I.INTRODUCTION Since the 1970s, the study of stimulated emission of CdS and other Ⅱ--Ⅵ compound semiconductors has speeded up the development of the study of highly excited semiconductors. It was shown that the ex-e...I.INTRODUCTION Since the 1970s, the study of stimulated emission of CdS and other Ⅱ--Ⅵ compound semiconductors has speeded up the development of the study of highly excited semiconductors. It was shown that the ex-el scattering induces the main recombination process that yields high gain above 100 K both experimentally and theoretically. The results obtained so far concern mainly the stimulated emission, and most of the efforts are devoted to the temperature dependence of emission spectra. Only a few works are concerning the dynamics of the luminescence due to scattering.展开更多
Hydrogen generation and related energy applications heavily rely on the hydrogen evolution reaction(HER),which faces challenges of slow kinetics and high overpotential.Efficient electrocatalysts,particularly single-at...Hydrogen generation and related energy applications heavily rely on the hydrogen evolution reaction(HER),which faces challenges of slow kinetics and high overpotential.Efficient electrocatalysts,particularly single-atom catalysts (SACs) on two-dimensional (2D) materials,are essential.This study presents a few-shot machine learning (ML) assisted high-throughput screening of 2D septuple-atomic-layer Ga_(2)CoS_(4-x)supported SACs to predict HER catalytic activity.Initially,density functional theory (DFT)calculations showed that 2D Ga_(2)CoS4is inactive for HER.However,defective Ga_(2)CoS_(4-x)(x=0–0.25)monolayers exhibit excellent HER activity due to surface sulfur vacancies (SVs),with predicted overpotentials (0–60 mV) comparable to or lower than commercial Pt/C,which typically exhibits an overpotential of around 50 m V in the acidic electrolyte,when the concentration of surface SV is lower than 8.3%.SVs generate spin-polarized states near the Fermi level,making them effective HER sites.We demonstrate ML-accelerated HER overpotential predictions for all transition metal SACs on 2D Ga_(2)CoS_(4-x).Using DFT data from 18 SACs,an ML model with high prediction accuracy and reduced computation time was developed.An intrinsic descriptor linking SAC atomic properties to HER overpotential was identified.This study thus provides a framework for screening SACs on 2D materials,enhancing catalyst design.展开更多
Liquefaction is one of the prominent factors leading to damage to soil and structures.In this study,the rela-tionship between liquefaction potential and soil parameters is determined by applying feature importance met...Liquefaction is one of the prominent factors leading to damage to soil and structures.In this study,the rela-tionship between liquefaction potential and soil parameters is determined by applying feature importance methods to Random Forest(RF),Logistic Regression(LR),Multilayer Perceptron(MLP),Support Vector Machine(SVM)and eXtreme Gradient Boosting(XGBoost)algorithms.Feature importance methods consist of permuta-tion and Shapley Additive exPlanations(SHAP)importances along with the used model’s built-in feature importance method if it exists.These suggested approaches incorporate an extensive dataset of geotechnical parameters,historical liquefaction events,and soil properties.The feature set comprises 18 parameters that are gathered from 161 field cases.Algorithms are used to determine the optimum performance feature set.Compared to other approaches,the study assesses how well these algorithms predict soil liquefaction potential.Early findings show that the algorithms perform well,demonstrating their capacity to identify non-linear connections and improve prediction accuracy.Among the feature set,σ,v(psf),MSF,CSRσ,v,FC%,Vs*,40f t(f ps)and N1,60,CS are the ones that have the highest deterministic power on the result.The study’s contribution is that,in the absence of extensive data for liquefaction assessment,the proposed method estimates the liquefaction potential using five parameters with promising accuracy.展开更多
