The obstacles of inferior microstructure and poor magnetic properties of(La,Ce)-Fe-B type magnets stand in the way of expanding their applications.In this work,(La,Ce)-Fe-B melt-spun ribbons were prepared with differe...The obstacles of inferior microstructure and poor magnetic properties of(La,Ce)-Fe-B type magnets stand in the way of expanding their applications.In this work,(La,Ce)-Fe-B melt-spun ribbons were prepared with different La/Ce ratios and rare earth contents.The microstructure and magnetic properties of these ribbons were investigated.With the La/Ce ratio increased,the fraction of the CeFe_(2)phase decreased and the β-La phase segregated among matrix grains,which deteriorated the coercivity of the ribbons.Reducing the rare earth content effectively suppressed the β-La phase and improved the proportion of the matrix phase in the ribbons.Here,the optimal alloy composite(La_(15)Ce_(85))_(14)Fe_(80)B_(6) has been obtained with modified microstructure and inhibited secondary phases.Good ribbon performance was tested,with H_(cj)=4.51 kOe,B_(r)=6.29 kG and(BH)_(max)=6.81 MGOe.展开更多
热电离质谱法(Thermal ionization mass spectrometry,简称TIMS)是一种测量同位素丰度比的经典分析方法,在地质学和核工业领域得到广泛应用。热电离质谱法测铀同位素丰度比时一般采用三带结构,由于铀的第一电离能较高,需要较高的电离温...热电离质谱法(Thermal ionization mass spectrometry,简称TIMS)是一种测量同位素丰度比的经典分析方法,在地质学和核工业领域得到广泛应用。热电离质谱法测铀同位素丰度比时一般采用三带结构,由于铀的第一电离能较高,需要较高的电离温度,长时间测试蒸发出铀化合物或电离出的铀离子在灯丝支架上沉积,影响灯丝支架上悬浮高压与源电压间的绝缘电阻,降低两者之间的电压差,导致绝大部分离子因动能不足无法进入离子透镜,最终影响离子流的稳定性,引起测试时信号产生波动。针对热电离质谱仪灯丝支架铀沉积导致的灯丝支架绝缘失效问题,采用激光剥蚀电感耦合等离子体质谱法(Laser ablation inductively coupled plasma mass spectrometry,简称LA-ICP-MS)对灯丝支架铀沉积分布进行了分析,取得以下结果:建立了LA-ICP-MS原位表面分析技术,其最佳激光频率为10 Hz,能量密度为6 J·cm-2,束斑直径为60μm。校准曲线相关系数R2=0.9992,表明建立的方法线性关系良好。应用建立的方法,测定了灯丝支架表面铀沉积的分布特征。结果显示:灯丝支架表面铀沉积随着灯丝支架使用时间的增加,对应的绝缘电阻变小;并沿着支架向两端延伸,铀沉积量逐渐降低。铀沉积主要集中在电离带灯丝支架中心上端,且蒸发带上铀沉积量明显低于电离带。同时绝缘挡片可以有效降低陶瓷绝缘体上铀的沉积,因此可以通过增大绝缘挡片来提高灯丝支架的绝缘效果。展开更多
Composite analyses were performed in this study to reveal the difference in spring precipitation over southern China during multiyear La Ni?a events during 1901 to 2015. It was found that there is significantly below-...Composite analyses were performed in this study to reveal the difference in spring precipitation over southern China during multiyear La Ni?a events during 1901 to 2015. It was found that there is significantly below-normal precipitation during the first boreal spring, but above-normal precipitation during the second year. The difference in spring precipitation over southern China is correlative to the variation in western North Pacific anomalous cyclone(WNPC), which can in turn be attributed to the different sea surface temperature anomaly(SSTA) over the Tropical Pacific. The remote forcing of negative SSTA in the equatorial central and eastern Pacific and the local air-sea interaction in the western North Pacific are the usual causes of WNPC formation and maintenance.SSTA in the first spring is stronger than those in the second spring. As a result, the intensity of WNPC in the first year is stronger, which is more likely to reduce the moisture in southern China by changing the moisture transport, leading to prolonged precipitation deficits over southern China. However, the tropical SSTA signals in the second year are too weak to induce the formation and maintenance of WNPC and the below-normal precipitation over southern China. Thus, the variation in tropical SSTA signals between two consecutive springs during multiyear La Ni?a events leads to obvious differences in the spatial pattern of precipitation anomaly in southern China by causing the different WNPC response.展开更多
