Synthesis and thermal stability of W-doped VO2 nanocrystals

Pure and W-doped vanadium dioxide nanocrystals have been synthesized by using V₂O₅ and oxalic acid as precursors via a thermolysis method. The VO₂ nanocrystals have a nearly spherical morphology with size ranging from 50 to 100 nm. The metal-insulator transition (MIT) temperature of the nanocrystals decreases with increasing W-doping content. The successive heat-induced fatigue character of the MIT in W-doped VO₂ nanocrystals was investigated by DSC analysis together with structural study, and a high stability upon heating–cooling cycles was found with respect to MIT temperature, peak temperature and latent heat of the phase transition.     

Silicon nanostructures fabricated by Au and SiH4 co-deposition technique using hot-wire chemical vapor deposition

In this study, the fabrication of Si nanostructures by Au and SiH₄ co-deposition technique using hot-wire chemical vapor deposition was demonstrated. A high deposition rate of 2.7 nm/s and a high density of silicon nanostructures with a diameter of about 140 nm were obtained at T_s of 250 °C. An increase in T_s led to a significant reduction in the size of the nanostructures. However, coalescence on the nanostructures was observed at T_s of 400 °C. The Si nanostructures exhibited a highly crystalline structure, which was induced by Au crystallites. The crystallite size and crystallinity of the Si nanostructures amplified with the increase in T_s. The presence of nanostructures enhanced the surface roughness of the samples and clearly reduced the reflection, especially in the visible region.     

大城市历史城区绿色交通发展对策

以大城市历史城区道路交通需求与供给特征为切入点,对其存在的交通问题进行分析可知,发展绿色交通是大城市历史城区改善和解决交通拥堵问题的必由之路.在绿色交通理念指导下,历史城区的交通发展应重点关注道路通行能力与需求匹配问题,合理分配路权,引导路网分流,疏导过境交通,注重对信息化和智能化等技术的综合应用.     

不等肢配箍钢筋混凝土矩形截面柱双向受剪试验研究

为了解两向不等肢配箍普通钢筋混凝土柱在双向受剪作用下的受力性能,设计了8根试验柱.通过低周反复加载试验,详细描述了试件的整个试验过程,分析了试件的滞回特性以及承载力和变形性能.试验结果表明,双向受剪柱表现出明显的空间受力特性.各试件的屈强比、变形等性能体现了试件具有良好抗震性能.     

Dynamic modeling and simulation of electrodynamic tether system in stationkeeping phase

Dynamics is one of the fundamentally important aspects of all space tether research. This paper derives the dynamic equations of electrodynamic tether system (EDT) in stationkeeping phase using Newton’s laws. This paper further analyzes the tether system motion rules under electrodynamic drag, gravity induced force, and tether tension. Numerical simulation of electrodynamic tether system in station-keeping phase is calculated using an approach that combines the central difference method, fourth-order Runge-Kutta method, and predictor-corrector method, among others. The simulation results show that the motion of electrodynamic tether in stationkeeping phase not only contains librations caused by the motion of endmass, but also contains vertical and longitudinal vibrations of tether. If the motion of endmass is ignored, it is much similar to the vibration of cable with two immovable pinned-supports, in which the mid-span has the largest amplitude of vibration. Based on this, the main satellite and the endmass at both ends of tether can be treated as immovable pinned-supports when the tether vibration and tension of electrodynamic tether system in impermanency are investigated.     

Phytoplankton development and ecological status during a cyanobacterial bloom in a tributary bay of the Three Gorges Reservoir, China

Reservoirs can provide suitable conditions for cyanobacterial bloom development, which may impact on water quality and biological communities. Weekly surveys in a cyanobacterial bloom process were carried out in the mainstream and Xiangxi Bay of the Three Gorges Reservoir (China), from June 6 to July 18 in 2008. By application of the phytoplankton functional group approach, the spatiotemporal pattern, impact factors, and the ecological status based on Q index (assemblage index) were analyzed. The depth of euphotic layer was apparently the key factor driving the phytoplankton functional group variations. Longitudinal patterns of phytoplankton distribution were detected during this bloom: in the beginning phase, groups D (mainly Stephanodiscus hantzschii) and B (Cyclotella stelligera) dominated in the mainstream of the Three Gorges Reservoir and the mouth area of Xiangxi Bay, group Y (Cryptomonas species) dominated in the upper area, while groups J (mainly Pediastrum duplex), F (mainly Sphaerocystis schroeteri) and G (Pandorina morum and Eudorina elegans) were important in other areas; in the mid phase, group M became absolutely dominant in the whole region; and in the ending phase, besides groups M and Y, groups X2 (Chroomonas acuta, Pyramimonas nanella, etc.) and Lo (Ceratium hirundinella) became more important in the lower and upper area respectively. Generally the ecological status was bad, temporally varied with the bloom process. No spatial difference of ecological status was found in the mainstream, while longitudinal patterns in Xiangxi Bay were detected for different phases: firstly a few sites had relatively better status than the others, then nearly all the sites were in the bad condition, and at last the status in the downstream was better than that in the upstream. The longitudinal patterns of ecological status were related to phytoplankton distribution, disturbed by jacking from the downstream and flood from the upstream of Xiangxi Bay.     

辐射供冷与贴附射流复合空调系统空气品质研究

针对辐射供冷技术存在的结露问题,提出了辐射供冷与贴附射流复合空调系统.在贴附射流空气参数选择合理的前提下,该系统不仅能避免冷辐射板表面结露,而且能将辐射板承担的冷量提高20%以上.数值模拟结果表明,该系统的空气温度、相对湿度和速度分布满足人体的舒适性要求.     

浅析中国揭开公司法人面纱制度

<正>何谓"揭开公司面纱"?这一法学术语作为一个一般性规则,直接起源于普通法国家的司法实践。简单地讲,它是关涉导致其他主体(公司债权人及其他股东)经济损失的公司股东及股东自身承担民事责任的方式。一般而言,在我国立法中,公司被拟制为具有独立民事主     

干砂地层中盾构开挖面失稳模式及土拱效应试验研究

盾构开挖面的稳定直接关系到盾构施工的安全,而国内外关于开挖面失稳模式的大型模型试验研究却很少。利用直径1m的盾构模型,对干砂地层中盾构开挖面稳定性问题进行了研究。通过对开挖面前方土体应力状态变化的监测,从土体应力变化的角度,揭示了随着土拱的形成、发挥和发展过程,开挖面经历了局部失稳和整体失稳这样一个渐进破坏的模式。将试验结果和楔体模型计算结果进行对比,对计算模型参数的选取提出了建议。     

考虑水合物分解的海底斜坡稳定计算方法研究

采用随时间变化参数的摩尔库伦本构模型和应力释放法模拟水合物分解过程中模量的软化和强度的衰化过程,开发相应计算程序并通过数值计算研究水合物分解对海底斜坡稳定与变形的影响规律。计算结果表明:本文开发的计算方法能够较好地模拟水合物分解过程,根据收敛的迭代步数可以判断斜坡在水合物分解过程中是否达到极限平衡状态;水合物分解导致的强度衰化和模量软化是海底斜坡发生水平位移和竖向沉降的主要原因。