基于Single-Pass的网络舆情热点发现算法

考虑网络事件的时间距离,基于半结构化网页中不同位置特征项重要程度的不同,提出改进的single-pass文本聚类算法single-pass*,优势在于对Web文本不同位置特征项的加权处理,仅需计算新文档与同类别种子文档间的相似度。实验结果表明,相比single-pass,改进算法极大减少了漏检率和错检率,降低了由于新文本流内文档进行相似度计算导致系统性能的下降,平均提高Web文本聚类效率40%。将聚类后的Web文本应用于网络舆情分析,进行主题关注度分析和话题热度特性分析。     

一种单遍扫描频繁模式树结构

针对频繁模式增长算法无法适应数据流的无限性和流动性的特点,提出一种新颖的FP-tree的变形结构-SP-tree,只需单遍扫描便能容纳全部数据库信息。为使SP-tree具有与FP-tree一样良好的压缩性能,给出一种有效的动态重构树的方法,称为宽度排序方法,该方法能够在挖掘过程中动态地逐条分支地重构树,最终产生一棵频繁递减的前缀树。实验结果表明,SP-tree的压缩性能优于其他单遍扫描的前缀树结构。     

Assessment of Intestinal Absorption of Vitexin-2″-O-Rhamnoside in Hawthorn Leaves Flavonoids in Rat Using In Situ and In Vitro Absorption Models

The purpose of this study was to investigate the absorption mechanism of vitexin-2″-O-rhamnoside, the index component in hawthorn leaves flavonoids (HLF) in the rat intestine, using two different absorption models, the in situ single-pass intestinal perfusion and the in vitro everted gut sac model. The effective permeability coefficients (P_eff) in the in situ single-pass intestinal perfusion experiments and the apparent permeability coefficients (P_app) in the in vitro everted gut sac experiments were calculated. Furthermore, the influences of the P-glycoprotein inhibitors, verapamil and digoxin, on the intestinal absorption of vitexin-2″-O- rhamnoside in HLF were studied using the above-mentioned two models. Results showed that there were no significant differences in the absorption of vitexin-2″-O-rhamnoside in HLF in four segments of the rat intestine, duodenum, jejunum, ileum, and colon, and at different concentrations of HLF ranging from 0.05 mg/ml to 0.5 mg/ml (P > 0.05). The P_eff values for vitexin-2″-O-rhamnoside in the rat jejunal perfusion at the concentration of 0.05, 0.1, 0.25, and 0.5 mg/ml were (2.48 ± 0.33) × 10^?5; (2.23 ± 0.67) × 10^?5; (2.18 ± 0.48) × 10^?5; and (2.25 ± 0.17) × 10^?5 cm/s, respectively. But there was significant difference between absence and presence of verapamil or digoxin (P < 0.05). P_eff and P_app values of vitexin-2″-O-rhamnoside in HLF were increased in the presence of verapamil or digoxin. In conclusion, vitexin-2″-O-rhamnoside can be classified into high permeability class drug according to the biopharmaceutical classification system. Passive diffusion dominates the absorptive transport behavior of vitexin-2″-O-rhamnoside in HLF. The absorption and secretion are mediated by the efflux transport system, P-gp. The absorption of vitexin-2″-O-rhamnoside in HLF can be enhanced administered together with P-gp inhibitors.     

核电用508-III钢窄间隙脉冲TIG单层单道钨极摆动焊工艺

文中介绍了窄间隙脉冲TIG单层单道钨极摆动焊的工艺特点,针对核电用508-III钢材料进行了焊接工艺性试验,设计了合适的窄间隙焊接坡口形式,根据试验数据,得出了不同厚度核电用508-III钢材料的窄间隙脉冲TIG单层单道钨极摆动焊坡口尺寸范围,分析了焊接电流、电弧电压、焊接速度、送丝速度、钨极摆角、热丝电流形式、保护气体流量对焊接过程和焊接质量的影响,制定了相应的工艺过程控制措施。通过焊接工艺试验,获得了探伤合格的焊缝,接头力学性能指标满足国内三代核电产品技术条件的要求。     

