梳型聚合物在固液界面吸附形态的Monte Carlo模拟

采用Monte Carlo模拟方法对PAA/PEO梳型聚合物在固液界面吸附形态进行了模拟,得到了聚合物在液相中聚集形态以及在固液界面上吸附形态的瞬时构型,同时获得了聚合物的吸附层厚度、均方回转半径和吸附在固液界面的各种链段数等微观信息. 结果证实：随着聚合物的接枝数Np增大,聚合物在液相中的扩散系数逐渐降低、相对粘度逐渐增大;当Np≥6时,羧基阴离子基团置于吸附层最外围,吸附层厚度近似等于PEO侧链长度,聚合物在固体表面形成空间排斥为主、静电排斥为辅的吸附状态;吸附聚合物分子密度过低或过高均不能起到良好的空间屏蔽或阻隔效应;吸附在固体粒子表面聚合物应该具有适宜的吸附-脱附自平衡能力.     

微通道背板热管系统最佳充液率实验研究

为研究不同工况和工质对微通道背板热管系统最佳充液率的影响,设计系统充液率实验,通过分析充液率对换热量、背板竖向出风温度分布、蒸发器及冷凝器进出口工质温度及压力的影响,确定不同条件下的系统最佳充液率。结果表明:1)标准工况下,采用R22工质的系统最佳充液率为65%~75%,背板竖向各位置出风温度最低,蒸发器进出口工质温差达到最小;2)系统最佳充液率随着背板进风温度的上升而增大,进风温度超过40℃后,最佳充液率保持不变;3)系统最佳充液率随冷凝器进水温度的降低而增大;4)R134a系统和R22系统最佳充液率基本一致,最大换热量不同。     

分子印迹电化学传感器的制备及其快速检测饮水中草甘膦残留的应用研究

以吡咯(Py)为功能单体,草甘膦(Gly)为模板,采用电化学聚合法构建了草甘膦分子印迹电化学传感器。通过循环伏安法(CV)、差分脉冲伏安法(DPV)、电化学交流阻抗法(EIS)对印迹电极性能进行了表征,筛选了印迹电极的聚合体系和模板分子的洗脱方法,优化了检测体系的p H值和吸附时间等。结果表明,以铁氰化钾为电活性探针,在最优检测体系中该印迹传感器对草甘膦具有特异性快速响应、灵敏度高和稳定性好的优点,传感器的峰电流与草甘膦浓度在5~800 ng/m L范围内呈良好的线性关系,相关系数(r2)为0.981 7,检出限(S/N=3)为0.27 ng/m L。该传感器具有良好的重现性和稳定性,放置3周后对目标物的响应峰电流无明显变化。用于实际样品中草甘膦的测定,加标回收率为78.6%~99.0%,能满足现场快速检测的要求。     

Spectroscopic properties of Yb~(3+)-doped TeO_2–BaO–BaF_2–Nb_2O_5-based oxyfluoride tellurite glasses

A series of oxyfluoride glasses with the compositions of 75 mol% TeO2, 10 mol% Nb2O5,(15 mol%-x) BaO, x BaF2(x = 0 mol%, 5 mol%, 10 mol%, 15 mol%) doped with Yb2O3 were prepared by the melt-quenching method. Their emission cross-sections, fluorescence lifetimes, and gain properties were investigated by using the absorption spectra and the fluorescence decay curves. The results show that by substituting BaF2 for BaO, the emission cross-section decreases from 1.37 pm2 to 1.21 pm2, and the fluorescence lifetime increases from 0.71 ms to 0.96 ms. These properties indicate that this oxyfluoride tellurite glass may have potential uses as the Yb2O3-doped gain medium in a solid laser.     

平行板间方势阱偶极流体的结构性质研究

在密度泛函理论(DFT)框架下, 应用改进的基本度量理论(MFMT)表达硬球作用对自由能泛函的贡献, 根据统计力学理论结合加权密度近似(WDA)表达偶极作用对自由能泛函的贡献,得到了方势阱偶极流体在平行板间的密度分布表达式, 计算了偶极流体在两平行板间的密度分布, 并探讨了方势阱深度和宽度对体系密度分布的影响. 此外, 通过体系密度分布, 进一步分析了方势阱宽度和深度以及板间尺度与溶剂化力的关系.     

