某工程地下室土方开挖及基底施工

结合基坑工程实际，详细介绍了基坑开挖及基底施工的过程，进一步说明场地的地质勘察是基坑工程施工的基础，基坑开挖必须在施工过程不断完善改进中进行，以保证工程质量。     

Synthesis,spectroscopic and structural studies on YOF,LaOF and GdOF nanocrystals doped with Eu3+, synthesized via stearic acid method

Nanocrystalline Eu³⁺ doped REOF oxofluorides (where RE = Y, La, Gd) were synthesized using stearic acid as the reaction medium. Optimal conditions for the synthesis of pure and single-phased oxyfluorides were found. The obtained products were analysed using thermogravimetric analysis, X-ray analysis, transmission electron microscopy and the Rietveld method. The influence of calcination temperature on the physicochemical properties was studied. Spectroscopic properties of the tetragonal and rhombohedral oxyfluoride nanocrystals were investigated using excitation and emission spectra and luminescence lifetime measurements. Effectiveness of the Eu³⁺ dopant red emission intensity and energy transfer processes were examined in relation to the structure and the presence of the RE ion in oxyfluorides studied. The highest luminescence efficiency was observed for the GdOF:Eu³⁺ nanomaterial. Judd–Ofelt intensity parameters were calculated and analysed.     

Polymerization of styrene with a simple rare earth metal initiator

The catalytic activity in the polymerization of styrene has been examined using commercially available simple rare earth metal compounds such as Sm(OiPr)₃, Sm(acac)₃, Sm(OCOMe)₃, SmI₂(THF)₂ or SmCl₃ coupled with Et₃Al or methylaluminoxane (MAO). Among these compounds, the Sm(OiPr)₃/AlEt₃ system shows the highest catalytic activity, especially in the presence of a minor amount of toluene at 60 °C. The random copolymerization of styrene with methyl methacrylate suggests that the present polymerization proceeds with a radical polymerization mechanism. (C₅Me₅)SmCl₃Na(THF) and (C₅Me₅)SmCl₃Li(THF) systems exhibit relatively low catalytic activity, even in the presence of AlEt₃. © 2001 Society of Chemical Industry     

Structural characteriztion of Nd-doped in silica host matrix prepared by net chemical process

Silica host matrix containing neodymium which is potentially important for the formation of nanocrystalline metal oxides was prepared by solgel method, using tetra-ethoxysilane and Nd(NO3)3 as precursor materials. The prepared samples were changed from amorphous to nanocrystallites phase at sintered temperature 550℃ (4 h), 750℃ (8 h) and 950 ℃ (12 h). The thermally treated sample microstructures were investigated using X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). While a further increase of the temperature at 750 ℃ and annealing time (8 h) resulted in the formation of cubic and hexagonal Nd2O3 nanocrystallites. At constant sintering temperature 950℃ for 12 h, the samples showed sharper and intense peaks. The sizes of Nd2O3 nanocrystallites were characterized by XRD with average size～46 nm.     

Mechanochemical synthesis of cerium orthophosphate

A facile, simple and rapid preparation method of cerium orthophosphate was presented. The synthesis of low-crystalline CePO₄ occurred upon mixing of cerium (III) nitrate and sodium phosphate, and was an exchange-type reaction. The phase composition of the obtained powder was checked by the XRD and FTIR methods, indicating the presence of cerium phosphate. Further investigations on thermal behavior of the synthesized cerium salt had shown that the obtained orthophosphate crystallized at first in rhabdophane-type structure. It converted to monazite (monoclinic symmetry) during heating at the temperatures of above 600 ºC. Oxidation of Ce³⁺ to Ce⁴⁺ was avoided during the syntheses, as confirmed by the XPS experiments.     

提高灌浆压力对土坝帷幕灌浆效果影响的实践

针对灌浆压力选择的重要性,通过分析相关的现场资料,对土坝帷幕灌浆压力进行了较大幅度的提高,在保证大坝安全和稳定的前提下,取得了较好的灌浆效果,以期对类似病险水库的治理具有借鉴作用.     

Electroanalytical tools to investigate the divalent state of Eu（III） and Nd（III） ions in non-aqueous medium

The divalent state of Ln(Ⅲ) ions has attracted much interest because of their ability to serve isomorphously in many biological sys-tem of divalent Ca(II) ion. Therefore, present paper deals with the study of divalent state of Eu(Ⅲ) and Nd(Ⅲ) ions in non-aqueous medium. In present study, cyclic voltammetry and chronopotentiometry were utilized to establish the divalent state of Eu(Ⅲ) and Nd(Ⅲ) ions. The cy-clic voltammetric technique showed two-step reduction process at cathode for both Ln(Ⅲ) ions under specified experimental conditions and chronopotentiometric method also showed two different transition times (). Looking to the shape of cyclic voltammogram we calculated het-erogeneous forward rate constant (K0fh, cm/s) and diffusion coefficient (D, cm2/s) for both ions, which suggested that sweep rate had great ef-fect on the shape of cyclic voltammogram of Eu(Ⅲ) and Nd(Ⅲ) ions. The result of chronopotentiometry also suggested that stable divalent states of Eu(Ⅲ) and Nd(III) ions existed with chronopotentiogram with two distinct transition times. The diffusion coefficients (D, cm2/s) were calculated from Sand equation. The diffusion coefficients of both techniques were compared and the results suggested that the system at electrode surface was changing from being reversible to irreversible.     

Graphic Manifestation of the Ability of Selected Alkaline Earth Chlorides to Impart Flame-Retardancy to Cotton Fabric

Optimum percent quanties of selected alkaline earth chlorides used for imparting flame-retardancy to cotton fabric have been chosen from one of the author's ACS-presented articles. Based on the afore mentioned data and gathering information concerning their physicochemical specifications from scientific literature the related graphical representations were obtained. The results illustrate a reasonable dependence in lowering the ability of the alkaline earth chlorides on their higher stabilities that is, the optimum percent of the applied chlorides decreased according to the metals position in the periodic table. Therefore a better understanding has been achieved and deduced.     

电感耦合等离子体质谱法测定砂金中稀土元素

建立了砂金中15种稀土元素的电感耦合等离子体质谱测定方法。考察了基体Au的谱线干扰及基体效应,采用In内标补偿基体对待测信号的抑制作用。仪器检测限为0.000 9～0.002 9μg/L,加入标准物质的回收率为98%～106.7%,分析结果的相对标准偏差（RSD）为0.33%～1.79%。该方法简单、快速、灵敏、准确。