1. RE Permanent Materials Chinese demand for RE permanent magnets increases at 20% per year. The output of sintered NdFeB magnets will reach 70,000 tons in 2010, 75% of the world total, with sales value of RMB $26 bil...1. RE Permanent Materials Chinese demand for RE permanent magnets increases at 20% per year. The output of sintered NdFeB magnets will reach 70,000 tons in 2010, 75% of the world total, with sales value of RMB $26 billion. 2. RE Catalyst展开更多
【目的】探讨梵净山典型优势树种根系土壤细菌群落结构、多样性、生态系统功能及其不同树种间差异的环境驱动因子。【方法】以梵净山世界自然遗产地的丝栗栲、西南米槠、厚皮栲、长柄水青冈、云山青冈和亮叶水青冈6种优势树种为研究对象...【目的】探讨梵净山典型优势树种根系土壤细菌群落结构、多样性、生态系统功能及其不同树种间差异的环境驱动因子。【方法】以梵净山世界自然遗产地的丝栗栲、西南米槠、厚皮栲、长柄水青冈、云山青冈和亮叶水青冈6种优势树种为研究对象,通过高通量测序技术分析根系土壤细菌群落组成及其在树种间的多样性差异,并应用PICRUSt(phylogenetic investigation of communities by reconstruction of unobserved states)对功能基因进行预测,基于冗余分析或相关性分析揭示土壤细菌群落、功能基因及环境因子(气候因素和土壤化学性质)间的相互关系。【结果】土壤化学性质因树种不同而存在一定差异,梵净山6种优势树种根系土壤碱解氮(AN)、有效磷(AP)和速效钾(AK)含量分别为4.09~12.98,5.64~9.91和29.38~68.33 mg/kg;全氮(TN)、全磷(TP)和全碳(TC)含量分别为1.85~3.41,0.29~0.50和33.01~85.77 g/kg;pH和C/N分别为4.45~4.82和17.19~27.58。高通量测序结果表明,从72份土壤样品中共鉴定出851个属的细菌,分属38个门、99个纲、238个目、394个科。在不同树种间,细菌群落组成存在一定差异,其中酸杆菌门、变形菌门和放线菌门是根系土壤细菌的主要优势门类,三者相对丰度之和的均值为88.27%。多样性分析表明,虽然不同树种根系土壤中的细菌群落在丰富度和多样性上表现出很高的相似性,但也存在一定差异,其中厚皮栲根系土壤的Chao1指数最高,为5284.8;亮叶水青冈的Shannon指数最高,为9.1;而长柄水青冈的Chao1指数和Shannon指数均为最低,分别为4469.8和8.5。PICRUSt功能预测表明,不同树种根系土壤细菌主要参与5类一级代谢通路及其下属的33个子功能代谢通路,其中厚皮栲和长柄水青冈的KEGG功能基因相对丰度明显高于其他树种。冗余分析显示,海拔(Alt)和土壤AN含量是驱动土壤细菌群落结构变化的关键影响因素。相关性分析表明,细菌多样性指数与年平均温度(MAT)、年均大气湿度(AAH)呈显著负相关,而与土壤全碳(TC)呈显著正相关;KEGG功能基因相对丰度与环境因子的相关性较弱,而与细菌门水平的相对丰度存在较强相关性。【结论】梵净山6种优势树种根系土壤的化学性质、细菌群落组成、多样性及KEGG功能基因相对丰度存在一定差异。Alt和土壤AN含量是不同树种根系土壤细菌群落结构产生差异的关键环境驱动因子,而KEGG功能基因相对丰度主要与细菌群落结构变化相关。展开更多
As the Rural Revitalization Strategy is gradually implemented, China’s rural areas are set to have more diverse function requirements. This paper selects the Changsha-Zhuzhou-Xiangtan region(Chang-Zhu-Tan) consisting...As the Rural Revitalization Strategy is gradually implemented, China’s rural areas are set to have more diverse function requirements. This paper selects the Changsha-Zhuzhou-Xiangtan region(Chang-Zhu-Tan) consisting of 23 county-level units) as a case study and looks at its economic development, agricultural product supply, social security and ecological service functions during 1996–2016. It then constructs an index system to evaluate the temporal evolution of the region’s rural functions. SPSS 19.0 and DPS 7.05 software, as well as Pearson’s correlation coefficient analysis, system clustering, optimal segmentation of ordered samples and other methods, are used to study the evolution traits, regional differentiation characteristics and driving forces of rural functions in the region. The results show, first of all, that the overall evolution trend is increasing in functions with periodic characteristics, the key nodes being 2000 and 2008. Second, there is clear geographical differentiation in the evolution of rural functions. The economic development function shows rapid growth in the urban agglomeration’s center and relatively weak growth at the periphery;the agricultural product supply function and ecological service function are concentrated in county-level units with abundant cultivated and forest land;and the social security function displays similar geographical differentiation to the economic development function. Overall, there is an obvious discrepancy in the degree of development of rural functions among county-level units of the Changsha-Zhuzhou-Xiangtan urban agglomeration;the rural functions of the agglomeration and peripheral county-level units have different development traits;and county-level units display functional differentiation. Third, rural functions have evolved as a result of interactions between various factors, such as natural resources, socio-economic conditions and local transport conditions. The new driving forces caused by urbanization are ultimately leading the evolution of rural functions toward multi-functional comprehensive development.展开更多
