First-principles investigation on stability and electronic structure of Sc-dopedθ′/Al interface in Al−Cu alloys

The properties of Sc-dopedθ′(Al_(2)Cu)/Al interface in Al−Cu alloys were investigated by first-principles calculations.Sc-doped semi-coherent and coherentθ′(Al_(2)Cu)/Al interfaces(Sc doped in Al slab(S1 site),Sc doped inθ′slab(S2 site))were modeled based on calculated results and reported experiments.Through the analysis of interfacial bonding strength,it is revealed that the doping of Sc at S1 site can significantly decrease the interface energy and increase the work of adhesion.In particular,the doped coherent interface with Sc at S1 site which is occupied by interstitial Cu atoms has very good bonding strength.The electronic structure shows the strong Al—Cu bonds at the interfaces with Sc at S1 site,and the Al—Al bonds at the interfaces with Sc at S2 site are formed.The formation of strong Al—Cu and Al—Al bonds plays an important role in the enhancement of doped interface strength.

Investigation of a non-explosive directional roof cutting technology for self-formed roadway

Traditional explosives have characteristics of high risk,large vibration,and poor directional fracturing.Consequently,an instantaneous expander with a single crack surface(IESCS),which is a novel nonexplosive directional rock-breaking technique,has been developed.The directional roof-cutting mechanism of the IESCS method,driven by high-pressure gas,was theoretically analyzed.Laboratory experiments and numerical simulations proved the directional slitting effect of the IESCS method to be excellent.Compared with shaped-charge blasting,the charge of IESCS was reduced by 8.9%,but the crack rate increased by 9%in field tests.After IESCS pre-splitting,the roof directionally collapsed along the cutting line,and the gangue filled the goaf.Moreover,the directional roof cutting by the IESCS could decrease roadway stress.The average pressure of hydraulic supports on the cutting side of the roof was 31%lower than that on the non-cutting side of the roof after pre-splitting.After the self-formed roadway constructed by the IESCS was stabilized,the final relative displacement of the roof and floor was 157.3 mm,meeting the required standard of the next working face.Thus,the IESCS was effectively applied to directional roof pre-splitting.The results demonstrate the promising potential of IESCS in the mining and geotechnical fields.

Effect of cyclic wetting-drying on tensile mechanical behavior and microstructure of clay-bearing sandstone

The understanding of the weakening mechanism of tensile strength of rock subjected to cyclic wetting-drying is critical for rock engineering.Tensile strength tests were conducted on a total of 35 sandstone specimens with different wetting-drying cycles.The crack propagation process and acoustic emission characteristics of the tested samples were obtained through a high-speed camera and acoustic emission system.The results indicate that the tensile strength is observably reduced after cyclic wetting-drying,and the extent of the reduction is not only related to the number of wettingdrying cycle,but also closely related to the clay mineral content of the sample.In addition,as the cycles of wetting-drying increase,the effect of each single cycle on tensile strength get reduced until it becomes constant.Moreover,the crack initiation and penetration time is prolonged as the number of wetting-drying cycle increases,which indicates that cyclic wetting-drying weakens the rock stiffness and enhances the ductility of sandstone.Meanwhile,the acoustic emission characteristics of the tested samples further confirmed the ductile behaviour of the sandstone samples with increasing wetting-drying cycle.Furthermore,through the analysis of the microstructure and mineral composition of the samples with different wetting-drying cycles,it is concluded that the main weakening mechanisms of sandstones containing clay minerals are frictional reduction,chemical and corrosive deterioration.

Sequential invasive-noninvasive mechanical ventilation weaning strategy for patients after tracheostomy

BACKGROUND: Because the continuity and integrity of the trachea are likely damaged to some extent after tracheostomy, the implementation of sequential ventilation has certain difficulties, and sequential invasive-noninvasive ventilation on patients after tracheostomy is less common in practice. The present study aimed to investigate the feasibility of invasive-noninvasive sequential weaning strategy in patients after tracheostomy.METHODS: Fifty patients including 24 patients with withdrawal of mechanical ventilation(conventional group) and 26 patients with sequential invasive-noninvasive weaning by directly plugging of tracheostomy(sequential group) were analyzed retrospectively after appearance of pulmonary infection control(PIC) window. The analysis of arterial blood gases, ventilator-associated pneumonia(VAP) incidence, the total duration of mechanical ventilation, the success rate of weaning and total cost of hospitalization were compared between the two groups.RESULTS: Arterial blood gas analysis showed that the sequential weaning group was better than the conventional weaning group 1 and 24 hours after invasive ventilation. The VAP incidence was lowered, the duration of mechanical ventilation shortened, the success rate of weaning increased, and the total cost of hospitalization decreased.CONCLUSION: Sequential invasive-noninvasive ventilator weaning is feasible in patients after tracheostomy.

