Dynamics of a small vibro-impact pile driver

A mathematical model is developed to study periodic-impact motions and bifurcations in dynamics of a small vibro-impact pile driver. Dynamics of the small vibro-impact pile driver can be analyzed by means of a three-dimensional map, which describes free flight and sticking solutions of the vibro-impact system, between impacts, supplemented by transition conditions at the instants of impacts. Piecewise property and singularity are found to exist in the Poincaré map. The piecewise property is caused by the transitions of free flight and sticking motions of the driver and the pile immediately after the impact, and the singularity of map is generated via the grazing contact of the driver and the pile immediately before the impact. These properties of the map have been shown to exhibit particular types of sliding and grazing bifurcations of periodic-impact motions under parameter variation. The influence of piecewise property, grazing singularities and parameter variation on the performance of the vibro-impact pile driver is analyzed. The global bifurcation diagrams for the impact velocity of the driver versus the forcing frequency are plotted to predict much of the qualitative behavior of the actual physical system, which enable the practicing engineer to select excitation frequency ranges in which stable period one single-impact response can be expected to occur, and to predict the larger impact velocity and shorter impact period of such response.     

Study on Chromium‐Containing Aluminophosphate CrAPO‐5 via Density Functional Theory

Various structures of CrAPO‐5 clusters are studied via density functional B3LYP exchange‐correlation method. The optimized structures are compared with data from X‐ray absorption. Their total energies and atomic net charges are also analyzed. Results indicate that the substitution of the aluminum site of an AFI framework by chromium is in general not feasible. The chromium ion is more likely docked in between two neighboring 12‐membered rings of the framework of AFI. To further verify our claim, the excitation energies of the representative chromium structures of CrAPO‐5 clusters are calculated via the TDDFT method. The results for excitation energies further support that Cr³⁺ is not incorporated into the framework.     

Synthesis, structure and physicochemical characterization of a noncentrosymmetric, quaternary thiostannate: EuCu2SnS4

EuCu₂SnS₄ was prepared by a stoichiometric combination of the elements heated to 700 °C for 125 h. The structure was determined by single crystal X-ray diffraction methods. The compound crystallizes in the noncentrosymmetric, orthorhombic space group Ama2 with a=10.4793(1) Å, b=10.3610(2) Å, c=6.4015(1) Å, Z=4, R1=0.99% and wR2=2.37%. The structure type is that of SrCu₂GeSe₄. The structure can be described as a three-dimensional network built from near perfect SnS₄ and distorted CuS₄ tetrahedra together with EuS₈ square antiprisms. The dark red compound is a semiconductor with an optical bandgap of 1.85 eV.     

Determination of ferruginol in rat plasma via high‐performance liquid chromatography and its application in pharmacokinetics study

Ferruginol, a diterpene phenol, has recently received attention for its extensive pharmacological properties, including anti‐tumor, antibacterial, cardio‐protective and gastroprotective effects. In the present study, a high‐performance liquid chromatographic (HPLC) method was developed for determination of ferruginol in rat plasma and applied for the pharmacokinetics study. The HPLC assay was performed with a VP ODS‐C₁₈ column. The mobile phaseconsisted of methanol and 1% acetic acid solution (90:10, v/v). The flow rate was 1.0 mL/min, and the wavelength was set at 270 nm. This method was linear over the studied range of 0.1–10.0 µg/mL for ferruginol. The correlation coefficient was 0.9998. The intra‐day and inter‐day precisions were better than 4 and 5%, respectively. The extraction recovery and accuracy were greater than 97 and 96%, respectively. The detection limit was 30 ng/mL. The mean maximum concentration of ferruginol in rat plasma was 3.14 µg/mL at 40 min after oral administration at a dose of 20 mg/kg. Ferruginol was absorbed quickly p.o. with t_1/2ka = 14.86 min and had a high rate of elimination with t_1/2 = 41.73 min. The pharmacokinetic process of ferruginol in rat was well described with a one‐compartment model. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and properties of porous polyvinylamine microspheres from acrylonitrile

A novel route to synthesize crosslinked porous polyvinylamine (PVAm) microspheres from acrylonitrile (AN) was developed. In the first step, crosslinked porous polyacrylonitrile (PAN) spheres were prepared by copolymerization of AN and divinylbenzene (DVB). Then they were hydrolyzed to form polyacrylamide (PAM) spheres. And lastly, the porous PVAm spheres were successfully obtained via Hofmann degradation of PAM spheres. Scanning electron microscope (SEM) indicated that these PVAm microspheres have rough surfaces and porous interior structure. The pore size, the amino content, and the content of equilibrium water were also investigated. The pore size of these PVAm microspheres increased with the hydrolytic process. The contents of equilibrium water was changed from 49.6 to 96.5% depending on the different crosslinking degrees, and the amino contents were varied between 9.60 and 15.30 mmol/g depending on the different molar ratio of n(NaClO)/n(NaOH). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1674–1682, 2008     

纳米SiC蓝光发射的研究

在４．６８ｅＶ的激光激发下，室温ＣＶＤ合成的纳米ＳｉＣ粉体，可发射４７５ｎｍ的蓝光，经６００～１１００℃在Ｎ２气氛下进行快速退火（ＲＴＡ）处理，其荧光强度随退火温度升高而增强，当Ｔ≥９００℃时，荧光强度下降，但发光峰位与退火温度无关．通过ＸＲＤ、ＩＲ、ＴＥＭ、ＸＰＳ等研究，认为纳米ＳｉＣ中与氧有关的缺陷可能是引起４７５ｎｍ蓝光发射的主要原因     

机电产品材料PVC中二噁英的高分辨质谱法定量测定

二噁英是指包括75种多氯代二苯并-对-二噁英(polychlorodibenzo-p-dioxin,PCDD)和135种多氯代二苯并呋喃(polychlom-dibenzofuran,PCDF)的一组多氯代的平面芳烃化合物.二噁英是目前已知最毒的化合物,研究发现17种具有2,3,7,8位氯取代的二嗯英同族体毒性远高于其它同族体,其中,2,3,7,8.四氯二苯并-对-二噁英(2,3,7,8.TCDD)对于雄性小豚鼠的LD50仅为0.6μg/kg[1].二噁英还有极强的致癌和内分泌干扰作用,人体长期低剂量的接触二噁英会导致癌症、雌性化和胎儿畸形等.