基于动态朴素贝叶斯分类器的明渠水华风险评估模型

水华风险不仅是水利工程规划时需要考虑的环境问题,也是水利设施运营时不能忽视的监测项目。为了提高明渠水化风险等级预测的准确率,针对水华成因的不确定性和发展的时序性,基于动态朴素贝叶斯网络分类器提出一种应用于明渠的水华风险评估模型。模型用水华风险等级结点对应藻叶绿素a(Chla)的浓度,并考虑了9项影响水藻生长的因素。采用主成分分析法,处理专家咨询结果,进行参数的设计。在苏州河道北门桥2011年6月初至9月初观测的53例连续监测数据上,与基于朴素贝叶斯网络分类器的评估模型进行比较实验。混淆矩阵显示对中等风险情况的预测识别率提高了15.625%,单尾配对t检验表明在显著性水平0.05时,两模型预测识别率差异显著。考虑了时序特征的基于动态贝叶斯网络分类器的评估模型对明渠中等水化风险的预测识别率提高显著。     

A spectroscopic study of the self-association and inter-molecular aggregation behaviour of pH-responsive poly(l-lysine iso-phthalamide)

The pH mediated intra-molecular association and inter-molecular aggregation of a range of amphiphilic poly(l-lysine iso-phthalamide) polymers have been investigated in aqueous solution over a range of pH values and concentrations. The desired functionality of these novel bioresponsive amphiphilic polymers was achieved by incorporating pendant hydrophilic carboxyl groups along the polymer backbone, via the l-lysine moiety, balanced by a degree of hydrophobicity introduced via the iso-phthaloyl moiety. Incorporation of low levels of bis-functional Cy3 (poly-Cy3) and/or Cy5 dye (poly-Cy3/5 or poly-Cy5) co-monomers in the responsive polymer backbone allowed detailed probing of the pH mediated hydrophobic association using a combination of optical spectroscopic techniques. Both steady-state fluorescence spectroscopy and fluorescence lifetime measurements of poly-Cy3 revealed a conformational transition at pH 4.5. Thus, below a critical pH the polymer collapsed into a compact globular structure (hypercoil) bringing the fluorophore molecules into close proximity with one another. This resulted in a dramatic reduction in fluorescence intensity and fluorescent lifetime in the single fluorophore systems (poly-Cy3) accompanied by a red shift in the maximum emission wavelength. Observed redshifts in the emission maxima and enhancements of fluorescent lifetimes with increasing polymer concentration suggested the formation of polymer aggregates. Fluorescence resonance energy transfer (FRET) was measured in mixtures of single fluorophore containing poly-Cy3 (donor) and poly-Cy5 (acceptor) and dual fluorophore containing poly-Cy3 (donor)/Cy5 (acceptor) in an effort to distinguish between intra-molecular versus inter-molecular association. The relevance of the results with respect to potential in vivo applications (drug delivery and biodiagnostics) is discussed.     

Study on pH‐sensitive and thermosensitive polymer networks containing polyacetal segments

A series of pH‐sensitive and thermosensitive polymer networks were first obtained by copolymerization of telechelic poly(1,3‐dioxolane) (PDXL) with acrylic acid (AA), acrylamide (AM), and N‐isopropylacrylamide (NIPAM), respectively. The copolymerization of PDXL diacrylate (PDXLDA) with AA, AM, or NIPAM is expected to lead to polymer networks in which homopolymeric segments of the monomer are connected by polyacetal segments. As a combination of these two parts, these polymer networks can have some interesting physical properties. For example, the copolymer networks of poly(AA‐b‐DXL) showed pH sensitivity, and both the copolymer networks of poly(AM‐b‐DXL) and poly(NIPAM‐b‐DXL) showed temperature sensitivity. Moreover, because of the low ceiling temperature of polyDXL, the networks containing polyacetal segments (PDXL) can degrade by treatment with a trace of appropriate cationic initiator. The polymer networks prepared were characterized by Fourier transform infrared, differential scanning calorimetry, and swelling data. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3002–3006, 2002; DOI 10.1002/app.2329     

Factors influencing the efficacy of an interfacial modifier for the interface in an immiscible polymer blend

The modification of the interface in immiscible polymer blends is critical in order to optimize physical properties. Despite the great commercial importance of polymer blends, many aspects of the emulsification process remain unclear In this paper, it will be shown that an emulsification curve can be used to estimate the influence of the architecture molar mass of styrene/hydrogenated butadiene block copolymer interfacial modifiers on the emulsifion of polystyrene/ethylene-propylene rubber blends under melt processing conditions. An expression for eing the critical amount of copolymer to saturate the interface, as well as aspects concerning the localisation of the modifier in the blend system will also be addressed.     

