because the accelerated corrosion caused by the oral microbiota can trigger the release of Cr and Ni ions.This study investigated the corrosion behavior and mechanism of subgingival microbiota on 316L SS by 16S rRNA and metagenome sequencing,electrochemical measurements,and surface characterization techniques.Multispecies biofilms were formed by the oral subgingival microbiota in the simulated oral anaerobic environment on 316L SS surfaces,significantly accelerating the corrosion in the form of pitting.The microbiota samples collected from the subjects differed in biofilm compositions,corrosion behaviors,and mechanisms.The oral subgingival microbiota contributed to the accelerated corrosion of 316L SS via acidic metabolites and extracellular electron transfer.Our findings provide a new insight into the underlying mechanisms of oral microbial corrosion and guide the design of oral microbial corrosion-resistant materials.

In-situ Horizontal Extrusion Test of Herbaceous Root-Soil with Different Root Types

The influence of different types of roots on the soil is complex and still remains unclear.Four in-situ extrusion tests were conducted on two types of root systems,namely fibrous and tap root system,for three plants,Eleusine indica,Potentilla anserine,and Artemisia argyi,according to the classification in Botany,and the thrust-displacement curves and failure patterns of different samples were analysed by comparison to fill the aforementioned gap.Results reveal that the roots can reduce the characteristics of soil brittleness and enhance its capability to resist large deformation,and different root types contribute different effects to the strain-hardening behavior of the root-soil mass.The contribution of the fibrous root system to strength is limited,whilst the tap root system substantially enhances strength and stiffness.Results of failure patterns show that fibrous and tap root systems affect soil solidification and surface cracking reduction.However,the effect of the tap root system depends on the composition of lateral and tap roots:long and rich lateral roots are effective for resisting the creation of cracks,but thick tap roots with few and thin lateral roots may lead to several surface cracks.

Effect of Y and Ce Micro-alloying on Microstructure and Hot Tearing of As-Cast Al-Cu-Mg Alloy

In this work,the Al-Cu-Mg alloy with different Y(0-0.2 wt%)and Ce(0.5-1.5 wt%)are designed.The effect of mixed addition of Y and Ce on the grain structure and hot tearing for Al-4.4Cu-1.5Mg-0.15Zr alloy was investigated using"cross"hot tearing mould.The results indicate that as rare earth Y and Ce increases,the grain size becomes finer,the grain morphology changes from dendrite to equiaxed grain,and effectively reduce the hot tearing sensitivity coefficient(HTS1)and crack susceptibility coefficient(CSC)of the alloy.With the increase of Ce element(0.5-1.5 wt%),the hot tearing susceptibility of the alloy decreases first and then increases.With the increase of Y element(0-0.2 wt%),the hot tearing sensitivity of the alloy decreases.When the content of rare earth is 0.2 wt%Y+1.0 wt%Ce,the minimum HTS1 value and CSC value of the alloy are 68 and 0.53,respectively.Rare earth Ce refines the alloy microstructure,shortens the feeding channel,and reduces the hot tearing initiation.Meanwhile,the rare earth Y can form Al6Cu6Y phase at the grain boundary,improve the feeding capacity of the alloy.Therefore,appropriate addition of rare earth Y and Ce can effectively reduce the hot tearing tendency of the alloy.

Spatially resolved metabolomics visualizes heterogeneous distribution of metabolites in lung tissue and the anti-pulmonary fibrosis effect of Prismatomeris connate extract

Pulmonary fibrosis (PF) is a chronic progressive end-stage lung disease. However, the mechanisms underlying the progression of this disease remain elusive. Presently, clinically employed drugs are scarce for the treatment of PF. Hence, there is an urgent need for developing novel drugs to address such diseases. Our study found for the first time that a natural source of Prismatomeris connata Y. Z. Ruan (Huang Gen, HG) ethyl acetate extract (HG-2) had a significant anti-PF effect by inhibiting the expression of the transforming growth factor beta 1/suppressor of mothers against decapentaplegic (TGF-β1/Smad) pathway. Network pharmacological analysis suggested that HG-2 had effects on tyrosine kinase phosphorylation, cellular response to reactive oxygen species, and extracellular matrix (ECM) disassembly. Moreover, mass spectrometry imaging (MSI) was used to visualize the heterogeneous distribution of endogenous metabolites in lung tissue and reveal the anti-PF metabolic mechanism of HG-2, which was related to arginine biosynthesis and alanine, asparate and glutamate metabolism, the downregulation of arachidonic acid metabolism, and the upregulation of glycerophospholipid metabolism. In conclusion, we elaborated on the relationship between metabolite distribution and the progression of PF, constructed the regulatory metabolic network of HG-2, and discovered the multi-target therapeutic effect of HG-2, which might be conducive to the development of new drugs for PF.

