A Geometry Model for Tortuosity of Flow Path in Porous Media

A simple geometry model for tortuosity of flow path in porous media is proposed based on the assumption that some particles in a porous medium are unrestrictedly overlapped and the others are not. The proposed model is expressed as a function of porosity and there is no empirical constant in this model. The model predictions are compared with those from available correlations obtained numerically and experimentally, both of which are in agreement with each other. The present model can also give the tortuosity with a good approximation near the percolation threshold. The validity of the present tortuosity model is thus verified.     

关于一个三次系统的极限环数目

关于一个三次系统的极限环数目@李建华...     

解三维波方程逆散射势问题的新特征迭代法

本文提出了一种求解三维波方程在边界脉冲激发下逆散射势问题的新特征迭代法。根据文献[1]的思想,已定义了上述逆问题的非线性算子,并求出它的Frechet导算子的简洁形式。又从在边界脉冲激发下三维波方程奇异解的结果,进一步获得了上述Frechet导算子的具体表现形式即线性化积分方程,它是从在一簇旋转半椭球上的积分值去重构增量势函数的问题。那簇椭球有一个焦点固定在原点,而另一个焦点扫遍z=0的平面。这就是有趣的积分几何的问题,可恰当地而有效地运用Tiknonov的正则法去数值地解这个困难的积分几何问题,这个迭代法是稳定且有效的。     

Amino acids functionalized graphene oxide for enhanced hydrophilicity and antifouling property of poly(vinylidene fluoride) membranes

Herein, functionalized graphene oxide (GO) was prepared by the covalent functionalization with amino acids (lysine, glycine, glutamic acid and tyrosine) in this study. Zeta potential results demonstrated that covalent functionalization of GO with amino acids was favourable for their homogeneous dispersion in water and organic solvents. Based on the higher absolute value of zeta potential and the better dipersion stability of GO-lysine, the PVDF/GO-lysine hybrid membranes were then prepared via the phase inversion induced by immersion precipitation technique. SEM images showed a better pore diameter and porosity distribution on the PVDF/GO-lysine membrane surface. The zeta potential absolute value of the PVDF/GO-lysine membrane surface was higher than that of the virgin PVDF membrane. Furthermore, the PVDF/GO-lysine membranes surface exhibited good hydrophilicity. The water flux of PVDF/GO-lysine membranes can reach to two times of that of the virgin PVDF membrane. And the BSA adsorbed amount on PVDF/GO-lysine surface was decreased to 0.82 mg/cm² for PVDF/GO-lysine-8% membrane. Filtration experiment results indicated that the fouling resistance was significantly improved for the PVDF/GO-lysine membranes. As a result, lysine functionalized GO will provide a promising method to fabricate graphene oxide based hybrid membranes with effective antifouling property and hydrophilicity.     

S_2N_2环夹心配合物的MO研究

根据ＭＡＤ－ＳＣＣ－ＥＨＭＯ法的计算结果,用衡量相对稳定性的三个指标：稳定化能、ＨＯＭＯ－ＬＵＭＯ能隙和重迭集居比较了无机环Ｓ２Ｎ２与有机环的夹心和半夹心配合物的相对稳定性,并用碎片分子轨道法讨论了Ｓ２Ｎ２环分子轨道与过渡金属ｄ轨道间的相互作用以及配合物的成键情况和电子结构．     

电容式MEMS环形振动陀螺结构设计及加工

微机械环形振动陀螺仪采用四波腹工作原理,具有精度高、抗冲击性能好等优点。通常情况下为了提高电容值和信噪比,环形结构会采用高深宽比方案,因此带来的footing效应直接影响了结构加工的成品率。本文在设计环形结构的基础上提出了一种在硅下表面溅射一层Al金属层的方法,能够避免footing效应的发生。实验结果表明,该方法有效提高了结构加工精度。同时,为了验证所设计结构的正确性,对加工出的结构进行了扫频测试,结构驱动模态谐振频率与设计值相差仅0.13%,并在此基础上搭建了测控系统,进一步进行了静态实验,结果表明其零偏稳定性指标为101(°)/h证明了设计和加工的可行性。     

超高效液相色谱-串联质谱法测定浓缩苹果汁中的熊果苷

建立浓缩苹果汁样品中熊果苷的固相萃取-超高效液相色谱-串联质谱(SPE-UPLC-MS/MS)检测方法。浓缩苹果汁样品用水溶解、过滤后,用聚苯乙烯-二乙烯基苯共聚物(PS-DVB)固相萃取柱净化,外标法定量。测定时用Eclipse Plus C18色谱柱(100 mm×2.1 mm, 1.8 μm)分离,甲醇-水系统梯度洗脱;MS测定采用多反应监测(MRM)模式。熊果苷的检出限为0.02 mg/L,在0.04～2.0 mg/L的范围内标准溶液的峰面积与质量浓度呈良好的线性关系,回收率为75.2%～102.7%,相对标准偏差(RSD)低于8.9%。该方法简便、快速、灵敏,可用于浓缩苹果汁样品中熊果苷的检测和确证。     

同步荧光光谱法测定石油中的晕苯

用苯做溶剂对原油样品进行逐级稀释,恒波长同步荧光法对原油样品中晕苯进行定性、定量分析。分别从溶剂选择、波长差、狭缝宽度等参数对其测定的光谱条件进行优化。实验结果表明：用苯为溶剂、Δλ=6nm,狭缝宽度为2.5nm,为原油样品中晕苯的最佳测试条件。所建立方法测定晕苯的线性范围为0.5—100μg/mL,校准曲线的相关系数r大于0.99,相对标准偏差小于3%（n=5）。该法分析快速、准确,对石化工厂中对原油样品中晕苯的快速检测具有一定的应用价值。     

侧链含炔丙基的PLGA-PEG-PLGA三嵌段共聚物的合成与表征

通过简单易行的技术路线合成了炔丙基化乙交酯单体,以1,4-二甲氨基吡啶为催化剂,亲水性和生物相容性良好的聚乙二醇为大分子引发剂,在较滥条件下引发炔丙基化乙交酯和丙交酯的开环共聚,制备了侧链含炔丙基的聚(乳酸-羟基乙酸)-聚乙二醇-聚(乳酸-羟基乙酸)(PLGA-PEG-PLGA)三嵌段共聚物,并对产物的组成与结构进行了表征.为生物孤犊触乳聚酯的分子修饰、生物相容性的提高探索一条简单而有效的途径     

固相萃取-高效液相色谱法测定辣椒中甲基硫菌灵的残留量

甲基硫菌灵的化学名称为1,2-双(3-甲氧羰基-2-硫脲基)-苯,是内吸性杀菌剂,对蔬菜、水果、麦类等的真菌病害有良好的防治效果。它在生物体内和环境中不稳定,因而增加了测定的难度。已报道的分析方法有生物测定法、紫外分光光度法、气相色谱法和液相色谱法。这些方法的样品前处理繁琐,有机溶剂用量多,分析时间长。本文采用中性氧化铝固相萃取小柱净化样品,