疏水缔合聚丙烯酰胺溶液性质研究

用粘度法和核孔膜过滤法研究了实验室自制相对分子质量约1000万的疏水缔合聚丙烯酰胺(HAP)溶液的缔合效应,用粘度计考察了电解质浓度、温度和剪切速率对HAP溶液表观粘度的影响,并与相同测试条件下相对分子质量为1770万的部分水解聚丙烯酰胺3530进行对比。结果表明:HAP溶液在70℃的高温和矿化度为5727的高盐条件下,在1000mg/kg附近存在一临界缔合浓度,在临界缔合浓度以上,HAP溶液粘度迅速增加;而3530不存在临界缔合浓度,粘度增加缓慢。浓度为1250mg/kg的HAP溶液通过核孔膜20mL的过滤时间是347.3min,而相同浓度下3530的过滤时间仅为2.1min。浓度为1000mg/kg的HAP溶液即使在矿化度为30000、70℃的高温、30r/min转速的条件下,粘度仍达到32.8mPa·s,而聚合物3530的粘度仅有4.11mPa·s;当剪切速率增加到140r/min、温度为70℃,用矿化度为5727的模拟采出水配制的HAP溶液的粘度为9.21mPa·s,而3530溶液的粘度仅5.18mPa·s。HAP具有良好的耐温抗盐抗剪切能力。     

基于BP网络的保护渣性能预测模型的研究

结合BP网络计算机实验研究 ,建立了保护渣化学组成与性能的预测模型 ,并利用化学组成与性能的关系 ,对网络的实用性进行了检验 ,结果符合保护渣化学组成与性能的关系。保护渣粘度随着保护渣碱度的增大而减小 ,而半球点温度随碱度增大而增大 ;保护渣的半球点温度和粘度都随着渣中CaF2 含量的增加而减小。用BP网络的误差反向传播算法建立的保护渣的化学组成与性能的预测模型 ,得出的预测值与实际值的误差小 ,对保护渣的设计与应用都有一定的指导作用。     

一种高吸水性新型高分子复合肥载体的研究

研究了一种新型高吸水率和高吸收利用率的高分子复合肥 ,它以脲甲醛缩聚物作为载体 ,以聚乙烯醇缩甲醛作为吸水功能体 ,以磷酸钙、氯化钾作为包覆体 ,以硬质聚氨酯泡沫作为支撑体并采用发泡工艺制备。     

聚乙烯与聚丙烯单组分复合材料研究进展

综述了聚乙烯、聚丙烯单组分复合材料的发展概况及最新研究动态。介绍了熔融膜压法、粉末浸渍法、溶液浸渍法三类制备聚乙烯单组分复合材料的传统方法。重点介绍了热压法、共挤出热压法两类制备单组分复合材料的创新方法。分析了各制备方法的优缺点:熔融法、粉末法与溶液法效率均较低且复合材料中纤维含量较少,力学性能不佳;热压法由于初始材料为100％纤维,从而综合效率较高,力学性能良好,缺点为加工温度过于苛刻;共挤出热压法效率较高,在具有高的增强相含量的同时拥有较宽的加工温度范围,缺点为增强相强度需进一步提高。最后介绍了单组分复合材料的应用并对其研究与应用前景作了展望。     

面向水环境的传感网虚拟距离覆盖算法

针对水面传感器随机部署时网络覆盖率较低的问题,采用了一种面向水环境的无线传感网虚拟距离覆盖算法,在保证连通性的前提下提高网络的覆盖率。在虚拟距离算法中,每个传感器节点的运动受到3个虚拟距离的影响:节点之间的虚拟距离、未被覆盖区域格点与节点的虚拟距离以及边界与节点间的虚拟距离。仿真结果表明:该算法可以有效地提高网络覆盖率。可以得出以下结论:虚拟距离算法通过对节点位置的控制更新有效提高了网络覆盖率,使节点得到优化部署。