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1.
Lizhi Fang 《中国物理 B》2022,31(12):127802-127802
By using an improved Bridgman method, 0.3 mol% Tm$^{3+}/0.6$ mol% Tb$^{3+}/y$ mol% Eu$^{3+}$ ($y = 0$, 0.4, 0.6, 0.8) doped Na$_{5}$Y$_{9}$F$_{32}$ single crystals were prepared. The x-ray diffraction, excitation spectra, emission spectra and fluorescence decay curves were used to explore the crystal structure and optical performance of the obtained samples. When excited by 362 nm light, the cool white emission was realized by Na$_{5}$Y$_{9}$F$_{32}$ single crystal triply-doped with 0.3 mol% Tm$^{3+}/0.6$ mol% Tb$^{3+}/0.8$ mol% Eu$^{3+}$, in which the Commission Internationale de l'Eclairage (CIE) chromaticity coordinate was (0.2995, 0.3298) and the correlated color temperature (CCT) was 6586 K. The integrated normalized emission intensity of the tri-doped single crystal at 448 K could keep 62% of that at 298 K. The internal quantum yield (QY) was calculated to be $\sim 15.16$% by integrating spheres. These results suggested that the single crystals tri-doped with Tm$^{3+}$, Tb$^{3+}$ and Eu$^{3+}$ ions have a promising potential application for white light-emitting diodes (w-LEDs).  相似文献   
2.
延安是中国共产党领导革命的中心和战略总后方,是革命的红色摇篮。延安时期出版了大量具有历史、文化以及教育意义的红色文献,这些红色文献记载了中国共产党波澜壮阔的发展历程,也反映了延安时期不断发展的科技生产水平与独特的制浆造纸工艺,具有重要的研究价值。然而,延安时期出版的红色文献虽距今不到百年时间,但其保存现状不容乐观,普遍存在纸张老化、焦脆易碎等问题,大量文献急需科学检测与修复保护,以延长其保存寿命。目前,针对延安时期红色文献的检测研究仍存在较大空白。考虑到红色文献的珍贵性与特殊性,应当尽可能选择无损检测方法对其分析检测。基于衰减全反射-傅里叶变换红外光谱法(ATR-FTIR),以木素1 510 cm-1处特征峰与纤维素1 030 cm-1处特征峰的强度作为定量依据,建立了造纸原料与红色文献纸张中木素相对含量的无损检测方法。通过检测不同碱强度与碱浓度处理后的构皮、苦竹与杨木的木素含量,考察了制浆过程中碱处理条件对造纸原料脱木素程度的影响,同时体现了红外光谱法测定木素相对含量的普适性。以复旦大学图书馆藏的76册延安时期红色文献为研究对象,分析了红色文献的纸张木素含量与纸张pH值以及纸张氧化度的相互关系。结果表明,木素相对含量高于25%的红色文献,其纸张pH集中在3~4之间且纸张氧化度较高,文献整体保存状况堪忧;而木素相对含量低于25%的红色文献,其纸张氧化度与酸度较低,文献整体保存情况较好。以上结果验证了红外光谱无损检测法用于延安时期红色文献木素含量分析的可行性,并结合纸张氧化度与酸度数据提出了纸张木素含量的合适范围,为制浆造纸中植物原料的脱木素过程提供参考。拓展了红外光谱法在红色文献无损检测中的应用范围,以期为延安时期红色文献的修复与保护研究提供科学依据。  相似文献   
3.
建立了氟化氢铵消解地球化学样品,电感耦合等离子体质谱(ICP-MS)法测定样品中钨、锡和钼的方法。方法经过国家土壤和水系沉积物标准参考物质验证,方法的检出限钨为0.048μg/g、锡为0.079μg/g、钼为0.063μg/g,准确度(相对误差)钨为0.64%~6.28%、锡为0.29%~3.74%、钼为2.12%~7.41%,精密度(相对标准偏差)钨为0.13%~0.72%、锡为0.05%~1.2%、钼为0.03%~1.1%,能够满足《地质矿产实验室测试质量管理规范》的质量要求。方法具有操作简便、测试成本低、分析效率高、环境污染小等特点,适合于批量样品的分析测试。  相似文献   
4.
