The evolution of the microstructure and morphology of Cu55Ni45 and Cu60Ni40 alloys under varying degrees of undercooling was investigated through molten glass purification and cyclic superheating technology.By increas...The evolution of the microstructure and morphology of Cu55Ni45 and Cu60Ni40 alloys under varying degrees of undercooling was investigated through molten glass purification and cyclic superheating technology.By increasing the Cu content,the effect of Cu on the evolution of the microstructure and morphology of the Cu-Ni alloy during undercooling was studied.The mechanism of grain refinement at different degrees of undercooling and the effect of Cu content on its solidification behaviour were investigated.The solidification behaviour of Cu55Ni45 and Cu60Ni40 alloys was investigated using infrared thermometry and high-speed photography.The results indicate that both Cu55Ni45 and Cu60Ni40 alloy melts undergo only one recalescence during rapid solidification.The degree of recalescence increases approximately linearly with increasing undercooling.The solidification front of the alloy melts undergoes a transition process from a small-angle plane to a sharp front and then to a smooth arc.However,the growth of the subcooled melt is constrained to a narrow range,facilitating the formation of a coarse dendritic crystal morphology in the Cu-Ni alloy.At large undercooling,the stress breakdown of the directionally growing dendrites is primarily caused by thermal diffusion.The strain remaining in the dendritic fragments provides the driving force for recrystallisation of the tissue to occur,which in turn refines the tissue.展开更多
Different compositions of yttrium silicates coatings were deposited on SiC-C/C by plasma spraying and an outer borosilicate glass was applied on the yttrium silicates coatings surfaces. The structure of the multi-laye...Different compositions of yttrium silicates coatings were deposited on SiC-C/C by plasma spraying and an outer borosilicate glass was applied on the yttrium silicates coatings surfaces. The structure of the multi-layer coatings was characterized by XRD and SEM analyses. High temperature oxidation behavior of the multi-layer coatings coated C/C composites was investigated. Results show that SiC/2SiO2 Y2O3/1.5SiO2 Y203/ SiO2 Y2O3/glass multi-layer coating has better high temperature oxidation resistance, protecting carbon/ carbon composites from oxidation at 1 773 K in air for 164 h with the weight loss of 1.65%. The oxidation weight loss of the coated C/C with time accorded with parabolic rule in the temperature range 1 573 K-1 873 K; and the corresponding oxidation activation energy of the coated carbon/carbon composites is 132.2 kJ/mol.展开更多
La-doped Li2Mo0.9La0.2O4 was synthesized as an active anode material via the sol-gel process. The structural and morphological characteristics of the target product and the precursor were analyzed by XRD, SEM, and TG-...La-doped Li2Mo0.9La0.2O4 was synthesized as an active anode material via the sol-gel process. The structural and morphological characteristics of the target product and the precursor were analyzed by XRD, SEM, and TG-DTA. Crystal started to format at 300℃ and the optimum crystal structure was obtained at 700℃. By detecting battery performance, the charged and discharged platform was over 3.6 V; the anode exhibited a discharge capacity decay of 2% from its initial capacity （165 mA·h/g） after 20 cycles. Therefore, it was a perfect anode material.展开更多