Improved design and construction of an ionization chamber for the CSNS beam loss monitor (BLM)

Based on the first ionization chamber (IC) prototype, the structure, working gas component and electrode material of the IC are improved. The test of the improved IC shows that the plateau length is about 2000 V, the plateau slope is less than 0.2%/100 V, the sensitivity is 19.6 pA/rad·h^-1, the up-limitation of the linearity can be up to 3.6×10⁵ rad/h, and the applied voltage can be operated to 3500 V. The test results show that the performance of the improved IC meets the requirements of the beam loss monitor.     

Interference effects on the photoionization cross sections between two neighbouring atoms: nitrogen as an example

Interference effects on the photoionization cross sections between two neighbouring atoms are considered based on the coherent scattering of the ionized electrons by the two nuclei when their separation is less than or comparable to the de Broglie wave length of the ionized electrons. As an example, the single atomic nitrogen ionization cross section and the total cross sections of two nitrogen atoms with coherently added photoionization amplitudes are calculated from the threshold to about 60~\AA (1~\AA=0.1~nm) of the photon energy. The photoionization cross sections of atomic nitrogen are obtained by using the close-coupling R-matrix method. In the calculation 19 states are included. The ionization energy of the atomic nitrogen and the photoionization cross sections agree well with the experimental results. Based on the R-matrix results of atomic nitrogen, the interference effects between two neighbouring nitrogen atoms are obtained. It is shown that the interference effects are considerable when electrons are ionized just above the threshold, even for the separations between the two atoms are larger than two times of the bond length of N₂ molecules. Therefore, in hot and dense samples, effects caused by the coherent interference between the neighbours are expected to be observable for the total photoionization cross sections.     

InGaAs/Si键合界面a-Si键合层厚度对InGaAs/Si雪崩光电二极管性能的影响

为从根本上阻断InGaAs/Si之间的失配晶格,获得低噪声的InGaAs/Si雪崩光电二极管,理论上在InGaAs/Si键合界面插入超薄a-Si键合层,彻底隔断键合界面异质晶格,同时保证InGaAs吸收层和Si倍增层超高的晶体质量和良好的电学传输.模拟了a-Si键合层厚度对InGaAs/Si雪崩光电二极管性能影响.由于...     

体外预应力混凝土梁的受弯承载力研究

体外预应力混凝土结构的受弯承载力同多种因素有关,目前还没有较好的计算方法.本文在14根体外预应力混凝土梁模型试验研究基础上,对影响受弯承载力的主要因素进行了分析,并通过对国内外主要规范的比较研究,提出了具有较高精度的体外预应力梁受弯承载力计算公式.     

基于光纤SPR光谱分析的污水降解过程监测研究

讨论了光纤表面等离子体波传感器的工作原理,并对将其用于监测以甲基橙为代表的环境污水降解过程的可行性进行了探讨。用光纤SPR传感器监测了50 mL初始浓度为30 mg·L-1的甲基橙原溶液在降解过程浓度的变化,对降解过程中光纤SPR传感器的光谱进行了详细的分析;同时采用紫外-分光光度计对降解过程中溶液浓度的变化进行了监测,并对2种方法所测的数据进行了分析对比。结果表明,光纤SPR同常规方法的测量结果一致,随着降解时间的增加,甲基橙溶液的吸光度和浓度逐渐减小,光纤SPR传感器的共振波长逐渐发生蓝移,同初始标定的甲基橙原溶液共振光谱比较,说明甲基橙逐渐被降解,且在2 h内降解率达到73%,说明用光纤SPR传感器监测污水降解过程是完全可行的。研究结果不仅为环境污水降解过程提供了一种新的监测方法,同时促进了我国SPR传感技术与环保监测研究结合,为光纤SPR技术走向实用,并最终实现产业化积累了经验。