The adiabatic control is a powerful technique for many practical applications in quantum state engineering,light-driven chemical reactions and geometrical quantum computations.This paper reveals a speed limit of nonad...The adiabatic control is a powerful technique for many practical applications in quantum state engineering,light-driven chemical reactions and geometrical quantum computations.This paper reveals a speed limit of nonadiabatic transition in a general time-dependent parametric quantum system that leads to an upper bound function which lays down an optimal criteria for the adiabatic controls.The upper bound function of transition rate between instantaneous eigenstates of a time-dependent system is determined by the power fluctuations of the system relative to the minimum gap between the instantaneous levels.In a parametric Hilbert space,the driving power corresponds to the quantum work done by the parametric force multiplying the parametric velocity along the parametric driving path.The general two-state time-dependent models are investigated as examples to calculate the bound functions in some general driving schemes with one and two driving parameters.The calculations show that the upper bound function provides a tighter real-time estimation of nonadiabatic transition and is closely dependent on the driving frequencies and the energy gap of the system.The deviations of the real phase from Berry phase on different closed paths are induced by the nonadiabatic transitions and can be efficiently controlled by the upper bound functions.When the upper bound is adiabatically controlled,the Berry phases of the electronic spin exhibit nonlinear step-like behaviors and it is closely related to topological structures of the complicated parametric paths on Bloch sphere.展开更多
轨道交通站点的功能综合反映了城市土地利用状况和城市空间活力。轨道交通站点与城市用地的和谐发展,对于优化城市交通、提升土地使用效率具有显著的正面影响。首先运用信息熵测算站点功能多样性,进一步运用优势度与均匀度探究站点功能...轨道交通站点的功能综合反映了城市土地利用状况和城市空间活力。轨道交通站点与城市用地的和谐发展,对于优化城市交通、提升土地使用效率具有显著的正面影响。首先运用信息熵测算站点功能多样性,进一步运用优势度与均匀度探究站点功能演变的空间分布特征和结构特征,最后使用XGBoost-SHAP机器学习模型探讨了其驱动因素以及它们之间的交互效应。研究表明:从时间维度上看,2012—2023年间站点功能信息熵总体呈现波动下降趋势。从空间维度上看,二环内变化型站点居多,二环至五环相对稳定,五环至六环站点变化明显,整体站点功能动态不稳定,变化型站点占比高达76%。从结构维度上看,站点功能构成经历了明显的变化,商服型和交通型站点增长,居住型、产业型及公共型站点减少或波动下降。从驱动因素上看,站点范围内的POI(point of interest)数量、路网密度和生产总值等是影响北京地铁站点功能混合度水平的主导因素,且各个主导因素之间存在交互效应。本文研究结果对于改善地铁站点周边土地的使用效率和增强站点的活力具有重要意义。展开更多
The drive control system of the permanent magnetic direct current motor with the enhanced magnetism windings used in the electric transit bus is developed. The mathematics model of the drive control system for this mo...The drive control system of the permanent magnetic direct current motor with the enhanced magnetism windings used in the electric transit bus is developed. The mathematics model of the drive control system for this motor is established. The new mode that the added exiting magnetism field could be weakened and the speed of the motor could be controlled automatically is proposed and realized. The method of root locus design is applied to analyze the acceleration control characteristic. The results of simulation show that the new drive motor control system has extraordinary response characteristic and adjustable performance. Experiments of vehicle running show that the drive control system's antijamming ability is strong and the adjustable performance is fast and smooth, it can meet the demand of power characteristic very well.展开更多
