Synthesis,Characterization and Real Molecule DFT Calculations for Neutral Organogallium(I) Aryl Dimers and Monomers: Weakness of Gallium?Gallium Bonds in Digallenes and Digallynes

Move closer : The gallium? gallium bond strength in terphenyl gallium(I) dimers [ArGaGaAr] (see figure) is similar to those in other molecules with closed shell interactions, implying that the Ga? Ga bond in doubly reduced Na₂[ArGaGaAr] is much closer to a single than a triple one.

     

Crystal structure of dinitro(2,9-dimethyl-1,10-phenanthroline)-palladium(II)

Dinitro(2,9-dimethyl-1,10-phenanthroline)-palladium(II) crystallizes in the orthorhombic system, space groupP2₁ nb, with cell dimensionsa = 6·790,b = 19·807,c = 10·625 Å andZ = 4. The structure was determined from three-dimensional Fourier syntheses and refined by full-matrix least squares, the finalR for 1155 measured reflexions being 0·07.     

Nanocrystals of CdSe Formed by the Pressure Cycle Method

CdSe nanocrystals were prepared by the pressure cycle method using the Paris-Edinburgh cell up to 7 GPa. The recovered samples are nanocrystals in the cubic phase (zinc-blende structure) and were characterized using transmission electron microscopy (TEM), electron diffraction and Raman scattering. Transmission electron micrographs shows that these nanocrystals are nearly spherical with diameters ranging from 20 to 50 nm. The Raman scattering measurement confirm the existence of CdSe nanocrystals in the cubic phase (ZB).     

II–VI and II1−x Mn x VI semiconductor nanocrystals formed by the pressure cycle method

II–VI and II_1?x Mn _x VI nanocrystals were prepared by the pressure cycle method using the Paris–Edinburgh cell. The recovered samples are nanocrystals in the cubic phase zinc-blend (ZB) structure and were characterized using transmission electron microscopy, electron diffraction, X-ray diffraction and Raman scattering. Transmission electron micrographs show that these nanocrystals are nearly spherical with diameters ranging from 20 to 50 nm depending on the sample under investigation. The Raman scattering measurements confirm the existence of II–VI nanocrystals in the cubic phase (ZB). The magnetic properties of Cd_0.5Mn_0.5Te nanoparticles were found to vary with the particle size and were different from those observed for the Cd_0.5Mn_0.5Te bulk initial samples. The χ vs. T data show temperature hysteresis due to spin-glass form, which occurs at T _g=21 K, for both the bulk as well as for the recovered nanoparticle samples. The zero-field cooled and field-cooled χ vs. T curves for the nanoparticles showed a monotonous increase below T _g. Below ～21 K, the M vs. B curve for the recovered nanoparticle samples exhibited magnetic hysteresis, and this is attributed to a weak ferromagnetic contribution. This contribution is also observed in the χ(T) curves and is due to a large surface/volume ratio of the nanoparticles, which enhances the magnetic interaction.     

Numerical solution of thermal convection problems using the multidomain boundary element method

The multidomain dual reciprocity method (MD‐DRM) has been effectively applied to the solution of two‐dimensional thermal convection problems where the momentum and energy equations govern the motion of a viscous fluid. In the proposed boundary integral method the domain integrals are transformed into equivalent boundary integrals by the dual reciprocity approach applied in a subdomain basis. On each subregion or domain element the integral representation formulas for the velocity and temperature are applied and discretised using linear continuous boundary elements, and the equations from adjacent subregions are matched by additional continuity conditions. Some examples showing the accuracy, the efficiency and flexibility of the proposed method are presented. © 2002 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 18: 469–489, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/num.10016     

An Evolution of the WebCom Metacomputer

Functional enhancements to the WebCom metacomputer are described which give rise to dynamic reconfigurability and extendability of the computer platform. Component modules and interactions are described, with particular attention to the communications module that enables dynamic reconfigurability. The machines of the metacomputer can be configured to act in client/server or peer to peer mode on a number of interconnection topologies such as NOWs, Clusters or Grids. This paper addresses the dynamically extendable machine structure of WebCom facilitated by this new communications structure. This revised version was published online in July 2006 with corrections to the Cover Date.     

辐冷器视场角对其制冷性能的影响

本文对抛物面G型辐冷器,在水平视场角变化的情况下不同工况下的制冷性能进行了计算。通过数值计算发现,视场角的减小导致辐冷器制冷性能的明显下降,虽然视场角影响辐冷器的因素很复杂,但最后的结果是两者呈现出良好的线性关系。其次,通过对辐冷器降温特性的研究,提出了通过改变辐冷器外壳控温方式来减小视场角变化对辐冷器制冷性能的负面影响,计算结果表明这种解决措施是非常有效的。     

环形浅液池内中等Pr数流体的热毛细对流

为了了解微重力下水平温度梯度作用时环形浅液池内的热毛细对流特性,利用有限差分法进行了非稳态二维数值模拟,环形液池外壁被加热,内壁被冷却,流体为 0.65 cSt的硅油,其Pr 数为 6.7。结果表明,当温度梯度较小时,流动为稳态流动,随着温度梯度的增加,流动将会失去其稳定性,转化成各种振荡流动,模拟结果与实验结果基本吻合。     

池厚对SiO2胶体光子带隙的影响

在薄池中，胶体晶体生长的速度比在厚池中快而且质量好。不同分散度的小球自排的实验结果表明：较差分散度的SiO2小球在超薄池中也能形成质量较好的单昌。光子带隙波长在薄池中有明显的红移，池厚为0.07mm的胶体单晶的带隙波长比池厚为1mm的胶体单晶的带隙波长红移了24nm。