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961.
山西省引黄工程国际一标主要包括2只大型地下泵站及引水洞,通过对具备不同特征的泵房、洞室、立井等结构部位的围岩及内衬结构应力、应变、位移等监测与分析,及时总结围岩变形规律以指导施工,控制围岩动态,掌握围岩断面尺寸的变化,了解围岩的松弛程度及影响范围,确保施工期和运行期的安全,为其他类似大型地下复杂结构围岩及内衬结构的安全性及耐久性研究提供可靠的技术支持。 相似文献
962.
Structures of Ionic Di(arenesulfonyl)amides. 2. Silver(I) Di(arenesulfonyl)amides and a Silver(I) (Arenesulfonyl)(alkanesulfonyl)amide: From Ribbons to Lamellar Layers Exhibiting Short C–H…Hal–C or C–Br…Br–C Interlayer Contacts Low‐temperature X‐ray crystal structures are reported for AgN(SO2C6H4‐4‐X)2 · H2O, where X is Cl ( 4 ) or Br ( 5 ), and for AgN(SO2Ph)(SO2Me) ( 6 ). Compounds 4 and 5 and the previously described F analogue ( 3 ) are isotypic, though not strictly isostructural (monoclinic, space group P21/c, Z = 4, but egregiously large discrepancies of x and z coordinates for corresponding atoms). Throughout this triad, glide‐plane related formula units are linked along the z axis to form infinite ribbons [(ArSO2)2N–Ag(μ‐H2O)]∞, in which Ag extends its coordination number to five by accepting one Ag–O bond from each of the (ArSO2)2N⊖ ligands in the adjacent units. By means of O–H…O(S) hydrogen bonds, the ribbons are associated into lamellar layers parallel to the xz plane. Owing to the folded conformation of the anions, the layers display an inner polar region of Ag atoms, H2O molecules and N(SO2)2 groups, outer apolar regions of stacked pairs of aryl rings, and interlayer regions hosting the halogen atoms. Inspection of the latter areas provides sound evidence that the distinct juxtapositions of adjacent layers arise from specific interlamellar attractions and repulsions ( 3 : two C–H…F, all F…F beyond the van der Waals limit dW; 4 : one C–H…Cl, close packing of Cl atoms at Cl…Cl ≈ dW; 5 : one C–H…Br, one short Br…Br contact < dW, all other Br…Br > dW). Structure 6 (monoclinic, P21/n, Z = 4) consists of a lamellar coordination polymer, in which the cation accepts one Ag–N and three Ag–O bonds drawn from four different anions. On account of crystal symmetry, the extended ligand has its Ph and Me groups distributed on both sides of the sheet, the phenyl rings forming the apolar regions of the lamella, whereas the smaller methyl groups are integrated into the corrugated inorganic region by means of weak C–H…O hydrogen bonds. 相似文献
963.
Yuri V. Mironov Alexander V. Virovets Sofia B. Artemkina Vladimir E. Fedorov 《Angewandte Chemie (International ed. in English)》1998,37(18):2507-2509
Diffusion of aqueous solutions of K4[Re4Te4(CN)12] and CuCl2 in the opposite direction through silica gel gives rise to the new polymer-like compound 1 . This complex has a layered structure built from the interconnected cubane-like cluster cations [Cu4(μ3-OH)4]4+ and the cluster anions [Re4Te4(CN)12]4− (see picture). 相似文献
964.
诺氟沙星插层镁铝水滑石新型药物-无机复合材料的超分子结构、热稳定性和缓释性能 总被引:6,自引:0,他引:6
采用共沉淀和离子交换方法将抗生素类药物诺氟沙星(Nor)插入到Mg-Al-LDHs层间, 制备了一种新型的药物-无机复合材料. 借助XRD, FTIR, UV-Vis, TG-DTA和ICP等手段对样品进行了表征. 结果表明, Nor-阴离子可取代层间的NO3-, 组装得到晶体结构良好的Nor-LDHs. XRD表征得到Nor-LDHs的层间距为1.29~1.33 nm, 并与根据PM3半经验分子轨道法优化计算得到的Nor-三维尺寸进行比较, 推测客体Nor-是沿短轴方向以单层垂直交替的方式排布于层间, 与主体层板通过氢键与静电作用形成超分子结构; 该超分子结构诺氟沙星-水滑石复合材料与诺氟沙星相比, 其热稳定性、耐酸性及缓释性能均有大幅度提高, 缓释实验数据符合Bhaskar方程和一级动力学方程模型. 相似文献
965.
