国产SEBS流变性能评价

通过对国产SEBS(氢化苯乙烯-丁二烯-苯乙烯嵌段共聚物)流变性能进行测试．分析不同结构、不同嵌段的S／B质量比值、不同相对分子质量、不同加工温度对SEBS产品流变性能的影响．促进用户对国产SEBS性能的了解。     

Agronomical evaluation of phosphate fertilizer as a nutrient source of phosphorus for crops: Isotopic procedure

The agronomic effectiveness of P fertilizers, as sources of phosphorus for crops, was evaluated using the quantities, P_f, of phosphorus taken up byLolium perenne grown on 14 soils during greenhouse experiments in pot cultures. The P_f quantities were determined using³²P-labelled fertilizers. Data were analysed using a new concept: the Isotopic Relative Agronomic Effectiveness (IRAE). The IRAE value was defined as the ratio of the P_f quantity, taken up by a crop, of a tested fertilizer over the P_f quantity, taken up by a crop, of a fertilizer used as standard. In our experiments diammonium phosphate (DAP) was used as standard P fertilizer and two rock phosphates, the North Carolina rock phosphate (NCPR) and a calcium-iron-aluminium phosphate (Phospal), were tested. As a linear relationship between P_f(NCPR) quantities and P_f(DAP) quantities was obtained, with r² = 0.95, when the application rates increased from 15 mgP (kg soil)^–1 to 200 mgP (kg soil)^–1, it is conciuded that IRAE values for a given fertilizer, other than the standard fertilizer, could be determined with a single rate of application. As regards soil pH in the range 4.7 to 8.2 the IRAE_NCPR is related to soil pH by a curvilinear relationship: log IRAE_NCPR = –(0.44) pH + 4.05 with r² = 0.89. The average of IRAE_phospal values was 0.15 with a standard error = 7% irrespective of soil pH. Then a logarithmic relationship was obtained between IRAE values of the two tested fertilizers and their water P-solubility determined at the soil pH where they were applied.     

A variable gap penalty function and feature weights for protein 3-D structure comparisons

We have developed a variable gap penalty function for use inthe comparison program COMPARER which aligns protein sequenceson the basis of their 3-D structures. For deletions and insertions,components are a function of structural features of individualamino acid residues (e.g. secondary structure and accessibility).We have also obtained relative weights for different featuresused in the comparison by examining the equivalent residuesin weight matrices and in alignments for pairs of 3-D structureswhere the equivalences are relatively unambiguous. We have usedthe new parameters and the varible gap penalty function in COMPARERto align protein structures in the Brookhaven Data Bank. Thevariable gap penalty function is useful especially in avoidinggaps in secondary structure elements and the new feature weightsgive improved alignments. The alignments for both azurins andplastocyanins and N- and C-terminal lobes for aspartic proteinasesare discussed     

On the importance of some surface and interface characteristics in the formation of the properties of adhesive joints

The importance of some relative surface characteristics which determines the strength of adhesive joints: specific surface of substrate , relative contact area β and specific contact area β in the adhesion interaction process were emphasised. Existing and potential methods of experimental evaluation of these characteristics were shortly analysed. The durability of the adhesive joints in water media significantly increases with growth of specific surface ^* of chemically treated substrate evaluated from the SEM micrographs. Specific surface calculated from the experimental data of hexane adsorption measurements for iron particles (particulate model of steel substrate) is more then ten times greater than respective ^* values. The relative contact area β of the Al₂O₃ particles (in wide range of ) with PE melt was in a roundabout way evaluated by experimental determination of the affect of on kinetic of peel strength formation of adhesive joints: Al₂O₃ filled PE-steel. The speculation was based on the ability of Al₂O₃ to adsorb low-molecular products of contact oxidation of PE which takes place in the process of formation of adhesive joints and determines their strength. The ability of sorption in its turn is proportional to efficient value of β. The availability of the Al₂O₃ surface was evaluated.     