The paper approaches the problem of the command functions of galvanometer-based scanners （GS） that are necessary to produce the linear plus parabolic scanning function of the GS, which we have proved previously to p...The paper approaches the problem of the command functions of galvanometer-based scanners （GS） that are necessary to produce the linear plus parabolic scanning function of the GS, which we have proved previously to produce the highest possible duty cycle （i.e., time efficiency） of the device. We have completed this theoretical aspect （which contradicted what has been stated previously in the literature, where it has been considered that the linear plus sinusoidal scanning function was the best） with the experimental study of the most used scanning functions of the GSs （sawtooth, sinusoidal and triangular）, with applications in biomedical imaging, in particular in optical coherence tomography, demonstrating that the triangular function is always the best one to be applied, from both an optical and a mechanical point of view. In the present study the input voltage/command function which should be applied to the GS to produce the desired triangular scanning function （with controlled non-linearity for the fastest possible stop-and-turn portions） was determined analytically, in relationship with the active torque that drives the device. This command function is analyzed with regard to the specific, respectively required parameters of the GS： natural frequency and damping factor, respectively scan speed and amplitude. The modeling in an open loop control structure of the GS is finally discussed as a trade-off between using the highest possible duty cycle and minimizing the maximum peaks of the input voltage.展开更多
探索土地利用功能(Land use functions,LUFs)间的权衡/协同效应及其空间非平稳性和驱动机制,对有效缓解人地矛盾、提升区域国土空间总体效益具有重要意义。现有研究多从宏观尺度探讨土地利用功能间权衡/协同效应的时空分布格局与影响因...探索土地利用功能(Land use functions,LUFs)间的权衡/协同效应及其空间非平稳性和驱动机制,对有效缓解人地矛盾、提升区域国土空间总体效益具有重要意义。现有研究多从宏观尺度探讨土地利用功能间权衡/协同效应的时空分布格局与影响因素,但难以真实反映人地关系地域系统的复杂性及内在机制。本文以昆明市为例,基于网格尺度采用地理加权回归(GWR)揭示2000—2020年昆明市土地利用功能权衡/协同效应的空间异质性;运用地理探测器模型和多尺度地理加权回归模型(MGWR)深入探析“自然-社会-经济”因素对土地利用功能间权衡/协同效应的作用机制。结果表明:土地利用功能间权衡/协同效应呈显著的空间异质性,生态功能与生产功能、生活功能与生产功能呈倒“U”形凹函数分布,并存在边界效应,而生态功能与生活功能呈“U”形凸函数分布。在“自然-经济-社会”因素中,降水量、高程、坡度、与市中心距离、与县中心距离、土地利用程度和人类活动强度是影响昆明市土地利用功能权衡/协同效应的主导因素。土地利用功能间权衡/协同效应与主导因素的空间异质性呈显著关系,降水量对生态功能与生产功能的权衡效应具有负向影响,与市中心距离、与县中心距离、高程和坡度则呈正向影响;与市中心距离对生态功能与生活功能的权衡效应具有负向影响,高程、土地利用强度、坡度和人类活动强度呈正向影响;与市中心距离、降水量和高程对生活功能与生产功能的权衡效应主要呈负向影响,与县中心距离和坡度呈正向影响。研究结果有助于更深入地理解土地利用功能系统的内在机制,为土地资源的多功能开发、合理利用及科学管理提供理论依据和技术支持。展开更多
文摘1. RE Permanent Materials Chinese demand for RE permanent magnets increases at 20% per year. The output of sintered NdFeB magnets will reach 70,000 tons in 2010, 75% of the world total, with sales value of RMB $26 billion. 2. RE Catalyst
文摘【目的】探讨梵净山典型优势树种根系土壤细菌群落结构、多样性、生态系统功能及其不同树种间差异的环境驱动因子。【方法】以梵净山世界自然遗产地的丝栗栲、西南米槠、厚皮栲、长柄水青冈、云山青冈和亮叶水青冈6种优势树种为研究对象,通过高通量测序技术分析根系土壤细菌群落组成及其在树种间的多样性差异,并应用PICRUSt(phylogenetic investigation of communities by reconstruction of unobserved states)对功能基因进行预测,基于冗余分析或相关性分析揭示土壤细菌群落、功能基因及环境因子(气候因素和土壤化学性质)间的相互关系。【结果】土壤化学性质因树种不同而存在一定差异,梵净山6种优势树种根系土壤碱解氮(AN)、有效磷(AP)和速效钾(AK)含量分别为4.09~12.98,5.64~9.91和29.38~68.33 mg/kg;全氮(TN)、全磷(TP)和全碳(TC)含量分别为1.85~3.41,0.29~0.50和33.01~85.77 g/kg;pH和C/N分别为4.45~4.82和17.19~27.58。高通量测序结果表明,从72份土壤样品中共鉴定出851个属的细菌,分属38个门、99个纲、238个目、394个科。在不同树种间,细菌群落组成存在一定差异,其中酸杆菌门、变形菌门和放线菌门是根系土壤细菌的主要优势门类,三者相对丰度之和的均值为88.27%。多样性分析表明,虽然不同树种根系土壤中的细菌群落在丰富度和多样性上表现出很高的相似性,但也存在一定差异,其中厚皮栲根系土壤的Chao1指数最高,为5284.8;亮叶水青冈的Shannon指数最高,为9.1;而长柄水青冈的Chao1指数和Shannon指数均为最低,分别为4469.8和8.5。PICRUSt功能预测表明,不同树种根系土壤细菌主要参与5类一级代谢通路及其下属的33个子功能代谢通路,其中厚皮栲和长柄水青冈的KEGG功能基因相对丰度明显高于其他树种。冗余分析显示,海拔(Alt)和土壤AN含量是驱动土壤细菌群落结构变化的关键影响因素。相关性分析表明,细菌多样性指数与年平均温度(MAT)、年均大气湿度(AAH)呈显著负相关,而与土壤全碳(TC)呈显著正相关;KEGG功能基因相对丰度与环境因子的相关性较弱,而与细菌门水平的相对丰度存在较强相关性。【结论】梵净山6种优势树种根系土壤的化学性质、细菌群落组成、多样性及KEGG功能基因相对丰度存在一定差异。Alt和土壤AN含量是不同树种根系土壤细菌群落结构产生差异的关键环境驱动因子,而KEGG功能基因相对丰度主要与细菌群落结构变化相关。
基金National Natural Science Foundation of China,No.41571168Key Project of Philosophy and Social Science Foundation of Hunan Province,No.18ZDB015
