Polystyrene‐grafted Al surface with excellent superhydrophobicity and corrosion resistance

A superhydrophobic Al surface was successfully fabricated by a facile and environmentally friendly method as the boiling water treatment and 3‐glycidoxypropyl trimethoxysilane (GPS) as well as carboxyl‐terminated polystyrene (PS‐COOH) modification. The fabrication procedure, morphology, composition, and corrosion resistance of the superhydrophobic Al surface were investigated. Results show that the treatment in the boiling water endows the Al surface with the porous and roughened structure, while the modification with GPS as well as PS‐COOH grafts the long PS chains onto the micro‐scale and nano‐scale hierarchical structure. Consequently, a superhydrophobic Al surface with a contact angle of 153.6° and a rolling angle of 3° is obtained. Additionally, a vast majority of surface area is covered by the air in the solid–liquid contact area for the superhydrophobic Al surface, and which can prevent the corrosive ions entering into the Al surface. As a result, the corrosion resistance is improved greatly. Copyright © 2015 John Wiley & Sons, Ltd.     

Joule heating monitoring in a microfluidic channel by observing the Brownian motion of an optically trapped microsphere

Electric fields offer a variety of functionalities to Lab‐on‐a‐Chip devices. The use of these fields often results in significant Joule heating, affecting the overall performance of the system. Precise knowledge of the temperature profile inside a microfluidic device is necessary to evaluate the implications of heat dissipation. This article demonstrates how an optically trapped microsphere can be used as a temperature probe to monitor Joule heating in these devices. The Brownian motion of the bead at room temperature is compared with the motion when power is dissipated in the system. This gives an estimate of the temperature increase at a specific location in a microfluidic channel. We demonstrate this method with solutions of different ionic strengths, and establish a precision of 0.9 K and an accuracy of 15%. Furthermore, it is demonstrated that transient heating processes can be monitored with this technique, albeit with a limited time resolution.     

X射线荧光光谱法测定彩涂板涂层中铅、镉和总铬

自行制备了12块校准样品,其涂层厚度和涂层中铅、镉和铬含量均按梯度分布。涂层的厚度采用GB/T 13448-2019标准所推荐的DJH法测定和定值。分析这系列样品时,测定涂层中铅、镉和总铬时用IEC 62321-5的微波法溶解后,按电感耦合等离子体原子发射光谱法定值。应用上述校正样品试验,并提出了直接测定彩涂板涂层中铅、镉和总铬含量的X射线荧光光谱法(XFS)彩涂板的基板为冷轧板,在其外表面有镀锌层。在这2种材料中都可能含有与有机涂层中待测定的含量近似的相同元素,将对测定造成干扰。此外,有机涂层中的基体元素钛及硅也对测定造成干扰。利用XRF仪器自带的薄层分析软件和基本参数法软件对上述干扰分别予以校正,使铅、镉、铬校准曲线的线性相关系数达到0.9。所提出方法测定铅、镉、铬的检出限(3s)依次为5×10^-4%,3×10^-4%,5×10^-4%。随机取3个校正样品,按所提出方法测定其中铅、镉与总铬的含量,并用IEC 62321-5标准方法进行校对分析。结果表明:两种方法的结果相互一致,所得测定值的相对标准偏差(n=6)为8.5%(铅),9.2%(镉)和11%(铬),均分别小于IEC标准方法测定值的相对标准偏差(n=6)为29%,14%,17%。本方法达到快速、准确的要求,适合用于RoHS规定对彩涂层的检量检测。     

A limit theorem for the solutions of slow-fast systems with fractional Brownian motion

A limit theorem which can simplify slow—fast dynamical systems driven by fractional Brownian motion with the Hurst parameter H inside the (1/2, 1) interval has been proved. The slow variables of the original system can be approximated by the solution of the simplified equations in the sense of mean square. An example is presented to illustrate the applications of the limit theorem.     

平面激光诱导荧光实验中激励激光的光束整形

分析了激励激光光强分布对平面激光诱导荧光（PLIF）实验中荧光强度的影响。基于柱面微透镜列阵设计了一套激光片状光束匀滑整形系统,并根据PLIF实验的具体要求,通过光线追迹方法优化了系统参数。建立了片状光束整形实验系统,对染料激光进行了匀滑整形,获得了不均匀性〈4%的均匀片状光束,满足了PLIF实验所需。在此基础上建立了PLIF实验系统,获得了酒精灯火焰和CH4/air预混火焰中OH的二维荧光分布。     

Effects of glow-discharge nitrogen-plasma on the linear birefringence of polyester sheets

A simple white light interferometric method is used to study the effects of plasma on the steady-state linear birefringence of polyester sheet films. Glow-discharge nitrogen-plasma of power 13 W with nine different exposure times from 0 to 25 min is applied to films of 0.22 mm thickness. The relationship between the linear birefringence and some atomic parameters is derived theoretically and tested experimentally. Effects on the linear birefringence, the linear retardance and Herman's orientation parameter are investigated. The increase of plasma exposure time produces an increase in the linear birefringence and Herman's orientation parameter. Characterization of plasma-treated and plasma-untreated polyester samples have been thoroughly examined using Fourier transform infrared (FTIR) spectroscopy. It is noted that no new bands have appeared after treatment for all the tested samples at different time intervals. There is an increase in intensity and band definition, and a shift of some bands that were already present in the spectrum of the untreated sample, assigned to the trans conformer.     

利用液氮冷能的小型天然气液化流程

为了简化小型天然气液化流程中的制冷装置,增加产品的收益率,设计了一种利用液氮冷能且带精馏的天然气液化流程,在得到液化天然气(LNG)的同时得到液化石油气(LPG)。采用HYSYS软件对流程进行模拟,选取P-R方程计算天然气气液相平衡特性,以生产单位质量的LNG耗功最小为目标函数进行优化,得到了关键节点参数,主要分析了塔内工作状况和换热器管路的热负荷分布情况。结果表明:塔的操作压力对产品纯度影响很大,换热器过大的温差和负荷造成了主要的火用损失,LNG回收率大于90%。     

Monotonicity properties of the Neumann heat kernel in the ball

A well-known conjecture of R. Laugesen and C. Morpurgo asserts that the diagonal of the Neumann heat kernel of the unit ball U⊂Rn is a strictly increasing radial function. In this paper we use probabilistic arguments to settle this conjecture and to prove some inequalities for the Neumann heat kernel in the ball.     

On a probabilistic approach to the Schrödinger equation with a time-dependent potential

We study, by probabilistic methods, some classes of Schrödinger equations related to time-dependent potentials, analytic with respect to the space variable.     

Exponential stability of impulsive stochastic functional differential equations

In this paper, we investigate the pth moment and almost sure exponential stability of impulsive stochastic functional differential equations with finite delay by using Lyapunov method. Several stability theorems of impulsive stochastic functional differential equations with finite delay are derived. These new results are employed to impulsive stochastic equations with bounded time-varying delays and stochastically perturbed equations. Meanwhile, an example and simulations are given to show that impulses play an important role in pth moment and almost sure exponential stability of stochastic functional differential equations with finite delay.