多羟基化合物键合亲水色谱固定相的制备及其分离性能

用硅胶与氨丙基三甲氧基硅烷反应,再与δ-葡萄糖酸内酯反应,制备了一种多羟基化合物键合的新型亲水色谱固定相。以水-有机溶剂(乙醇、乙腈、四氢呋喃)为流动相,通过改变流动相中有机溶剂的种类及浓度、缓冲盐浓度和柱温,考察了该固定相对6种强极性中药组分的保留行为和保留机理。当水的比例在0～40%(v/v)范围时,溶质的保留随着流动相中水的比例的增大而减小,属于典型的亲水色谱分离模式;而当流动相中水的比例在0～100%(v/v)范围内变化时,溶质的保留随着水的比例变化呈“U”形曲线,属于亲水色谱和反相色谱的混合保留机理。缓冲盐的浓度和pH效应说明,所选用的中药组分与所制备的固定相间还存在弱的静电作用。该固定相对6种中药组分以及丹参注射液具有良好的分离性能,表明其在强极性中药有效成分的分离及其他强极性物质的分离分析中具有一定的应用前景。     

一种启发式Web信息检索方法

针对目前Web信息庞杂无序和半结构化特征所带来的信息检索质量低下的问题,在基于查询意图分类研究的基础上,提出了一种结合定题检索的启发式Web信息检索方法;在该方法中,Web信息检索采用一次预处理两次检索机制,根据该机制设计了Web信息检索模型,详细讨论了该模型的设计思想、关键技术和算法描述;通过仿真实验对该方法进行了测试和分析,测试结果表明该方法能够有效提高信息检索性能,在一定程度上满足用户个性化的查询需求。     

Rheology and Structure of Quenched Binary Mixtures Under Oscillatory Shear

We applied the D2Q9 BGK lattice Boltzmann method to study the rheology and structure of the phaseseparating binary fluids under oscillatory shear in the diffusive regime. The method is suitable for simulating systemswhose dynamicsis described by the Navier-Stokes equation and convection-diffusion equation. The shear oscillationinduces different rheological patterns from those under steady shear. With the increasing of the frequency of the shearthe system shows more isotropic behavior, while with the decreasing of the frequency we find more configurations similarto those under steady shear. By decreasing the frequency of the shear, the period of the applied flow becomes thesame order of the relaxation time of the shear velocity profile, which is inversely proportional to the viscosity, and moreanisotropic effects become observable. The structure factor and the velocity profile contribute to the understanding ofthe configurations and the kinetic process. Oscillatory shear induces nonlinear pattern of the horizontal velocity profile.Therefore, configurations are found where lamellar order close to the wall coexists with isotropic domains in the middleof the system. For very slow frequencies, the morphology of the domains is characterized by lamellar order everywherethat resembles what happens in the case of steady shear.     

用水槽试验研究水库洪水传播特性

采用大型水模高变率变态模型,对非恒定流用模型试验与理论分析相结合的方法,借汉江安康水库洪水资料来研究水库洪水传播特性,对洪水波在水库中的传播时间,入库洪水与回水末端入库洪水的关系,各频率设计洪水的最高库水位,下泄洪水过程,调蓄滞洪历时,洪型对水库防洪的影响等问题得出相应的结论,与可对比资料吻合良好,其成果对安康水库及类似水库的防洪具有实际意义。     

肼及其衍生物在固体电极上的直接电化学行为研究

肼及其衍生物被广泛应用于医药,化工,军事,航天等领域,并被用作推进剂,水处理剂,农药,医药,燃料电池,光稳定剂以及化工生产助剂等诸多方面。因此对肼及其衍生物的研究和开发有着极其重要的理论意义和应用价值。本文研究了肼(Hydrzdine,DH),苯肼(Phenylhydrazine,PH),对硝基苯肼(p-Nitrophenykhzille,PNPH)和2,4-二硝基苯肼(2,4-DinitrophenyIhydrazine,DPH)在固体玻碳电极和铂电极上的不可逆电化学氧化行为,     

