Upconversion Luminescence from Ho3+ and Yb3+ Codoped α-NaYF4 Single Crystals

The Ho³⁺/Yb³⁺ co-doped α-NaYF<sub>4sub> single crystal was grown successfully for the first time by a modified Bridgman method in which KF was used as assisting flux and a large temperature gradient (70-90 oC/cm) of solid-liquid interface was adopted. Upconversion emissions at green ～544 nm, red ～657 and ～751 nm were obtained under 980 nm laser diode excitation. The intensity at ～544 nm was much stronger than those of ～657 and ～751 nm. The mechanisms of the upconversion emissions were investigated by studying the relationship between the upconversion intensity and pump power. The optimized Yb³⁺ concentration was about 8.08 mol% when Ho³⁺ concentration was hold at about 1.0 mol%. The results showed that Ho³⁺/Yb³⁺+ doped α-NaYF<sub>4sub> single crystal was a possible candidate upconversion material for the green solid-state laser.     

High‐Strength Sub‐Micrometer Spherical Particles Fabricated by Pulsed Laser Melting in Liquid

Sub‐micrometer spherical particles that are obtained by pulsed laser melting in liquid (PLML) are usually observed to be single crystalline, and it is suggested that they are mechanically very strong. In this study, fracture tests of various sub‐micrometer spherical particles are performed by compressive force application. The results indicate that B<sub>4sub>C and TiO<sub>2sub> sub‐micrometer spherical particles exhibit brittle fracture behavior under tensile fracture mode at the center of the particles. The fracture strength of the sub‐micrometer spherical particles is larger than that of the bulk material reported in the literature by about one order of magnitude. TiO<sub>2sub> sub‐micrometer spherical particles obtained by PLML are stronger than the commercially available TiO<sub>xsub> sub‐micrometer spherical particles with a porous structure. In addition, due to the single crystallinity of particles, smaller particles have larger fracture strength, becoming up to 10–40% of ideal tensile fracture strength calculated based on density functional theory. Thus, these results demonstrate that sub‐micrometer spherical particles obtained using PLML exhibit fairly strong and unique mechanical properties, and therefore they are very promising for various mechanical applications at the sub‐micrometer size scale.     

多层次模糊综合评价在高校管理中的应用

本文利用多层次模糊综合评价 ,对高校管理工作进行评价 .由于高校管理工作中某些因素具有模糊性 ,所以用模糊数学的方法来研究、处理它 ,可以更客观、更实际地为高校管理者提供决策依据     

P-congruence-free Epigroups

Let P denote the equivalence relation on an epigroup in which any of its classes consists precisely of those elements owning the same pseudo-inverse. The purpose of the paper is to characterize epigroups on which any congruence either contains P or its join with P is the identity relation on epigroups. As a special subclass of epigroups, completely 0-simple semigroups having the same property are also described.     

First Principle Study on the Influence Mechanism of Impurity Gas O2 on the Adsorption Properties of Alloy ZrCo北大核心CSCD

The adsorption behavior of impurity gases on the surface of alloy ZrCo has an important influence on its hydrogen storage performance. The adsorption behavior of O2 on the ZrCo(110) surface was investigated with the first principles based on the pseudopotential plane wave method. The results of adsorption energy and charge analysis show that, the most stable geometry configuration was B3 (the Zr—Co bridge site) where the adsorption energy was –8.124 eV. The analysis of the density of states and the differential charge density show that, the adsorption behavior of O2 on the ZrCo(110) surface is a strong chemical adsorption, where the oxygen-oxygen bond breaks. The essence of bonding between atom O and the ZrCo(110) surface atom is that the electron orbit of atom O overlaps with the electron orbit of the surface atom, i.e. the 2s and 2p orbital electrons of atom O overlapped with the 4p and 4d orbital electrons of atom Zr and the 3d orbital electrons of atom Co on the surface. The research results make senses in revealing the poisoning mechanism of alloy ZrCo in impurity gases. © 2023 Editorial Office of Applied Mathematics and Mechanics. All rights reserved.     

