A suitable computational strategy for the parametric analysis of problems with multiple contact

The aim of the present work is to develop an application of the LArge Time INcrement (LATIN) approach for the parametric analysis of static problems with multiple contacts. The methodology adopted was originally introduced to solve viscoplastic and large‐transformation problems. Here, the applications concern elastic, quasi‐static structural assemblies with local non‐linearities such as unilateral contact with friction. Our approach is based on a decomposition of the assembly into substructures and interfaces. The interfaces play the vital role of enabling the local non‐linearities, such as contact and friction, to be modelled easily and accurately. The problem on each substructure is solved by the finite element method and an iterative scheme based on the LATIN method is used for the global resolution. More specifically, the objective is to calculate a large number of design configurations. Each design configuration corresponds to a set of values of all the variable parameters (friction coefficients, prestress) which are introduced into the mechanical analysis. A full computation is needed for each set of parameters. Here we propose, as an alternative to carrying out these full computations, to use the capability of the LATIN method to re‐use the solution to a given problem (for one set of parameters) in order to solve similar problems (for the other sets of parameters). Copyright © 2003 John Wiley & Sons, Ltd.     

利用框架理论对信号进行重建

在Hilbert空间中讨论了框架的一些重要的性质,定义了一个框架算子,并讨论了该算子的性质。根据实际问题构造了一框架,使信号在此框架下的投影正好为非均匀采样值。给出了一种框架界的估计方法和重建原信号的迭代算法,最后,用仿真验证了此算法的有效性。     

可靠性试验样本量和截尾时间的计算

可靠性寿命试验中，一般都因受到费用和时间的限制，因此要用截尾试验获得信息，再据此对其可靠性进行统计推断，用非参数估计的方法探讨了进行可靠性试验的样本量或截尾时间的估计方法。     

准噶尔盆地侏罗系储集层的基本特征及其主控因素分析

从描述储集层基本特征、分析储集层性质的主控因素、建立储集层成因模式和评价、预测储集层性质这 4个层次 ,研究准噶尔盆地重点勘探目标区的侏罗系储集层。系统总结侏罗系储集层岩石学特征 ,认为成岩压实作用强弱是控制储集层性质的关键因素 ;指出相对优质储集层均为剩余原生粒间孔隙型储集层 ,溶蚀作用对渗透率贡献小 ;非煤系储集层的孔隙保存条件明显比煤系储集层好 ,这是三工河组、头屯河组和吐谷鲁群的物性普遍优于八道湾组和西山窑组的原因。在确定储集层性质的控制因素和控制机理基础上 ,建立了煤系和非煤系两大类储集层的成因 演化模型。在上述研究的基础上 ,分地区、分层位评价了储集层 ,并预测了不同渗透率储集层的深度界线及相对优质储集层的平面分布。图 6参 10     

絮凝剂品种对水下不分散混凝土性能影响的比较

通过电荷中和、吸附架桥和表面吸附分析了絮凝剂作用机理 ,运用絮凝机理进一步分析了絮凝剂在水泥体系中的作用以及絮凝剂对流动度的影响 ,从而对掺加JHP (纤维素类 )和Pj (丙烯类 )絮凝剂的水下不分散混凝土性能作了综合比较。掺Pj絮凝剂的混凝土 ,其坍扩度损失大 ,抗分散性能不如掺JHP絮凝剂的好 ;掺JHP絮凝剂的混凝土坍扩度在 3h内损失很小     

发酵法改良早籼谷品质的工艺研究

本研究用有益微生物对早籼谷进行发酵处理，使早籼谷中的淀粉，蛋白质，脂肪等成份适度分解，以改良早籼谷的结构与品质，通过一系列的单因素试验和正交试验，对照研究各因素对发酵影响。试验结果表明：先对早籼谷进行蒸汽处理15min，然后采用L－F－6根霉曲，酵母＝2：1，接种量1．2％，在酵温度23℃的发酵上，发酵48h。碾米后做出的米饭口感好，色泽洁白，有良好的发酵香味。     

烯烃聚合单活性中心非茂催化剂的最新研究进展

综述了近几年来烯烃聚合用单活性中心非茂催化剂的研究进展。简要介绍了 2 3种由前、后过渡金属组成的配位化合物催化剂的结构与性能     

Poly(butylene terephthalate)–clay nanocomposites prepared by melt intercalation: morphology and thermomechanical properties

Nanocomposites based on poly(butylene terephthalate) (PBT) and an organoclay (Cloisite 30B) were prepared by melt blending using a twin‐screw extruder. Two kinds of PBTs, ie PBT‐A and PBT‐B, with different inherent viscosities (η_inh), were used for this study (η_inh of PBT‐A and PBT‐B were 0.74 and 1.48, respectively). Dispersion of the clay layers in the PBT nanocomposites was characterized by using X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Tensile and dynamic mechanical properties and non‐isothermal crystallization temperatures of the nanocomposites were also examined. Nanocomposites based on the higher‐viscosity PBT (PBT‐B) showed a higher degree of exfoliation of the clay and a higher reinforcing effect when compared to the composites based on the lower‐viscosity PBT (PBT‐A). The clay nanolayers dispersed in PBT matrices lead to increases in the non‐isothermal crystallization temperatures of the PBTs, with such increases being more significant for the PBT‐B nanocomposites than for the PBT‐A nanoocomposites. Copyright © 2004 Society of Chemical Industry     

A p‐version,first order shear deformation,finite element for geometrically non‐linear vibration of curved beams

A p‐version, hierarchical finite element for curved, moderately thick, elastic and isotropic beams is introduced. The convergence properties of the element are analysed and some results are compared with results published elsewhere or calculated using a commercial finite element package. It is verified that, with the proposed element, shear locking does not affect the computation of the natural frequencies and that low dimensional, accurate models are obtainable. Geometrically non‐linear vibrations due to finite deformations, which occur for harmonic excitations with frequencies close to the first three natural frequencies of vibration, are investigated using Newmark's method. The influence of the thickness, longitudinal inertia and curvature radius on the dynamic behaviour of curved beams are studied. Copyright © 2004 John Wiley & Sons, Ltd.     

大型储罐基础非平面倾斜问题的探讨

大型储罐因基础产生非平面倾斜而影响其正常使用的情况在工程中时有发生,文章通过对某油罐工程中基础沉降观测结果的分析,探讨了储罐基础产生非平面倾斜的原因。相邻储罐之间的相互影响、充水预压未达到规范要求以及地基处理措施不当是引起储罐基础非平面倾斜的主要因素。针对相邻储罐间的相互影响,根据现行《石油化工企业设计防火规范》和《石油化工企业钢储罐地基与基础设计规范》的规定,提出以下建议:储罐布置的净距除应满足防火规范规定外,有条件时也应适当考虑对基础沉降的影响,当采用复合地基时,相邻储罐间的净距不宜小于0.6 D;当占地面积成为主要矛盾,储罐间的净距只能限制在防火规范规定的最小范围时,在地基处理时就应采取有效措施,以尽可能减少相邻储罐的相互影响。