文摘As the Rural Revitalization Strategy is gradually implemented, China’s rural areas are set to have more diverse function requirements. This paper selects the Changsha-Zhuzhou-Xiangtan region(Chang-Zhu-Tan) consisting of 23 county-level units) as a case study and looks at its economic development, agricultural product supply, social security and ecological service functions during 1996–2016. It then constructs an index system to evaluate the temporal evolution of the region’s rural functions. SPSS 19.0 and DPS 7.05 software, as well as Pearson’s correlation coefficient analysis, system clustering, optimal segmentation of ordered samples and other methods, are used to study the evolution traits, regional differentiation characteristics and driving forces of rural functions in the region. The results show, first of all, that the overall evolution trend is increasing in functions with periodic characteristics, the key nodes being 2000 and 2008. Second, there is clear geographical differentiation in the evolution of rural functions. The economic development function shows rapid growth in the urban agglomeration’s center and relatively weak growth at the periphery;the agricultural product supply function and ecological service function are concentrated in county-level units with abundant cultivated and forest land;and the social security function displays similar geographical differentiation to the economic development function. Overall, there is an obvious discrepancy in the degree of development of rural functions among county-level units of the Changsha-Zhuzhou-Xiangtan urban agglomeration;the rural functions of the agglomeration and peripheral county-level units have different development traits;and county-level units display functional differentiation. Third, rural functions have evolved as a result of interactions between various factors, such as natural resources, socio-economic conditions and local transport conditions. The new driving forces caused by urbanization are ultimately leading the evolution of rural functions toward multi-functional comprehensive development.
基金Project supported by the National Natural Science Foundation of China(Emergency Project,Grant Nos.11447025 and 11847308)
文摘The adiabatic control is a powerful technique for many practical applications in quantum state engineering,light-driven chemical reactions and geometrical quantum computations.This paper reveals a speed limit of nonadiabatic transition in a general time-dependent parametric quantum system that leads to an upper bound function which lays down an optimal criteria for the adiabatic controls.The upper bound function of transition rate between instantaneous eigenstates of a time-dependent system is determined by the power fluctuations of the system relative to the minimum gap between the instantaneous levels.In a parametric Hilbert space,the driving power corresponds to the quantum work done by the parametric force multiplying the parametric velocity along the parametric driving path.The general two-state time-dependent models are investigated as examples to calculate the bound functions in some general driving schemes with one and two driving parameters.The calculations show that the upper bound function provides a tighter real-time estimation of nonadiabatic transition and is closely dependent on the driving frequencies and the energy gap of the system.The deviations of the real phase from Berry phase on different closed paths are induced by the nonadiabatic transitions and can be efficiently controlled by the upper bound functions.When the upper bound is adiabatically controlled,the Berry phases of the electronic spin exhibit nonlinear step-like behaviors and it is closely related to topological structures of the complicated parametric paths on Bloch sphere.
