Kinetic studies of antimony and selenium atomization processes including a chemical modifier during their determination by electrothermal atomic absorption spectrometry

We have studied antimony and selenium atomization processes including a chemical matrix modifier (palladium-containing activated carbon) during their determination by electrothermal atomic absorption spectrometry. We have developed and fine-tuned an experimental setup for determining the kinetic characteristics (activation energy and frequency factor) for element atomization processes from measurements in the initial section of the analytical signal. We provide a rationale for the most likely mechanism for the interactions that occur. The results of the kinetic studies of the atomization processes showed that the modifier we developed was highly effective, as a result of formation of a thermally stable condensed system C-Pd-A (where A is the analyte). __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 530–534, July–August, 2006.     

高折射率椭圆芯布拉格光纤的偏振特性

应用带完全匹配层边界条件的全矢量有限元方法,分析了高折射率椭圆芯布拉格光纤的偏振特性,详细讨论了光纤结构参量对模式双折射度以及群速度走离的影响,结果发现:高折射率椭圆芯布拉格光纤的模式双折射度可达10-2量级,比传统保偏光纤至少高出一个量级,并且表现出不同于传统保偏光纤的群速度走离特性;在保持较高双折射度的同时,通过合理的结构设计,可在一定的波长处灵活地获得较大的群速度走离或零走离特性,具有重要的潜在应用价值;最后,简要分析了低折射率区域的折射率变化对偏振特性的影响;研究结果有助于设计高性能的微结构保偏光纤。     

高双折射微结构光纤特性的研究

采用基于单轴各向异性完美匹配层吸收边界的频域有限差分方法研究一种椭圆芯高双折射微结构光纤的特性.通过计算,分析了空气孔尺寸和孔距对模式双折射、泄漏损耗以及模式截止波长的影响;综合研究了双折射微结构光纤的几种特性及其相互之间的影响和制约关系;并首次采用有效面积的方法研究高双折射微结构光纤的模式截止特性,分析单模传输条件;从而为高双折射微结构光纤的设计提供了一定的理论依据.     

碳纳米管辐射太赫兹波的理论分析与数值验证

基于简单紧束缚方法理论,利用一维碳纳米管的量子化周期边界条件得到了碳纳米管的电子能级结构关系.并结合已报道的碳纳米管中电子与声子相互作用的实验结果,得到了碳纳米管能够辐射太赫兹波的结论.通过数值结果验证了碳纳米管在外场作用下能够产生太赫兹波,并对数值计算结果中太赫兹波的振荡现象给予合理的解释.其结果为进行碳纳米管产生太赫兹辐射的实验研究提供深入的理论基础. 关键词： 太赫兹波 碳纳米管     

磁性碳纳米管吸附去除水中甲基橙的研究

采用高温催化裂解法制备碳纳米管,对其用浓硝酸氧化法进行纯化处理,并用化学共沉淀方法制备了磁性碳纳米管(简称磁性管)。利用场发射扫描电子显微镜对磁性管进行了表征。将磁分离技术应用于碳纳米管吸附性能研究,探索碳纳米管负载磁性颗粒后对甲基橙的吸附性能,寻找最佳实验条件,对吸附质溶液进行紫外-可见吸收光谱分析。同时,进行了磁性管的脱附和再吸附性能研究。     

Characterization of hydrogenated amorphous carbon thin films by end-Hall ion beam deposition

Pure hydrogenated amorphous carbon (α-C:H) and nitrogen doped hydrogenated amorphous carbon (α-C:H:N) thin films were prepared using end-Hall (EH) ion beam deposition with a beam energy ranging from 24 eV to 48 eV. The composition, microstructure and mechanical properties of the films were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning probe microscopy (SPM), and nano-scratch tests. The films are uniform and smooth with root mean square roughness values of 0.5-0.8 nm for α-C:H and 0.35 nm for α-C:H:N films. When the ion energy was increased from 24 eV to 48 eV, the fraction of sp³ bonding in the α-C:H films increased from 36% to 55%, the hardness increased from 8 GPa to 12.5 GPa, and the Young's modulus increased from 100 GPa to 130 GPa. In the α-C:H:N films, N/C atomic ratio, the hardness and Young's modulus of the α-C:H:N films are, 0.087, 15 and 145 GPa, respectively. The results indicate that both higher ion energy and a small amount of N doping improve the mechanical properties of the films. The results have demonstrated that smooth and uniform α-C:H and α-C:H:N films with large area and reasonably high hardness and Young's modulus can be synthesized by EH ion source.     

Absence of field anisotropy in the intrinsic ferromagnetic signals of highly oriented pyrolytic graphite

We have measured the magnetization of bulk samples of highly oriented pyrolytic graphite (HOPG) at magnetic fields applied parallel and perpendicular to the graphene layers. Within experimental error the intrinsic ferromagnetic signals of the samples show similar magnetic moments at saturation for the two magnetic field directions, in contrast to recently published data (J. ?ervenka et al., Nat. Phys. 5 (2009) 840). To check that the SQUID device provides correctly the small ferromagnetic signals obtained after subtracting the 100 times larger diamagnetic background, we have prepared a sample with a superconducting Pb-film deposited on one of the HOPG surfaces. We show that the field dependence of the measured magnetic moment and after the background subtraction is highly reliable even in the sub-μ emu range providing the real magnetic properties of the embedded small ferromagnetic and superconducting signals.     

Akhmediev breather evolution in optical fiber for realistic initial conditions

We study numerically Akhmediev breather dynamics in optical fibers under initial conditions that do not correspond to an ideal infinitesimal modulation on a plane wave. We examine two modifications that are commonly encountered in realistic experiments: (i) a finite-amplitude (not necessarily weak) initial modulation; (ii) the use of pulsed excitation. In the first case, we derive an expression for the propagation distance required to generate a train of compressed breather pulses. In the second case, we show that breather dynamics with pulsed excitation can be interpreted in terms of local breather states at different points on the pulse envelope.     

一种新型多芯-双模-大模场面积光纤的设计和分析

提出了一种新型双空气孔多芯-双模-大模场面积光纤结构, 计算了其模场分布、基模有效面积及弯曲损耗特性, 分析了各结构参量对其有效折射率及有效面积的影响. 这种结构在增大有效面积的同时使得二阶模的TE₀₁, TM₀₁模截止, 实现双模传输, 基模有效面积约为1044 μm².调整其结构参量, 甚至可以达到单模传输.这种结构制作简单、设计灵活, 可用于高速大容量无源光纤及有源器件中.合理设计各结构参量, 可以使有效面积达到3512 μm²甚至更高, 从而满足光通信领域中大容量、高功率传输等实际应用的需求. 关键词： 多芯光纤 双模 大模场面积 弯曲损耗     

利用光反射精确测量亚共析碳钢的含碳量

本文从光学角度出发提出了一种经济实用、精度高的测量亚共析碳钢中碳的含量的新方法。阐述了该方法的测量原理，即以金相试样表面对光的反射程度来判定其含碳量，并给出了有关经验公式及数据处理方法。