Nanocrystalline zirconia（ZrO） was synthesized using a microwave-hydrothermal process.The effect of pH on the crystallization of the ZrO2 powders was investigated.The phase and microstructure of ZrO2 powders were exa...Nanocrystalline zirconia（ZrO） was synthesized using a microwave-hydrothermal process.The effect of pH on the crystallization of the ZrO2 powders was investigated.The phase and microstructure of ZrO2 powders were examined using X-ray diffraction（XRD）,Raman spectroscopy,and transmission electron microscopy（TEM）.Results show that pure m-ZrO2 can be obtained at low pH（pH＆lt;2）.Pure t-ZrO2 is formed at pH = 7 and 14.The size of the ZrO2 crystals is in the range of 8-26 nm and decreases with increasing pH.The formation of m-ZrO2 results from the precipitation of ZrO2 from solution.The t-ZrO2 is formed through the in-situ structural rearrangement of amorphous Zr（OH）xOy.The stabilization of t-ZrO2 is attributed to the small crystal size and the adsorption of hydroxy ions on the surfaces of the crystals.展开更多
随着数字孪生技术在水利信息化中的深入应用,传统二维洪涝展示方式较难满足动态模拟、实时交互的需求。以虚幻引擎5(UE5)为核心技术平台,将水动力模型与三维可视化技术耦合,研究其在水利数字孪生3D场景中的创新应用模式。通过集成UE5的N...随着数字孪生技术在水利信息化中的深入应用,传统二维洪涝展示方式较难满足动态模拟、实时交互的需求。以虚幻引擎5(UE5)为核心技术平台,将水动力模型与三维可视化技术耦合,研究其在水利数字孪生3D场景中的创新应用模式。通过集成UE5的Nanite高精度建模、Lumen动态光照与Sequencer时间轴工具等,构建支持大规模地形渲染与实时数据驱动的数字孪生框架;结合Cesium for Unreal插件实现地理空间数据融合,并基于蓝图系统开发交互逻辑,真正实现水灾害过程的实时动态展示,如洪水演进、城市内涝等场景的三维可视化,以准确展示洪水到达时间,洪水淹没范围等水力要素,为决策人员提供有效科学依据。为智慧水利构建水利数字孪生平台,推动其从“静态可视化”向“沉浸式交互”转型提供基础。展开更多
【目的】绿茶是我国茶叶的第一大茶类,但已有调查发现在茶叶流通环节中存在拟除虫菊酯类农药残留问题。本研究旨在系统评估我国市售绿茶中拟除虫菊酯类农药的残留状况,并针对现状提出相应对策。【方法】检索2015年1月1日至2025年1月15日...【目的】绿茶是我国茶叶的第一大茶类,但已有调查发现在茶叶流通环节中存在拟除虫菊酯类农药残留问题。本研究旨在系统评估我国市售绿茶中拟除虫菊酯类农药的残留状况,并针对现状提出相应对策。【方法】检索2015年1月1日至2025年1月15日PubMed、Web of Science、CNKI、万方、维普数据库中关于中国绿茶中拟除虫菊酯类农药残留的文献,筛选后纳入符合条件的研究文献10篇。应用Stata软件进行Meta分析,合并拟除虫菊酯类农药检出率,并进一步进行敏感性分析及亚组分析,探讨异质性来源。此外,通过整理农药的残留量与国家标准GB 2763—2021的最大残留量限量(MRLs)对比,评估市售绿茶的合格状况,并与国际组织标准进行对比分析;分析探讨农药残留检测方法的现状。【结果】(1)我国市售绿茶中拟除虫菊酯类农药检出率由高到低依次为:联苯菊酯30%[95%置信区间(CI)=0.21~0.39]、氯氟氰菊酯13%(95%CI=0.08~0.19)、甲氰菊酯10%(95%CI=0.06~0.13)、氯氰菊酯10%(95%CI=0.06~0.15)、氯菊酯6%(95%CI=0~0.20)、溴氰菊酯6%(95%CI=0~0.28)、氰戊菊酯3%(95%CI=0~0.09)、氟氰戊菊酯2%(95%CI=0~0.08)。(2)从地区来看,华南地区的农药残留检出率较高,西南地区的农药残留检出率相对较低。(3)8种拟除虫菊酯类残留量均未超过GB 2763—2021规定的对应的最大残留量限量值。(4)氰戊菊酯虽已禁用,但仍存在微量残留。(5)我国拟除虫菊酯类农药MRLs部分指标与国际严苛标准存在差距,存在国际贸易壁垒风险。(6)农药残留检测方法存在缺陷需优化改进。【结论】我国市售绿茶拟除虫菊酯类农药残留总体符合国家标准,但仍存在禁用组分残留,加之检测技术的缺陷未能检出,导致人体可能面临长期暴露的健康风险;部分MRLs指标的差异,客观存在国际贸易壁垒风险。为此,应兼顾国内安全与国际贸易需求,通过标准国际化、防控绿色化、检测精准化和监管智能化,构建绿茶产业的全链条风险管控体系。同时,加强科研投入与公众教育,推动产业从“合规”向“优质”升级,在保障消费者健康的基础上,助力中国茶叶突破国际贸易壁垒,增强全球市场竞争力。展开更多
基金Funded by the Basic Research Project in Shanxi Province(No.202103021224183)the 2024 Science and Technology PlanProject of Jiaozuo City,Henan Province(No.2024410001)。
文摘The evolution of the microstructure and morphology of Cu55Ni45 and Cu60Ni40 alloys under varying degrees of undercooling was investigated through molten glass purification and cyclic superheating technology.By increasing the Cu content,the effect of Cu on the evolution of the microstructure and morphology of the Cu-Ni alloy during undercooling was studied.The mechanism of grain refinement at different degrees of undercooling and the effect of Cu content on its solidification behaviour were investigated.The solidification behaviour of Cu55Ni45 and Cu60Ni40 alloys was investigated using infrared thermometry and high-speed photography.The