The creep characteristics of rock under high crustal stress are of important influence on the long‐term stability of deep rock engineering.To study the creep characteristics and engineering application of sandstone u...The creep characteristics of rock under high crustal stress are of important influence on the long‐term stability of deep rock engineering.To study the creep characteristics and engineering application of sandstone under high crustal stress,this study constructed nonlinear creep damage(NCD)constitutive mode based on the triaxial graded loading‒unloading creep test of sandstone in the Yuezhishan Tunnel.A numerical NCD constitutive model and a breakable lining(BL)model were developed based on FLAC3D and then applied to the stability analysis of the Yuezhishan Tunnel.Based on the creep test results of sandstone,a power function of creep rate and stress level was constructed,by which the long‐term strength was solved.The results show that the long‐term strength of the red sandstone based on the related function of the steady‐state creep rate and stress level is close to the measured stress value in engineering.The NCD model considering damage factors reflects the instantaneous and viscoelastic plasticity deformation characteristics of the red sandstone.The numerical NCD constitutive model and the BL model can reflect surrounding rock deformation characteristics and lining failure characteristics in practical engineering.The research results provide theoretical references for long‐term stability analysis of rock engineering and the deformation control of surrounding rock under high crustal stress.展开更多
近年来,建设清洁低碳安全高效的能源体系,发展可再生能源替代,构建以新能源为主体的新型电力系统成为我国能源发展的必然趋势。在风光资源富集地区,随着新能源装机不断增加,大型综合能源基地得到快速发展。该文基于主客观赋权法建立多...近年来,建设清洁低碳安全高效的能源体系,发展可再生能源替代,构建以新能源为主体的新型电力系统成为我国能源发展的必然趋势。在风光资源富集地区,随着新能源装机不断增加,大型综合能源基地得到快速发展。该文基于主客观赋权法建立多能互补综合能源基地评估体系,对我国“三北”、西南及东部沿海区域发展布局多能互补基地进行评估。为进一步提升多能互补基地经济效益,建立基于长短期记忆神经网络(long short term memory,LSTM)的电价预测模型及多能互补日前优化调度模型,利用粒子群优化算法进行寻优,以实现能源基地综合收益最大化的日前优化调度目标。最后,以甘肃陇东千万kW级多能互补综合能源基地为例,分别开展夏季及冬季典型日的优化调度算例仿真,结果表明,该优化调度方法能够促进基地内新能源消纳的同时最大化能源基地综合收益,为大型综合能源基地的日前优化调度提供技术支撑。展开更多
BELl-like transcription factors are ubiquitous in plants and interact with KNOTTEDI-types to regulate numerous developmental processes. In potato, the RNA of several BELl-like transcription factors has been identified...BELl-like transcription factors are ubiquitous in plants and interact with KNOTTEDI-types to regulate numerous developmental processes. In potato, the RNA of several BELl-like transcription factors has been identified in phloem cells. One of these, StBEL5, and its Knox protein partner regulate tuber formation by targeting genes that control growth. RNA detection methods and grafting experiments demonstrated that StBEL5 transcripts move across a graft union to localize in stolon tips, the site of tuber induction. This movement of RNA originates in source leaf veins and petioles and is induced by a short-day photoperiod, regulated by the untranslated regions, and correlated with enhanced tuber production. Addition of the StBEL5 untranslated regions to another BELl.like mRNA resulted in its preferential transport to stolon tips leading to increased tuber production. Upon fusion of the untranslated regions of StBEL5 to a β-glucuronidase marker, translation in tobacco protoplasts was repressed by those constructs containing the 3＇ untranslated sequence. The untranslated regions of the StBEL5 mRNA are involved in mediating its long-distance transport and in controlling translation. The 3＇ untranslated sequence contains an abundance of conserved motifs that may serve as binding motifs for RNA-binding proteins. Because of their presence in the phloem sieve tube system, their unique untranslated region sequences and their diverse RNA accumulation patterns, the family of BEL1-like RNAs from potato represents a valuable model for studying the long-distance transport of full-length mRNAs and their role in development.展开更多