Effect of quenching-partitioning treatment on the microstructure, mechanical and abrasive properties of high carbon steel

The present work employed the X-ray diffraction, scanning electron microscopy, electron backscattered diffraction, and electron probe microanalysis techniques to identify the microstructural evolution and mechanical and abrasive behavior of high carbon steel during quenching-partitioning treatment with an aim to enhance the toughness and wear resistance of high carbon steel.Results showed that, with the increase in partitioning temperature from 250 to 400℃, the amount of retained austenite(RA) decreased resulting from the carbide precipitation effect after longer partitioning times.Moreover, the stability of RA generally increased because of the enhanced degree of carbon enrichment in RA.Given the factors affecting the toughness of high carbon steel, the stability of RA associated with size, carbon content, and morphology plays a significant role in determining the toughness of high carbon steel.The analysis of the wear resistance of samples with different mechanical properties shows that hardness is the primary factor affecting the wear resistance of high carbon steel, and the toughness is the secondary one.

Impact of crosslinking/riboflavin-UVA-photodynamic inactivation on viability,apoptosis and activation of human keratocytes in vitro

Riboflavin-UVA photodynamic inactivation is a potential treatment altemative in therapy resistant infectious keratitis. The purpose of our study was to determine the impact of riboflavin-UVA photodynamic inactivation on viability, apop- tosis and activation of human keratocytes in vitro. Primary human keratocytes were isolated from human corneal buttons and cultured in DMEM/Ham＇s F12 medium supplemented with 10% fetal calf serum. Keratocytes underwent UVA light illumination （375 nm） for 4.10 minutes （2 J/cm2） during exposure to different concentrations of riboflavin. Twenty-four hours after treatment, cell viability was evaluated photometrically, whereas apoptosis, CD34 and alpha-smooth muscle actin （α-SMA） expression were assessed using flow cytometry. We did not detect significant changes in cell viability, apoptosis, CD34 and α-SMA expression in groups only treated with riboflavin or UVA light. In the group treated with riboflavin-UVA-photodynamic inactivation, viability of keratocytes decreased significantly at 0.1% riboflavin （P〈0.01） while the percentage of CD34 （P〈0.01 for both 0.05% and 0.1% riboflavin） and alpha-SMA positive keratocytes （P〈0.01 and P〈0.05 for 0.05% and 0.1% riboflavin, respectively） increased significantly compared to the controls. There was no significant change in the percentage of apoptotic keratocytes compared to controls at any of the used ribo- flavin concentrations （P=0.09 and P=0.13）. We concluded that riboflavin-UVA-photodynamic-inactivation decreases viability of myofibroblastic transformation and multipotent haematopoietic stem cell transformation; however, it does not have an impact on apoptosis of human keratocytes in vitro.

Tuning the reversible chemisorption of hydroxyl ions to promote the electrocatalysis on ultrathin metal-organic framework nanosheets

Interfacial engineering to alter the configuration of active sites in heterogeneous catalysts is a potential strategy for activity enhancement,but it remains unelucidated for metal-organic frameworks(MOFs).Here,we demonstrate that the surface of two-dimensional Co-based MOF is modified by decorating Ag quantum dots(QDs)simply through in-situ reduction of Ag+ions.Toward oxygen evolution reaction(OER),it reveals that the catalysis is mediated by the reversible redox of Co sites between Co^(3+) and Co^(4+) states coupling with transfer of OHions.The decoration of Ag QDs decreases the redox potential of Co sites,and thus effectively decreases the overpotential of OER.The TOFs of Co sites are increased by 77 times to reach 5.4 s^(-1) at an overpotential of 0.35 V.We attribute the activity enhancement to the tuning of the coupling process between Co sites and OHions during the redox of Co sites by Ag QDs decoration based on Pourbaix analysis.

