Manipulating the self-assembly of transition metal telluride nanocrystals(NCs) creates opportunities for exploring new properties and device applications. Iron ditelluride(FeTe2) has recently emerged as a new class of...Manipulating the self-assembly of transition metal telluride nanocrystals(NCs) creates opportunities for exploring new properties and device applications. Iron ditelluride(FeTe2) has recently emerged as a new class of magnetic semiconductor with three-dimensional(3D) magnetic ordering and narrow band gap structure, yet the self-assembly of FeTe2 NCs has not been achieved. Herein, the tree-like FeTe2 nanoarchitectures with orthorhombic crystal structure have been successfully synthesized by hot-injection solvent thermal approach using phosphine-free Te precursor. The morphology, size, and crystal structure have been investigated using transmission electron microscopy(TEM), high-resolution TEM(HRTEM),and powder x-ray diffraction(XRD). We study the formation process of tree-like FeTe2 NCs according to trace the change of the sample morphology with the reaction time. It was found that the FeTe2 nanoparticles show oriented aggregation and self-assembly behavior with the increase of reaction time, which is attributed to size-dependent magnetism properties of the samples. The magnetic interaction is thought to be the driving force of nanoparticle self-organization.展开更多
Asymmetric tree-like branched networks are explored by geometric algorithms. Based on the network, an analysis of the thermal conductivity is presented. The relationship between effective thermal conductivity and geom...Asymmetric tree-like branched networks are explored by geometric algorithms. Based on the network, an analysis of the thermal conductivity is presented. The relationship between effective thermal conductivity and geometric structures is obtained by using the thermal-electrical analogy technique. In all studied cases, a clear behaviour is observed, where angle （δ,θ） among parent branching extended lines, branches and parameter of the geometric structures have stronger effects on the effective thermal conductivity. When the angle δ is fixed, the optical diameter ratio β＋ is dependent on angle θ. Moreover, γand m are not related to β＊. The longer the branch is, the smaller the effective thermal conductivity will be. It is also found that when the angle θ〈δ2, the higher the iteration m is, the lower the thermal conductivity will be and it tends to zero, otherwise, it is bigger than zero. When the diameter ratio β1 〈 0.707 and angle δ is bigger, the optimal k of the perfect ratio increases with the increase of the angle δ; when β1 〉 0.707, the optimal k decreases. In addition, the effective thermal conductivity is always less than that of single channel material. The present results also show that the effective thermal conductivity of the asymmetric tree-like branched networks does not obey Murray＇s law.展开更多
The comparison of networks with different orders strongly depends on the stability analysis of graph features in evolving systems. In this paper, we rigorously investigate the stability of the weighted spectral distri...The comparison of networks with different orders strongly depends on the stability analysis of graph features in evolving systems. In this paper, we rigorously investigate the stability of the weighted spectral distribution（i.e., a spectral graph feature） as the network order increases. First, we use deterministic scale-free networks generated by a pseudo treelike model to derive the precise formula of the spectral feature, and then analyze the stability of the spectral feature based on the precise formula. Except for the scale-free feature, the pseudo tree-like model exhibits the hierarchical and small-world structures of complex networks. The stability analysis is useful for the classification of networks with different orders and the similarity analysis of networks that may belong to the same evolving system.展开更多
