The Boundary Element Method with a Fast Multipole Accelerated Integration Technique for 3D Elastostatic Problems with Arbitrary Body Forces

A line integration boundary element method (LIBEM) is proposed for three-dimensional elastostatic problems with body forces. The method is a boundary-only discretization method like the traditional boundary element method (BEM), and the boundary elements created in BEM can be used directly in the proposed method for constructing the integral lines. Finally, the body forces are computed by summing one-dimensional integrals on straight lines. Background cells can be used to cut the lines into sub-lines to compute the integrals more easily and efficiently. To further reduce the computational time of LIBEM, the fast multipole method is applied to accelerate the method for large-scale computations and the details of the fast multipole line integration method for 3D elastostatic problems are given. Numerical examples are presented to demonstrate the accuracy and efficiency of the proposed method.     

从土壤水动力学到生态水文学的发展与展望

在20世纪80年代,土壤水动力学成为我国水文水资源领域的一个新兴研究方向。在此后的30多年中,土壤水动力学得到了巨大发展,并对我国农田水利、水文水资源等领域的科学与技术起到了巨大的推动作用。以土壤水动力学为基础,逐步认识了非饱和土壤中水分与热量、溶质等耦合运移机理与规律,在20世纪90年代发展了土壤-作物-大气之间的水热交换和传输理论(即土壤-植物-大气连续体理论,简称SPAC理论)。以SPAC理论为基础,农田作物模型得到了快速发展,成为本世纪研究气候变化对农业水资源和粮食生产影响的主要工具。与此同时,从农田到区域的水转化机理与规律、不同尺度的农业用水效率、以及水资源开发利用的生态和环境影响等基础科学问题和生产实践问题逐渐被重视,从而形成了新的交叉学科——生态水文学。生态水文学以水分-能量-物质耦合循环的动力学过程为基础,注重区域气候-植被/作物-水文相互作用的基础科学问题,旨在为区域水资源、生态和环境评价与管理提供科学依据。     

氮掺杂改性二氧化钛光催化剂的研究进展

综述了近年来国内外利用氮掺杂改性二氧化钛的光催化剂性能、提高可见光的利用效率的最新研究进展；分析和讨论了氮掺杂二氧化钛的制备方法、理论计算和结构模型、掺杂机理等；总结了氮掺杂改性二氧化钛存在的问题，同时讨论了今后的研究方向．     

发泡剂对人造革发泡倍率与泡孔结构的影响

对比分析了纯放热性发泡剂AC与吸－放热复合发泡剂DDL－105的分解与发泡特性。详细比较了以这两类发泡剂在相同配方和加工条件下样品的发泡倍率、泡孔结构差别以及对温度和时间的依赖关系。     

Numerical analysis of flow field in the hot gas filter vessel during the pulse cleaning process

The flow field is simulated for a ceramic filter vessel containing three candle filters which are arranged in the form of an equilateral triangle. Grids generated by GAMBIT are adopted for the simulations. The Reynolds stress model provided by FLUENT code is applied to evaluate gas flow and temperature field in the filter vessel. The temperature profiles in the ceramic candle filter cavity during the pulse cleaning process are analyzed under different operating conditions and for different lengths of candle filter. The evolution of radial velocity in the porous wall of the filters being cleaned and the normal working filters as well as around the filters is discussed. Sharp temperature change takes place in the top of the candle filter which is subject to thermal stress. The phenomenon of temperature increase during the pulse cleaning process has been carefully observed and interpreted based on the effect of gas compression. The simulated results show qualitative agreement with the experimental field observations with the filter vessel.     

Synthesis and cure of liquid crystalline diallyl modifiers for bismaleimide resin

Three kinds of liquid crystalline aromatic azomethine modifiers were synthesized with high yield, and the modification of bismaleimide resin (BMI) with them was studied by scanning electron microscope, polarizing optical microscope, thermogravimetric analyzer, differential scanning calorimetry, and rheolometry. Blends cured at the temperature of liquid crystalline phase were found to have oriented liquid crystal‐rich phase and improved mechanical properties. The addition of o,o′‐diallyl bisphenol A in the blends of BMI decreases thermal properties but shows little effect on phase structures. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4366–4371, 2006     

乙烯聚合用树枝状过渡金属催化剂研究进展

树枝状过渡金属催化剂是在树枝状大分子上负载上过渡金属活性中心,因此,此类催化剂既具有树枝状大分子特有的艺术结构,同时还具有过渡金属配合物的功能化性能,使其两者能够协同发挥作用,兼具均相和非均相催化体系的特点,在催化烯烃聚合方面具有较高的催化活性和良好的催化稳定性,近年来备受关注,催化乙烯聚合就是其中的研究热点之一。本文按其过渡金属活性中心进行分类,综述了近年来国内外树枝状过渡金属催化剂在这乙烯聚合方面的进展,阐述了多种树枝状效应产生的原因,并且对乙烯聚合用树枝状过渡金属催化剂的发展前景进行了展望。     

一种基于GPS单差模型的姿态解算算法

针对采用双差模型无法克服双差观测量的强相关性这一问题,以观测量不相关的单差模型为基础,提出一种可递归处理的定姿算法.该方法用码观测量辅助载波相位观测值,增加了信息量,通过递归估计模糊度浮点解及其方差协方差矩阵,从而可以利用LAMBDA算法估计整周模糊度.该算法计算量较小,且具有数值稳定性.实验结果表明,该算法的初始化时...     

生物质能及应用技术

概述了生物质能的来源,包括农作物秸秆、薪柴、禽畜粪便、城镇垃圾和工业有机废弃物等;与常规能源相比的特性如可再生性、洁净性和温室气体CO2零排放效应;论述了生物质能利用技术、国内外利用现状及发展前景,目前世界上生物质能开发利用的前沿技术以热解气化和热解制油为主,制取液体燃料乙醇的技术已进入商业示范阶段.     

促分裂原活化蛋白激酶激活的蛋白激酶-2全新抑制剂的3D-QSAR研究

促分裂原活化蛋白激酶激活的蛋白激酶-2(MK-2)可以作为治疗类风湿性关节炎(RA)的靶标,并显示出巨大的潜力,此类酶的抑制剂用于治疗RA具有相当好的疗效,一系列β咔啉衍生物对于MK-2具有高的活性和选择性。通过自组织分子场(SoMFA)分析方法建立了MK-2抑制剂———β咔啉衍生物的三维定量构效关系(3D-QSAR)模型。SoMFA模型的相关系数r2=0.731,交叉验证相关系数q2=0.686,标准偏差s=0.388,Fisher检验值F=63.538。该模型具有很好的稳定性和较为满意的预测能力。