In this paper,the advantage of using numerical models with the strength reduction method(SRM) to evaluate entry stability in complex multiple-seam conditions is demonstrated.A coal mine under variable topography from ...In this paper,the advantage of using numerical models with the strength reduction method(SRM) to evaluate entry stability in complex multiple-seam conditions is demonstrated.A coal mine under variable topography from the Central Appalachian region is used as a case study.At this mine,unexpected roof conditions were encountered during development below previously mined panels.Stress mapping and observation of ground conditions were used to quantify the success of entry support systems in three room-and-pillar panels.Numerical model analyses were initially conducted to estimate the stresses induced by the multiple-seam mining at the locations of the affected entries.The SRM was used to quantify the stability factor of the supported roof of the entries at selected locations.The SRM-calculated stability factors were compared with observations made during the site visits,and the results demonstrate that the SRM adequately identifies the unexpected roof conditions in this complex case.It is concluded that the SRM can be used to effectively evaluate the likely success of roof supports and the stability condition of entries in coal mines.展开更多
Based on the closed connections among the homogeneous balance （HB） method and Clarkson-KruSkal （CK） method, we study the similarity reductions of the generalized variable coefficients 2D KdV equation. In the meant...Based on the closed connections among the homogeneous balance （HB） method and Clarkson-KruSkal （CK） method, we study the similarity reductions of the generalized variable coefficients 2D KdV equation. In the meantime it is shown that this leads to a direct reduction in the form of ordinary differential equation under some integrability conditions between the variable coefficients. Two different cases have been discussed, the search for solutions of those ordinary differential equations yielded many exact travelling and solitonic wave solutions in the form of hyperbolic and trigonometric functions under some constraints between the variable coefficients.展开更多
In Europe, computation of displacement demand for seismic assessment of existing buildings is essentially based on a simplified formulation of the N2 method as prescribed by Eurocode 8(EC8). However, a lack of accurac...In Europe, computation of displacement demand for seismic assessment of existing buildings is essentially based on a simplified formulation of the N2 method as prescribed by Eurocode 8(EC8). However, a lack of accuracy of the N2 method in certain conditions has been pointed out by several studies. This paper addresses the assessment of effectiveness of the N2 method in seismic displacement demand determination in non-linear domain. The objective of this work is to investigate the accuracy of the N2 method through comparison with displacement demands computed using non-linear timehistory analysis(NLTHA). Results show that the original N2 method may lead to overestimation or underestimation of displacement demand predictions. This may affect results of mechanical model-based assessment of seismic vulnerability at an urban scale. Hence, the second part of this paper addresses an improvement of the N2 method formula by empirical evaluation of NLTHA results based on EC8 ground-classes. This task is formulated as a mathematical programming problem in which coefficients are obtained by minimizing the overall discrepancy between NLTHA and modified formula results. Various settings of the mathematical programming problem have been solved using a global optimization metaheuristic. An extensive comparison between the original N2 method formulation and optimized formulae highlights benefits of the strategy.展开更多
We for the first time systematically studied the structures and electrochemical nitrogen reduction reaction properties of two-dimensional single transition-metal anchored square tetracyanoquinodimethane monolayers(lab...We for the first time systematically studied the structures and electrochemical nitrogen reduction reaction properties of two-dimensional single transition-metal anchored square tetracyanoquinodimethane monolayers(labeled as:TM-sTCNQ,TM=3d,4d,5d series transition metals)by employing density functional theory method.Through highthroughput screenings and full reaction path researches,two promising electrochemical nitrogen reduction reaction catalysts Nb-sTCNQ and MosTCNQ have been obtained.The nitrogen reduction reaction onset potential on Nb-sTCNQ is as low as−0.48 V.Furthermore,the Nb-sTCNQ catalyst can quickly desorb NH3 produced with a free energy of 0.65 eV,giving Nb-sTCNQ excellent catalytic cycle performance.The high catalytic activity of the two materials might be attributed to the effective charge transfer between the active center and adsorbed N_(2),which enables the active center to adsorb and activate inert N_(2) molecules well,and the reduction processes require small energy input(i.e.,the maximum free energy changes are small).This work provides insights for finding highly efficient,stable,and low-cost nitrogen reduction reaction electrocatalysts.We hope our results can promote further experimental and theoretical research of this field.展开更多