results indicate that both Cu55Ni45 and Cu60Ni40 alloy melts undergo only one recalescence during rapid solidification.The degree of recalescence increases approximately linearly with increasing undercooling.The solidification front of the alloy melts undergoes a transition process from a small-angle plane to a sharp front and then to a smooth arc.However,the growth of the subcooled melt is constrained to a narrow range,facilitating the formation of a coarse dendritic crystal morphology in the Cu-Ni alloy.At large undercooling,the stress breakdown of the directionally growing dendrites is primarily caused by thermal diffusion.The strain remaining in the dendritic fragments provides the driving force for recrystallisation of the tissue to occur,which in turn refines the tissue.
基金Supported by National Natural Science Foundation of China(No.50772063)the Program for New Century Excellent Talents in University(No.NCET-06-0893)
文摘Different compositions of yttrium silicates coatings were deposited on SiC-C/C by plasma spraying and an outer borosilicate glass was applied on the yttrium silicates coatings surfaces. The structure of the multi-layer coatings was characterized by XRD and SEM analyses. High temperature oxidation behavior of the multi-layer coatings coated C/C composites was investigated. Results show that SiC/2SiO2 Y2O3/1.5SiO2 Y203/ SiO2 Y2O3/glass multi-layer coating has better high temperature oxidation resistance, protecting carbon/ carbon composites from oxidation at 1 773 K in air for 164 h with the weight loss of 1.65%. The oxidation weight loss of the coated C/C with time accorded with parabolic rule in the temperature range 1 573 K-1 873 K; and the corresponding oxidation activation energy of the coated carbon/carbon composites is 132.2 kJ/mol.
文摘La-doped Li2Mo0.9La0.2O4 was synthesized as an active anode material via the sol-gel process. The structural and morphological characteristics of the target product and the precursor were analyzed by XRD, SEM, and TG-DTA. Crystal started to format at 300℃ and the optimum crystal structure was obtained at 700℃. By detecting battery performance, the charged and discharged platform was over 3.6 V; the anode exhibited a discharge capacity decay of 2% from its initial capacity （165 mA·h/g） after 20 cycles. Therefore, it was a perfect anode material.
基金Funded by National Natural Science Foundation of China(No.51302160)Natural Science Foundation of Shaanxi Province(Nos.2014JQ6226 and 2014JQ6213)+1 种基金China Postdoctoral Science Foundation(No.2015M570808)the Doctoral Scientific Research Foundation of Shaanxi University of Science&Technology(No.BJ14-20)
文摘Nanocrystalline zirconia（ZrO） was synthesized using a microwave-hydrothermal process.The effect of pH on the crystallization of the ZrO2 powders was investigated.The phase and microstructure of ZrO2 powders were examined using X-ray diffraction（XRD）,Raman spectroscopy,and transmission electron microscopy（TEM）.Results show that pure m-ZrO2 can be obtained at low pH（pH＆lt;2）.Pure t-ZrO2 is formed at pH = 7 and 14.The size of the ZrO2 crystals is in the range of 8-26 nm and decreases with increasing pH.The formation of m-ZrO2 results from the precipitation of ZrO2 from solution.The t-ZrO2 is formed through the in-situ structural rearrangement of amorphous Zr（OH）xOy.The stabilization of t-ZrO2 is attributed to the small crystal size and the adsorption of hydroxy ions on the surfaces of the crystals.
