Modulation instability scenario in negative index materials

We present an investigation of the critical frequency windows permitting modulation instability in negative index materials. The principal motivation for our analysis stems from the impact of the inevitable presence of the effective dispersive magnetic permeability in addition to the effective dielectric permittivity determining the propagation model for ultrashort pulses in negative index materials. We emphasize the influence of nonlinear dispersion terms, arising out of the combinatorial effect of the dispersive permeability with the nonlinear polarization, over the MI phenomena, the outcome of its development achieved by using linear stability analysis. Gain spectrum investigation has been carried out for both anomalous and normal dispersion regime in the focusing and defocusing cases of nonlinearity and near zero dispersion regime where higher order linear dispersive effects emerge. The results of linear stability analysis have been validated by direct numerical simulation of the governing equation using the split-step Fourier transform method. We show that second-order nonlinear dispersion opens up distinct MI windows with their appropriate conditions and unlike the first-order nonlinear dispersion term, the sign of it has got deep consequences in the modulation instability scenario.     

Cu2O-WO3复合物的制备及其光催化性质研究

采用室温液相还原法制备了Cu2O微米立方块和Cu2O-WO3复合物,利用XRD和FESEM对产物进行了表征。研究了太阳光照下氧化亚铜微米立方块对不同染料的光催化降解性能,结果表明合成产物对阴离子染料有较好的降解效果,对阳离子染料降解效果不明显。Cu2O-WO3复合物对阳离子染料亚甲基蓝的光催化活性明显高于纯的Cu2O,其中10%Cu2O-WO3复合物的光催化效果最好。借助荧光光谱分析了复合物提高阳离子染料亚甲基蓝的光催化效果的原因。     

热压罐工艺环境对于先进复合材料框架式成型模具温度场的影响

热压罐固化工艺过程中的模具温度分布对于先进复合材料成形质量影响很大。本文在之前相关文献研究的基础上,对模具温度场分布的工艺环境因素作了进一步的研究。结果表明,工艺环境因素中,风速、升降温速率对于模具型面温差影响显著,而模具在罐内的摆放位置则对模具型面温度场温差影响很小。     

SiO2/胶原水解物-聚乙烯醇杂化复合膜的制备与性能

以正硅酸乙酯(TEOS)为前驱体,采用溶胶-凝胶法原位制备了SiO2/胶原水解物-聚乙烯醇杂化复合膜(SiO2/CH-PVA杂化膜).通过溶胀、热重(TG)、红外光谱(FTIR)、扫描电镜(SEM)和拉伸实验,考察了SiO2对杂化膜性能的影响.结果表明,SiO2的引入减小了膜的平衡溶胀度,减缓了膜的溶胀速率,有效地抑制...     

新型耐高温复合反渗透膜的制备与性能

以杂萘联苯聚芳醚腈酮超滤膜为基膜,间苯二胺作为水相单体、均苯三甲酰氯作为有机相单体,通过界面聚合法制备了新型耐高温聚芳香酰胺复合反渗透膜.研究了单体浓度、反应时间对膜性能的影响,用扫描电子显微镜和红外光谱仪表征了界面聚合反应前后膜表面形貌和化学结构的变化,并对膜的耐高温性能进行了考察.随着操作温度从20℃升高到95℃,膜的脱盐率保持在97.9%,通量从7.4 L/(m~2·h)上升至31.4 L/(m~2·h);膜在沸水中煮沸至3 h,其脱盐率基本不变而通量先增加后趋于稳定,表明杂萘联苯聚芳醚腈酮复合反渗透膜具有优良的耐高温性能.     

高地温隧道施工的爆破安全技术

针对高地温隧道爆破施工条件恶劣,爆破器材不稳定的问题,通过采取综合降温措施降低施工环境温度和炮孔温度,有效解决了高温对施工人员及爆破器材不良影响的问题;根据不同温度等级设置了对应的爆破器材和装药结构,保证了爆破器材在高温环境下的稳定性;采取水压爆破和选用并簇联法的起爆网路,保证了爆破施工安全。较好地解决了桑珠岭隧道穿越高地温洞段的钻爆施工安全控制难题,对于类似工程的实施具有一定的指导作用。     

新型亚超硬—超硬材料与硬-超硬材料晕圈图的研究

文章介绍了亚超硬—超硬材料的研究进展,并从配位场理论和原子结构等方面对金刚石的高硬度、高强度进行了探讨,并对硬-超硬材料晕圈图进行了补充和修正,以期指导今后其他超硬材料的研究开发。     

Simultaneous determination of sorbic and benzoic acids in milk products using an optimised microextraction technique followed by gas chromatography

A rapid and reliable method for direct determination of sorbic and benzoic acids in milk products was developed by dispersive liquid–liquid microextraction (DLLME) and gas chromatography with flame ionisation detector (GC-FID). A response surface methodology (RSM) based on a central composite design (CCD) was applied for optimisation of the main variables, such as volume of extraction and dispersive solvents, pH and salt effect. The primary extraction of sorbic and benzoic acids were performed in 8 mL NaOH (0.1 M) in a closed-vessel system. Carrez solutions (potassium hexaferrocyanide and zinc acetate) were used for protein sedimentation. The best simultaneous extraction efficiency was identified using acetone and 1-octanal as dispersive and extraction solvents, respectively. For DLLME, central composite design resulted in the optimised values of microextraction parameters as follows: 475 µL of dispersive and 60 µL of extraction solvents, 2 g NaCl at pH 2.5. Under optimum conditions, the calibration curve was linear over the range 0.1–50 μg mL^?1 and the square of correlation coefficient (R²) was 0.9992 for sorbic acid and 0.9994 for benzoic acid. Relative standard deviation (RSD %) was 6.1% and 3.1% (n = 5) for sorbic and benzoic acids, respectively. Limits of detection were 150 ng g^?1 for sorbic acid and 140 ng g^?1 for benzoic acid and recoveries were 88% and 103.7% respectively. Good reproducibility (RSD %), short extraction time and no matrix interference were advantages of the proposed method which was successfully applied to the determination of sorbic and benzoic acids in milk products.     

超高分子量聚乙烯纤维增强中空蜂窝模压复合材料性能研究

为研制车船等壳体所用的轻质、高强复合板材,选用超高分子量聚乙烯(UHMWPE)短纤维纱,制备成单层经纬为120根/(10 cm)的平纹组织,采用多组经纱持续更替交织层的方法制成2L(1+0)型、4L(2+1)型、6L(3+2)型3种多层角联锁结构织物,采用扦插芯棒、模压成型方法制成菱形蜂窝状的热固性环氧树脂基中空板,并与2块真空吸液法制成的面板组成“三合一”复合板,同时测定了复合板材的结构特征及其平拉、平压和弯曲性能。结果表明:3种类型复合板的密度均远小于水的密度,其中6L(3+2)型最小,为0.48 g/cm³;复合板层数越多,环氧树脂越难渗透尤其是在中空板菱形交叉点处,复合板平拉、平压、抗弯曲强度则呈现递增,制成的6L(3+2)型复合板试样平压强度可达到1.03 MPa。     

石墨烯复合纤维的开发与应用

石墨烯及其复合材料近年来成为研究热点,目前对石墨烯复合纤维材料的潜在应用已有大量研究,如储能材料、转换设备、传感器、导线等。与石墨烯基气溶胶和石墨烯复合膜等多维材料相比,石墨烯复合纤维的机械性能和导电性能突出。此外,石墨烯复合纤维可以弯曲、打结,甚至织成柔性导电织物。本文综述了石墨烯复合纤维的主要制备方法、性能及应用,并对这一领域的发展进行了展望。