A statistical sensing method by utilizing Wi-Fi CSI subcarriers:Empirical study and performance enhancement

In modern Wi-Fi systems,channel state information(CSI)serves as a foundational support for various sensing applications.Currently,existing CSI-based techniques exhibit limitations in terms of environmental adaptability.As such,optimizing the utilization of subcarrier CSI stands as a critical avenue for enhancing sensing performance.Within the OFDM communication framework,this work derives sensing outcomes for both detection and estimation by harnessing the CSI from every individual measured subcarrier,subsequently consolidating these outcomes.When contrasted against results derived from CSI based on specific extraction protocols or those obtained through weighted summation,the methodology introduced in this study offers substantial improvements in CSI-based detection and estimation performance.This approach not only underscores the significance but also serves as a robust exemplar for the comprehensive application of CSI.

Nonlinear system identification framework of folding fins with freeplay using backbone curves

Due to wear and manufacturing tolerance,the freeplay is unavoidable in the hinges of folding fins,which exerts significant effects on the aerodynamic characteristics.This paper proposes a backbone-curve-based framework for the dynamical identification of folding fins containing the freeplay nonlinearity.With no need to measure the input force signal and the response signals of nonlinear related Degrees of Freedom(DOFs),the proposed method is more direct and elegant than most existing nonlinear identification approaches,and it contains three steps:Firstly,the underlying linear model of the folding fin structure is obtained through the modal test on its linear sub-parts,and then,the harmonic approximation solves the analytical expressions of the backbone curves of measurable DOFs.Secondly,response data measured from the sine-sweep test are used to extract the fitting points of backbone curves for these DOFs.Finally,the curve fitting approach is applied to identify the freeplay parameters.A series of numerical experiments verify the effectiveness of the proposed method.A real-life folding fin structure is also employed to illustrate how the method can be applied.These examples demonstrate that the identification framework can give an accurate dynamic model of the folding fin structure.

Recent progress in the all-solid-state flexible supercapacitors

In the past few years,supercapacitors(SCs)have attracted great attention in both academic and industrial sectors due to their high energy storage efficiency,reliable stability,and eco-friendly process.Flexible solid-state SCs as one of the ongoing focuses for the development of wearable and portable electronics have become the most promising energy storage devices for the smart power system due to their high power density,fast electrochemical response,high efficiency on the charge-discharge process,and excellent electrochemical stability.In this study,the recent progress in the electrodes and electrolytes used for approaching high-performance of the all-solid-state flexible SCs is reviewed.We first introduce basic operational principles of various SCs.And then we overview the electrode materials including carbon materials,conducting polymers,transition metal oxides/chalcogenides/nitrides,MXenes,metal-organic frameworks,covalent-organic frameworks,and the polymer-based solid-state electrolytes in different systems.Afterward,we summarize recent progress in the development of the all-solid-state flexible SCs and outlook for future research directions.

Geological evaluation for the carbon dioxide geological utilization and storage(CGUS)site:A review

Carbon dioxide(CO_(2))geological utilization and storage(CGUS)is the key link of CO_(2)capture,utilization,and storage(CCUS).The accurate characterization of the geological body structure is a vital prerequisite of CGUS.This paper gives a review of the multi-scale three-dimensional geological structure characterization and site selection of CO_(2)storage.It shows that there is a lack of systematic and high-precision methods for transparency characterization of multi-scale three-dimensional engineering geological structure and hydrogeological structure of a CO_(2)storage site.There is no clear understanding of the fracture evolution and gas-liquid migration process of multi-scale geological body structure under the disturbance of CO_(2)injection.There is a lack of sufficient quantitative methods for the dynamic evaluation of CO_(2)geological storage potential.The geological suitability evaluation method for site selection of CO_(2)storage is rough and has poor applicability,which is difficult to satisfy the urgent needs of CGUS site selection in the whole process of CO_(2)sequestration industrialization in the future.Thus,it is required to conduct studies on the transparency characterization of geological body structure and intelligent site selection for CO_(2)storage,which is of great importance for CGUS engineering practice.