含联芴烯单元共轭聚合物的合成及表征

以六羰基钨[W(CO)₆]为催化剂, 合成了聚吲哚芴(P1)、 聚梯型四苯(P2)、 聚梯型五苯(P3)和小分子9-联吲哚芴烯(S1).该类聚合物的重复单元含有联芴烯结构, 通过芴9位的双键连接. 光学和电化学等实验结果表明, 聚合物无荧光发射, 是一类窄带隙的共轭聚合物, 其中聚合物P1薄膜的紫外吸收值最大波长为710 nm.     

Above-Threshold Dissociation of HD+ in Femtosecond Laser Field

The above-threshold dissociation （ATD） of the HD＋ molecular ion in femtosecond laser field is investigated theoretically. The energy-dependent distribution of the dissociated fragments is calculated using an asymptoticflow expression in the momentum space. The calculations show that the ATD of HD＋ is sensitive to the initial vibrational level of ground electronic state. Multiphoton ATDs can be observed in the dissociation processes. The dynamics phenomena are interpreted by using the concept of light-dressed potential.     

不用固定规范的微扰论

本文建议从趋向平衡的Langevin方程出发,建立量子场论的微扰展开.文中证明了这种表述可用于规范理论,无需固定规范就能正确算出规范不变的量.文中还给出了简单例子的计算细节,并讨论了Langevin方程的微扰解趋向平衡的速率.     

Capacity improvement of mechanically and chemically treated Sri Lanka natural graphite as an anode material in Li-ion batteries

Sri Lanka natural graphite is found in various morphologies with different structural and physical characteristics. The most abundant morphology, the shiny–slippery–fibrous graphite found in Bogala mines (BSSI), has a very high purity of more than 98% and high crystallinity. Pure natural graphite as well as mechanically ball-milled and chemically oxidated in air or with (NH₄)₂S₂O₈ graphite has been evaluated as an anode material for Li-ion battery application, with a focus on improvement of the reversible capacity. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006.     

A new approach to variable selection in least squares problems

The title Lasso has been suggested by Tibshirani (1996) as acolourful name for a technique of variable selection which requiresthe minimization of a sum of squares subject to an l₁ bound on the solution. This forces zero components in the minimizingsolution for small values of . Thus this bound can functionas a selection parameter. This paper makes two contributionsto computational problems associated with implementing the Lasso:(1) a compact descent method for solving the constrained problemfor a particular value of is formulated, and (2) a homotopymethod, in which the constraint bound becomes the homotopyparameter, is developed to completely describe the possibleselection regimes. Both algorithms have a finite terminationproperty. It is suggested that modified Gram-Schmidt orthogonalizationapplied to an augmented design matrix provides an effectivebasis for implementing the algorithms.     

MXenes复合材料的发展:界面调控及结构设计

MXenes作为一类新兴的二维材料, 因具有独特的亲水性、 优异的力学性能、 丰富的表面官能团、 高导电率、 光热以及光电效应等性能而成为研究热点, 广泛应用在电磁屏蔽、 电化学储能、 生物医药、 分离、 传感器和海水淡化等领域. 虽然MXenes具有这些优异的性能, 但是其存在的与疏水性高分子相容性差、 带负电的官能团阻碍电解质运输及易氧化等问题限制了其实际应用. 近年来, 通过对MXenes进行界面调控以解决其固有缺陷, 并在此基础上对MXenes进行针对性的结构设计以提升界面稳定性, 其性能得到了进一步提升. 本文对MXenes复合材料发展过程中在界面调控和结构设计方面的研究进展进行总结, 并重点介绍了MXenes的结构和性质及MXenes在复合材料中的界面调控手段, 对MXenes复合材料的结构设计进行了阐述, 并对MXenes复合材料的发展前景进行了展望.     

Bound states of schrödinger equations with electromagnetic fields and vanishing potentials

We study the bound states to nonlinear Schrödinger equations with electro-magnetic fields $\text{i}h\frac{?\psi }{?t}={(\frac{h}{i}?-A(x))}^2\psi +V(x)\psi -K(x){|}^{p-1}\psi =0,\text{on}{?}_{+}\times {?}^N$. Let $G(x)={[V(x)]}^{\frac{p+1}{p-1}-\frac{N}{2}}{[K(x)]}^{-\frac{2}{p-1}}$ and suppose that G(x) has k local minimum points. For h > 0 small, we find multi-bump bound states ψh(x,t) = _e^?lEt/^h_Uh(χ) with Uh concentrating at the local minimum points of G(x) simultaneously as h → 0. The potentials V(x) and K(x) are allowed to be either compactly supported or unbounded at infinity.     

超支化高分子结构和聚集态研究的新进展

超支化高分子上具有大量的活性末端基,对这些末端基的修饰和功能化会使其聚集态结构发生变化.文中针对超支化高分子所具有的独特结构和性能特点,概述了超支化高分子的构象结构和聚集态结构的研究现状,系统讨论了超支化高分子的支化度、分子量分布、空间尺度、玻璃化转变温度和特性粘度等分子结构参数,并在此基础上介绍了超支化高分子的物理化学性质和分析表征方法,同时综述了国内外学者在该领域的贡献,展望了该领域的研究进程和发展前景.     

质子交换膜燃料电池动态特性数值分析

本文基于CFD手段计算分析了质子交换膜燃料电池在启动过程、负载突变两种工况下的动态响应特性,与实验结果进行了对比,分析了其影响因素.分析了燃料电池动态工况下膜内含水量、极板电流和阴极扩散层水饱和度三个参数在负载变化时的响应速度,认为膜内含水量、极板电流在2s左右即可达到平衡,而阴极扩散层水饱和度需较长时间才能达到平衡.     

Aquaphotomics Research of Cold Stress in Soybean Cultivars with Different Stress Tolerance Ability: Early Detection of Cold Stress Response

The development of non-destructive methods for early detection of cold stress of plants and the identification of cold-tolerant cultivars is highly needed in crop breeding programs. Current methods are either destructive, time-consuming or imprecise. In this study, soybean leaves’ spectra were acquired in the near infrared (NIR) range (588–1025 nm) from five cultivars genetically engineered to have different levels of cold stress tolerance. The spectra were acquired at the optimal growing temperature 27 °C and when the temperature was decreased to 22 °C. In this paper, we report the results of the aquaphotomics analysis performed with the objective of understanding the role of the water molecular system in the early cold stress response of all cultivars. The raw spectra and the results of Principal Component Analysis, Soft Independent Modeling of Class Analogies and aquagrams showed consistent evidence of huge differences in the NIR spectral profiles of all cultivars under normal and mild cold stress conditions. The SIMCA discrimination between the plants before and after stress was achieved with 100% accuracy. The interpretation of spectral patterns before and after cold stress revealed major changes in the water molecular structure of the soybean leaves, altered carbohydrate and oxidative metabolism. Specific water molecular structures in the leaves of soybean cultivars were found to be highly sensitive to the temperature, showing their crucial role in the cold stress response. The results also indicated the existence of differences in the cold stress response of different cultivars, which will be a topic of further research.