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81.
论述了利用光纤应力双折射效应研制的挤压式光纤电动偏振控制器的工作原理,并进行了实验验证,分析了输出光偏振态在邦加球上的轨迹及相位延迟量与各通道电压的关系。 相似文献
82.
林建强 《激光与光电子学进展》2014,51(6):60606-67
为降低偏振拍长对波长变化的敏感性,扩大多孔光纤偏振器件的工作带宽,针对一种包层空气孔呈圆形阵列分布的多孔光纤,应用全矢量有限差分光束传播法分析了不同参数的包层结构对偏振拍长及其相对变化率的影响,通过横向伸缩形变在包层中引入特定的非对称结构,这种方法不仅有效降低了偏振拍长的波长敏感性,而且偏振拍长对这些特定包层结构参数的误差微扰不敏感,在1.2~1.7 mm波长范围内,偏振拍长的相对变化率小于±4%,工作带宽达到500 nm,同时包层结构几何参数的误差容限达到0.1 mm量级,较好地兼顾了偏振拍长的宽带稳定性与多孔光纤工艺制作可行性。 相似文献
83.
84.
基于分布式压缩感知理论,提出了一种全极化逆合成孔径雷达超分辨成像算法,联合各极化通道进行超分辨处理.首先,建立全极化信号模型及超分辨字典,利用各极化通道信号的联合稀疏性将全极化超分辨成像建模为最小L2,1范数的优化问题,运用一种快速算法求解该优化问题.由于利用联合稀疏约束,多极化通道联合成像相比于单通道成像能够获得更好的超分辨性能和噪声抑制能力,最终有效提高图像极化融合的效果.同时,采用快速傅里叶变换操作提升了算法的运算效率.基于backhoe的仿真数据实验验证了该算法的优越性. 相似文献
85.
针对普通滤光片通常采用不多于3片组合方式,不能满足特殊测量范围要求的情况,利用单轴晶体的双折射效应及偏光干涉原理来研究双折射滤光片的滤光原理及其参数特性,在综合考虑各种参数的前提下,应用近似理论条件,研究设计了4片组合的石英晶体双折射滤光片,分析了设计滤光片所需要的各个参数,给出了4片组合双折射滤光片的透射曲线。此双折射滤光片的透射光谱具有透射带宽得到很大压窄、次峰的透过率被抑制在8%以下等特点。当它被用在脉冲激光器中时,具有550nm至1200nm的宽调谐范围。可以知道,设计滤光片的关键是各个参数的选取,利用法布里-珀罗干涉仪可以压窄光谱线宽。 相似文献
86.
87.
C. Jiang X. Wang R. Gunawidjaja Y.‐H. Lin M. K. Gupta D. L. Kaplan R. R. Naik V. V. Tsukruk 《Advanced functional materials》2007,17(13):2229-2237
Robust ultrathin multilayer films of silk fibroin were fabricated by spin coating and spin‐assisted layer‐by‐layer assembly and their mechanical properties were studied both in tensile and compression modes for the first time. The ultrathin films were characterized by a high elastic modulus of 6–8 GPa (after treatment with methanol) with the ultimate tensile strength reaching 100 MPa. The superior toughness is also many times higher than that usually observed for conventional polymer composites (328 kJ m–3 for the silk material studied here versus typical values of < 100 kJ m–3). These outstanding properties are suggested to be caused by the gradual development of the self‐reinforcing microstructure of highly crystalline β‐sheets, serving as reinforcing fillers and physical crosslinks, a process that is well known for bulk silk materials but it is demonstrated here to occur in ultrathin films as well, despite their limited dimensions. However, the confined state within films thinner than the lengths of the extended domains causes a significantly reduced elasticity which should be considered in the design of nanosized films from silk materials. Such regenerated silk fibroin films with outstanding mechanical strength have potential applications in microscale biodevices, biocompatible implants, and synthetic coatings for artificial skin. 相似文献
88.
89.
Pankaj Kumar Abhishek Sharma Dwijendra Pratap Singh 《Progress in Photovoltaics: Research and Applications》2013,21(5):950-959
Investigations on the effect of direction of voltage sweeps, on the current density–voltage (J–V) characteristics in polymer bulk‐heterojunction solar cells, based on the blend of poly(3‐hexylthiophene) (P3HT) and phenyl [6,6] C61 butyric acid methyl ester (PCBM), are reported with time. On the freshly prepared device, the direction of the voltage sweep did not have any effect; however, as the device started degrading, the change in direction of the voltage sweep resulted into different characteristics. Analysis beyond complete degradation, when all the photovoltaic parameters reduced to zero, revealed some interesting results. The J–V characteristics, measured with voltage sweep from −ve to +ve voltage, both in the dark and under illumination, were observed to pass through the second quadrant. On the other hand, with the change in the direction of voltage sweep, viz. from +ve to −ve voltage, the characteristics both in the dark and under illumination passed through the fourth quadrant. These results have been explained on the basis of polarization of the degraded active layer due to applied external voltage. This is an important effect and is observed to depend on the applied voltages during performance evaluation and becomes more prominent with time. This effect puts a question mark on the correctness of the method for calculation of the parameters of a degraded device. Studies on degradation of P3HT : PCBM solar cells showed that both the short circuit current density (Jsc) and the power conversion efficiency (η) decay exponentially, whereas the open circuit voltage (Voc) decays almost linearly with time. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
90.
Marijan eruga Damir Hasenay 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1996,202(4):308-312
The corrosion of aluminium (A1) in several brands of soft drinks (cola- and citrate-based drinks) has been studied, using an electrochemical method, namely potentiodynamic polarization. The results show that the corrosion of A1 in soft drinks is a very slow, time-dependent and complex process, strongly influenced by the passivation, complexation and adsorption processes. The corrosion of A1 in these drinks occurs principally due to the presence of acids: citric acid in citrate-based drinks and orthophosphoric acid in cola-based drinks. The corrosion rate of A1 rose with an increase in the acidity of soft drinks, i.e. with increase of the content of total acids. The corrosion rates are much higher in the cola-based drinks than those in citrate-based drinks, due to the facts that: (1) orthophosphoric acid is more corrosive to A1 than is citric acid, (2) a quite different passive oxide layer (with different properties) is formed on A1, depending on whether the drink is cola or citrate based. The method of potentiodynamic polarization was shown as being very suitable for the study of corrosion of A1 in soft drinks, especially if it is combined with some non-electrochemical method, e.g. graphite furnace atomic absorption spectrometry (GFAAS). 相似文献