The electrochemical reduction of CO2 is a promising solution for sustainable energy research and carbon emissions.However,this solution has been challenged by the lack of active and selective catalysts.Here,we report ...The electrochemical reduction of CO2 is a promising solution for sustainable energy research and carbon emissions.However,this solution has been challenged by the lack of active and selective catalysts.Here,we report a two-step synthesis of 3D ordered mesoporous Cu sphere arrays,which is fabricated by a dual template method using a poly methyl methacrylate(PMMA) inverse opal and the nonionic surfactant Brij 58 to template the mesostructure within the regular voids of a colloidal crystal.Therefo re,the well-ordered 3D interconnected bi-continuous mesopore s structure has advantages of abundant exposed catalytically active sites,efficient mass transport,and high electrical conductivity,which result in excellent electrocatalytic CO2 RR perfo rmance.The prepared 3D ordered mesoporous Cu sphere array(3 D-OMCuSA) exhibits a low onset potential of-0.4 V at a 1 mA cm^-2 electrode current density,a low Tafel slope of 109.6 mV per decade and a long-term durability in 0.1 M potassium bicarbonate.These distinct features of 3 D-OMCuSA render it a promising method for the further develo p ment of advanced electrocatalytic materials for CO2 reduction.展开更多
The production-oriented approach （POA） has been developed over a decade. It is driven by the need to improve English classroom instruction for university students in China （Wen, 2016）. It is also motivated by the ...The production-oriented approach （POA） has been developed over a decade. It is driven by the need to improve English classroom instruction for university students in China （Wen, 2016）. It is also motivated by the aspiration to enhance the quality of foreign language education in other similar pedagogical contexts outside China. A volume of research has been done by Wen Qiufang and her research team, to formulate the theory of POA and to test its effectiveness in classroom pedagogy （e.g. Wen, 2016, 2015; Yang, 2015; Zhang, 2015）. At the moment, the POA is still at an early stage of theory building and almost all empirical research is done in the Chinese context. In order to improve the quality of this theory and to make it intelligible to the international academic community, a one-day symposium was held in Beijing Foreign Studies University on May 15, 2017. The symposium was entitled ＇The first international forum on innovative foreign language education in China： Appraisal of the POA＇. In the forum, leading experts in applied linguistics were invited to discuss the strengths and weaknesses of the POA and the directions for its future development. The symposium was the first attempt for the POA research team to discuss its latest work with international scholars. This Viewpoint section collects the responses of four experts who participated in the symposium, listed in alphabetical order. The collection of articles covers three topics related to the POA： its pedagogical application, its use for teacher training, and its research. Alister Cumming is Professor Emeritus and the former Head of the Centre for Educational Research on Languages and Literacies, University of Toronto, Canada. His article focuses primarily on POA research as an exemplary case of design-based research. Rod Ellis is Research Professor in the School of Education at Curtin University, Australia. He discusses POA in terms of pedagogy, teacher training and research, with both critiques and constructive suggestions. Paul Kei Matsuda is Professor of English and Director of Second Language Writing at Arizona State University, the writed states. He responds to POA from the perspective of an expert researcher and teacher of L2 writing. Charlene Polio is Professor and Associate Chair in the Department of Linguistics ＆ Germanic, Slavic, Asian ＆ African Languages atMichigan State University, the writed states. She conceptualises POA as a useful method to address some issues in pre-service teacher development. Overall, the articles in this section are insightful and reader-friendly. They are not only useful for the development of POA in particular, but may also be valuable to a broad range of researchers as they touch upon pertaining issues, as well as emerging topics, in the field of applied linguistics. We therefore find it necessary to make them accessible to a wide readership.展开更多
文摘In this paper,the advantage of using numerical models with the strength reduction method(SRM) to evaluate entry stability in complex multiple-seam conditions is demonstrated.A coal mine under variable topography from the Central Appalachian region is used as a case study.At this mine,unexpected roof conditions were encountered during development below previously mined panels.Stress mapping and observation of ground conditions were used to quantify the success of entry support systems in three room-and-pillar panels.Numerical model analyses were initially conducted to estimate the stresses induced by the multiple-seam mining at the locations of the affected entries.The SRM was used to quantify the stability factor of the supported roof of the entries at selected locations.The SRM-calculated stability factors were compared with observations made during the site visits,and the results demonstrate that the SRM adequately identifies the unexpected roof conditions in this complex case.It is concluded that the SRM can be used to effectively evaluate the likely success of roof supports and the stability condition of entries in coal mines.