Artificial synapses utilizing spike signals are essential elements of new generation brain-inspired computers.In this paper,we realize light-stimulated adaptive artificial synapse based on nanocrystalline zinc oxide f...Artificial synapses utilizing spike signals are essential elements of new generation brain-inspired computers.In this paper,we realize light-stimulated adaptive artificial synapse based on nanocrystalline zinc oxide film.The artificial synapse photoconductivity shows spike-type signal response,long and short-term memory(LTM and STM),STM-to-LTM transition and paired-pulse facilitation.It is also retaining the memory of previous exposures and demonstrates spike-frequency adaptation properties.A way to implement neurons with synaptic depression,tonic excitation,and delayed accelerating types of response under the influence of repetitive light signals is discussed.The developed artificial synapse is able to become a key element of neuromorphic chips and neuromorphic sensorics systems.展开更多
Within the past ten years,spark plasma sintering(SPS)has become an increasingly popular process for Mg manufacturing.In the SPS process,interparticle diffusion of compressed particles is rapidly achieved due to the co...Within the past ten years,spark plasma sintering(SPS)has become an increasingly popular process for Mg manufacturing.In the SPS process,interparticle diffusion of compressed particles is rapidly achieved due to the concept of Joule heating.Compared to traditional and additive manufacturing(AM)techniques,SPS gives unique control of the structural and microstructural features of Mg components.By doing so,their mechanical,tribological,and corrosion properties can be tailored.Although great advancements in this field have been made,these pieces of knowledge are scattered and have not been contextualized into a single work.The motivation of this work is to address this scientific gap and to provide a groundwork for understanding the basics of SPS manufacturing for Mg.To do so,the existing body of SPS Mg literature was first surveyed,with a focus on their structural formation and degradation mechanisms.It was found that successful Mg SPS fabrication highly depended on the processing temperature,particle size,and particle crystallinity.The addition of metal and ceramic composites also affected their microstructural features due to the Zener pinning effect.In degradative environments,their performance depends on their structural features and whether they have secondary phased composites.In industrial applications,SPS'd Mg was found to have great potential in biomedical,hydrogen storage,battery,automotive,and recycling sectors.The prospects to advance the field include using Mg as a doping agent for crystallite size refinement and using bulk metallic Mg-based glass powders for amorphous SPS components.Despite these findings,the interactions of multi-composites on the processing-structure-property relationships of SPS Mg is not well understood.In total,this work will provide a useful direction in the SPS field and serve as a milestone for future Mg-based SPS manufacturing.展开更多
基金Project supported by the fifth batch of major scientific and technological research projects in the Panxi Experimental Zone of Sichuan Province,the new functional materials and applications of rare earth vanadium titanium(Grant No.2020SCUNG201).
文摘The obstacles of inferior microstructure and poor magnetic properties of(La,Ce)-Fe-B type magnets stand in the way of expanding their applications.In this work,(La,Ce)-Fe-B melt-spun ribbons were prepared with different La/Ce ratios and rare earth contents.The microstructure and magnetic properties of these ribbons were investigated.With the La/Ce ratio increased,the fraction of the CeFe_(2)phase decreased and the β-La phase segregated among matrix grains,which deteriorated the coercivity of the ribbons.Reducing the rare earth content effectively suppressed the β-La phase and improved the proportion of the matrix phase in the ribbons.Here,the optimal alloy composite(La_(15)Ce_(85))_(14)Fe_(80)B_(6) has been obtained with modified microstructure and inhibited secondary phases.Good ribbon performance was tested,with H_(cj)=4.51 kOe,B_(r)=6.29 kG and(BH)_(max)=6.81 MGOe.