《Wave Motion》2020
The two-dimensional elastic wave propagation in an infinite layered structure with nonlinear interlayer interfaces is analyzed theoretically to investigate the second-harmonic generation due to interfacial nonlinearity. The structure consists of identical isotropic linear elastic layers that are bonded to each other by spring-type interfaces possessing identical linear normal and shear stiffnesses but different quadratic nonlinearity parameters. Explicit analytical expressions are derived for the second-harmonic amplitudes when a single monochromatic Bloch mode propagates in the structure in arbitrary directions by applying the transfer-matrix approach and the Bloch theorem to the governing equations linearized by a perturbation method. The second-harmonic generation by a single nonlinear interface and by multiple consecutive nonlinear interfaces are shown to be profoundly influenced by the band structure of the layered structure, the fundamental Bloch wave mode, and its propagation direction. In particular, the second harmonics generated at multiple consecutive interfaces are found to grow cumulatively with the propagation distance when the phase matching occurs between the Bloch modes at the fundamental and double frequencies. 相似文献
966.
《Wave Motion》2020
This article presents a study of the dispersion characteristics of wave propagation in layered piezoelectric structures under plane strain and open-loop conditions. The exact dispersion relation is first determined based on an electro-elastodynamic analysis. The dispersion equation is complicated and can be solved only by numerical methods. Since the piezoelectric layer is very thin and can be modeled as an electro-elastic film, a simplified model of the piezoelectric layer reduces this complex problem to a non-trivial solution of a series of quadratic equations of wave numbers. The model is simple, yet captures the main phenomena of wave propagation. This model determines the dispersion curves of PZT4-Aluminum layered structures and identifies the two lowest modes of waves: the generalized longitudinal mode and the generalized Rayleigh mode. The model is validated by comparing with exact solutions, indicating that the results are accurate when the thickness of the layer is smaller or comparable to the typical wavelength. The effect of the piezoelectricity is examined, showing a significant influence on the generalized longitudinal wave but a very limited effect on the generalized Rayleigh wave. Typical examples are provided to illustrate the wave modes and the effects of layer thickness in the simplified model and the effects of the material combinations. 相似文献
967.
《Particuology》2023
Spherical (Y0.98Er0.02)2(OH)5(NO3)·xH2O particles were synthesized by controlled double-jet precipitation, with a “core” of pure layered yttrium hydroxide nitrate, and a “shell” of co-precipitated yttrium-erbium layered hydroxide nitrates. With an increase in precipitation pH from 7 to 9.5, the size of layered “building units” decreases and the architecture of their assemblies changes from flower-like through network-like spherical to irregular agglomerates. From there, spherical particles gradually increase their diameter due to the continuous uniform growth of curved layered sheets on their surface. It was established that such growth behavior and network-like architecture of spherical particles was retained even when yttrium was replaced by erbium ions in the layered host lattice during the formation of an Er-enriched “shell”. Analysis of SEM, EDS, XPS, photoluminescence spectra and concentration quenching effects of heat-treated Y2O3:Er (2 at.%) particles indicate that the radial distribution of erbium in particles is most controllable in a narrow pH range of co-precipitation of layered precursors (pH 8). Вy widely varying the elemental composition of “building units” during co-precipitation, one can simultaneously finely control the composition of layered hydroxides in the radial direction of the spherical particles and grow multicomponent “multi-shell” powders with desired properties. 相似文献
968.
层状LiNi0.5Mn0.5O2正极材料的优化合成及电化学性能 总被引:1,自引:0,他引:1
采用沉淀法首先得到了Ni0.5Mn0.5(OH)2沉淀物,以其为原料与LiOH反应制备了LiNi0.5Mn0.5O2正极材料。采用XRD、SEM、充放电测试等研究了其结构与电化学性能,同时研究了Li过量时对材料电化学性能和结构的影响。SEM分析表明,Ni0.5Mn0.5(OH)2与LiNi0.5Mn0.5O2产物均为微小晶粒团聚成的颗粒。LiNi0.5Mn0.5O2材料在2.5~4.4V电位区间内,首次放电容量为130mAh/g,0.2C倍率下,50次循环后的容量保持率为87.8%。锂过量有助于形成良好的层状结构材料,并能显著提高材料的比容量和循环性能,Li1.1Ni0.5Mn0.5O2的首次放电容量为149mAh/g,0.2C倍率下,50次循环后的容量保持率为92.6%。 相似文献
969.
970.
Soft X-ray spectromicroscopy on solid-stabilized emulsions 总被引:2,自引:0,他引:2
Oil–water emulsions stabilized by solids have been imaged with sub-100 nm spatial resolution and analyzed spectroscopically
using a scanning transmission X-ray microscope. The emulsions are stabilized by particle heterocoagulate cages surrounding
the oil droplets. These cages form due to the interaction of negatively charged clay mineral particles (sodium montmorillonite,
Wyoming) and positively charged particles of calcium/aluminum layered double hydroxide (LDH). The emulsions were studied at
atmospheric pressure, without any pretreatment using carbon K and calcium L X-ray absorption edges. Oil- and calcium-rich LDH were separately mapped, and the clay mineral dispersions were also imaged.
Applying X-ray absorption-edge contrast, oil could be distinguished from water in the emulsion near the carbon K absorption edge (284 eV, 4.4 nm). Spectromicroscopy near the calcium L absorption edge (346 eV, 3.6 nm) allowed the structural details of heterocoagulate formation to be revealed.
Received: 11 December 1998 Accepted in revised form: 10 January 1999 相似文献