Despite extensive research on computational geomechanics and fluid dynamics,accurately simulating convection-diffusion(CD)processes in complex fractured systems remains a significant challenge.This study develops a 3D...Despite extensive research on computational geomechanics and fluid dynamics,accurately simulating convection-diffusion(CD)processes in complex fractured systems remains a significant challenge.This study develops a 3D numerical framework for modelling CD processes in fractured geological media.The framework integrates Darcy's law and Fick's law,considering flux interactions between the matrix and fractures.The meshing strategy generates high-quality grids even in scenarios involving intersecting fractures.Then,a unified numerical scheme for solving the CD system is proposed.The novelties of this work include:(1)The proposed framework enables effective simulation of 3D fractured media,including more complex fractured vuggy media;(2)The numerical method precisely discretizes the CD terms in governing equations;(3)A Non-Orthogonal Correction(NOC)method,combined with an adaptive time integration scheme,is proposed for eliminating errors induced by skewed grids;and(4)The effects of fracture patterns and heterogeneity on flow are thoroughly analysed.The proposed method is validated through benchmark tests,demonstrating the superiority of the NOC method compared to classical methods.Further analysis reveals the evolution characteristics of pressure and concentration,offering insights into the effects of fracture patterns and heterogeneity on flow and diffusion processes.展开更多
Dissolution kinetics of CaO·2Al_(2)O_(3)(CA_(2))particles in a synthetic CaO-Al_(2)O_(3)-SiO_(2)steelmaking slag system have been investigated using the high-temperature confocal laser scanning microscope.Effects...Dissolution kinetics of CaO·2Al_(2)O_(3)(CA_(2))particles in a synthetic CaO-Al_(2)O_(3)-SiO_(2)steelmaking slag system have been investigated using the high-temperature confocal laser scanning microscope.Effects of temperature(i.e.,1500,1550,and 1600℃)and slag composition on the dissolution time of CA_(2)particles are investigated,along with the time dependency of the projection area of the particle during the dissolution process.It is found that the dissolution rate was enhanced by either an increase in temperature or a decrease in slag viscosity.Moreover,a higher ratio of CaO/Al_(2)O_(3)(C/A)leads to an increased dissolution rate of CA_(2)particle at 1600℃.Thermodynamic calculations suggested the dissolution product,i.e.,melilite,formed on the surface of the CA_(2)particle during dissolution in slag with a C/A ratio of 3.8 at 1550℃.Scanning electron microscopy equipped with energy dispersive X-ray spectrometry analysis of as-quenched samples confirmed the dissolution path of CA_(2)particles in slags with C/A ratios of 1.8 and 3.8 as well as the melilite formed on the surface of CA_(2)particle.The formation of this layer during the dissolution process was identified as a hindrance,impeding the dissolution of CA_(2)particle.A valuable reference for designing or/and choosing the composition of top slag for clean steel production is provided,especially using calcium treatment during the secondary refining process.展开更多
目的获得噪声下声调识别测试（t o n e identification in noise test,TINT）材料的听力正常人识别成绩-强度（performance-intensity,PI）函数。方法利用已确立的TINT测试材料对16名年龄在21~28岁、以普通话作为日常交流语言的听力正...目的获得噪声下声调识别测试（t o n e identification in noise test,TINT）材料的听力正常人识别成绩-强度（performance-intensity,PI）函数。方法利用已确立的TINT测试材料对16名年龄在21~28岁、以普通话作为日常交流语言的听力正常人进行声调识别测试,使用SPSS17.0统计软件对结果进行分析。结果听力正常成人PI斜率分别为8.6%/d B（男声）、7.3%/d B（女声）（P=0.11）;听力正常成人PI函数信噪比50阈值分别为男声（-12.9±0.8）d B、女声（-13.6±1）d B（t=2.7,P=0.016）;声调类型和播音者性别对PI曲线阈值的影响即存在交互作用（F=11.7,P〈0.001）、亦存在独立作用（声调类型：F=83.7,P〈0.001;播音员性别：F=31.0,P〈0.05）,其中听力正常人一声和四声识别阈值明显低于二声和三声识别阈值。结论本研究初步建立基于TINT测试材料的听力正常人噪声下声调识别PI函数,以期为临床工作和科学研究提供一个可选择的测量工具。展开更多
Porous biodegradable Mg and its alloys are considered to have a great potential to serve as ideal bone substitutes.The recent progress in additive manufacturing(AM) has prompted its application to fabricate Mg scaffol...Porous biodegradable Mg and its alloys are considered to have a great potential to serve as ideal bone substitutes.The recent progress in additive manufacturing(AM) has prompted its application to fabricate Mg scaffolds with geometrically ordered porous structures.Extrusionbased AM,followed by debinding and sintering,has been recently demonstrated as a powerful approach to fabricating such Mg scaffolds,which can avoid some crucial problems encountered when applying powder bed fusion AM techniques.However,such pure Mg scaffolds exhibit a too high rate of in vitro biodegradation.In the present research,alloying through a pre-alloyed Mg-Zn powder was ultilized to enhance the corrosion resistance and mechanical properties of AM geometrically ordered Mg-Zn scaffolds simultaneously.The in vitro biodegradation behavior,mechanical properties,and electrochemical response of the fabricated Mg-Zn scaffolds were evaluated.Moreover,the response of preosteoblasts to these scaffolds was systematically evaluated and compared with