文摘轨道交通站点的功能综合反映了城市土地利用状况和城市空间活力。轨道交通站点与城市用地的和谐发展,对于优化城市交通、提升土地使用效率具有显著的正面影响。首先运用信息熵测算站点功能多样性,进一步运用优势度与均匀度探究站点功能演变的空间分布特征和结构特征,最后使用XGBoost-SHAP机器学习模型探讨了其驱动因素以及它们之间的交互效应。研究表明:从时间维度上看,2012—2023年间站点功能信息熵总体呈现波动下降趋势。从空间维度上看,二环内变化型站点居多,二环至五环相对稳定,五环至六环站点变化明显,整体站点功能动态不稳定,变化型站点占比高达76%。从结构维度上看,站点功能构成经历了明显的变化,商服型和交通型站点增长,居住型、产业型及公共型站点减少或波动下降。从驱动因素上看,站点范围内的POI(point of interest)数量、路网密度和生产总值等是影响北京地铁站点功能混合度水平的主导因素,且各个主导因素之间存在交互效应。本文研究结果对于改善地铁站点周边土地的使用效率和增强站点的活力具有重要意义。
文摘The drive control system of the permanent magnetic direct current motor with the enhanced magnetism windings used in the electric transit bus is developed. The mathematics model of the drive control system for this motor is established. The new mode that the added exiting magnetism field could be weakened and the speed of the motor could be controlled automatically is proposed and realized. The method of root locus design is applied to analyze the acceleration control characteristic. The results of simulation show that the new drive motor control system has extraordinary response characteristic and adjustable performance. Experiments of vehicle running show that the drive control system's antijamming ability is strong and the adjustable performance is fast and smooth, it can meet the demand of power characteristic very well.
基金the support of the US Department of State through Fulbright Scholar Grant 474/2009
文摘The paper approaches the problem of the command functions of galvanometer-based scanners （GS） that are necessary to produce the linear plus parabolic scanning function of the GS, which we have proved previously to produce the highest possible duty cycle （i.e., time efficiency） of the device. We have completed this theoretical aspect （which contradicted what has been stated previously in the literature, where it has been considered that the linear plus sinusoidal scanning function was the best） with the experimental study of the most used scanning functions of the GSs （sawtooth, sinusoidal and triangular）, with applications in biomedical imaging, in particular in optical coherence tomography, demonstrating that the triangular function is always the best one to be applied, from both an optical and a mechanical point of view. In the present study the input voltage/command function which should be applied to the GS to produce the desired triangular scanning function （with controlled non-linearity for the fastest possible stop-and-turn portions） was determined analytically, in relationship with the active torque that drives the device. This command function is analyzed with regard to the specific, respectively required parameters of the GS： natural frequency and damping factor, respectively scan speed and amplitude. The modeling in an open loop control structure of the GS is finally discussed as a trade-off between using the highest possible duty cycle and minimizing the maximum peaks of the input voltage.
文摘探索土地利用功能(Land use functions,LUFs)间的权衡/协同效应及其空间非平稳性和驱动机制,对有效缓解人地矛盾、提升区域国土空间总体效益具有重要意义。现有研究多从宏观尺度探讨土地利用功能间权衡/协同效应的时空分布格局与影响因素,但难以真实反映人地关系地域系统的复杂性及内在机制。本文以昆明市为例,基于网格尺度采用地理加权回归(GWR)揭示2000—2020年昆明市土地利用功能权衡/协同效应的空间异质性;运用地理探测器模型和多尺度地理加权回归模型(MGWR)深入探析“自然-社会-经济”因素对土地利用功能间权衡/协同效应的作用机制。结果表明:土地利用功能间权衡/协同效应呈显著的空间异质性,生态功能与生产功能、生活功能与生产功能呈倒“U”形凹函数分布,并存在边界效应,而生态功能与生活功能呈“U”形凸函数分布。在“自然-经济-社会”因素中,降水量、高程、坡度、与市中心距离、与县中心距离、土地利用程度和人类活动强度是影响昆明市土地利用功能权衡/协同效应的主导因素。土地利用功能间权衡/协同效应与主导因素的空间异质性呈显著关系,降水量对生态功能与生产功能的权衡效应具有负向影响,与市中心距离、与县中心距离、高程和坡度则呈正向影响;与市中心距离对生态功能与生活功能的权衡效应具有负向影响,高程、土地利用强度、坡度和人类活动强度呈正向影响;与市中心距离、降水量和高程对生活功能与生产功能的权衡效应主要呈负向影响,与县中心距离和坡度呈正向影响。研究结果有助于更深入地理解土地利用功能系统的内在机制,为土地资源的多功能开发、合理利用及科学管理提供理论依据和技术支持。