李军  姚道新 《中国物理 B》2022,31(1):17403-017403
This article reviews the basic theoretical aspects of octagraphene, an one-atom-thick allotrope of carbon, with unusual two-dimensional(2 D) Fermi nesting, hoping to contribute to the new family of quantum materials. Octagraphene has an almost strongest sp2hybrid bond similar to graphene, and has the similar electronic band structure as iron-based superconductors, which makes it possible to realize high-temperature superconductivity. We have compared various possible mechanisms of superconductivity, including the unconventional s;superconductivity driven by spin fluctuation and conventional superconductivity based on electron–phonon coupling. Theoretical studies have shown that octagraphene has relatively high structural stability. Although many 2 D carbon materials with C;carbon ring and C;carbon ring structures have been reported, it is still challenging to realize the octagraphene with pure square-octagon structure experimentally.This material holds hope to realize new 2 D high-temperature superconductivity.  相似文献   
5.
Ruppeiner geometry has been successfully applied in the study of the black hole microstructure by combining with the small–large black hole phase transition, and the potential interactions among the molecular-like constituent degrees of freedom are uncovered. In this paper, we will extend the study to the triple point, where three black hole phases coexist acting as a typical feature of black hole systems quite different from the small–large black hole phase transition. For the six-dimensional charged Gauss–Bonnet anti-de Sitter black hole, we thoroughly investigate the swallow tail behaviors of the Gibbs free energy and the equal area laws. After obtaining the black hole triple point in a complete parameter space, we exhibit its phase structures both in the pressure–temperature and temperature–horizon radius diagrams. Quite different from the liquid–vapor phase transition, a double peak behavior is present in the temperature–horizon radius phase diagram. Then we construct the Ruppeiner geometry and calculate the corresponding normalized curvature scalar. Near the triple point, we observe multiple negatively divergent behaviors. Positive curvature scalar is observed for the small black hole with high temperature, which indicates that the repulsive interaction dominates among the microstructure. Furthermore, we consider the variation of the curvature scalar along the coexisting intermediate and large black hole curves. Combining with the observation for different fluids, the result suggests that this black hole system behaves more like the argon or methane. Our study provides a first and preliminary step towards understanding black hole microstructure near the triple point, as well as uncovering the particular properties of the Gauss–Bonnet gravity.  相似文献   
6.
Liang'an Huo 《中国物理 B》2022,31(3):30202-030202
The appearance of rumors intensifies people's panic and affects social stability. How to control the spread of rumors has become an important issue which is worth studying. In order to more accurately reflect the actual situation in the real world, a stochastic model incorporating media coverage and Lévy noise is proposed to describe the dynamic process of rumor propagation. By introducing two control strategies of popular science education and media coverage in an emergency event, an near-optimal control problem that minimizes the influence and control cost of rumor propagation is proposed. Sufficient conditions for near-optimal control of the model are established by using a Hamiltonian function. Then the necessary conditions for near-optimal control are obtained by using the Pontryagin maximum principle. Finally, the effect of popular science education, media coverage and Lévy noise on rumor propagation process control is verified by numerical simulation.  相似文献   
7.
Lijun Ni 《中国物理 B》2022,31(12):128504-128504
We report the temperature dependence of the spin pumping effect for Y3Fe5O12 (YIG, 0.9 μm)/NiO (tNiO)/W (6 nm) (tNiO = 0 nm, 1 nm, 2 nm, and 10 nm) heterostructures. All samples exhibit a strong temperature-dependent inverse spin Hall effect (ISHE) signal Ic and sensitivity to the NiO layer thickness. We observe a dramatic decrease of Ic with inserting thin NiO layer between YIG and W layers indicating that the inserting of NiO layer significantly suppresses the spin transport from YIG to W. In contrast to the noticeable enhancement in YIG/NiO (tNiO ≈ 1-2 nm)/Pt, the suppression of spin transport may be closely related to the specific interface-dependent spin scattering, spin memory loss, and spin conductance at the NiO/W interface. Besides, the Ic of YIG/NiO/W exhibits a maximum near the TN of the AF NiO layer because the spins are transported dominantly by incoherent thermal magnons.  相似文献   
8.