their response to pure Mg scaffolds.The Mg-Zn scaffolds with a porosity of 50.3% and strut density of 93.1% were composed of the Mg matrix and MgZn2second phase particles.The in vitro biodegradation rate of the Mg-Zn scaffolds decreased by 81% at day 1,as compared to pure Mg scaffolds.Over 28 days of static immersion in modified simulated body fluid,the corrosion rate of the Mg-Zn scaffolds decreased from 2.3± 0.9 mm/y to 0.7±0.1 mm/y.The yield strength and Young’s modulus of the Mg-Zn scaffolds were about 3 times as high as those of pure Mg scaffolds and remained within the range of those of trabecular bone throughout the biodegradation tests.Indirect culture of MC3T3-E1 preosteoblasts in Mg-Zn extracts indicated favorable cytocompatibility.In direct cell culture,some cells could spread and form filopodia on the surface of the Mg-Zn scaffolds.Overall,this study demonstrates the great potential of the extrusion-based AM Mg-Zn scaffolds to be further developed as biodegradable bone-substituting biomaterials.展开更多
Meteorological drought has been an inevitable natural disaster throughout Mexican history and the northern and northwestern parts of Mexico（i.e., the studied area）, where the mean annual precipitation（MAP） is less...Meteorological drought has been an inevitable natural disaster throughout Mexican history and the northern and northwestern parts of Mexico（i.e., the studied area）, where the mean annual precipitation（MAP） is less than 500 mm, have suffered even more from droughts in the past. The aim of this study was to conduct a meteorological drought analysis of the available MAP data（1950–2013） from 649 meteorological stations selected from the studied area and to predict the drought features under the different IPCC-prescribed climate change scenarios. To determine the long-term drought features, we collected 1×10~4 synthetic samples using the periodic autoregressive moving average（PARMA） model for each rainfall series. The simulations first consider the present prevailing precipitation conditions（i.e., the average from 1950 to 2013） and then the precipitation anomalies under IPCC-prescribed RCP 4.5 scenario and RCP 8.5 scenario. The results indicated that the climate changes under the prescribed scenarios would significantly increase the duration and intensity of droughts. The most severe impacts may occur in the central plateau and in the Baja California Peninsula. Thus, it will be necessary to establish adequate protective measures for the sustainable management of water resources in these regions.展开更多
基金Project supported by the National Natural Science Foundation of China
文摘I.INTRODUCTION Since the 1970s, the study of stimulated emission of CdS and other Ⅱ--Ⅵ compound semiconductors has speeded up the development of the study of highly excited semiconductors. It was shown that the ex-el scattering induces the main recombination process that yields high gain above 100 K both experimentally and theoretically. The results obtained so far concern mainly the stimulated emission, and most of the efforts are devoted to the temperature dependence of emission spectra. Only a few works are concerning the dynamics of the luminescence due to scattering.
文摘Hydrogen generation and related energy applications heavily rely on the hydrogen evolution reaction(HER),which faces challenges of slow kinetics and high overpotential.Efficient electrocatalysts,particularly single-atom catalysts (SACs) on two-dimensional (2D) materials,are essential.This study presents a few-shot machine learning (ML) assisted high-throughput screening of 2D septuple-atomic-layer Ga_(2)CoS_(4-x)supported SACs to predict HER catalytic activity.Initially,density functional theory (DFT)calculations showed that 2D Ga_(2)CoS4is inactive for HER.However,defective Ga_(2)CoS_(4-x)(x=0–0.25)monolayers exhibit excellent HER activity due to surface sulfur vacancies (SVs),with predicted overpotentials (0–60 mV) comparable to or lower than commercial Pt/C,which typically exhibits an overpotential of around 50 m V in the acidic electrolyte,when the concentration of surface SV is lower than 8.3%.SVs generate spin-polarized states near the Fermi level,making them effective HER sites.We demonstrate ML-accelerated HER overpotential predictions for all transition metal SACs on 2D Ga_(2)CoS_(4-x).Using DFT data from 18 SACs,an ML model with high prediction accuracy and reduced computation time was developed.An intrinsic descriptor linking SAC atomic properties to HER overpotential was identified.This study thus provides a framework for screening SACs on 2D materials,enhancing catalyst design.