A sentence over a finite alphabet A, is a finite sequence of non-empty words over A. More generally, we define a graphical sentence over A by attaching a non-empty word over A to each arrow and each loop of a connecte...A sentence over a finite alphabet A, is a finite sequence of non-empty words over A. More generally, we define a graphical sentence over A by attaching a non-empty word over A to each arrow and each loop of a connected directed graph (digraph, for short). Each word is written according to the direction of its corresponding arrow or loop. Graphical sentences can be used to encode sets of sentences in a compact way: the readable sentences of a graphical sentence being the sentences corresponding to directed paths in the digraph. We apply combinatorial equations on enriched trees and rooted trees, in the context of combinatorial species and Pólya theories, to analyze parameters in classes of tree-like sentences. These are graphical sentences constructed on tree-like digraphs.展开更多
A multi-lateral horizontal well is one of the main well types employed in the coal bed methane(CBM)development.In a traditional CBM multi-lateral horizontal well,either a major hole or laterals will go crossing throug...A multi-lateral horizontal well is one of the main well types employed in the coal bed methane(CBM)development.In a traditional CBM multi-lateral horizontal well,either a major hole or laterals will go crossing through coal beds to the largest extent,which may eventually result in bed collapse,footage failing to meet the design requirement,and the major hole unable to be monitored,re-entered and flushed.Therefore,this paper puts forward a design idea of a tree-like horizontal well composed of a major hole(for dredging passage),laterals(for controlling drainage area)and sub-laterals(for enhancing production).The major hole is usually drilled on the stable roof or floor of a coal bed,laterals are drilled from the major hole into coal beds,and several sub-laterals are drilled from laterals.The major hole,laterals and sub-laterals constitute a tree-like drainage and recovery system,whose major hole remains stable for a long period and can be monitored and maintained.The technique has been successfully applied in Well ZS 1P-5H in the Qinshui Basin,Shanxi.The well included one major hole,13 laterals,and 26 sub-laterals,with a total drilling footage of 12288 m,a total coal bed footage of 9512 m,and a total pure coal footage of 9408 m.Its major hole was fully placed in the mudstone of the coal bed roof.This well records a successful case of incident-free single well drilling with a footage of more than 10,000 m and serves as a new well type for efficient CBM development in China.展开更多
The intersection of economic development,energy dynamics,environmental policy,and environmental sustainability presents complex challenges for European Union(EU)countries.This study investigatedthe impact of environme...The intersection of economic development,energy dynamics,environmental policy,and environmental sustainability presents complex challenges for European Union(EU)countries.This study investigatedthe impact of environmental taxes,hydroelectricity consumption,economic globalization,and gross domestic product(GDP)on the load capacity factor(LCF)in the 10 EU member countries(including Austria,Finland,France,Germany,Italy,Poland,Portugal,Slovakia,Spain,and Sweden)using data from 1995 to 2020.To ensure the reliability and validity of the data,this study applied several advanced econometric tests,including the Pesaran and Yamagata slopeheterogeneitytest,Pesaran cross-sectional dependence(CSD)test,second-generation unit root test,and Westerlund cointegration test.The data showed important statistical issues such as slope heterogeneityacross panels,CSD,mixed-orderunit root structures,and long-run associations between variables.To address these issues,we applied an augmented mean group(AMG)model as the main regression approach,andusedthe pooled mean group-autoregressive distributed lag(PMG-ARDL)method to check the robustness.Specifically,the AMG results indicate that a 1.000%rise in hydroelectricity consumptionresults in a 0.048% rise in the LCF,while a 1.000% increase in environmental taxes leads toa 0.175% increase in the LCF.Contrary to this,a 1.000% increase in economic globalization results in a 0.370% decrease in the LCF,and a 1.000% increase in GDP leads toa 0.850% decrease in the LCF.Environmental taxes have a more beneficial impact on the environment,and GDP has the most detrimental effect.The findings provide empirical evidence on the role of environmental taxes,hydroelectricity consumption,economic globalization,and GDP in driving the LCF.Additionally,the findings provide valuable information to policy-makers,academicians,and stakeholders shaping energy and environmental policies in the 10 EU member countries.展开更多