Differences of polygonal faults related to upper Miocene channels:a case study from the Beijiao sag of Qiongdongnan basin,South China Sea

Deep-water coarse-grained channels are embedded within a polygonal fault tier,and the polygonal faults(PFs)present non-polygonal geometries rather than classic polygonal geometry in plan view.However,PFs present differences when they encounter deep-water(coarse-grained vs.fine-grained)channels with different lithology,which has not been further studied to date.Three-dimensional(3D)seismic data and a drilling well from Beijiao sag of Qiongdongnanbasin,South China Sea were utilized to document the plan view and cross-sectional properties of the PFs and their differences and genetic mechanism were investigated.Results show that,first,PFs can be divided morphologically into channel-segmenting PFs and channel-bounding PFs in plan view.The former virtually cuts or segments the axes of channels in highand low-amplitudes,and the latter nearly parallels the boundaries of the channels.Both are approximately perpendicular to each other.Secondly,channel-bounding PFs that related to low-amplitude channels are much longer than those of high-amplitude ones;channel-segmenting PFs related to low-amplitude channels are slightly longer than the counterparts related to high-amplitude channels.Lastly,the magnitudes(e.g.,heights)of the PFs are proportional to the scales(e.g.,widths and heights)of low-amplitude channels,whereas the magnitudes of the PFs are inversely proportional to the scales of high amplitude channels.Coarse-grained(high amplitude)channels act as a mechanical barrier to the propagation of PFs,whereas fine-grained(low-amplitude)channels are beneficial to the propagation and nucleation of PFs.Additionally,the genetic mechanism of PFs is discussed and reckoned as combined geneses of gravitational spreading and overpressure hydrofracture.The differences of the PFs can be used to reasonably differentiate coarse-grained channels from fine-grained channels.This study provides new insights into understanding the different geometries of the PFs related to coarse-grained and fine-grained channels and their genetic mechanism.

Dynamic Spatial Evolution of Market-oriented Supply Level of State-owned Land

The purpose of this study is to analyze the characteristics of the spatial distribution and change trend of the marketing level of stateowned land supply so as to provide policy recommendations. Method of spatial autocorrelation analysis is employed. The results indicate that the spatial layout of the land supply marketing level is generally dispersed,but it does assemble in some specific area. The correlation between the marketing level of state-owned land supply and the economic development is not statistically significant. But their relations fluctuate obviously. The overall marketing level of state-owned land supply is increasing and spatially concentrated. The expansion rate of marketing has decreased first and then increased and stabilized now. The high-value cluster center of marketing level of state-owned land supply exists all over the country; however the existence probability of the cluster is bigger in undeveloped areas. It is concluded that spatial autocorrelation analysis is a good method to quantitatively analyze the spatial variation of marketing level of state-owned land supply in China. To grasp the spatial and temporal variations of the marketing level of state-owned land supply is also good to enhance running of the state-owned land market.

Floor heave mechanism for gob-side entry retaining with concrete blocks and control method:A case study

The issue of significant floor heave deformation in gob-side entry retaining has long been a challenging problem in the context of longwall mining.This paper studies the floor heave failure mechanism and control method for gob-side entry retaining with concrete blocks in Guizhou Faer Coal Mine in China.Based on Rankine’s earth pressure theory,the effective shear stress equation for the plastic slip of roadway floor is established.The deformation mechanism of floor heave in a retaining roadway with a block wall is revealed in this study.The new comprehensive control method is proposed,encompassing roof pre-splitting blasting for pressure relief,reinforcing cables for roof control,double directions control bolts for concrete block,and pliability cushion yielding pressure.FLAC3D numerical calculation model is established,which shows that the new method can effectively reduce the average vertical stress peak value of the entity coal floor by 34.6%and significantly reduce the pressure source causing the roadway floor heave.Besides,a multi-parameter real-time online monitoring system for mine pressure was designed,and field tests were carried out.The results show that the maximum value of roadway floor heave under the new method is 163 mm,reduced by 66.9%,and the roadway floor heave is effectively controlled.These research findings offer a fresh perspective and new ideas for controlling floor heave in mining operations.