Grammar-translation teaching method(GTTM as a shorthand below) has long been a buzzword when it is adopted in the class of English as a foreign language.It has been universally acknowledged that such teaching method c...Grammar-translation teaching method(GTTM as a shorthand below) has long been a buzzword when it is adopted in the class of English as a foreign language.It has been universally acknowledged that such teaching method contradicts the development of communicative language competence advocated in recent decades.However,I positively argue that GTTM in English class,as a comparative and intercultural model,should be given a due reconsideration to improve L2 learners' pragmatic competence.展开更多
青少年早期专项化训练(Early sport specialization,ESS)是关乎青少年竞技运动训练科学化的重要问题,也是国内外体育科学领域持续关注的热点问题。通过文献资料法,明晰青少年早期专项化的概念,梳理早期专项化的基本内涵,归纳青少年早期...青少年早期专项化训练(Early sport specialization,ESS)是关乎青少年竞技运动训练科学化的重要问题,也是国内外体育科学领域持续关注的热点问题。通过文献资料法,明晰青少年早期专项化的概念,梳理早期专项化的基本内涵,归纳青少年早期专项化训练的国际经验及可能导致的负面影响,提出青少年专项化训练科学化的应对之策。基于此,拟定如下学者共识:第一、青少年早期专项化训练是指在青春期之前围绕一个特定运动项目进行的高强度的训练;第二、尽管诸如体操、跳水等运动项目要求很早(6~9岁)进行专项化训练,但绝不能忽视早期专项化训练极易对动作技能学习、运动技能学习、体能训练科学化、长期职业生涯发展及身体健康等造成的不良影响;第三、对于大多数运动项目来说,青少年相对较晚的进行专项化训练、或早期进行多样化训练且在晚期进行高水平专项化训练,成年后在竞技体育领域获得成功的概率更高;第四、技术主导类项目可以在正确动作模式基础上开展早期专项化训练,训练过程中应高度关注动作质量,避免出现动作模式异常诱发运动损伤;第五、青少年专项训练科学化的根本在于建立集体能、技术、战术、心理、运动智商及人文素养于一体的训练体系;第六、青少年专项训练科学化的关键在于依据生理年龄和身体机能发育特征,强化青少年各个时期体能训练科学化;第七、青少年早期专项化训练的综合应对策略为:选择合适的早期专项化训练时机、构建青少年长期发展模型、强化青少年多样化训练、训练与监控充分结合,以及建立与年龄相适应的赛事体系;第八、倡导以健康和快乐作为青少年参与体育运动的价值导向,以培养终身体育素养作为青少年参与体育运动的根本目标。展开更多
基金National Science and Technology Major Project,Grant/Award Number:2017YFC1503102National Natural Science Foundation of China,Grant/Award Number:51704144。
文摘The creep characteristics of rock under high crustal stress are of important influence on the long‐term stability of deep rock engineering.To study the creep characteristics and engineering application of sandstone under high crustal stress,this study constructed nonlinear creep damage(NCD)constitutive mode based on the triaxial graded loading‒unloading creep test of sandstone in the Yuezhishan Tunnel.A numerical NCD constitutive model and a breakable lining(BL)model were developed based on FLAC3D and then applied to the stability analysis of the Yuezhishan Tunnel.Based on the creep test results of sandstone,a power function of creep rate and stress level was constructed,by which the long‐term strength was solved.The results show that the long‐term strength of the red sandstone based on the related function of the steady‐state creep rate and stress level is close to the measured stress value in engineering.The NCD model considering damage factors reflects the instantaneous and viscoelastic plasticity deformation characteristics of the red sandstone.The numerical NCD constitutive model and the BL model can reflect surrounding rock deformation characteristics and lining failure characteristics in practical engineering.The research results provide theoretical references for long‐term stability analysis of rock engineering and the deformation control of surrounding rock under high crustal stress.
