深过冷Ag-Cu-Ge三元共晶合金的相组成与凝固特征

在Ag_38.5Cu_33.4Ge_28.1三元共晶合金的深过冷实验中，获得的最大过冷度为175 K(0.22T_E). XRD分析表明，不同过冷条件下其共晶组织均由(Ag),(Ge)和η(Cu₃Ge)三相组成. 在小过冷条件下，三个共晶相协同生长，凝固组织粗大.随着过冷度的增大，共晶组织明显细化，(Ge)相与其他两相分离，以初生相方式生长，而(Ag)相与η相始终呈二相层片共晶方式共生生长. 当过冷度超过80 K时，初生相(Ge)由小过冷时的块状转变为具有小面相特征的枝晶方式生长. 部分小面相(Ge)枝晶出现规则的花状，花瓣数介于5—8之间，并且过冷度越大(Ge)相越容易分瓣. 花状(Ge)枝晶的晶体表面为{111}晶面簇，择优生长方向为〈100〉晶向族. 关键词： 三元共晶 晶体形核 深过冷 快速凝固     

Indecomposable representations and boson realizations of the nonlinear deformed angular momentum algebra of Witten’s first type

In this paper indecomposable representations and boson realizations of the nonlinear angular momentum algebra $\mathcal{R}_{q,p}^{c_1,c_2,c_3}$ of Witten’s first type are investigated in a purely algebraic manner. Explicit form of the master representation of $\mathcal{R}_{q,p}^{c_1,c_2,c_3}$ on the space of its universal enveloping algebra is given. Then, from this master representation, other indecomposable representations are obtained in explicit form. Various kinds of single-boson, single inverse boson, and double-boson realizations of $\mathcal{R}_{q,p}^{c_1,c_2,c_3}$ are respectively obtained by generalizing the Holstein–Primakoff realization, the Dyson realization, and the Jordan–Schwinger realization of the Lie algebras SU(2) and SU(1,1). For each kind, the unitary realization, the nonunitary realization, and their connection by the corresponding similarity transformation are respectively discussed. Using a kind of double-boson realizations, the irreducible representation of $\mathcal{R}_{q,p}^{c_1,c_2,c_3}$ in the angular momentum basis is given.     

Effect of Stress-Dependent Thermal Conductivity on Thermo-Mechanical Coupling Behavior in GaN-Based Nanofilm Under Pulse Heat Source

The thermal properties of a nanostructured semiconductor are affected by multi-physical fields,such as stress and electromagnetic fields,causing changes in temperature and strain distributions.In this work,the influence of stress-dependent thermal conductivity on the heat transfer behavior of a GaN-based nanofilm is investigated.The finite element method is adopted to simulate the temperature distribution in a prestressed nanofilm under heat pulses.Numerical results demonstrate the effect of stress field on the thermal conductivity of GaN-based nanofilm,namely,the prestress and the thermal stress lead to a change in the heat transfer behavior in the nanofilm.Under the same heat source,the peak temperature of the film with stress-dependent thermal conductivity is significantly lower than that of the film with a constant thermal conductivity and the maximum temperature difference can reach 8.2 K.These results could be useful for designing GaN-based semiconductor devices with higher reliability under multi-physical fields.     

Mode theory of three-layer cylindrical waveguides and its application to aurum(Au)/polystyrene(PS)-coated terahertz hollow waveguides

In this paper, we present a generic mode theory for the three-layer cylindrical waveguides consisting of three arbitrary material mediums. Based on derived eigenvalue equations of the TE, TM, and hybrid modes, the mode conditions of metal/dielectric-coated terahertz hollow waveguides are extracted. In addition, we quantitatively describe both the effective refractive indexes and the loss characteristics of the aurum/polystyrene-coated terahertz hollow waveguides operating at the TE₀₁, TM₀₁, and HE₁₁ modes. It is indicated that the loss coefficient of the TE₀₁ mode can be much lower than that of the TM₀₁, and HE₁₁ modes, and, especially, can tend to that of the terahertz wave in air. So the TE₀₁ mode is very significant for the hollow waveguides in term of low loss propagating of the terahertz wave. We expect these results to enable a variety of new long-distance THz applications in sensing, detecting and communicating.     

Seeking magneto-structural correlations in easily tailored pentagonal bipyramid Dy(III) single-ion magnets

Science China Chemistry - Controlling molecular magnetic anisotropy via structural engineering is delicate and fascinating, especially for single-molecule magnets (SMMs). Herein a family of...     

Inclusion Complexes of Coenzyme Q10 with Polyamine‐Modified β‐Cyclodextrins: Characterization,Solubilization, and Inclusion Mode

The inclusion‐complexation behavior of coenzyme Q10 (CoQ10) with the three polyamine‐modified β‐cyclodextrins (CDs) 1 – 3 was investigated in both solution and the solid state by means of NMR, XRD, and FT‐IR spectroscopy. The results showed that the apparent solubility of CoQ10 increased linearly upon addition of hosts 1 – 3 , giving A_L‐type phase‐solubility curves. These hosts 1 – 3 were able to solubilize CoQ10 to high levels, up to 1.35, 1.52, and 1.44 mg/ml (calculated as CoQ10), respectively. The host 2 with a moderate‐length chain is the most suitable for inclusion complexation of CoQ10. Accroding to the ROESY experiments, the MeO groups of CoQ10 and the tether of 2 can be co‐included into the cavity of β‐CD through the induced‐fit interaction between host and guest. The binding ability of modified β‐CDs 1 – 3 upon complexation with CoQ10 are discussed from the viewpoints of the size/shape‐matching relationship and the induced‐fit concept between host CDs and guest CoQ10 molecule.     

衍生化高效液相色谱法拆分1,1′-联萘-2,2′-二酚光学异构体

以基碳酸酰氯作衍生化试剂 ,采用高效液相色谱拆分 1,1′ 联萘 2 ,2′ 二酚光学异构体。当采用LichrosorbSi 6 0 (4mm× 30 0mm ,5 μm)柱 ,紫外 2 75nm检测 ,正己烷 乙醇 (98.5 1.5 ,V V)为流动相 ,1,1′ 联萘 2 ,2′ 二酚单基碳酸酯的分离因子和分离度分别为 1.36 8、3.0 5 1;用正己烷 乙醚 (98.5 1.5 ,V V)为流动相 ,1,1′ 联萘 2 ,2′ 二酚双基碳酸酯的分离因子和分离度分别为 1.0 5 5、1.347。这一方法可简便、快速地测定联萘二酚单基碳酸酯拆分样品的光学纯度     

Preparation of walnut shell-based activated carbon and its properties for simultaneous removal of H2S,COS and CS2 from yellow phosphorus tail gas at low temperature

Research on Chemical Intermediates - Walnut shell-based activated carbon (WSBAC) was prepared used to simultaneously remove H2S, COS and CS2 from yellow phosphorus tail gas and closed carbide...     

电位溶出法测定金属在汞中的扩散系数

本文提出电位溶出法作为一种测定金属在汞中的扩散系数的新方法。建立了该法的理论基础, 并用该法测定了10种金属在单一汞齐中的扩散系数和锌、镉在多元复合汞齐中的扩散系数。