用直接纺丝法制芳纶短纤维

研究了直接纺丝制取芳纶短纤维的新方法。讨论了纤维长度、直径及力学性能与纺丝条件的关系。发现影响纤维长度的主要因素是空气层高度和喷丝速度,影响纤维直径的主要因素为喷口直径及喷丝速度。此外,还用PPTA短纤维制成了均匀的PPTA"浆粕"纤维。     

Strength, durability and micro-structural aspects of high performance volcanic ash concrete

This paper presents the results of investigations to assess the suitability of using volcanic ash (VA) as a cement replacement material to produce high performance concrete. Tests were conducted on concrete mixtures replacing 0 to 20% by mass of ordinary Portland cement (OPC) by VA. The performance of high performance volcanic ash concrete (HPVAC) mixtures was evaluated by conducting comprehensive series of tests on fresh and hardened properties as well as durability. The mechanical properties were assessed by compressive strength, while durability characteristics were investigated by rapid chloride permeability (RCP), drying shrinkage (DS), mercury intrusion porosimetry (MIP), differential scanning calorimetry (DSC) and microhardness tests. HPVACs showed better durability properties compared to control concrete with 0% VA. The improved performance of HPVACs was attributed to the refinement of pore structure, and pozzolanic action of VA. HPVAC having a minimum 28-day compressive strength of 60 MPa can be obtained by replacing up to 20% (by mass) of cement by VA. Development of non-expensive and environmentally friendly HPVAC with acceptable strength and durability characteristics (as illustrated in this study) is extremely helpful for the sustainable development and rehabilitation of volcanic disaster areas around the world.     

鄂尔多斯盆地镇北地区三叠系延长组长8油组储层特征

鄂尔多斯盆地镇北地区延长组长8油层段是盆地重要的储集层之一。通过储层岩石学、储层物性、孔隙结构等方面对储层特征进行深入研究,研究结果表明,储层岩石类型主要为中细粒长石砂岩和岩屑长石砂岩,成分成熟度低,结构成熟度中—高;发育粒间孔隙、溶蚀孔隙、晶间孔等孔隙类型,喉道以中细喉—细喉为主。岩石物性总体较差,属低孔、低渗砂岩储层。研究结果对油田开发具有重要的指导意义。     

水位下降条件下西安D7裂缝土体孔隙变化特征试验

为研究压缩性土体在孔隙水压力下降下所引起的孔隙变化特征,选取孔隙度及分形维数作为评判指标,以西安D7地裂缝两侧可压缩性土层为研究对象,借助三维CT扫描成像技术,依托Matlab计算平台及VG Studio Max图像处理软件,对在水位下降过程中可压缩性土体压缩变形引起的孔隙度和分形维数孔隙变化进行定量评价,并探讨了固结压缩过程中土体孔隙分形维数的变化规律及其影响因素。研究表明:孔隙度随压缩进行大幅降低,由压缩前4.36%降至0.61%;土体分形维数与孔隙度、上覆压力均呈线性相关性,相关系数分别为0.947 2和0.966 0;而且分形维数可以很好的表征孔隙分布特点,是孔隙度的有效补充;通过分析土样孔隙度与分形维数关系,为后期建立区域上地裂缝—地下水开采耦合模型提供参数赋值基础。     

水辅助注塑大直径介质导管制品的冷却分析

采用数学分析方法，通过假设、简化分析模型，用数学模型来表述物理模型，确定了水辅助注塑(VAIM)大直径介质导臂制品的冷却时间，并运用算例和国外试验的结果进行验证。结果发现：水辅助注射成型新工艺可以更加显著地缩短注塑周期，降低制件壁厚，允许制件有更大的实际直径。因此，VAIM技术可用来高效率地生产大直径、高质量、薄壁的介质导臂。     