Delivering quantum dots to lubricants: Current status and prospect

Very recently,two-dimensional quantum dots(2D QDs)have been pioneeringly investigated as lubricant additives,which exhibit superior friction-reducing and wear resistance.Compared with 2D nanoparticles,2D QDs possess small size(~10 nm)and abundant active groups.These distinguished advantages enable them to quickly disperse into common lube mediums and maintain long-term storage stability.The good dispersion stability of 2D QDs not only effectively improves their embedding capacity,but also enables continuous supplements of lubricants during the sliding process.Therefore,2D QDs are attracting increasing research interest as efficient lubricants with desirable service life.In this review,we focus on the latest studies of 2D QDs as liquid lubricant additives(both in polar and nonpolar mediums),self-lubricating solid coatings and gels,etc.Various advanced strategies for synthesis and modification of 2D QDs are summarized.A comprehensive insight into the tribological behavior of a variety of 2D QDs together with the associated mechanism is reviewed in detail.The superior lubricating performances of 2D QDs are attributed to various mechanisms,including rolling effect,self-mending performance,polishing effect,tribofilm formation,nanostructure transfer and synergistic effects,etc.Strategies for friction modulation of 2D QDs,including internal factors(surface modification,elemental doping)and extrinsic factors(counter surfaces,test conditions)are discussed,special attentions for achieving intelligent tribology toward superlubricity and bio-engineering,are also included.Finally,the future challenges and research directions regarding QDs as lubricants conforming to the concept of“green tribology”toward a sustainable society are discussed.

Methods to Make Conductive Covalent Organic Frameworks for Electrocatalytic Applications

Covalent organic frameworks(COFs) represent a new class of crystalline organic polymer materials with the characteristics of high specific surface area, uniform pore distribution, high porosity, low density, devisable chain structures and good structural stability. These collective features play an important role in creating highly efficient electrocatalysts for energy conversion and fuel generation. Recent years have witnessed considerable advances in COF-based electrocatalysts for major electrocatalytic reactions such as oxygen reduction, oxygen evolution, hydrogen evolution, and reduction of carbon dioxide and nitrogen. However, it has been widely accepted that the poor electrical conductivity of most pristine COFs limits the further progress in electrocatalytic field. In this review, recent structural engineering strategies are summarized toward improving the electrical conductivity of COFs for achieving high performance. The researches of conductive COFs and their derivatives are described in detail. The structure-activity relationship between molecular structures of COFs and their electrocatalytic performance is emphasized. Lastly, current challenges and future perspectives on fabricating COFs as promising electrocatalysts are discussed. The purpose of this review is to provide guidelines for the preparation of highly efficient COF-based electrocatalytic materials with a view to replacing the commercially available noble metal-based electrocatalysts.

A novel computational model for isotropic interfacial energies in multicomponent alloys and its coupling with phase-field model with finite interface dissipation

In this work,a novel computational model for the description of the temperature-and composition-dependent isotropic interfacial energy in multicomponent alloys was first developed in the framework of the CALculation of PHAse Diagram(CALPHAD)approach and implemented in a home-made code.By linking to the open-source code for interfacial energy calculation in alloys,OpenIEC,the databases for isotropicγ/liquid andγ/γ’interfacial energies in Ni-Al,Ni-Cr,Al-Cr,and Ni-Al-Cr systems were then efficiently established.After that,a direct coupling strategy between the current CALPHAD interfacial en-ergy database and the phase-field model with finite interface dissipation was proposed and applied to three-dimensional(3-D)phase-field simulations of the primaryγdendritic growth in both Ni-Al and Ni-Al-Cr alloys during isothermal solidification.The effect of the interfacial energy on the morphology,tip growth rate,and partitioning coefficients in primaryγdendrites of binary Ni-Al and ternary Ni-Al-Cr alloys was investigated by comprehensively comparing the phase-filed simulation results using the composition-/temperature-dependent interfacial energies with those using the constant value.It is an-ticipated that the presently developed CALPHAD model for interfacial energy is of general validity for different multicom ponent alloys and should be integrated with the phase-field model for quantitative simulation of their microstructure evolution.

Long-Term Trend Analysis of Major Human Helminth Infections — Guangdong Province, China, 1988–2021

Introduction:Although helminth infections threaten millions of people worldwide,the spatiotemporal characteristics remain unclear across China.This study systematically describes the spatiotemporal changes of major human helminth infections and their epidemiological characteristics from 1988 to 2021 in Guangdong Province,China.Methods:The survey data in Guangdong Province were primarily obtained from 3 national surveys implemented during 1988–1992,2001–2004,and 2014–2016,respectively,and from the China Information System for Disease Control and Prevention during 2019–2021.A modified Kato-Katz technique was used to detect parasite eggs in collected fecal samples.Results:The overall standardized infection rates(SIRs)of any soil-transmitted helminths(STH)and Clonorchis sinensis decreased from 65.27%during 1988–1992 to 4.23%during 2019–2021.In particular,the SIRs of STH had even more of a decrease,from 64.41%during 1988–1992 to 0.31%during 2019–2021.The SIRs of Clonorchis sinensis in the 4 surveys were 2.40%,12.17%,5.20%,and 3.93%,respectively.This study observed different permutations of gender,age,occupation,and education level on the SIRs of helminths.Conclusions:The infection rate of STH has substantially decreased.However,the infection rate of Clonorchis sinensis has had fewer changes,and it has become the dominant helminth.