文摘Liquefaction is one of the prominent factors leading to damage to soil and structures.In this study,the rela-tionship between liquefaction potential and soil parameters is determined by applying feature importance methods to Random Forest(RF),Logistic Regression(LR),Multilayer Perceptron(MLP),Support Vector Machine(SVM)and eXtreme Gradient Boosting(XGBoost)algorithms.Feature importance methods consist of permuta-tion and Shapley Additive exPlanations(SHAP)importances along with the used model’s built-in feature importance method if it exists.These suggested approaches incorporate an extensive dataset of geotechnical parameters,historical liquefaction events,and soil properties.The feature set comprises 18 parameters that are gathered from 161 field cases.Algorithms are used to determine the optimum performance feature set.Compared to other approaches,the study assesses how well these algorithms predict soil liquefaction potential.Early findings show that the algorithms perform well,demonstrating their capacity to identify non-linear connections and improve prediction accuracy.Among the feature set,σ,v(psf),MSF,CSRσ,v,FC%,Vs*,40f t(f ps)and N1,60,CS are the ones that have the highest deterministic power on the result.The study’s contribution is that,in the absence of extensive data for liquefaction assessment,the proposed method estimates the liquefaction potential using five parameters with promising accuracy.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51991392 and 42293355).
文摘Despite extensive research on computational geomechanics and fluid dynamics,accurately simulating convection-diffusion(CD)processes in complex fractured systems remains a significant challenge.This study develops a 3D numerical framework for modelling CD processes in fractured geological media.The framework integrates Darcy's law and Fick's law,considering flux interactions between the matrix and fractures.The meshing strategy generates high-quality grids even in scenarios involving intersecting fractures.Then,a unified numerical scheme for solving the CD system is proposed.The novelties of this work include:(1)The proposed framework enables effective simulation of 3D fractured media,including more complex fractured vuggy media;(2)The numerical method precisely discretizes the CD terms in governing equations;(3)A Non-Orthogonal Correction(NOC)method,combined with an adaptive time integration scheme,is proposed for eliminating errors induced by skewed grids;and(4)The effects of fracture patterns and heterogeneity on flow are thoroughly analysed.The proposed method is validated through benchmark tests,demonstrating the superiority of the NOC method compared to classical methods.Further analysis reveals the evolution characteristics of pressure and concentration,offering insights into the effects of fracture patterns and heterogeneity on flow and diffusion processes.
基金the Natural Sciences and Engineering Research Council of Canada(NSERC)for funding this researchThis research used a high temperature confocal laser scanning microscope-VL2000DX-SVF17SP funded by Canada Foundation for Innovation John Evans Leaders Fund(CFI JELF,Project Number:32826),a PANalytical X’Pert diffraction instrument located at the Centre for crystal growth,Brockhouse Institute for Materials Research,and a scanning electron microscope-JEOL 6610 located at the Canadian Centre for Electron Microscopy at McMaster University.W.Mu would like to acknowledge Swedish Iron and Steel Research Office(Jernkonteret),STINT and SSF for supporting the time for international collaboration research regarding clean steel.
文摘Dissolution kinetics of CaO·2Al_(2)O_(3)(CA_(2))particles in a synthetic CaO-Al_(2)O_(3)-SiO_(2)steelmaking slag system have been investigated using the high-temperature confocal laser scanning microscope.Effects of temperature(i.e.,1500,1550,and 1600℃)and slag composition on the dissolution time of CA_(2)particles are investigated,along with the time dependency of the projection area of the particle during the dissolution process.It is found that the dissolution rate was enhanced by either an increase in temperature or a decrease in slag viscosity.Moreover,a higher ratio of CaO/Al_(2)O_(3)(C/A)leads to an increased dissolution rate of CA_(2)particle at 1600℃.Thermodynamic calculations suggested the dissolution product,i.e.,melilite,formed on the surface of the CA_(2)particle during dissolution in slag with a C/A ratio of 3.8 at 1550℃.Scanning electron microscopy equipped with energy dispersive X-ray spectrometry analysis of as-quenched samples confirmed the dissolution path of CA_(2)particles in slags with C/A ratios of 1.8 and 3.8 as well as the melilite formed on the surface of CA_(2)particle.The formation of this layer during the dissolution process was identified as a hindrance,impeding the dissolution of CA_(2)particle.A valuable reference for designing or/and choosing the composition of top slag for clean steel production is provided,especially using calcium treatment during the secondary refining process.