我国结构抗浮水位研究现状与展望

目前我国结构抗浮水位方面研究成果虽然很丰富, 但分歧很大, 不仅直接影响了实际工程中的应用, 同时也造成了研究工作自身缺乏系统性和延续性。为解决这一问题, 利用水文学、水力学和土力学等科学理论, 分别从抗浮水位基本概念、抗浮水位分析中两个基本问题(孔隙水压力和远期最高水位)的方法论和抗浮水位分析的技术体系等3个角度对既有研究成果进行了系统综述与客观分析。在抗浮水位基本概念方面, 根据地下水赋存和渗流理论, 将目前研究成果划分为二维、准三维和三维等3种类型, 提出了各自的数学表达式, 分析了三者之间逻辑关系, 讨论了各自的科学性和适用性。在孔隙水压力分析方法方面, 尤其是孔隙水压力折减问题, 对基于渗流理论和有效应力原理的经典分析方法进行系统评述的同时, 还对当前讨论热烈的基于结合水理论的分析方法进行了梳理评价。在地下水远期最高水位预测方面, 着重讨论了历史最高水位法、基于宏观数据反演法和数值分析法等3种方法的优缺点及需要完善之处。在抗浮水位分析技术体系方面, 以北京地区为例对该类问题作了简要总结与评述。最后, 对抗浮水位研究与应用现状进行了概要性评述, 并结合我国国情, 对未来工作提出了展望与建议。     

Characterization of microporous-mesoporous MCM-41 silicates prepared in the presence of octyltrimethylammonium bromide

MCM-41 silicates prepared in the presence of octyltrimethylammonium bromide either by a conventional method or by post-synthesis hydrothermal treatment were characterized by nitrogen adsorption in a wide range of relative pressure from 10^-6 to 1. Hydrothermally restructured samples were found to have lower BET surface areas, lower external surface areas and thicker silica walls than the non-treated sample. More importantly, in addition to their characteristic mesopores (ca. 3 nm), they were shown to have considerable amounts of micropores. The relative amount of micropores and mesopores was shown to be dependent on the treatment conditions. Thus, it is demonstrated that the postsynthesis hydrothermal restructuring is a convenient synthesis route to MCM-41 silicates with bimodal pore size distribution involving controllable amounts of microporosity. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of Mode of Drying on Microstructure of Potato

Potato v. Irga was subjected to blanching, and thereafter was dried by convection, puff-drying, and freeze-drying. Microstructure of raw, blanched, and dried tissue was analyzed under the light microscope using computer image analysis. It was found that the tissue of the investigated variety is built up from cells much smaller than those described in literature for other cultivars. Blanching caused starch gelatinization and increase of cross-sectional area of cells. There was no evidence of broken cell walls. Convective drying resulted in cell shrinkage and some breaking of cell walls. It was estimated that some 12% of cells lost integrity during drying. Limited disintegration of the tissue caused by convective drying is attributed to small size of cells, large contact area, and high cohesive forces between cells. Puff-drying damaged the tissue much more than the convective drying. The most devastating to tissue microstructure was freeze-drying, probably freezing per se.     

Breakthrough and Sulfate Conversion Analysis during Removal of Sulfur Dioxide by Calcium Oxide Sorbents

Sorption of sulfur dioxide (SO₂) was carried out on calcium‐based sorbents under dynamic conditions in a fixed bed. The experimental conditions were reaction temperature (700 to 1000°C), SO₂ concentration (1000‐10 000 ppm), sorbent particles size (1 to 2 mm) and the types of sorbents (hydroxide or carbonate). The sorption process was found to be effective at low concentration levels (less than 10 000 ppm) as the breakthrough time significantly decreased with increase in concentration. The maximum removal of SO₂ was observed at a reaction temperature of 950°C. The hydroxide‐based sorbents of relatively smaller particle size were found to exhibit superior sorption performance in terms of longer breakthrough time and higher sulfate conversion. A mathematical model developed, assuming a porous structure of the sorbent materials, attributed the low sulfation conversion during SO₂ sorption due to a pore diffusion mechanism.     

改善普通水泥耐久性的研究

研究了活性组分及少量的引气剂对水泥性能的影响。实验表明：活性组分或与少量的引气剂复合使用，降低了水泥砂浆的大孔体积和干缩率，提高了其抗渗性、抗化学侵蚀性、抗钢筋锈蚀性，并改善了水泥砂浆的某些力学性能。