Understanding the physical,mechanical behavior,and seepage characteristics of coal under hydro-mechanical coupling holds significant importance for ensuring the stability of surrounding rock formations and preventing ...Understanding the physical,mechanical behavior,and seepage characteristics of coal under hydro-mechanical coupling holds significant importance for ensuring the stability of surrounding rock formations and preventing gas outbursts.Scanning electron microscopy,uniaxial tests,and triaxial tests were conducted to comprehensively analyze the macroscopic and microscopic physical and mechanical characteristics of coal under different soaking times.Moreover,by restoring the stress path and water injection conditions of the protective layer indoors,we explored the coal mining dynamic behavior and the evolution of permeability.The results show that water causes the micro-surface of coal to peel off and cracks to expand and develop.With the increase of soaking time,the uniaxial and triaxial strengths were gradually decreased with nonlinear trend,and decreased by 63.31%and 30.95%after soaking for 240 h,respectively.Under different water injection pressure conditions,coal permeability undergoes three stages during the mining loading process and ultimately increases to higher values.The peak stress of coal,the deviatoric stress and strain at the permeability surge point all decrease with increasing water injection pressure.The results of this research can help improve the understanding of the coal mechanical properties and seepage evolution law under hydro-mechanical coupling.展开更多
The experimental study on the macro and micro characteristics of the spray from a pressure swirl nozzle embraces the growth of surface unstable wave,disintegration process,spray angle,breakup length and so on.The e...The experimental study on the macro and micro characteristics of the spray from a pressure swirl nozzle embraces the growth of surface unstable wave,disintegration process,spray angle,breakup length and so on.The effects of injection pressure,nozzle geometry and liquid properties on these characteristics are also discussed.The results are helpful to understand the underlying physics of the pressure swirl nozzle and serve as the basis for the practical design,usage and improvement of the nozzle.展开更多
壤全氮、土壤有机质的测定对农业生产和科学研究都有重要意义。因此在许多实验室里,土壤全氮、土壤有机质都被作为一项常规分析项目。土壤全氮量的测定百余年来沿用杜马氏法和凯氏定氮法。测定土壤有机质的方法主要有3种:干烧法、化学...壤全氮、土壤有机质的测定对农业生产和科学研究都有重要意义。因此在许多实验室里,土壤全氮、土壤有机质都被作为一项常规分析项目。土壤全氮量的测定百余年来沿用杜马氏法和凯氏定氮法。测定土壤有机质的方法主要有3种:干烧法、化学氧化法、灼烧法,1989年农业部颁布了国标GB9843-88《土壤有机质测定法》。近年来使用元素分析仪(Elementar Vario MACRO)测定土壤C、N也越来越广泛,元素分析仪是一台用于快速,定量测定元素C、H、N、S的全自动分析仪。用元素分析仪测定C、H、N的方法属于灼烧法,灼烧温度为960摄氏度,对酸性、中性土壤的测定无疑是省时准确的首选。石灰性土壤中由于碳酸盐的存在,在高温灼烧时碳酸盐分解,形成CO2,使土壤有机质的测定结果偏高。降低燃烧管温度测定(630摄氏度),由于样品用锡箔纸包裹,锡箔纸在燃烧管内燃烧生成氧化锡为放热反应,增加燃烧管内的温度高于设定温度,增加碳酸钙的分解测定值偏高,燃烧管温度设定在低于碳酸盐分解点时仪器密封不严实,使测定结果偏低。用盐酸处理土壤中碳酸盐,其后测定有机质时,因土壤中的富里酸溶于酸,使测定结果偏低。因此元素分析仪不适于石灰性土壤有机质的测定。展开更多
This paper is based on three observations and independent thinking of the classroom teaching of the author’s colleagues.It attempts to examine how macro and micro contexts affect teaching and learning in the classroo...This paper is based on three observations and independent thinking of the classroom teaching of the author’s colleagues.It attempts to examine how macro and micro contexts affect teaching and learning in the classroom.The author focuses the discussion on three aspects:(i)the present EFL contextual setting in China;(ii)the influence of the evaluation system on both teachers and students;(iii)his own beliefs as a teacher.Finally,he comes to the implications that teachers should often reflect on their teaching by means of observing other teachers’teachings;In order to bring more effective teaching and learning to the class,Teachers should change their class from a teacher-centered one to a students-centered one.展开更多