基金The National Natural Science Foundation of China under contract Nos 41576029, 41976221 and 42030410the National Key Research and Development Program of China under contract No. 2019YFA0606702the Startup Foundation for Introducing Talent of Nanjing University of Information Science and Technology。
文摘Composite analyses were performed in this study to reveal the difference in spring precipitation over southern China during multiyear La Ni?a events during 1901 to 2015. It was found that there is significantly below-normal precipitation during the first boreal spring, but above-normal precipitation during the second year. The difference in spring precipitation over southern China is correlative to the variation in western North Pacific anomalous cyclone(WNPC), which can in turn be attributed to the different sea surface temperature anomaly(SSTA) over the Tropical Pacific. The remote forcing of negative SSTA in the equatorial central and eastern Pacific and the local air-sea interaction in the western North Pacific are the usual causes of WNPC formation and maintenance.SSTA in the first spring is stronger than those in the second spring. As a result, the intensity of WNPC in the first year is stronger, which is more likely to reduce the moisture in southern China by changing the moisture transport, leading to prolonged precipitation deficits over southern China. However, the tropical SSTA signals in the second year are too weak to induce the formation and maintenance of WNPC and the below-normal precipitation over southern China. Thus, the variation in tropical SSTA signals between two consecutive springs during multiyear La Ni?a events leads to obvious differences in the spatial pattern of precipitation anomaly in southern China by causing the different WNPC response.
基金supported by the Ministry of Science and Higher Education of the Russian Federation (Grant№075-15-2020-801)by Non-commercial Foundation for support of Science and Education 《INTELLECT》.
文摘Artificial synapses utilizing spike signals are essential elements of new generation brain-inspired computers.In this paper,we realize light-stimulated adaptive artificial synapse based on nanocrystalline zinc oxide film.The artificial synapse photoconductivity shows spike-type signal response,long and short-term memory(LTM and STM),STM-to-LTM transition and paired-pulse facilitation.It is also retaining the memory of previous exposures and demonstrates spike-frequency adaptation properties.A way to implement neurons with synaptic depression,tonic excitation,and delayed accelerating types of response under the influence of repetitive light signals is discussed.The developed artificial synapse is able to become a key element of neuromorphic chips and neuromorphic sensorics systems.
文摘Within the past ten years,spark plasma sintering(SPS)has become an increasingly popular process for Mg manufacturing.In the SPS process,interparticle diffusion of compressed particles is rapidly achieved due to the concept of Joule heating.Compared to traditional and additive manufacturing(AM)techniques,SPS gives unique control of the structural and microstructural features of Mg components.By doing so,their mechanical,tribological,and corrosion properties can be tailored.Although great advancements in this field have been made,these pieces of knowledge are scattered and have not been contextualized into a single work.The motivation of this work is to address this scientific gap and to provide a groundwork for understanding the basics of SPS manufacturing for Mg.To do so,the existing body of SPS Mg literature was first surveyed,with a focus on their structural formation and degradation mechanisms.It was found that successful Mg SPS fabrication highly depended on the processing temperature,particle size,and particle crystallinity.The addition of metal and ceramic composites also affected their microstructural features due to the Zener pinning effect.In degradative environments,their performance depends on their structural features and whether they have secondary phased composites.In industrial applications,SPS'd Mg was found to have great potential in biomedical,hydrogen storage,battery,automotive,and recycling sectors.The prospects to advance the field include using Mg as a doping agent for crystallite size refinement and using bulk metallic Mg-based glass powders for amorphous SPS components.Despite these findings,the interactions of multi-composites on the processing-structure-property relationships of SPS Mg is not well understood.In total,this work will provide a useful direction in the SPS field and serve as a milestone for future Mg-based SPS manufacturing.