文摘Based on the closed connections among the homogeneous balance （HB） method and Clarkson-KruSkal （CK） method, we study the similarity reductions of the generalized variable coefficients 2D KdV equation. In the meantime it is shown that this leads to a direct reduction in the form of ordinary differential equation under some integrability conditions between the variable coefficients. Two different cases have been discussed, the search for solutions of those ordinary differential equations yielded many exact travelling and solitonic wave solutions in the form of hyperbolic and trigonometric functions under some constraints between the variable coefficients.
文摘In Europe, computation of displacement demand for seismic assessment of existing buildings is essentially based on a simplified formulation of the N2 method as prescribed by Eurocode 8(EC8). However, a lack of accuracy of the N2 method in certain conditions has been pointed out by several studies. This paper addresses the assessment of effectiveness of the N2 method in seismic displacement demand determination in non-linear domain. The objective of this work is to investigate the accuracy of the N2 method through comparison with displacement demands computed using non-linear timehistory analysis(NLTHA). Results show that the original N2 method may lead to overestimation or underestimation of displacement demand predictions. This may affect results of mechanical model-based assessment of seismic vulnerability at an urban scale. Hence, the second part of this paper addresses an improvement of the N2 method formula by empirical evaluation of NLTHA results based on EC8 ground-classes. This task is formulated as a mathematical programming problem in which coefficients are obtained by minimizing the overall discrepancy between NLTHA and modified formula results. Various settings of the mathematical programming problem have been solved using a global optimization metaheuristic. An extensive comparison between the original N2 method formulation and optimized formulae highlights benefits of the strategy.
基金support from the National Natural Science Foundation of China(22073033,21873032,21673087,21903032)startup fund(2006013118 and 3004013105)from Huazhong University of Science and Technology+5 种基金the Fundamental Research Funds for the Central Universities(2019kfyRCPY116)the Innovation and Talent Recruitment Base of New Energy Chemistry and Device(B21003)support from Guangdong Basic and Applied Basic Research Foundation(2021A1515010382)the computational resources from the computing cluster at the Key Laboratory of Theoretical Chemistry of Environment,Ministry of Education&School of Chemistry,South China Normal UniversityThe work was carried out at the LvLiang Cloud Computing Center of China,and the calculations were performed on TianHe-2The computing work in this paper is supported by the Public Service Platform of High Performance Computing by Network and Computing Center of HUST.
文摘We for the first time systematically studied the structures and electrochemical nitrogen reduction reaction properties of two-dimensional single transition-metal anchored square tetracyanoquinodimethane monolayers(labeled as:TM-sTCNQ,TM=3d,4d,5d series transition metals)by employing density functional theory method.Through highthroughput screenings and full reaction path researches,two promising electrochemical nitrogen reduction reaction catalysts Nb-sTCNQ and MosTCNQ have been obtained.The nitrogen reduction reaction onset potential on Nb-sTCNQ is as low as−0.48 V.Furthermore,the Nb-sTCNQ catalyst can quickly desorb NH3 produced with a free energy of 0.65 eV,giving Nb-sTCNQ excellent catalytic cycle performance.The high catalytic activity of the two materials might be attributed to the effective charge transfer between the active center and adsorbed N_(2),which enables the active center to adsorb and activate inert N_(2) molecules well,and the reduction processes require small energy input(i.e.,the maximum free energy changes are small).This work provides insights for finding highly efficient,stable,and low-cost nitrogen reduction reaction electrocatalysts.We hope our results can promote further experimental and theoretical research of this field.
