PVC／OMMT／WF纳米复合材料性能研究

对蒙脱土进行有机改性制得有机蒙脱土（OMMT），并制备了聚氯乙烯侑机蒙脱土／木粉（PVC／OMMT／WF）纳米复合材料。采用硅烷偶联剂对木粉表面进行改性，有效提高了聚氯乙烯／木粉（PVC／WF）复合材料的力学性能，其中加入1．5％（质量含量，下同）硅烷偶联剂可使复合材料的冲击强度和拉伸强度分别提高14．8％和18．5％。研究了OMMT的加入对木粉改性前后的PVC／WF复合材料力学性能、耐热性能及阻燃性能的影响，结果表明，木粉未经改性时，OMMT加入无助于PVC／OMMT／WF复合材料力学性能的提高；木粉用硅烷偶联剂改性后，添加少量的OMMT，可使PVC／OMMT／WF复合材料的冲击强度和拉伸强度明显提高。研究表明，添加OMMT可显著延迟复合材料的点燃时间，燃烧残余率也明显增加，OMMT是PVC／WF复合材料的高效阻燃剂。     

工业PTA氧化过程4-CBA浓度的模糊神经网络模型

A fuzzy neural network (FNN) model is developed to predict the 4-CBA concentration of the oxidation unit in purified terephthalic acid process. Several technologies are used to deal with the process data before modeling.First,a set of preliminary input variables is selected according to prior knowledge and experience. Secondly,a method based on the maximum correlation coefficient is proposed to detect the dead time between the process variables and response variables. Finally, the fuzzy curve method is used to reduce the unimportant input variables.The simulation results based on industrial data show that the relative error range of the FNN model is narrower than that of the American Oil Company (AMOCO) model. Furthermore, the FNN model can predict the trend of the 4-CBA concentration more accurately.     

后掺粗骨料工艺对高性能泵送混凝土性能影响研究

为解决建筑工程中高性能泵送混凝土的环境问题、成本问题,基于粗骨料嵌锁效应和界面水灰比强度理论,在保证高性能和泵送要求的条件下,提出了后掺骨料工艺,并对不同粗骨料后掺比例下的混凝土进行了力学性能和抗冻性能的研究。结果表明,随着粗骨料后掺比例的增大,7 d、28 d混凝土抗压强度持续增大,而28 d混凝土劈裂抗拉强度和抗折强度均呈先增大后减小的趋势;在冻融循环作用下,质量损失率的上升速率呈先减小后增大的趋势,而抗压、抗拉、抗折强度、动弹性模量以及超声波速的下降速率均呈先减小后增大的趋势。据此建议本C30高性能泵送混凝土的粗骨料最佳后掺比例为20%。     

On the complexity of role updating feasibility problem in RBAC

In Role Based Access Control (RBAC) systems, it is necessary and important to update the role–permission assignments in order to reflect the evolutions of the system transactions. However, role updating is generally complex and challenging, especially for large-scale RBAC systems. This is because the resulting state is usually expected to meet various requirements and constraints. In this paper, we focus on a fundamental problem of role updating in RBAC, which determines whether there exists a valid role–permission assignment, i.e., whether it can satisfy all the requirements of the role updating and without violating any role–capacity or permission–capacity constraint. We formally define such a problem as the Role Updating Feasibility Problem (RUFP), and study the computational complexity of RUFP in different subcases. Our results show that although several subcases are solvable in linear time, this problem is NP-complete in the general case.     

北江下游推移质输沙研究

采用数值模拟与实测资料相结合的方法研究了北江下游推移质输沙率公式的适用性、洪枯季推移质输沙率及空间分布。结果表明以切应力为主要参量的推移质输沙率公式较适用于北江下游河道,洪季Bijker公式、枯季Van Rijn公式计算误差较小。石角断面洪季推移质输沙率为9.06万t/月,枯季为2.43万t/月,年推移质输沙量为49.54万t。推移质输沙主要集中在大塘以上河段,洪枯季均在山塘上游、廻岐洲、界牌洲等处出现输沙率峰值,大塘下游推移质输沙较弱。水面比降是推移质输沙率沿程变化的主导因素。     

反应型纳米碳酸钙补强NR的研究

采用具有反应性的改性剂,在纳米碳酸钙水悬浮液中进行改性,制备一种新型改性纳米碳酸钙（简称M-CaCO3）及其与NR的复合材料,对改性前后纳米碳酸钙的结构和形态进行分析,并对NR/纳米碳酸钙复合材料的结构和性能进行研究.结果表明,与未改性纳米碳酸钙相比,改性纳米碳酸钙的透过率下降,在正己烷中的分散性明显提高;NR/M-CaCO3复合材料具有良好的界面相容性和耐热分解性能、较高的交联密度以及优良的综合物理性能和耐老化性能,M-CaCO3的最佳用量为8份.     

NBR/Zn(MAA)2/蒙脱土纳米复合材料的研究

研究NBR／基丙烯酸锌[Zn(MAA)2]／蒙脱土纳米复合材料的性能。结果表明，Zn(MAA)2可以通过原位聚合反应在与NBR发生接枝交联的同时，实现对蒙脱土的插层，用该方法制备的NBR／Zn(MAA)2／蒙脱土纳米复合材料的物理性能优异，含有有机改性蒙脱土HMMT和USM的复合材料性能更为突出，且具有一定的透明性。     

氯溴异氰尿酸烟剂的快速分析方法

介绍了一种准确简便的测定氯溴异氰尿酸烟剂中的有效成份的分析方法——碘量法。在烘干的碘量瓶中,先放入KI和氯溴异氰尿酸,然后迅速加入H2SO4水溶液,用标准Na2S2O3滴定至无色,以Na2S2O3的消耗体积折算出烟剂中的有效成分含量。此法准确,操作简单,花费少,空白烟剂无干扰,非常适用于生产厂家控制氯溴异氰尿酸产品质量的要求。     

无油螺杆压缩机在燃料电池中的应用

由于环境污染、全球变暖、能源短缺等各方面原因,能量转换效率高且无污染的燃料电池汽车备受人们的青睐,作为燃料电池系统中重要部件之一的空气压缩机也成为研究的热点。西安交通大学压缩机研究所成功研制了可以应用于燃料电池的LG300型喷水螺杆空气压缩机以及具有体积小、质量轻、效率高的高速干式螺杆压缩机、膨胀机,并且经过与燃料电池系统配套使用,获得成功。     

Users’ interest grouping from online reviews based on topic frequency and order

Large volume of online review data can reveal consumers’ major interests on domain product, which attracts great research interests from the academic community. Most of the existing works focus on the problems of review summarization, aspect identification or opinion mining from an item’s point of view such as the quality or popularity of products. Considering the fact that users who generate those review texts draw different attentions to product aspects with respect to their own interests, in this article, we aim to learn K users’ interest groups indicated by their review writings. Such K interest groups’ identification can facilitate better understanding of major and potential consumers’ concerns which are crucial for applications like product improvement on customer-oriented design or diverse marketing strategies. Instead of using a traditional text clustering approach, we treat the groupId/clusterId as a hidden variable and use a permutation-based structural topic model called KMM. Through this model, we infer K interest groups’ distribution by discovering not only the frequency of product aspects (Topic Frequency), but also the occurrence priority of respective aspects (Topic Order). They jointly present an informative summarization on the raw review corpus. Our experiment on several real-world review datasets demonstrates a competitive solution.