18CrNiMo7-6齿轮钢的热变形行为及组织演变规律

利用Gleeble-3500热模拟试验机对18CrNiMo7-6齿轮钢进行了等温单道次压缩试验,研究了变形温度为900～1150℃,应变速率为0.01～5 s^-1,应变为0.76的条件下材料的热变形行为;并且通过光学显微镜对热变形后的微观组织进行了分析。建立了唯象型Arrhenius本构方程,预测的峰值应力与试验数据具有很好的一致性。高温热变形过程是加工硬化与动态回复以及动态再结晶的竞争过程,在热变形的过程中会形成变形晶粒、再结晶晶粒、等轴晶和晶粒长大等4种类型的微观组织。当应变速率为0.01 s^-1时,动态再结晶程度与变形温度成正比,当变形温度超过1050℃时,变形能转变成晶粒长大的驱动能,使得晶粒粗大;当应变温度一定(1050℃)时,随着应变速率的增大,动态再结晶发生不完全,导致晶粒组织出现细化、畸变、不完全再结晶共存的现象。变形程度越大,晶粒越细小。     

Combined Single-Pass Conversion of Methane Via Oxidative Coupling and Dehydroaromatization

A new reaction mode, i.e., the combined single-pass conversion of methane via oxidative coupling (OCM) over mixed metal oxide (SLC) catalysts and dehydroaromatization (MDA) over Mo/HZSM-5 catalysts, is reported. With the assistance of an OCM reaction over SLC catalysts in the top layer of the reactor, the deactivation resistance of Mo/HZSM-5 catalysts is remarkably enhanced. Under the selected reaction conditions, the CH₄ conversion decreased from 18 to 1% and the aromatics yield decreased from 12.8 to 0.1%, respectively, after running the reaction for 960min on both 6Mo/HZSM-5 and SLC-6Mo/HZSM-5 catalyst system without O₂ in the feed. On the other hand, for the SLC-6Mo/HZSM-5 catalyst system with O₂ in the feed, the deactivation was improved greatly, and after 960min onstream the CH₄ conversion and aromatics yield were still as high as 12.0 and 8.0%, respectively. The promotion effect mainly appears to be associated with in situ formation of CO₂ in the OCM layer, which reacts with coke via the reverse Boudouard reaction.     

面向不平衡数据的特征加权聚类算法

不平衡数据集类别分布严重倾斜,传统的聚类算法由于以提高整体学习性能为目标,往往偏向于聚集多数类,而忽视更有价值的稀有类.本文提出一种基于迭代的特征加权聚类算法,根据当前聚类后簇的特点以及特征重要性度量函数确定特征权值,利用所得权值进行下一轮聚类,直到权值稳定后结束迭代.在多个UCI不平衡数据集上的实验效果表明,本文算法能够较好地识别出重要特征并提高它们的权重,避免聚类算法过度偏向多数类,有效地提高了聚类性能.     

CR-3型中压加氢处理催化剂的性能与工业应用

新型CR-3型中压加氢处理催化剂具有较高的加氢活性、适宜的裂解活性、优良的再生性能和良好的稳定性。采用该催化剂单段加氢处理技术在大庆石化总厂260 kt·a^-1加氢裂化装置上运转, 经济效益显著。     

助留剂在瓦楞原纸生产中的应用试验

本文介绍了助留剂在瓦楞芯纸生产过程中的应用试验,分析了试验过程单程留着率和白水浓度的变化趋势以及添加助留剂对纸页强度的影响。     

基于X70高级管线钢多道焊缝和单道焊缝组织EBSD研究

本文选用X70管线钢两种不同形式焊接接头为研究对象,使用EBSD技术对径向焊缝的横截面的Fe3C相分布、取向差角分布、晶粒有效尺寸、大角度晶界和小角度晶界的比率以及Taylor因子进行表征.结果发现,多道焊缝析出相分布很均匀、随机;各种颜色的晶粒取向均有分布且少量呈柱状存在;晶粒有效尺寸起伏较大,大小不一,但总是交替进行;大角度晶界比率较大,韧性较好;Taylor因子灰度图分布略有起伏,平均数值较大,抵抗塑形变形能力较差.单道焊缝则反之.