文摘近年来,建设清洁低碳安全高效的能源体系,发展可再生能源替代,构建以新能源为主体的新型电力系统成为我国能源发展的必然趋势。在风光资源富集地区,随着新能源装机不断增加,大型综合能源基地得到快速发展。该文基于主客观赋权法建立多能互补综合能源基地评估体系,对我国“三北”、西南及东部沿海区域发展布局多能互补基地进行评估。为进一步提升多能互补基地经济效益,建立基于长短期记忆神经网络(long short term memory,LSTM)的电价预测模型及多能互补日前优化调度模型,利用粒子群优化算法进行寻优,以实现能源基地综合收益最大化的日前优化调度目标。最后,以甘肃陇东千万kW级多能互补综合能源基地为例,分别开展夏季及冬季典型日的优化调度算例仿真,结果表明,该优化调度方法能够促进基地内新能源消纳的同时最大化能源基地综合收益,为大型综合能源基地的日前优化调度提供技术支撑。
基金supported by the United States Departmentof Agriculture NRI-CGP award no.2008-02806National Science Foundation-Plant Genome Research Program award no.0820659
文摘BELl-like transcription factors are ubiquitous in plants and interact with KNOTTEDI-types to regulate numerous developmental processes. In potato, the RNA of several BELl-like transcription factors has been identified in phloem cells. One of these, StBEL5, and its Knox protein partner regulate tuber formation by targeting genes that control growth. RNA detection methods and grafting experiments demonstrated that StBEL5 transcripts move across a graft union to localize in stolon tips, the site of tuber induction. This movement of RNA originates in source leaf veins and petioles and is induced by a short-day photoperiod, regulated by the untranslated regions, and correlated with enhanced tuber production. Addition of the StBEL5 untranslated regions to another BELl.like mRNA resulted in its preferential transport to stolon tips leading to increased tuber production. Upon fusion of the untranslated regions of StBEL5 to a β-glucuronidase marker, translation in tobacco protoplasts was repressed by those constructs containing the 3＇ untranslated sequence. The untranslated regions of the StBEL5 mRNA are involved in mediating its long-distance transport and in controlling translation. The 3＇ untranslated sequence contains an abundance of conserved motifs that may serve as binding motifs for RNA-binding proteins. Because of their presence in the phloem sieve tube system, their unique untranslated region sequences and their diverse RNA accumulation patterns, the family of BEL1-like RNAs from potato represents a valuable model for studying the long-distance transport of full-length mRNAs and their role in development.
文摘Grammar-translation teaching method(GTTM as a shorthand below) has long been a buzzword when it is adopted in the class of English as a foreign language.It has been universally acknowledged that such teaching method contradicts the development of communicative language competence advocated in recent decades.However,I positively argue that GTTM in English class,as a comparative and intercultural model,should be given a due reconsideration to improve L2 learners' pragmatic competence.
文摘青少年早期专项化训练(Early sport specialization,ESS)是关乎青少年竞技运动训练科学化的重要问题,也是国内外体育科学领域持续关注的热点问题。通过文献资料法,明晰青少年早期专项化的概念,梳理早期专项化的基本内涵,归纳青少年早期专项化训练的国际经验及可能导致的负面影响,提出青少年专项化训练科学化的应对之策。基于此,拟定如下学者共识:第一、青少年早期专项化训练是指在青春期之前围绕一个特定运动项目进行的高强度的训练;第二、尽管诸如体操、跳水等运动项目要求很早(6~9岁)进行专项化训练,但绝不能忽视早期专项化训练极易对动作技能学习、运动技能学习、体能训练科学化、长期职业生涯发展及身体健康等造成的不良影响;第三、对于大多数运动项目来说,青少年相对较晚的进行专项化训练、或早期进行多样化训练且在晚期进行高水平专项化训练,成年后在竞技体育领域获得成功的概率更高;第四、技术主导类项目可以在正确动作模式基础上开展早期专项化训练,训练过程中应高度关注动作质量,避免出现动作模式异常诱发运动损伤;第五、青少年专项训练科学化的根本在于建立集体能、技术、战术、心理、运动智商及人文素养于一体的训练体系;第六、青少年专项训练科学化的关键在于依据生理年龄和身体机能发育特征,强化青少年各个时期体能训练科学化;第七、青少年早期专项化训练的综合应对策略为:选择合适的早期专项化训练时机、构建青少年长期发展模型、强化青少年多样化训练、训练与监控充分结合,以及建立与年龄相适应的赛事体系;第八、倡导以健康和快乐作为青少年参与体育运动的价值导向,以培养终身体育素养作为青少年参与体育运动的根本目标。