Structure and properties of nitrile rubber (NBR)–clay nanocomposites by co‐coagulating NBR latex and clay aqueous suspension

Nitrile rubber (NBR)–clay nanocomposites were prepared by co‐coagulating the NBR latex and clay aqueous suspension. Transmission electron microscopy showed that the silicate layers of clay were dispersed in the NBR matrix at the nano level and had a planar orientation. X‐ray diffraction indicated that there were some nonexfoliated silicate layers in the NBR–clay nanocomposites. Stress–strain curves showed that the silicate layers generated evident reinforcement, modulus, and tensile strength of the NBR–clay nanocomposites, which were significantly improved with an increase in the amount of clay, and strain‐at‐break was higher than that of the gum NBR vulcanizate when the amount of clay was more than 5 phr. The NBR–clay nanocomposites exhibited an excellent gas barrier property; the reduction in gas permeability in the NBR–clay nanocomposites can be described by Nielsen's model. Compared with gum NBR vulcanizate, the oxygen index of the NBR–clay nanocomposites increased slightly. The feasibility of controlling rubber flammability via the nanocomposite approach needs to be evaluated further. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3855–3858, 2003     

轻骨料混凝土应力应变关系的试验分析

通过轻骨料混凝土LC30,LC40与普通混凝土C30,C40的对比试验,研究了同等强度等级下轻骨料混凝土与普通混凝土的力学性能;得出了不同强度等级的轻骨料混凝土的应力应变关系曲线.将试验结果与规程模型进行对比,分析其差异,进一步给出下降段的应力应变曲线方程.     

Application of structural curvature of coalbed floor on CBM development in the Zaoyuan block of the southern Qinshui Basin

Based on controls of structural style and the position in coalbed methane(CBM)development,we used a method of curvatures to study its relations with CBM development parameters.We calculated structural curvatures of contours of the No.3coal seam floor of the Shanxi Formation in the Zaoyuan block of the Qinshui Basin and analyzed its relations with development parameters of coalbed methane wells.The results show that structural curvature is negatively related to coal reservoir pressure,while positively related to permeability.With an increase in structural curvature,the average production of coalbed methane wells increases at first and then decreases,reaching the highest production at 0.02 m-1 of structural curvature.Therefore,structural curvature can be an important index for potential evaluation of coalbed methane development and provide a basis for siting coalbed methane wells.     

Seepage-stress coupling constitutive model of anisotropic soft rock

To provide a seepage-stress coupling constitutive model that can directly describe the seepage-stress coupling relationship, a series of one-dimensional seepage-stress coupling tests on two kinds of soft rock (argillaceous siltstone and brown mudstone) were performed by using an MTS-815.02 tri-axial rock mechanics test system, with which the stress—strain curves according to the seepage variation were obtained. Based on the experimental results and by employing Hooke’s law, the formulation of the coefficient of strain-dependent permeability was presented and introduced to establish a coupling model. In addition, the mathematical expression and the incremental formulation for coupling model were advanced, in which five parameters that can be respectively determined by using the experimental results were included. The calculated results show that the proposed coupling model is capable of simulating the stress—strain relationship with considering the seepage-stress coupling in the nonlinear elastic stage of two kinds of soft rock. Foundation item: Projects(50378069, 50639090) supported by the National Natural Science Foundation of China; Project(50639090) supported by the Joint Fund of Yalong River Hydropower Development, China     

添加剂对PVDF／PU复合膜成膜速度、结构与性能的影响

研究成孔添加剂聚乙二醇（PEG）和LiCl对聚偏氟乙烯（PVDF）／聚氨酯（PU）铸膜液体系的成膜动力学以及膜性能的影响．结果表明：加入PEG、LiCl均能加快成膜速度,膜的水通量有很大程度的提高,而截留率下降．不同相对分子质量PEG对成膜的影响略有不同．相对分子质量越大,黏度因素起到的作用越大,使得成膜速度随相对分子质量增加而稍有降低;相对分子质量越大,截留率下降得越明显;相对分子质量为4000时,PVDF／PU复合膜的综合性能最好．     

高速铁路无碴轨道预应力连续梁徐变影响分析

随着我国高速铁路事业的发展,越来越多的大跨连续梁桥得到应用.但是过去建设的大跨连续梁已有不少出现了挠度增大及表面开裂等现象,引起这些现象最重要的原因是混凝土的收缩徐变效应.本文选取合理的徐变系数后,从相对湿度、加载张拉龄期、二期恒载上桥时间三个因素对徐变影响进行研究,提出控制后期挠度变形的建议.