生漆与二异氰酸酯的反应及漆膜性能

本文用红外光谱（IR）、动态机械热分析（DMTA）、扫描电镜等仪器和物理、化学手段,研究生漆和2,4-甲苯二异氰酸酯（TDI）的反应特性、聚合成膜机理及漆膜性能等。结果表明,在漆酶和TDI共同作用下,生漆／TDI混合物的固化成膜速率比生漆快得多。当生漆与TDI混合后,生漆乳液的连续相中的漆酚迅速与TDI发生加成反应并生成聚氨酯化合物;在漆酶的催化作用下,该化合物的漆酚基上不饱和侧链双键进一步发生氧化聚合;所得的生漆／TDI涂膜具有优良的物理机械性能。     

多孔材料微通道流动沸腾可视化实验研究

微通道换热器因其结构紧凑、换热能力高、工质消耗少等优点成为解决微小空间"散热难"问题的有效途径之一,采用多孔材料制作的微通道热沉能够极大地增加换热面体比,因而可以进一步提高其换热能力.本文利用可视化手段对槽道翅片顶部与盖板间留有狭缝、通道截面为矩形(400 μm×600 μm)的开放型多孔微通道的流动沸腾现象进行实验研...     

Phase structures and transition behaviors in polymers containing rigid rodlike backbones with flexible side chains. V. Methylene side‐chain effects on structure and molecular motion in a series of polyimides

A series of organo‐soluble hairy‐rod polyimides was recently synthesized from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA) and di[n‐alkyl]‐4,4′‐diamino‐6,6′‐dibromo‐2,2′‐biphenyldicarboxylate with side chains of varying lengths (the numbers of methylene units), BACBP(n). Dynamic mechanical (DM) results reveal two cooperative relaxation processes for BACBPs(n > 10), which correspond to the two (low‐ and high‐) transition temperatures observed in differential scanning calorimetry (DSC). For BACBPs(n < 10), although two DM relaxation processes can be observed, the low‐temperature relaxation peak shifts into a medium temperature region that is difficult to observe in DSC experiments. Measurements indicate that the density of BACBP(n)s decreases with increasing numbers of methylene units. A discontinuity in the rate of density change can be seen at BACBP(10). Variable temperature solid‐state nuclear magnetic resonance experiments were also carried out to determine the molecular origins of each of the observed DM relaxation processes. The low‐ [for BACBPs(n > 10)] and possibly the medium‐ [for BACBPs(n < 10)] temperature relaxations are associated with the onset of motion in the side chains, and the high‐temperature relaxation is associated with motion in the backbones. Wide‐angle X‐ray diffraction analysis indicates that the lateral packing periodicity of the backbones in the unoriented polyimides changes its relationship with the side‐chain length at around 10 methylene units. In the oriented films of these polyimides, furthermore, those having the long side chains [BACBPs(n > 10)] adopt monoclinic unit cells, whereas those having the short side chains [BACBPs(n ≤ 10)] possess hexagonal unit cells. The drastic temperature difference between the low‐ and medium‐relaxation processes observed in DM experiments may be explained because of a change in the lateral packing arising from the variation of the side‐chain length. The limited mobility afforded the BACBPs(n ≤ 10) is a result of their more ordered conformation and interdigitation between the neighboring side chains. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1633–1646, 1999     

中立型泛函微分方程解的振动性(Ⅰ)

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混杂钢纤维水泥基材料的力学行为

研究了微细钢纤维以及中等直径钢纤维混杂增强水泥基材料的力学行为．结果表明，在纤维体积分数一定的情况下，混杂钢纤维体系对水泥基材料抗折强度的改善作用可优于单一直径钢纤维，而且，不同直径钢纤维混杂还可显著提高水泥基材料的断裂能和弯曲韧性，普通纤维增强水泥基材料断裂破坏时裂缝为沿切口开展的单一贯穿裂缝，而混杂钢纤维增强的试件破坏时切口附近呈现多缝开裂的现象，采用适当体积比的两种尺度钢纤维混杂增强基体，制备出了综合力学性能优越的混杂钢纤维增强水泥基材料。