Flux-pinning-induced stress behaviors in a long superconducting slab with central cuboid hole

Acta Mechanica Sinica - This paper investigates the flux-pinning-induced stress behaviors in a long superconducting slab with a central cuboid hole. The distribution of flux density is analytically...     

静电纺丝结合溶胶-凝胶法制备MgNb2O6陶瓷纤维

以五氧化二铌(Nb2O5)和氧化镁(MgO)为原料,柠檬酸作配位剂,采用静电纺丝结合溶胶-凝胶法制备了铌酸镁(MgNb2O6)陶瓷纤维。在本合成体系中,高质量Nb5+溶液的获得是形成MgNb2O6前驱体溶胶的关键步骤。通过TGA,FTIR,XRD,TEM以及SEM技术对纤维的形貌,微观结构以及组成进行了表征。结果表明,900℃烧结以后得到的MgNb2O6纤维长度约为10 cm,具有中空结构,壁厚约为800 nm。     

运用“部分受激拉曼绝热通道”制备串行Λ系统相干叠加态

讨论了在串行Λ系统中制备初态和末态的连续叠加态的方法,这种方法是部分受激拉曼绝热通道的扩充.但是它又不同于部分受激拉曼绝热通道,每个斯托克斯脉冲先行相应的泵浦脉冲,但是所有的中间脉冲提前并且同时消失,而第一束斯托克斯脉冲和最后一束泵浦脉冲稍后同时消失.应用数值方法讨论了脉冲驰豫时间和失谐量对该方法的影响.数值结果表明要制备任意的叠加态,不仅要满足双光子共振,而且要满足单光子共振.     

吡啶季铵盐在有机合成中的应用

由于吡啶环的芳香性、碱性、吡啶氮原子的吸电子效应使得吡啶季铵盐具有丰富的化学反应性质, 可以进行亲核加成、Michael加成、1,3-偶极加成、亲核取代和σ-迁移重排等反应, 在有机合成化学中有广泛的应用.     

Strong decays of the low-lying bottom strange baryons

Andreev reflection(AR) refers to the electron-hole conversion at the normal metal-superconductor interface. In a threedimensional metal with a spherical Fermi surface, retro(specular) AR can occur with the sign reversal of all three(a single)components of particle velocity. Here, we predict a novel type of AR with the inversion of two velocity components, dubbed"anomalous Andreev reflection"(AAR), which can be realized in a class of materials with a torus-shaped Fermi surface, such as doped nodal line semimetals. For its toroidal circle perpendicular to the interface, the Fermi torus doubles the AR channels and generates multiple AR processes. In particular, the AAR and retro AR are found to dominate electron transport in the light and heavy doping regimes, respectively. We show that the AAR visibly manifests itself as a ridge structure in the spatially resolved nonlocal conductance, in contrast to the peak structure for the retro AR. Our work opens a new avenue for the AR spectroscopy and offers a clear transport signature of the torus-shaped Fermi surface.     

One-pot multicomponent synthesis of substituted 5,7-dihydro-1,6-naphthyridines and 5,6,7,8-tetrahydroquinolines

An one-pot approach was developed for the synthesis of substituted 5,7-dihydro-1,6-naphthyridines and 5,6,7,8-tetrahydroquinolines with moderate to good yields. This pathway is a modified two-step synthesis of Kröhnke pyridine and involves a four-component tandem reaction of N-phenacylpyridinium bromide, aromatic aldehydes, substituted or nitrogen-containing cyclic ketones and a nitrogen source. This multi-component reaction is performed using microwave irradiation heating of the reaction substrates under an environment of NH₄OAc/HOAc.

Open image in new window

     

带工具的高能聚焦超声变幅杆的有限元分析

在分析高能聚焦超声原理的基础上，本文研究了高能聚焦超声技术，并且对安装工具后的变幅杆进行了有限元分析。试验表明，高能聚焦超声技术在清洗、焊接领域具有高效、可连续工作的优势。     

流动态甲醇气相光催化降解的机制研究

在253.7 nm紫外光作用下, 研究纳米TiO₂光催化氧化流动态甲醇的机制, 结果表明, 甲醇的光催化降解不受水汽的影响, 只受氧气含量的影响. 在不含氧气的情况下, 即使有足量的水汽, 甲醇都不会有明显的降解. TiO₂受光诱导生成空穴-电子对后, 空穴直接氧化甲醇, 生成的甲醇正离子在氧气作用下进一步被氧化, 形成各种氧化产物. 甲醇氧化过程是多通道反应, 宏观表现为准一级反应. 空气和氧气条件下甲醇的总降解速率常数分别为9.78×10^－3和1.79×10^－2 s^－1.     

The ■ tetraquark states and the structure of X(2239) observed by the BESⅢ collaboration

We investigate the mass spectrum of the■tetraquark states in the relativized quark model.By solving the Schrodinger-like equation with the relativized potential,the masses of S-and P-wave■tetraquarks are obtained.The screening effects are also taken into account.It is found that the resonant structureX(2239)observed in thee+e-→K+K-process by the BESIII collaboration can be assigned as a P-wave 1--■tetraquark state.Furthermore,the radiative transition and the strong decay behavior of this structure are also estimated,which can provide helpful information for future experimental searches.