Padé–Legendre approximants for uncertainty analysis with discontinuous response surfaces

A novel uncertainty propagation method for problems characterized by highly non-linear or discontinuous system responses is presented. The approach is based on a Padé–Legendre (PL) formalism which does not require modifications to existing computational tools (non-intrusive approach) and it is a global method. The paper presents a novel PL method for problems in multiple dimensions, which is non-trivial in the Padé literature. In addition, a filtering procedure is developed in order to minimize the errors introduced in the approximation close to the discontinuities. The numerical examples include fluid dynamic problems characterized by shock waves: a simple dual throat nozzle problem with uncertain initial state, and the turbulent transonic flow over a transonic airfoil where the flight conditions are assumed to be uncertain. Results are presented in terms of statistics of both shock position and strength and are compared to Monte Carlo simulations.     

Aerosol‐Assisted Synthesis of Porous TiNxOy@C Nanocomposites

Porous TiN_xO_y‐based particles were synthesized by an aerosol spray process. At first, the starting sol solution containing the metal precursor and the nitrogen source is sprayed to form an aerosol that is subsequently pyrolysed at different temperatures. The obtained dried particles are an amorphous coordination “polymer” rich in carbon and nitrogen. These “glassy” particles are finally thermally treated at 800 °C, promoting the crystallization of the particles and the release of a major part of the carbon. As the particles keep their original shape, carbon loss and density increase during the crystallization step and lead to the development of an accessible pore structure. The process was analyzed and extended to the synthesis of other metal nitrides, such as VN and W₂N, thereby showing its general validity for the production of functional nanocrystalline nitride ceramics with high porosity still occupying a relatively small volume, and otherwise not easily accessible.     

Observation of dimethylaminoethyl methacrylate–myoglobin binding reaction using laser spray mass spectrometry

Covalent bonds are often created by a reaction between chemicals and protein before causing various adverse effects in a cell. Dimethylaminoethyl methacrylate (DMAEMA), which has moderate toxicity, causes skin inflammation and throat irritation. For this study, we investigated a reaction mechanism between myoglobin and (DMAEMA) using a new analytical tool developed at our laboratory: laser spray mass spectrometry technique. It was found that initially DMAEMA was added to the amino group of protein by the Michael addition mechanism; the added DMAEMA was hydrolyzed to methacrylic acid using an autocatalytic system. The results of this study indicate the feasibility of the laser spray technique in analyses of reaction dynamics. Copyright © 2012 John Wiley & Sons, Ltd.     

Prediction of entrance length and mass suction rate for a cylindrical sucking funnel

Conservation equations for mass, momentum and energy have been solved numerically for a cylindrical funnel with louvers (lateral openings on the side wall of the cylindrical funnel through which air can come into it) to compute the suction rate of air into the funnel. The nozzle placed centrally at the bottom of the cylinder ejects high‐velocity hot gaseous products so that atmospheric air gets sucked into the funnel. The objective of the work is to compute the ratio of the rate of mass suction to that of the mass ejected by the nozzle for different operating conditions and geometrical size of the funnel. From the computation it has been found that there exists optimum funnel diameter and optimum funnel height for which the mass suction is the highest. The protruding length of the nozzle into the funnel has almost no effect on the mass suction rate after a certain funnel height. The louvers opening area has a very high impact on the mass suction rate. The entrance length for such a sucking funnel is strikingly much lower compared with a simple cylindrical pipe having uniform flow at the inlet at same Reynolds number. A new correlation has been developed to propose the entrance length for a sucking pipe, the rate of mass suction into it and the exhaust plume temperature over a wide range of operating parameters that are normally encountered in a general funnel operations of naval or merchant ship. Copyright © 2009 John Wiley & Sons, Ltd.     

收缩喷嘴中的湍流Ⅰ——边界层解

应用边界层积分法,研究锥形喷嘴入口区域中湍动涡流的发展.球面坐标系中的控制方程,通过边界层的假定得到简化,并对边界层进行了积分.应用4阶Adams预测校正法求解该微分方程组.入口区域的切向和轴向速度,分别应用自由涡流和均匀速度分布来表示.由于缺乏收缩喷嘴中涡流的实验数据,需要用数值模拟对该发展模式进行逆向验证.数值模拟的结果证明,该解析模型在预测边界层参数中的能力,例如边界层的生长、剪切率和边界层厚度,以及不同锥度角时的涡流强度衰减率等.为所提出的方法引进一个简明而有效的程序,用以研究几何形状收缩设备内的边界层参数.     

Silver-doped calcium phosphate nanopowders prepared by electrostatic spraying

Silver-doped calcium phosphate nanopowders were successfully prepared by the cost-effective electrostatic spray-pyrolysis process. The properties of the silver-doped nanopowder annealed at 500°C for 30 min were investigated through X-ray diffraction analysis, field emission scanning electron microscope, and Fourier transform infrared spectroscopy. The silver-doped nanopowders with 70–90 nm particle size showed an antibacterial performance against Escherichia coli.     

锥型喷嘴组合射流特性试验研究

对锥型喷嘴组合射流特性进行了实验研究。组合喷嘴射流由初始段、基本段、过渡段和均匀混合段四部分组成。在射流的初始段中,每个喷嘴射流都存在等速核区。在基本段中,每个喷嘴射流的速度分布均有相似性,但其规律彼此不同,文中给出了各自的数学表达式。在过渡段中,各射流之间相互干扰、掺混十分显著,速度分布无相似性。在均匀混合段中,各射流混合的结果变为单一射流,又出现了相似性,本文也给出了其速度分布规律的数学表达式。研究得到的一些规律对进一步研究复杂射流和石油钻井工程中的喷射钻井机理有重要作用。     

高温冷却柴油机的燃油喷射特性和喷雾特性

目前,为了进一步提高车用涡轮增压柴油机的功率,而又不至于增大其散热器的尺寸,有利于车辆动力舱的布置,趋向于采用高温冷却发动机的气缸和燃烧室组件的技术。在高温冷却下,发动机的冷却水温度从80～90℃提高到120℃。这样可以减少冷却水所传走的热量,达到适当控制其冷却水散热器的尺寸的目的。 本文主要研究高温冷却柴油机在整机温度和环境温度提高之后,柴油机燃料密度和可压缩性的变化对燃油喷射和雾化特性的影响。     

四堡污水处理厂排污管喷口研究

介绍了四堡污水处理厂排污入江管工程中应用的新型三口单向阀型自动喷口结构。叙述了排污量、开启度、喷口流速、阻力系数等水力特性。对喷口的安装施工以及喷口流速、开启度、喷口冲坑形状的现场检测也作了说明。     

激光测速对喷气引纬流场的测试分析

气流引纬是喷气织机的技术关键之一。本文结合消化分析进口喷嘴和研制新型国产喷嘴的需要,应用激光多普勒测速仪对喷气织机主喷嘴、辅喷嘴及其射流流场进行了测试分析,并探索了提高射流能力的参数匹配规律,所得结果不仅为喷嘴选型提供了依据,还可作为选取有关气流参数的参考。另外,本文通过对计算机绘图软件的改进和开发,使得所绘制的流场变化图形直观易懂,便于比较。