This paper reconstructs in detail the course leading to the inception of the Chinese material medica(CMM)research at the Peking Union Medical College(PUMC)in 1920.By analyzing the primary materials from several archiv...This paper reconstructs in detail the course leading to the inception of the Chinese material medica(CMM)research at the Peking Union Medical College(PUMC)in 1920.By analyzing the primary materials from several archives,it provides,for the first time,a historiographical account of the major events and key figures in the process.These include the China Medical Board(CMB)Commission to East Asia in 1915 that shaped the attitudes of Drs.William H.Welch and Simon Flexner,the PUMC’s chief scientific architects,toward CMM and its scientific investigation;the influence of medical missionaries and Japanese scientists on these attitudes;the medical leaders’decisive roles in recruiting Ralph G.Mills and Bernard E.Read,two of medical missionaries with strong interests in and actual studies on CMM,to the PUMC,which serendipitously made them central figures associated with the CMM research at the College;and finally the critical role of Mills and other medical missionaries in introducing CMM research,both concept and material,to the CMB executives and in their reconciliating the research subject with the institutional aims.The findings of the study contextualize the inception of CMM research at PUMC from the perspective of broader narrative of transnational circulation and recognition of medical knowledge and highlight the intermediatory roles played by medical missionaries that were critical in the intersection between traditional Chinese medicine(TCM)and scientific medicine.The study also reveals multiple serendipitous occurrences associated with the eventual inception of the program,thus offers a fresh interpretation of the beginning of the most impactful research program of scientizing TCM in the first half of the 20th century.展开更多
[研究目的]量子科技作为一种具有颠覆性的前沿技术,未来可能完全改变军事国防和社会经济建设。欧盟(European Union,EU)于2025年7月出台的《量子欧洲战略:变化世界中的量子欧洲》(Quantum Europe Strategy:Quantum Europe in a Changing...[研究目的]量子科技作为一种具有颠覆性的前沿技术,未来可能完全改变军事国防和社会经济建设。欧盟(European Union,EU)于2025年7月出台的《量子欧洲战略:变化世界中的量子欧洲》(Quantum Europe Strategy:Quantum Europe in a Changing World)是其在全球量子竞争格局中力争上游的关键举措。本研究聚焦欧盟量子体系设计对中国量子技术产业化发展的启示。[研究方法]梳理政策内容和实施路径,分析战略目标和编制思路,并运用SWOT分析法深入剖析欧洲量子科技的内部优劣势与外部机遇挑战,以世界重要科技创新主体的前沿政策动态为基础,从顶层规划、应用领域、产业生态和人才培养等方面为中国量子技术及产业发展提出建议。[研究结论]《量子欧洲战略:变化世界中的量子欧洲》涵盖研发创新、基础设施、产业生态、国防安全与人才培养五大领域。其核心特点在于:一方面,以“技术生命周期管理方法”将上述领域整合为协同迭代的创新链;另一方面,这种系统工程思维也凸显了其强烈的危机驱动导向。中国应借鉴欧盟经验,致力于构建持之以恒且迭代优化的顶层战略,采用动态平衡的短期突破与长远布局策略,打造涵盖供应链安全与多元资本的全链条产业生态,并建立以能力认证为核心的人才培养体系,以夯实我国量子科技发展的系统性基础。展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11874027)the China Postdoctoral Science Foundation(Grant Nos.2019T120233 and 2017M621198)
文摘Manipulating the self-assembly of transition metal telluride nanocrystals(NCs) creates opportunities for exploring new properties and device applications. Iron ditelluride(FeTe2) has recently emerged as a new class of magnetic semiconductor with three-dimensional(3D) magnetic ordering and narrow band gap structure, yet the self-assembly of FeTe2 NCs has not been achieved. Herein, the tree-like FeTe2 nanoarchitectures with orthorhombic crystal structure have been successfully synthesized by hot-injection solvent thermal approach using phosphine-free Te precursor. The morphology, size, and crystal structure have been investigated using transmission electron microscopy(TEM), high-resolution TEM(HRTEM),and powder x-ray diffraction(XRD). We study the formation process of tree-like FeTe2 NCs according to trace the change of the sample morphology with the reaction time. It was found that the FeTe2 nanoparticles show oriented aggregation and self-assembly behavior with the increase of reaction time, which is attributed to size-dependent magnetism properties of the samples. The magnetic interaction is thought to be the driving force of nanoparticle self-organization.
