不同种植方式对陆生植物去除富营养化水体中磷的影响

以陆生植物美人蕉（Canna generalis）、紫背万年青（Rhoeo discolor）为对象,研究了其不同的种植方式对净化富营养化水体中磷的影响．结果表明,美人蕉、紫背万年青的双倍生物量组对水体中TP、DTP和DIP的去除率与它们的单倍生物量组呈显著性差异,植物对水体中P的去除效果随着植物生物量的适度增加而提高．两种陆生植物的复合种植体系对TP、DTP和DTP的去除率和单一种植体系差别不明显,说明美人蕉、紫背万年青的不同种植体系对水体中TP、DTP和DIP去除率的影响不大．从美人蕉、紫背万年青去除水体中TP、DTP和DIP的动态过程拟合模型可以看出各植物处理组对水体中不同形态P有良好的去除效应．     

反应扩散系统中波传播的锁频现象

在空间延展系统中,当增强外部光强时,作者观察到波传播的N∶N-1(N≥2)锁频现象.此现象是在光敏BZ反应实验中观察到的.通过构建一个映射函数,发现在波周期和外部光强的关系中存在魔鬼阶梯,并且此阶梯与实验数据相吻合.     

锯齿型石墨烯带缺陷改性方法研究

采用基于密度泛函理论的非平衡格林函数, 对具有不同缺陷构型的锯齿型石墨烯带(zigzag graphene nanoribbon, ZGNR) 的输运性质进行了理论计算与模拟. 研究表明, 相同数目、 不同构型缺陷结构对ZGNR的导电特性将产生不同的影响. 如A-B构型双空缺对ZGNR电导的影响最为显著, 而A-A构型双空缺对其电导的影响最小. 更为重要的是, 当引入碳环构型缺陷时, ZGNR将被改性, 即由原本的金属性质转变为半导体性质, 为缺陷调控石墨烯导电特性提供了理论依据.     

基于模态振型的载荷转换计算方法

在航空领域,将翼面载荷准确施加到结构有限元模型上是有限元响应计算的必要步骤之一,但计算流体力学 (computational fluid dynamics,CFD) 得到的气动载荷通常无法直接施加至有限元模型。目前翼面载荷的转换计算方法依然存在计算效率不高的问题。由于翼面载荷分布具有连续、光滑的特点,理论上可用合理的基函数加权叠加进行拟合。本文试用模态振型作为基函数拟合载荷,先针对气动与结构两种网格构建同一翼面的两个结构模型,这两个结构模型理论上具有相同的模态。再用气动网格构建的翼面模型的模态振型作为基函数,并基于模态截断理论近似拟合CFD端的翼面载荷,得到拟合函数的权系数。最后,利用该权系数并根据结构网格构建的翼面模型的模态振型,拟合得到气动性能计算和有限元法（finite element method,FEM）端的翼面载荷。通过一个算例进行计算验证,以合力与压心来评价载荷转换的精度,结果表明,此法具有较高的计算精度与速度。

     

Fabrication of extreme wettability patterns with water-film protection for organic liquids

Selective fabrication of superhydrophilic (S-philic) region on a superhydrophobic (S-phobic) surface requires complex technology and high cost, which has limited applications of extreme wettability patterns. In this paper, a twice-chemical-etching approach without special modification is used to prepare the extreme wettability patterns. Superhydrophobicity and superhydrophilicity can be successfully achieved after twice chemical etching for 20 seconds. The obtained patterns can maintain their extreme wettability for at least 30 days. Functional platforms with single-S-philic and multi-S-philic regions are fabricated to manipulate water and various organic liquids with water-film protection in an air environment.     

