大尺度粗糙地面的电磁散射特性

综合考虑空间区域分割、消息传递、负载平衡及同步和边界处理等因素,给出了计算随机粗糙地面电磁散射的并行时域有限差分算法流程,并在大型高性能并行机上应用。理论分析和仿真结果表明：该算法可以快速准确地计算大尺度随机粗糙地面的电磁散射特性;通过与经典解析方法的比较,验证了该算法的正确性和实用性,在大尺度情况下拟合结果更好,更能体现地面的统计特性。     

一种不同地面分辨率图像的拼接算法

航空遥感监测中变焦镜头的广泛应用以及飞行高度的变化会获得不同地面分辨率的航空影像,因此为了实时监控到飞行区域的整体情况,需要对不同地面分辨率的图像进行拼接。提出了针对不同地面分辨率图像进行拼接的方法。首先用四分法对图像进行分割,检测变化倍率,选择配准策略;然后用基于加速鲁棒性特征(Speeded-Up Robust Features,SURF)的算法对相邻图像进行拼接。获得了焦距变化从高倍过渡到低倍,或从低倍过渡到高倍的拼接图像。通过航空变焦模拟影像的拼接实验和地面变焦影像的拼接实验表明,该方法能够对不同地面分辨率的图像进行拼接,且拼接结果均以高分辨率为基准。     

Capacitance and potential coefficients at large distances

The design of capacitive sensors and devices for new and emerging applications would benefit from simple and reliable methods to estimate the capacitance between conductors in terms of the capacitance of the isolated bodies and of the distance between them. The coefficients of potential and capacitance of a pair of conductor are approximated with the first terms of an expansion formula in the inverse of their distance. The form given applies to conductors of generic shapes and position in space. A comparison with the exact value for two spheres shows agreement even for rather small distances.     

高容量超级电容器电极材料的设计与制备

超级电容器寿命长,安全性高,并可以实现快速充放电,是化学电源研究的热点之一。然而,超级电容器的能量密度较低限制了其更多的应用。因此,超级电容器领域的研究关注点在如何提高超级电容器的能量密度。其中,提高比容量是提高能量密度的一种有效途径。本文通过对电极材料和电解液的优化来研究制备得到高容量超级电容器的方法。电极材料的比表面积、孔道结构和导电性对其电化学性能有着直接的影响。一方面,通过优化电极材料的孔道结构和比表面积可以增加活性位点并提高电解液离子传导率,从而得到高比电容。另一方面,电极材料导电性的提高有利于提升其电子传导率从而得到较高的比容量。本文分别对碳材料和金属氧化物/氢氧化物的优化达到了增加双电层电容和赝电容的目的。不仅如此,还可以通过在电解液中增加氧化还原电对从而得到高比电容。这一方法为高容量超级电容器的制备提供了新的思路。     

Study of Ganga River – Groundwater Interaction Using Environmental Oxygen-18

The influent and effluent characteristics of river Ganga in the Hardwar-Narora sector in Uttar Pradesh, India was studied using environmental oxygen-18. δ¹⁸O of river water and also of groundwater close to the river course was monitored at 8 stations along the 220 km stretch for a period of ten months. δ¹⁸O of the river during the monsoon months (June to September) was about – 10 at all the stations. However, during the dry months from October to April, the δ¹⁸O of the river was enriched progressively from Hardwar to Narora. The enrichment indicated groundwater contribution to the river during the non-monsoon months. The contribution was comuted using the principle of isotope balance.     

Where the rubber meets the hand: Unlocking the sensing potential of dielectric elastomers

Practice makes perfect to some extent. Research has shown that musicians who practice the piano for long periods of time can suffer a range of hand problems from loss of control to diminished speed. Now imagine a rubber keyboard that is springy, soft, and elastic. This is the new type of input device that dielectric elastomers (DE) can create. However their usage in large sensing systems is limited by a scalability challenge. Each DE sensor is married to a pair of connection cables and electronics, adding to the complexity of the background overheads. A new efficient multi‐frequency method is presented that is capable of detecting internal pressure changes from a difference in the DE's capacitance without the need for any additional wires or connections. This effectively segments the DE into smaller sections, achieving information from a single sensor equivalent to multiple sensors. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 465–472     

PPy modified titanium foam electrode with high performance for supercapacitor

Pyrrole was polymerized on the surface of titanium foam using FeCl₃ as oxidant and the as-synthesized product could be directly used as electrode for supercapacitor. The globular polypyrrole (PPy) particles were firmly loaded on the substrate with high density. The morphology study of PPy film is observed in SEM images, the XRD, FTIR and UV–vis spectra reveal the structure and crystalline of PPy nanoparticles. The electrochemical properties of PPy modified electrode are investigated by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and cycle life techniques. The electrochemical measurements showed such a PPy–Ti electrode had a wide working potential window, a high specific capacitance of 855 F g⁻¹ and excellent cycle stability at a discharge current density of 1 A g⁻¹.     

Determination of Anionic Surfactants in Water

The use of ternary complexes in the determination of anionic surfactants has been investigated and an analytical method using linear alkyl sulfonates as a test substance has been developed. The method involves the formation of the chloroform-extractable bisphenanthroline Cu(II)-linear alkyl sulfonate (LAS) complex and the subsequent equilibration of the extract with erythrosine to form the extractable bisphenanthroline Cu(II)-erythrosine complex. In the equilibration step erythrosine displaces LAS quantitatively, allowing the determination of the LAS originally present by measuring the absorbance of the extracted bisphenanthroline-Cu(II)-erythrosine complex. Results are reported of studies made to determine the optimum analytical conditions, the sensitivity, and the precision for the method described.     

Chromatography of Uranium on High-Performance Ion Exchangers

Abstract

The potential of high-performance liquid chromatography (HPLC) for the determination of U(VI) in ground waters and urine has been examined under a variety of HPLC experimental conditions. Conventional cross-linked and bonded-phase ion exchangers, both cation and anion, were studied with aqueous mobile phases containing tartrate, citrate, or α-hydroxyisobutyrate. The best chromatography was obtained on bonded-phase cation exchangers with an α-hydroxyisobutyrate eluent. The metal ions were detected either by visible spectrophotometry after a post-column reaction with a complexing reagent, or with a polarographic detector. Dectection after post-column reaction gave the best sensitivity; the detection limit (2 × baseline noise was 6 ng or 60 ng.ml^?1 for 100 μl samples. In-line trace enrichment was used to decrease detection limits and linear calibration curves were observed in the ranges studied; 0.5 to 50 ng.mL^?1 for ground waters and 25 to 400 ng.mL^?1 for artificial urine.