基金Project supported by the State Key Development Program for Basic Research of China (Grant No 2006CB708612)the National Natural Science Foundation of China (Grant No 10572130)the Natural Science Foundation of Zhejiang Province, China (Grant No Y607425)
文摘Asymmetric tree-like branched networks are explored by geometric algorithms. Based on the network, an analysis of the thermal conductivity is presented. The relationship between effective thermal conductivity and geometric structures is obtained by using the thermal-electrical analogy technique. In all studied cases, a clear behaviour is observed, where angle （δ,θ） among parent branching extended lines, branches and parameter of the geometric structures have stronger effects on the effective thermal conductivity. When the angle δ is fixed, the optical diameter ratio β＋ is dependent on angle θ. Moreover, γand m are not related to β＊. The longer the branch is, the smaller the effective thermal conductivity will be. It is also found that when the angle θ〈δ2, the higher the iteration m is, the lower the thermal conductivity will be and it tends to zero, otherwise, it is bigger than zero. When the diameter ratio β1 〈 0.707 and angle δ is bigger, the optimal k of the perfect ratio increases with the increase of the angle δ; when β1 〉 0.707, the optimal k decreases. In addition, the effective thermal conductivity is always less than that of single channel material. The present results also show that the effective thermal conductivity of the asymmetric tree-like branched networks does not obey Murray＇s law.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61402485,61303061,and 71201169)
文摘The comparison of networks with different orders strongly depends on the stability analysis of graph features in evolving systems. In this paper, we rigorously investigate the stability of the weighted spectral distribution（i.e., a spectral graph feature） as the network order increases. First, we use deterministic scale-free networks generated by a pseudo treelike model to derive the precise formula of the spectral feature, and then analyze the stability of the spectral feature based on the precise formula. Except for the scale-free feature, the pseudo tree-like model exhibits the hierarchical and small-world structures of complex networks. The stability analysis is useful for the classification of networks with different orders and the similarity analysis of networks that may belong to the same evolving system.
文摘A sentence over a finite alphabet A, is a finite sequence of non-empty words over A. More generally, we define a graphical sentence over A by attaching a non-empty word over A to each arrow and each loop of a connected directed graph (digraph, for short). Each word is written according to the direction of its corresponding arrow or loop. Graphical sentences can be used to encode sets of sentences in a compact way: the readable sentences of a graphical sentence being the sentences corresponding to directed paths in the digraph. We apply combinatorial equations on enriched trees and rooted trees, in the context of combinatorial species and Pólya theories, to analyze parameters in classes of tree-like sentences. These are graphical sentences constructed on tree-like digraphs.
基金National Science and Technology Major Project“Demonstration project of horizontal well-based CBM development in the Qinshui Basin,Shanxi”(No.2011ZX05061).
文摘A multi-lateral horizontal well is one of the main well types employed in the coal bed methane(CBM)development.In a traditional CBM multi-lateral horizontal well,either a major hole or laterals will go crossing through coal beds to the largest extent,which may eventually result in bed collapse,footage failing to meet the design requirement,and the major hole unable to be monitored,re-entered and flushed.Therefore,this paper puts forward a design idea of a tree-like horizontal well composed of a major hole(for dredging passage),laterals(for controlling drainage area)and sub-laterals(for enhancing production).The major hole is usually drilled on the stable roof or floor of a coal bed,laterals are drilled from the major hole into coal beds,and several sub-laterals are drilled from laterals.The major hole,laterals and sub-laterals constitute a tree-like drainage and recovery system,whose major hole remains stable for a long period and can be monitored and maintained.The technique has been successfully applied in Well ZS 1P-5H in the Qinshui Basin,Shanxi.The well included one major hole,13 laterals,and 26 sub-laterals,with a total drilling footage of 12288 m,a total coal bed footage of 9512 m,and a total pure coal footage of 9408 m.Its major hole was fully placed in the mudstone of the coal bed roof.This well records a successful case of incident-free single well drilling with a footage of more than 10,000 m and serves as a new well type for efficient CBM development in China.