基金Project(52225403)supported by the National Natural Science Foundation of ChinaProject(2023YFF0615401)supported by the National Key Research and Development Program of China+1 种基金Projects(2023NSFSC0004,2023NSFSC0790)supported by Science and Technology Program of Sichuan Province,ChinaProject(2021-CMCUKFZD001)supported by the Open Fund of State Key Laboratory of Coal Mining and Clean Utilization,China。
文摘Understanding the physical,mechanical behavior,and seepage characteristics of coal under hydro-mechanical coupling holds significant importance for ensuring the stability of surrounding rock formations and preventing gas outbursts.Scanning electron microscopy,uniaxial tests,and triaxial tests were conducted to comprehensively analyze the macroscopic and microscopic physical and mechanical characteristics of coal under different soaking times.Moreover,by restoring the stress path and water injection conditions of the protective layer indoors,we explored the coal mining dynamic behavior and the evolution of permeability.The results show that water causes the micro-surface of coal to peel off and cracks to expand and develop.With the increase of soaking time,the uniaxial and triaxial strengths were gradually decreased with nonlinear trend,and decreased by 63.31%and 30.95%after soaking for 240 h,respectively.Under different water injection pressure conditions,coal permeability undergoes three stages during the mining loading process and ultimately increases to higher values.The peak stress of coal,the deviatoric stress and strain at the permeability surge point all decrease with increasing water injection pressure.The results of this research can help improve the understanding of the coal mechanical properties and seepage evolution law under hydro-mechanical coupling.
文摘The experimental study on the macro and micro characteristics of the spray from a pressure swirl nozzle embraces the growth of surface unstable wave,disintegration process,spray angle,breakup length and so on.The effects of injection pressure,nozzle geometry and liquid properties on these characteristics are also discussed.The results are helpful to understand the underlying physics of the pressure swirl nozzle and serve as the basis for the practical design,usage and improvement of the nozzle.
文摘壤全氮、土壤有机质的测定对农业生产和科学研究都有重要意义。因此在许多实验室里,土壤全氮、土壤有机质都被作为一项常规分析项目。土壤全氮量的测定百余年来沿用杜马氏法和凯氏定氮法。测定土壤有机质的方法主要有3种:干烧法、化学氧化法、灼烧法,1989年农业部颁布了国标GB9843-88《土壤有机质测定法》。近年来使用元素分析仪(Elementar Vario MACRO)测定土壤C、N也越来越广泛,元素分析仪是一台用于快速,定量测定元素C、H、N、S的全自动分析仪。用元素分析仪测定C、H、N的方法属于灼烧法,灼烧温度为960摄氏度,对酸性、中性土壤的测定无疑是省时准确的首选。石灰性土壤中由于碳酸盐的存在,在高温灼烧时碳酸盐分解,形成CO2,使土壤有机质的测定结果偏高。降低燃烧管温度测定(630摄氏度),由于样品用锡箔纸包裹,锡箔纸在燃烧管内燃烧生成氧化锡为放热反应,增加燃烧管内的温度高于设定温度,增加碳酸钙的分解测定值偏高,燃烧管温度设定在低于碳酸盐分解点时仪器密封不严实,使测定结果偏低。用盐酸处理土壤中碳酸盐,其后测定有机质时,因土壤中的富里酸溶于酸,使测定结果偏低。因此元素分析仪不适于石灰性土壤有机质的测定。
文摘This paper is based on three observations and independent thinking of the classroom teaching of the author’s colleagues.It attempts to examine how macro and micro contexts affect teaching and learning in the classroom.The author focuses the discussion on three aspects:(i)the present EFL contextual setting in China;(ii)the influence of the evaluation system on both teachers and students;(iii)his own beliefs as a teacher.Finally,he comes to the implications that teachers should often reflect on their teaching by means of observing other teachers’teachings;In order to bring more effective teaching and learning to the class,Teachers should change their class from a teacher-centered one to a students-centered one.