燃煤烟气中共存杂质对膜分离CO2性能影响的实验研究

利用自行搭建的膜分离实验台,考察了共存气态组分以及颗粒物对于聚二甲基硅氧烷/聚砜(PDMS-PSF)复合膜分离CO<sub>2sub>性能的影响.结果表明,共存气态组分中O<sub>2sub>对于膜分离CO<sub>2sub>有抑制作用;由于SO<sub>2sub>浓度显著低于CO<sub>2sub>,在短时间内对膜分离CO<sub>2sub>没影响;水汽可以促进CO<sub>2sub>的分离;燃煤飞灰细颗粒在分离膜表面沉积会导致膜性能的恶化.在此基础上,采用模拟湿法烟气脱硫系统装置,进行了燃煤湿法脱硫净烟气环境下的膜分离CO<sub>2sub>实验;在测试的50 h以内,水汽、SO<sub>2sub>和O<sub>2sub>的共同作用导致膜分离性能在前期有一定的提高,随着运行时间的延长,细颗粒物对膜的影响程度加大,导致PDMS-PSF复合膜的分离性能逐渐恶化,最终导致膜的CO<sub>2sub>/N<sub>2sub>分离因子和CO<sub>2sub>渗透速率分别下降了17.91%和28.21%.     

Weighted Compact Commutator of Bilinear Fourier Multiplier Operator

Let T_σ be the bilinear Fourier multiplier operator with associated multiplier σ satisfying the Sobolev regularity that sup κ∈Z∥σ_κ∥W~s(R~(2n)) ∞ for some s ∈ (n, 2n]. In this paper, it is proved that the commutator generated by T_σ and CMO(R~n) functions is a compact operator from L~(p1)(R~n, w_1) × L~(p2)(R~n, w_2) to L~p(R~n, ν_w) for appropriate indices p_1, p_2, p ∈ (1, ∞) with1 p=1/ p_1 +1/ p_2 and weights w_1, w_2 such that w = (w_1, w_2) ∈ A_(p/t)(R~(2n)).     

Synthesis of Hybrid Hollow Sub‐microspheres Assisted by Pre‐added Colloidal SiO2

A novel method was developed to synthesize organic–inorganic hybrid hollow sub‐microspheres (HHSs) through the addition of colloidal SiO<sub>2sub>. The hydrolysis rate of 3‐(methacryloyloxy)propyltrimethoxysilane (MPS) was accelerated by SiO<sub>2sub> particles; meanwhile, the condensation rate of the hydrolytic species was decelerated. Thus, the hydrolytic monomers and oligomers of MPS were preserved as emulsifiers. These emulsifiers can then emulsify the isopentyl acetate (PEA) to form a steady O/W emulsion. The HHSs were produced by subsequent free radical polymerization and removal of the oil core. The hydrolytic MPS acted as emulsifiers and polymerizable monomers at the emulsification and polymerization stage, respectively. Thus, extra emulsifiers, co‐emulsifiers, and organic monomers were omitted, which simplified the synthesis process. The good dispersion of HHSs in water and oil, as well as the EDX results, indicated the organic–inorganic hybrid structure of HHSs.     

Non‐Conjugated Polymer Dots with Crosslink‐Enhanced Emission in the Absence of Fluorophore Units

A new type of fluorescent material is presented, which is called non‐conjugated polymer dots (NCPDs). The NCPDs only possess sub‐fluorophores (which are groups such as C?O, C?N, N?O) instead of typical conjugated fluorophore groups, and thus these materials should not have strong photoluminescence (PL) in the usual sense. Nevertheless, the PL of these sub‐fluorophores can be enhanced by chemical crosslinking or physical immobilization of polymer chains, which is named the crosslink‐enhanced emission (CEE) effect. The significant advances achieved by us and other groups on both experimental and theoretical aspects are discussed, and the covalent‐bond CEE, rigidity‐aggregated CEE, or supramolecular CEE in NCPDs is elaborated. Moreover, synthetic strategies, unique optical properties, and the promise of NCPDs in bio‐related fields, such as bioimaging and drug delivery, are systematically discussed.