Complex hexagonal close-packed dendritic growth during alloy solidification by graphics processing unit-accelerated three-dimensional phase-field simulations:demo for Mg–Gd alloy

In this study,insights into the effect of interfacial anisotropy on a complex hexagonal close-packed(hcp) dendritic growth during alloy solidification were gained by graphics processing unit(GPU)-accelerated three-dimensional(3D) phase-field simulations,as demonstrated for a Mg-Gd alloy.An anisotropic phasefield model with finite interface dissipation was developed by incorporating the contribution of the anisotropy of interfacial energy into the total free energy functional.The modified spherical harmonic anisotropy function was then chosen for the hcp crystal.The GPU parallel computing algorithm was implemented in the present phase-field model,and a corresponding code was developed in the compute unified device architecture parallel computing platform.Benchmark tests indicated that the calculation efficiency of a single TESLA V100 GPU could be~80times that of open multi-processing(OpenMP) with eight central processing unit cores.By coupling the phase-field model with reliable thermodynamic and interfacial energy descriptions,the 3D phase-field simulation of α-Mg dendritic growth in the Mg-6Gd(in wt%) alloy during solidification was performed.Various two-dimensional dendrite morphologies were revealed by cutting the simulated 3D dendrite along different crystallographic planes.Typical sixfold equiaxed and butterflied microstructures observed in experiments were well reproduced.

Experimental investigation of the flow characteristics of jet pumps for zero flow-ratio conditions

Experimental research was conducted on the performance curves and the cavity evolution for different flow and geometric parameters in jet pumps for zero flow ratio(ZFR)conditions.New pressure ratio,Pr,flow ratio,qr,were used in place of the conventional performance parameters h,q,to characterize the jet pump flow performance.A super cavitation cavity in the jet pump was observed to fill most of the flow channel,which hindered further increases of the flow rate and increased qr to one,thus,created a critical point on the new P_(r)-q_(r)^(2)curve.Before the critical point,P_(r)was proportional to q_(r)^(2)with a coefficient that was much more sensitive to the area ratio than the relative throat length and the diffusion angle.After the critical point,the flow rate reached its maximum,the limiting flow rate,which only depended on the total inlet pressure and the area ratio.The total inlet pressure was proportional to the square of the limiting flow rate with a flow coefficient that was only a quadratic function of the area ratio.

Dynamic strain field for granite specimen under SHPB impact tests based on stress wave propagation

The full-field strain of rock material under dynamic compression load was studied using the high-speed three dimensional digital image correlation(3D-DIC)method.The dynamic test was conducted on Laizhou granite using a split Hopkinson pressure bar(SHPB)method.Wave propagation,dispersion and radial inertial effect on the specimen were found by DIC results.A recovery of strain in the post-peak stage was detected on the specimen by DIC,which was unrevealed in the traditional one-dimensional theory method.It can be found that the strain measured by strain gauge was a calculated average one,whereas the strain measured by 3D-DIC could reflect more variation details.Specifically,the testing principle with impact loads and rock dynamic behavior was re-examined using stress wave propagation theory.The theoretical results showed that the specimen reached equilibrium after a series of wave reflections and transmissions and its stress was infinitely close to the initial value of 109.2 MPa.Moreover,the specimen had the calculated maximum strain of 0.52% and strain rate of 15.11 s^(-1),improving the reasonable agreement with the experimental results and requirements of rock mechanical properties measured by SHPB technology.

To Break the Limit of Catalytic Site Density of Fe-NCs

Rational design of Fe and N co-doped carbon catalysts(FeNCs), one promising non-precious cathode catalyst, is critical to commercialization of proton exchange membrane fuel cells. The atomic Fe site density of Fe-NCs is critical to improve catalytic currents approaching industrial levels. One recent research proposes a template-guided strategy to break the limit of Fe site density, and greatly promotes the fuel cell performance.