文摘随着数字孪生技术在水利信息化中的深入应用,传统二维洪涝展示方式较难满足动态模拟、实时交互的需求。以虚幻引擎5(UE5)为核心技术平台,将水动力模型与三维可视化技术耦合,研究其在水利数字孪生3D场景中的创新应用模式。通过集成UE5的Nanite高精度建模、Lumen动态光照与Sequencer时间轴工具等,构建支持大规模地形渲染与实时数据驱动的数字孪生框架;结合Cesium for Unreal插件实现地理空间数据融合,并基于蓝图系统开发交互逻辑,真正实现水灾害过程的实时动态展示,如洪水演进、城市内涝等场景的三维可视化,以准确展示洪水到达时间,洪水淹没范围等水力要素,为决策人员提供有效科学依据。为智慧水利构建水利数字孪生平台,推动其从“静态可视化”向“沉浸式交互”转型提供基础。
文摘【目的】绿茶是我国茶叶的第一大茶类,但已有调查发现在茶叶流通环节中存在拟除虫菊酯类农药残留问题。本研究旨在系统评估我国市售绿茶中拟除虫菊酯类农药的残留状况,并针对现状提出相应对策。【方法】检索2015年1月1日至2025年1月15日PubMed、Web of Science、CNKI、万方、维普数据库中关于中国绿茶中拟除虫菊酯类农药残留的文献,筛选后纳入符合条件的研究文献10篇。应用Stata软件进行Meta分析,合并拟除虫菊酯类农药检出率,并进一步进行敏感性分析及亚组分析,探讨异质性来源。此外,通过整理农药的残留量与国家标准GB 2763—2021的最大残留量限量(MRLs)对比,评估市售绿茶的合格状况,并与国际组织标准进行对比分析;分析探讨农药残留检测方法的现状。【结果】(1)我国市售绿茶中拟除虫菊酯类农药检出率由高到低依次为:联苯菊酯30%[95%置信区间(CI)=0.21~0.39]、氯氟氰菊酯13%(95%CI=0.08~0.19)、甲氰菊酯10%(95%CI=0.06~0.13)、氯氰菊酯10%(95%CI=0.06~0.15)、氯菊酯6%(95%CI=0~0.20)、溴氰菊酯6%(95%CI=0~0.28)、氰戊菊酯3%(95%CI=0~0.09)、氟氰戊菊酯2%(95%CI=0~0.08)。(2)从地区来看,华南地区的农药残留检出率较高,西南地区的农药残留检出率相对较低。(3)8种拟除虫菊酯类残留量均未超过GB 2763—2021规定的对应的最大残留量限量值。(4)氰戊菊酯虽已禁用,但仍存在微量残留。(5)我国拟除虫菊酯类农药MRLs部分指标与国际严苛标准存在差距,存在国际贸易壁垒风险。(6)农药残留检测方法存在缺陷需优化改进。【结论】我国市售绿茶拟除虫菊酯类农药残留总体符合国家标准,但仍存在禁用组分残留,加之检测技术的缺陷未能检出,导致人体可能面临长期暴露的健康风险;部分MRLs指标的差异,客观存在国际贸易壁垒风险。为此,应兼顾国内安全与国际贸易需求,通过标准国际化、防控绿色化、检测精准化和监管智能化,构建绿茶产业的全链条风险管控体系。同时,加强科研投入与公众教育,推动产业从“合规”向“优质”升级,在保障消费者健康的基础上,助力中国茶叶突破国际贸易壁垒,增强全球市场竞争力。