基金This work was supported by the NSFC grant number21607113the Natural Science Foundation of Tianjin grant number 17JCQNJC07700。
文摘The electrochemical reduction of CO2 is a promising solution for sustainable energy research and carbon emissions.However,this solution has been challenged by the lack of active and selective catalysts.Here,we report a two-step synthesis of 3D ordered mesoporous Cu sphere arrays,which is fabricated by a dual template method using a poly methyl methacrylate(PMMA) inverse opal and the nonionic surfactant Brij 58 to template the mesostructure within the regular voids of a colloidal crystal.Therefo re,the well-ordered 3D interconnected bi-continuous mesopore s structure has advantages of abundant exposed catalytically active sites,efficient mass transport,and high electrical conductivity,which result in excellent electrocatalytic CO2 RR perfo rmance.The prepared 3D ordered mesoporous Cu sphere array(3 D-OMCuSA) exhibits a low onset potential of-0.4 V at a 1 mA cm^-2 electrode current density,a low Tafel slope of 109.6 mV per decade and a long-term durability in 0.1 M potassium bicarbonate.These distinct features of 3 D-OMCuSA render it a promising method for the further develo p ment of advanced electrocatalytic materials for CO2 reduction.
文摘The production-oriented approach （POA） has been developed over a decade. It is driven by the need to improve English classroom instruction for university students in China （Wen, 2016）. It is also motivated by the aspiration to enhance the quality of foreign language education in other similar pedagogical contexts outside China. A volume of research has been done by Wen Qiufang and her research team, to formulate the theory of POA and to test its effectiveness in classroom pedagogy （e.g. Wen, 2016, 2015; Yang, 2015; Zhang, 2015）. At the moment, the POA is still at an early stage of theory building and almost all empirical research is done in the Chinese context. In order to improve the quality of this theory and to make it intelligible to the international academic community, a one-day symposium was held in Beijing Foreign Studies University on May 15, 2017. The symposium was entitled ＇The first international forum on innovative foreign language education in China： Appraisal of the POA＇. In the forum, leading experts in applied linguistics were invited to discuss the strengths and weaknesses of the POA and the directions for its future development. The symposium was the first attempt for the POA research team to discuss its latest work with international scholars. This Viewpoint section collects the responses of four experts who participated in the symposium, listed in alphabetical order. The collection of articles covers three topics related to the POA： its pedagogical application, its use for teacher training, and its research. Alister Cumming is Professor Emeritus and the former Head of the Centre for Educational Research on Languages and Literacies, University of Toronto, Canada. His article focuses primarily on POA research as an exemplary case of design-based research. Rod Ellis is Research Professor in the School of Education at Curtin University, Australia. He discusses POA in terms of pedagogy, teacher training and research, with both critiques and constructive suggestions. Paul Kei Matsuda is Professor of English and Director of Second Language Writing at Arizona State University, the writed states. He responds to POA from the perspective of an expert researcher and teacher of L2 writing. Charlene Polio is Professor and Associate Chair in the Department of Linguistics ＆ Germanic, Slavic, Asian ＆ African Languages atMichigan State University, the writed states. She conceptualises POA as a useful method to address some issues in pre-service teacher development. Overall, the articles in this section are insightful and reader-friendly. They are not only useful for the development of POA in particular, but may also be valuable to a broad range of researchers as they touch upon pertaining issues, as well as emerging topics, in the field of applied linguistics. We therefore find it necessary to make them accessible to a wide readership.