文摘目的获得噪声下声调识别测试（t o n e identification in noise test,TINT）材料的听力正常人识别成绩-强度（performance-intensity,PI）函数。方法利用已确立的TINT测试材料对16名年龄在21~28岁、以普通话作为日常交流语言的听力正常人进行声调识别测试,使用SPSS17.0统计软件对结果进行分析。结果听力正常成人PI斜率分别为8.6%/d B（男声）、7.3%/d B（女声）（P=0.11）;听力正常成人PI函数信噪比50阈值分别为男声（-12.9±0.8）d B、女声（-13.6±1）d B（t=2.7,P=0.016）;声调类型和播音者性别对PI曲线阈值的影响即存在交互作用（F=11.7,P〈0.001）、亦存在独立作用（声调类型：F=83.7,P〈0.001;播音员性别：F=31.0,P〈0.05）,其中听力正常人一声和四声识别阈值明显低于二声和三声识别阈值。结论本研究初步建立基于TINT测试材料的听力正常人噪声下声调识别PI函数,以期为临床工作和科学研究提供一个可选择的测量工具。
基金China Scholarship Council (CSC) for financial support。
文摘Porous biodegradable Mg and its alloys are considered to have a great potential to serve as ideal bone substitutes.The recent progress in additive manufacturing(AM) has prompted its application to fabricate Mg scaffolds with geometrically ordered porous structures.Extrusionbased AM,followed by debinding and sintering,has been recently demonstrated as a powerful approach to fabricating such Mg scaffolds,which can avoid some crucial problems encountered when applying powder bed fusion AM techniques.However,such pure Mg scaffolds exhibit a too high rate of in vitro biodegradation.In the present research,alloying through a pre-alloyed Mg-Zn powder was ultilized to enhance the corrosion resistance and mechanical properties of AM geometrically ordered Mg-Zn scaffolds simultaneously.The in vitro biodegradation behavior,mechanical properties,and electrochemical response of the fabricated Mg-Zn scaffolds were evaluated.Moreover,the response of preosteoblasts to these scaffolds was systematically evaluated and compared with their response to pure Mg scaffolds.The Mg-Zn scaffolds with a porosity of 50.3% and strut density of 93.1% were composed of the Mg matrix and MgZn2second phase particles.The in vitro biodegradation rate of the Mg-Zn scaffolds decreased by 81% at day 1,as compared to pure Mg scaffolds.Over 28 days of static immersion in modified simulated body fluid,the corrosion rate of the Mg-Zn scaffolds decreased from 2.3± 0.9 mm/y to 0.7±0.1 mm/y.The yield strength and Young’s modulus of the Mg-Zn scaffolds were about 3 times as high as those of pure Mg scaffolds and remained within the range of those of trabecular bone throughout the biodegradation tests.Indirect culture of MC3T3-E1 preosteoblasts in Mg-Zn extracts indicated favorable cytocompatibility.In direct cell culture,some cells could spread and form filopodia on the surface of the Mg-Zn scaffolds.Overall,this study demonstrates the great potential of the extrusion-based AM Mg-Zn scaffolds to be further developed as biodegradable bone-substituting biomaterials.
基金supported by the Faculty of Engineering, National Autonomous University of Mexico
文摘Meteorological drought has been an inevitable natural disaster throughout Mexican history and the northern and northwestern parts of Mexico（i.e., the studied area）, where the mean annual precipitation（MAP） is less than 500 mm, have suffered even more from droughts in the past. The aim of this study was to conduct a meteorological drought analysis of the available MAP data（1950–2013） from 649 meteorological stations selected from the studied area and to predict the drought features under the different IPCC-prescribed climate change scenarios. To determine the long-term drought features, we collected 1×10~4 synthetic samples using the periodic autoregressive moving average（PARMA） model for each rainfall series. The simulations first consider the present prevailing precipitation conditions（i.e., the average from 1950 to 2013） and then the precipitation anomalies under IPCC-prescribed RCP 4.5 scenario and RCP 8.5 scenario. The results indicated that the climate changes under the prescribed scenarios would significantly increase the duration and intensity of droughts. The most severe impacts may occur in the central plateau and in the Baja California Peninsula. Thus, it will be necessary to establish adequate protective measures for the sustainable management of water resources in these regions.
