拓宽思路进行课堂演示的一点尝试

介绍了利用激光器及改装的螺旋测微计在课堂上演示障碍边缘衍射，反射衍射、单缝衍射和散斑现象的方法及取得的教学效果．     

具连续变量的二阶中立型差分方程的振动性

研究一类具有连续变量的二阶中立型时滞差分方程△r^2[x（t）-cx（t-τ）=p（t）x（t-σ）的解的振动性，给出了其有界振动的几个充分条件．     

可可西里-金沙江地震带震级频度关系及其参数的相关性分析

本文通过可可西里-金沙江地震带震级频度关系的确定及其参数b值与a值、ν值(地震年平均发生率)和Mmax(最大震级a/b)之间的相关性分析, 以说明地震危险性概率分析中的地震活动性参数ν值与b值也应有某种相关性。当地震带未来一定时期内地震活动震级上限Muz和b值被确定后, 未来地震活动的ν值的取值范围似将受到一定的限制。如假设可可西里-金沙江地震带的Muz为8级, b值为0.73后, 相应的ν值若取13.943, 可能偏小。     

自适应网格加密和多重网格求解严重病态方程

本文探讨用自适应网格加密技术结合多重网格法求解由有限元离散导致的病态方程。计算结果表明；自适应多重网格有限元法是求解严重病态方程珠有效方法。     

Melt shear rheology of carbon nanofiber/polystyrene composites

The rheological behavior and morphology of carbon nanofiber/polystyrene (CNF/PS) composites in their melt phase have been characterized both through experimental measurements and modeling. Composites prepared in the two different processes of solvent casting and melt blending are contrasted; melt-blended and solvent-cast composites were each prepared with CNF loadings of 2, 5, and 10 wt%. A morphological study revealed that the melt blending process results in composites with shorter CNFs than in the solvent-cast composites, due to damage caused by the higher stresses the CNFs encounter in melt blending, and that both processes retain the diameter of the as-received CNFs. The addition of carbon nanofiber to the polystyrene through either melt blending or solvent casting increases the linear viscoelastic moduli, G′ and G″, and steady-state viscosity, η, in the melt phase monotonically with CNF concentration, more so in solvent cast composites with their longer CNFs. The melt phase of solvent-cast composites with higher CNF concentrations exhibit a plateau of the elastic modulus, G′, at low frequencies, an apparent yield stress, and large first normal stress difference, N ₁, at low strain rates, which can be attributed to contact-based network nanostructure formed by the long CNFs. A nanostructurally-based model for CNF/PS composites in their melt phase is presented which considers the composite system as rigid rods in a viscoelastic fluid matrix. Except for two coupling parameters, all material constants in the model for the composite systems are deduced from morphological and shear flow measurements of its separate nanofiber and polymer melt constituents of the composite. These two coupling parameters are polymer–fiber interaction parameter, σ, and interfiber interaction parameter, C _I. Through comparison with our experimental measurements of the composite systems, we deduce that σ is effectively 1 (corresponding to no polymer–fiber interaction) for all CNF/PS nanocomposites studied. The dependence of CNF orientation on strain rate which we observe in our experiments is captured in the model by considering the interfiber interaction parameter, C _I, as a function of strain rate. Applied to shear flows, the model predicts the melt-phase, steady-state viscosities, and normal stress differences of the CNF/PS composites as functions of shear rate, polymer matrix properties, fiber length, and mass concentration consistent with our experimental measurements.     

桩基完整性测试的非线性最小二乘优化方法

针对桩基检测中低应变反射波法存在的应力波被桩土吸收和散射而衰减问题,把包含桩土衰减系数和介质不连续界面反射系数的反射波方程转化为非线性最小二乘优化问题,并采用信赖域法进行求解。由于采用信赖域法并采用了Gauss-Newton方向定义信赖域二维子空间,具有较好的收敛速度。通过模型桩算例表明该方法是确实可行的。     

Molecularly imprinted polymers with synthetic dummy templates for the preparation of capsaicin and dihydrocapsaicin from chili peppers

In this work, dummy molecularly imprinted polymers with high selectivity and affinity to capsaicin and dihydrocapsaicin are designed using N‐vanillylnonanamide as a dummy template. The performance of dummy molecularly imprinted polymers and nonimprinted polymers was evaluated using adsorption isotherms, adsorption kinetics, and selective recognition capacity. Dummy molecularly imprinted polymers were found to exhibit good site accessibility, taking just 20 min to achieve adsorption equilibrium; they were also highly selective toward capsaicin and dihydrocapsaicin. We successfully used dummy molecularly imprinted polymers as a specific sorbent for selectively enriching capsaicin and dihydrocapsaicin from chili pepper samples. In a scaled‐up experiment, the selective recovery of capsaicinoids was calculated to be 77.8% using solid‐phase extraction. To the best of our knowledge, this is the first example of the use of N‐vanillylnonanamide as a dummy template in molecularly imprinted polymers to simultaneously enrich capsaicin and dihydrocapsaicin.     

Nafion covered core–shell structured Fe3O4@graphene nanospheres modified electrode for highly selective detection of dopamine

Nafion covered core–shell structured Fe₃O₄@graphene nanospheres (GNs) modified glassy carbon electrode (GCE) was successfully prepared and used for selective detection dopamine. Firstly, the characterizations of hydro-thermal synthesized Fe₃O₄@GNs were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. Then Fe₃O₄@GNs/Nafion modified electrode exhibited excellent electrocatalytic activity toward the oxidations of dopamine (DA). The interference test showed that the coexisted ascorbic acid (AA) and uric acid (UA) had no electrochemical interference toward DA. Under the optimum conditions, the broad linear relationship was obtained in the experimental concentration from 0.020 μM to 130.0 μM with the detection limit (S/N = 3) of 0.007 μM. Furthermore, the core–shell structured Fe₃O₄@GNs/Nafion/GCE was applied to the determination of DA in real samples and satisfactory results were got, which could provide a promising platform to develop excellent biosensor for detecting DA.     

Thermal and pH Dual Responsive Copolymer and Silver Nanoparticle Composite for Catalytic Application

N‐Isopropylacrylamide and vinyl imidazole copolymer, P(NIPAM‐co‐VI), was synthesized by free radical emulsion polymerization. Then, the copolymer and silver nanoparticle composite, P(NIPAM‐co‐VI)‐Ag, was prepared by in situ reduction of AgNO₃ with NaBH₄. Due to the coexistence of thermal‐responsive PNIPAM and pH‐responsive PVI, P(NIPAM‐co‐VI) and P(NIPAM‐co‐VI)‐Ag exhibited both thermal and pH responsibility, their size would change while altering the temperature or pH of the circumvent. Their thermal and pH dual responsive properties were studied by dynamic light scattering (DLS). P(NIPAM‐co‐VI)‐Ag could be stably dispersed in water at a pH range from 3.0 to 9.3, which is favorable to use P(NIPAM‐co‐VI)‐Ag as a catalyst in the reduction reaction of p‐nitrophenol. The reaction rate constant (k_app) increased with the decrease of pH or the increase of VI content in the copolymer.