We devote to the calculation of Batalin–Vilkovisky algebra structures on the Hochschild cohomology of skew Calabi–Yau generalized Weyl algebras. We first establish a Van den Bergh duality at the level of complex. Then based on the results of Solotar et al., we apply Kowalzig and Krähmer's method to the Hochschild homology of generalized Weyl algebras, and translate the homological information into cohomological one by virtue of the Van den Bergh duality, obtaining the desired Batalin–Vilkovisky algebra structures. Finally, we apply our results to quantum weighted projective lines and Podleś quantum spheres, and the Batalin–Vilkovisky algebra structures for them are described completely.  相似文献   
9.
Kelvin−Helmholtz (KH) instability is a fundamental fluid instability that widely exists in nature and engineering. To better understand the dynamic process of the KH instability, the influence of the tangential velocity on the compressible KH instability is investigated by using the discrete Boltzmann method based on the nonequilibrium statistical physics. Both hydrodynamic and thermodynamic nonequilibrium (TNE) effects are probed and analyzed. It is found that, on the whole, the global density gradients, the TNE strength and area firstly increase and decrease afterwards. Both the global density gradient and heat flux intensity in the vertical direction are almost constant in the initial stage before a vortex forms. Moreover, with the increase of the tangential velocity, the KH instability evolves faster, hence the global density gradients, the TNE strength and area increase in the initial stage and achieve their peak earlier, and their maxima are higher for a larger tangential velocity. Physically, there are several competitive mechanisms in the evolution of the KH instability. (i) The physical gradients increase and the TNE effects are strengthened as the interface is elongated. The local physical gradients decrease and the local TNE intensity is weakened on account of the dissipation and/or diffusion. (ii) The global heat flux intensity is promoted when the physical gradients increase. As the contact area expands, the heat exchange is enhanced and the global heat flux intensity increases. (iii) The global TNE intensity reduces with the decreasing of physical gradients and increase with the increasing of TNE area. (iv) The nonequilibrium area increases as the fluid interface is elongated and is widened because of the dissipation and/or diffusion.  相似文献   
10.
植物精油是从芳香植物提取的天然复杂化合物,作为芳香植物的次生代谢产物具有挥发性和浓郁香味,其特有的多样化生物活性广泛应用于医药和化妆品行业。植物精油具有高渗透性,能以活跃的分子态渗透皮肤组织,经淋巴腺吸收后进入血液,其所含的重金属元素也极易随植物精油进入人体对健康构成潜在威胁。采用硝酸-双氧水对植物精油进行微波消解,在多模式样品导入系统(MSIS)的双重模式下,采用电感耦合等离子体发射光谱(ICP-OES)测定其中可形成蒸气重金属元素As,Sn,Sb,Hg和不可形成蒸气重金属元素Cr,Ni,Cd和Pb的含量。选择盐酸对样品进行酸化并预还原氧化态元素,通过在线加入L-半胱氨酸/酒石酸提高可形成蒸气元素的蒸气发生效率,利用硼氢化钠/氢氧化钠在MSIS中将As,Sn,Sb和Hg转变为蒸气状态;针对分析过程中存在的多个或单个光谱重叠和背景干扰,分别对空白溶液、分析元素和预期干扰元素的纯溶液进行测定,根据获得的光谱响应数据解卷积构建快速自动曲线拟合技术(FACT)模型,将分析谱线从干扰谱线中分离出来,从而实现光谱重叠干扰和背景干扰的实时校正;采用加标回收并与电感耦合等离子体质谱(ICP-MS)进行对比分析评价方法的准确性。各元素方法的检出限(MDL)为0.38~11.2 μg·kg-1,加标回收率为95.4%~104%,相对标准偏差(RSD)为1.9%~4.9%,对比分析的相对误差(RE)在-2.1%~2.7%之间,表明方法准确可靠,精密度高。对8种植物精油中的重金属元素进行了分析,所有植物精油样品中重金属元素As,Hg和Pb的含量远低于GB/T 26516—2011制定的限量标准,植物精油中重金属元素Cr,Ni,Sn,Cd和Sb的含量虽然没有制定限量标准,但均处于极低水平。MSIS兼具传统雾化和蒸气发生双重功能,在分析可形成蒸气元素和不可形成蒸气元素时无需切换不同进样系统,能满足大批量植物精油中微量重金属元素的高通量分析需要。  相似文献   
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