An efficient second‐order characteristic finite element method for non‐linear aerosol dynamic equations

In the paper we consider the non‐linear aerosol dynamic equation on time and particle size, which contains the advection process of condensation growth and the process of non‐linear coagulation. We develop an efficient second‐order characteristic finite element method for solving the problem. A high accurate characteristic method is proposed to treat the condensation advection while a second‐order extrapolation along the characteristics is proposed to approximate the non‐linear coagulation. The method has second‐order accuracy in time and the optimal‐order accuracy of finite element spaces in particle size, which improves the first‐order accuracy in time of the classical characteristic method. Numerical experiments show the efficient performance of our method for problems of log‐normal distribution aerosols in both the Euler coordinates and the logarithmic coordinates. Copyright © 2009 John Wiley & Sons, Ltd.     

Effects of Anti-Oxidant Migration on Friction and Wear of C/C Aircraft Brakes

The surfaces of carbon-carbon (C/C) aircraft brakes are usually coated with anti-oxidant to protect them from oxidation. These surfaces do not include the friction surfaces since it is known that when anti-oxidant get onto the friction surface, the friction coefficient decreases. The anti-oxidant migration (AOM), however, happens during processing, heat treatment and application. In this study, phosphorus based anti-oxidants inhibited 3-D C/C aircraft brake system was investigated. The effects of their migration on friction and wear in the 3-D C/C brakes were revealed by sub-scale dynamometer tests and microscopic analysis. Dynamometer results showed that when AOM occurred, both landing and taxi coefficients decreased in humid environment and the wear was slightly lowered. Microscopic study showed that under high humidity conditions there was no formation of the friction film.     

Antireflection and band gap extension effects of ZnO nanocrystalline films grown on ITO-coated glasses by low temperature process

Zinc oxide (ZnO) nanocrystalline films coated on indium tin oxides (ITO, 90:10 wt%) glasses were prepared by low temperature process. The thin films were composed of uniform nanoparticles with average diameter around 8.4 nm. All samples exhibited excellent optical antireflective phenomena, and the maximum transmission reached 92.8% for the sample spin coated at 1500 rpm at 453 nm, improved by 21.5%. The antireflective results were explained by the coherence theory. And the antireflective effects were induced by the ITO and ZnO films. The calculated thicknesses of the ZnO films agreed well with the experimental results. The theoretical calculated band gap from the average diameter of ZnO nanoparticles was also well consistent with the experimental ones obtained from the optical transmission spectra. This result was promising for applications in organic solar cells.     

往复副螺棱高度对单螺杆挤出机内混合行为的影响

建立了带有扰动副螺棱的单螺杆均化段数学模型,探讨了不同副螺棱高度对混合的影响。将有限体积方法与叠加网格技术相结合,得到了螺槽内牛顿流体三维等温周期性速度场。采用4阶Runge-Kutta方法进行流体前锋追踪计算,得到了粒子群及示踪剂界面混合行为。Poincaré截面揭示了混沌混合在螺槽横截面内呈现"8"字形带状分布,内外分别被准周期运动区域填充。副螺棱高度越大,混沌混合区域所覆盖的尺度越大,混合能力越好。     

Ultraviolet-visible and surface-enhanced Raman scattering spectroscopy studies on self-assembled films of ruthenium phthalocyanine on organic monolayer-modified silver substrates

A self-assembled film of ruthenium phthalocyanine (RuPc) fabricated on a silver substrate pre-modified with a monolayer of 4-mercaptopyridine (PySH) or 1,4-bis[2-(4-pyridyl)ethenyl]-benzene (BPENB) was studied by ultraviolet-visible (UV-Vis) and surface enhanced Raman scattering (SERS) spectroscopy. PySH or BPENB was used as a ligand to link RuPc since they not only modify the silver substrate, but also deliver a pyridyl group pointing out from the silver surface. Therefore, we can explore the relationship between the structure and orientation of metallophthalocyanine and the substrate modified by the two kinds of organic-monolayers with the different conjugates and molecular lengths. UV-Vis bands due to the organic-monolayer (PySH or BPENB) modified silver films shift to longer wavelengths and a new band arising from the metallophthlocyanine appears, suggesting the binding of RuPc to PySH/BPENB, as well as the interaction between the marcocycle of RuPc and the ring of PySH/BPENB. Vibrational bands arising from both the RuPc and PySH/BPENB moieties appear clearly in the SERS spectra of the RuPc-PySH/BPENB composite films, indicating that RuPc is successfully assembled on the top of PySH/BPENB film. The shifts and relative intensity changes of bands due to PySH or BPENB in the SERS spectra imply the binding of the metallophthalocyanine to the pyridyl group in the composite films. Furthermore, the comparison of the SERS spectra revealed that the orientations of PySH and BPENB in the two kinds of composite films are different; the BPENB moiety in the RuPc-BPENB composite film is more perpendicular to the silver surface compared with the PySH moiety in the RuPc-PySH composite film.     

Truly Concomitant and Independently Expressed Short‐ and Long‐Term Plasticity in a Bi2O2Se‐Based Three‐Terminal Memristor

Concomitance of diverse synaptic plasticity across different timescales produces complex cognitive processes. To achieve comparable cognitive complexity in memristive neuromorphic systems, devices that are capable of emulating short‐term (STP) and long‐term plasticity (LTP) concomitantly are essential. In existing memristors, however, STP and LTP can only be induced selectively because of the inability to be decoupled using different loci and mechanisms. In this work, the first demonstration of truly concomitant STP and LTP is reported in a three‐terminal memristor that uses independent physical phenomena to represent each form of plasticity. The emerging layered material Bi₂O₂Se is used for memristors for the first time, opening up the prospects for ultrathin, high‐speed, and low‐power neuromorphic devices. The concerted action of STP and LTP allows full‐range modulation of the transient synaptic efficacy, from depression to facilitation, by stimulus frequency or intensity, providing a versatile device platform for neuromorphic function implementation. A heuristic recurrent neural circuitry model is developed to simulate the intricate “sleep–wake cycle autoregulation” process, in which the concomitance of STP and LTP is posited as a key factor in enabling this neural homeostasis. This work sheds new light on the development of generic memristor platforms for highly dynamic neuromorphic computing.     

汽车座椅调角器耐久性试验机的研制

介绍了一种用于汽车座椅调角器疲劳耐久性试验的测试设备,叙述了该设备的设计思想,机械结构,硬件组成,控制系统,软件设计,试验方式等。实际运行表明,设备运行稳定安全可靠,试验方法简单方便。     

露天矿生产车辆安排计划优化设计

本文结合露天矿车辆生产安排计划的特点,全面分析了车辆安排问题约束条件,构建了基于整数规划的线路车次安排数学模型。利用线性规划对电铲进行初始布点,实现对模型的合理简化,加速模型的求解。考虑到电铲利用率很难达到1,为提高模型最优解的实际应用的可行性,增加了车辆调度的弹性,设置了电铲的最大利用率。为保证电铲有一定的利用率,设置了电铲最小利用率。计算表明本模型具有较好的实用性和通用性。