Dependency distance: A new perspective on syntactic patterns in natural languages

Dependency distance, measured by the linear distance between two syntactically related words in a sentence, is generally held as an important index of memory burden and an indicator of syntactic difficulty. Since this constraint of memory is common for all human beings, there may well be a universal preference for dependency distance minimization (DDM) for the sake of reducing memory burden. This human-driven language universal is supported by big data analyses of various corpora that consistently report shorter overall dependency distance in natural languages than in artificial random languages and long-tailed distributions featuring a majority of short dependencies and a minority of long ones. Human languages, as complex systems, seem to have evolved to come up with diverse syntactic patterns under the universal pressure for dependency distance minimization. However, there always exist a small number of long-distance dependencies in natural languages, which may reflect some other biological or functional constraints. Language system may adapt itself to these sporadic long-distance dependencies. It is these universal constraints that have shaped such a rich diversity of syntactic patterns in human languages.     

Experimental study on oil–water flow in horizontal and slightly inclined pipes

Oil–water two-phase flow experiments were conducted in a 15 m long, 8.28 cm diameter, inclinable steel pipe using mineral oil (density of 830 kg/m³ and viscosity of 7.5 mPa s) and brine (density of 1060 kg/m³ and viscosity of 0.8 mPa s). Steady-state data on flow patterns, two-phase pressure gradient and holdup were obtained over the entire range of flow rates for pipe inclinations of −5°, −2°, −1.5°, 0°, 1°, 2° and 5°. The characterization of flow patterns and identification of their boundaries was achieved via observation of recorded movies and by analysis of the relative deviation from the homogeneous behavior. A stratified wavy flow pattern with no mixing at the interface was identified in downward and upward flow. Two gamma-ray densitometers allowed for accurate measurement of the absolute in situ volumetric fraction (holdup) of each phase for all flow patterns. Extensive results of holdup and two-phase pressure gradient as a function of the superficial velocities, flow pattern and inclinations are reported. The new experimental data are compared with results of a flow pattern dependent prediction model, which uses the area-averaged steady-state two-fluid model for stratified flow and the homogeneous model for dispersed flow. Prediction accuracies for oil/water holdups and pressure gradients are presented as function of pipe inclination for all flow patterns observed. There is scope for improvement for in particular dual-continuous flow patterns.     

Visualized study on specific points on demand curves and flow patterns in a single-side heated narrow rectangular channel

A simultaneous visualization and measurement study on some specific points on demand curves, such as onset of nucleate boiling (ONB), onset of significant void (OSV), onset of flow instability (OFI), and two-phase flow patterns in a single-side heated narrow rectangular channel, having a width of 40 mm and a gap of 3 mm, was carried out. New experimental approaches were adopted to identify OSV and OFI in a narrow rectangular channel. Under experimental conditions, the ONB could be predicted well by the Sato and Matsumura model. The OSV model of Bowring can reasonably predict the OSV if the single-side heated condition is considered. The OFI was close to the saturated boiling point and could be described accurately by Kennedy’s correlation. The two-phase flow patterns observed in this experiment could be classified into bubbly, churn, and annular flow. Slug flow was never observed. The OFI always occurred when the bubbles at the channel exit began to coalesce, which corresponded to the beginning of the bubbly–churn transition in flow patterns. Finally, the evolution of specific points and flow pattern transitions were examined in a single-side heated narrow rectangular channel.     

Flow pattern characterization for R-245fa in minichannels: Optical measurement technique and experimental results

An optical measurement method using image processing for two-phase flow pattern characterization in minichannel is developed. The bubble frequency, the percentage of small bubbles as well as their velocity are measured. A high-speed high-definition video camera is used to measure these parameters and to identify the flow regimes and their transitions. The tests are performed in a 3.0 mm glass channel using saturated R-245fa at 60 °C (4.6 bar). The mass velocity is ranging from 100 to 1500 kg/m² s, the heat flux is varying from 10 to 90 kW/m² and the inlet vapor quality from 0 to 1. Four flow patterns (bubbly flow, bubbly–slug flow, slug flow and annular flow) are recognized. The comparison between the present experimental intermittent/annular transition lines and five transition lines from macroscale and microscale flow pattern maps available in the literature is presented. Finally, the influence of the flow pattern on the heat transfer coefficient is highlighted.