文摘The intersection of economic development,energy dynamics,environmental policy,and environmental sustainability presents complex challenges for European Union(EU)countries.This study investigatedthe impact of environmental taxes,hydroelectricity consumption,economic globalization,and gross domestic product(GDP)on the load capacity factor(LCF)in the 10 EU member countries(including Austria,Finland,France,Germany,Italy,Poland,Portugal,Slovakia,Spain,and Sweden)using data from 1995 to 2020.To ensure the reliability and validity of the data,this study applied several advanced econometric tests,including the Pesaran and Yamagata slopeheterogeneitytest,Pesaran cross-sectional dependence(CSD)test,second-generation unit root test,and Westerlund cointegration test.The data showed important statistical issues such as slope heterogeneityacross panels,CSD,mixed-orderunit root structures,and long-run associations between variables.To address these issues,we applied an augmented mean group(AMG)model as the main regression approach,andusedthe pooled mean group-autoregressive distributed lag(PMG-ARDL)method to check the robustness.Specifically,the AMG results indicate that a 1.000%rise in hydroelectricity consumptionresults in a 0.048% rise in the LCF,while a 1.000% increase in environmental taxes leads toa 0.175% increase in the LCF.Contrary to this,a 1.000% increase in economic globalization results in a 0.370% decrease in the LCF,and a 1.000% increase in GDP leads toa 0.850% decrease in the LCF.Environmental taxes have a more beneficial impact on the environment,and GDP has the most detrimental effect.The findings provide empirical evidence on the role of environmental taxes,hydroelectricity consumption,economic globalization,and GDP in driving the LCF.Additionally,the findings provide valuable information to policy-makers,academicians,and stakeholders shaping energy and environmental policies in the 10 EU member countries.
文摘This paper reconstructs in detail the course leading to the inception of the Chinese material medica(CMM)research at the Peking Union Medical College(PUMC)in 1920.By analyzing the primary materials from several archives,it provides,for the first time,a historiographical account of the major events and key figures in the process.These include the China Medical Board(CMB)Commission to East Asia in 1915 that shaped the attitudes of Drs.William H.Welch and Simon Flexner,the PUMC’s chief scientific architects,toward CMM and its scientific investigation;the influence of medical missionaries and Japanese scientists on these attitudes;the medical leaders’decisive roles in recruiting Ralph G.Mills and Bernard E.Read,two of medical missionaries with strong interests in and actual studies on CMM,to the PUMC,which serendipitously made them central figures associated with the CMM research at the College;and finally the critical role of Mills and other medical missionaries in introducing CMM research,both concept and material,to the CMB executives and in their reconciliating the research subject with the institutional aims.The findings of the study contextualize the inception of CMM research at PUMC from the perspective of broader narrative of transnational circulation and recognition of medical knowledge and highlight the intermediatory roles played by medical missionaries that were critical in the intersection between traditional Chinese medicine(TCM)and scientific medicine.The study also reveals multiple serendipitous occurrences associated with the eventual inception of the program,thus offers a fresh interpretation of the beginning of the most impactful research program of scientizing TCM in the first half of the 20th century.
文摘[研究目的]量子科技作为一种具有颠覆性的前沿技术,未来可能完全改变军事国防和社会经济建设。欧盟(European Union,EU)于2025年7月出台的《量子欧洲战略:变化世界中的量子欧洲》(Quantum Europe Strategy:Quantum Europe in a Changing World)是其在全球量子竞争格局中力争上游的关键举措。本研究聚焦欧盟量子体系设计对中国量子技术产业化发展的启示。[研究方法]梳理政策内容和实施路径,分析战略目标和编制思路,并运用SWOT分析法深入剖析欧洲量子科技的内部优劣势与外部机遇挑战,以世界重要科技创新主体的前沿政策动态为基础,从顶层规划、应用领域、产业生态和人才培养等方面为中国量子技术及产业发展提出建议。[研究结论]《量子欧洲战略:变化世界中的量子欧洲》涵盖研发创新、基础设施、产业生态、国防安全与人才培养五大领域。其核心特点在于:一方面,以“技术生命周期管理方法”将上述领域整合为协同迭代的创新链;另一方面,这种系统工程思维也凸显了其强烈的危机驱动导向。中国应借鉴欧盟经验,致力于构建持之以恒且迭代优化的顶层战略,采用动态平衡的短期突破与长远布局策略,打造涵盖供应链安全与多元资本的全链条产业生态,并建立以能力认证为核心的人才培养体系,以夯实我国量子科技发展的系统性基础。
