NO emission characteristics in counterflow diffusion flame of blended fuel of H2/CO2/Ar

Flame structure and NO emission characteristics in counterflow diffusion flame of blended fuel of H₂/CO₂/Ar have been numerically simulated with detailed chemistry. The combination of H₂, CO₂ and Ar as fuel is selected to clearly display the contribution of hydrocarbon products to flame structure and NO emission characteristics due to the breakdown of CO₂. A radiative heat loss term is involved to correctly describe the flame dynamics especially at low strain rates. The detailed chemistry adopts the reaction mechanism of GRI 2.11, which consists of 49 species and 279 elementary reactions. All mechanisms including thermal, NO₂, N₂O and Fenimore are taken into account to separately evaluate the effects of CO₂ addition on NO emission characteristics. The increase of added CO₂ quantity causes flame temperature to fall since at high strain rates a diluent effect is prevailing and at low strain rates the breakdown of CO₂ produces relatively populous hydrocarbon products and thus the existence of hydrocarbon products inhibits chain branching. It is also found that the contribution of NO production by N₂O and NO₂ mechanisms are negligible and that thermal mechanism is concentrated on only the reaction zone. As strain rate and CO₂ quantity increase, NO production is remarkably augmented. Copyright © 2002 John Wiley & Sons, Ltd.     

Formation of composites fabricated by exothermic dispersion reaction in A1-TiO2-B2O3 system

The formation of aluminum matrix composites fabricated by exothermic dispersion reaction in A1-TiO2-B2O3 system was investigated. The thermal analysis results show that the reactions are spontaneous and exothermic. The Gibbs free energy of α-Al2O3 is the lowest among all the combustion products, followed by TiB2 and Al3Ti. It is noted that when the B2O3/TiO2 mole ratio is below 1, the reaction products are composed of particle-like α-Al2O3, TiB2 and rod-like Al3Ti. The α-Al2O3 crystallites, resulting from the reaction between A1 and TiO2 or B2O3, are segregated at the grain boundaries due to a lower wettability with the matrix. SEM micrographs show that rod-like Al3Ti phase distributes uniformly in the matrix. When the BEO3/TiO2 mole ratio is around 1, the Al3Ti phase almost disappears in the composites, and the distribution of α-Al2O3 particulates is improved evidently.     

基于机器视觉的蟋蟀体态测量

设计一套基于机器视觉的蟋蟀体态测量装置,初步研究用图像处理和图像测量的方法实现对蟋蟀躯干长宽的测量.该装置构建一个PC-Based的机器视觉系统,利用VisuaI Basic开发工具编写图像处理算法和图像测量算法的程序.应用惯性主轴的方法实现蟋蟀图片位置的归一化,应用数学形态学分割算法实现了蟋蟀躯干与足和触角的分割,将分割后的躯干进行边缘提取,从而进行蟋蟀体态的测量.     

仿生挖掘机斗齿减阻试验

为了减小挖掘机斗齿的楔土阻力,提取了蝼蛄前足爪趾的构型,在JL80型斗齿的基础上进行了仿生斗齿设计。采用快速成型加工技术加工了仿生斗齿与JL80型斗齿试样。利用试验机对两种试样进行了楔土试验,测定了楔入阻力与楔入深度的关系。运用有限元分析软件对仿生斗齿和JL80斗齿的楔入过程进行了数值模拟。结果表明,在同样条件下仿生斗齿的楔入阻力较JL80型斗齿低11%。本文设计的仿生斗齿可以为挖掘机斗齿的优化设计提供参考。     

热学中多方过程的研究

有些普通物理教材中把多方过程看做一个绝热和等温之间的过程，作者认为这种观点有些片面。多方过程应是一些有规律的准静态过程的总称，理想气体的四个基本热力学过程仅是其特例。文章围绕多方指数n变化时过程性质的变化，对该观点进行了深入阐述。     

初始NCO/OH摩尔比对直接乳化法制备水性聚氨酯的影响

以异佛尔酮二异氰酸酯(IPDI)、聚醚二元醇(PPG-210)、二羟甲基丙酸(DMPA)等为主要原料,采用直接乳化法合成了一系列水性聚氨酯(WPU)乳液;通过傅立叶变换红外光谱分析、差示扫描量热分析、粒径分析及力学性能测试等,研究了WPU乳液粒径大小、分子链结构、力学性能和热性能,并探讨了初始NCO/OH摩尔比(nNCO/nOH)对胶膜性能的影响。结果表明,随着初始nNCO/nOH比值的增大,所得乳液的稳定性变差,粒径变大,胶膜的拉伸强度先变大后降低,断裂伸长率逐渐降低;其相应的热分解温度稍有降低。     

减少铝进入湿法磷酸的有效途径

在以湿法磷酸为原料生产精细磷酸盐时 ,影响磷收率的关键因素之一是在净化过程中磷的沉淀率。湿法磷酸中有大量杂质 ,在除杂过程中 ,与磷结合形成沉淀的元素主要有铝、铁、钙等。为了防止大量的铝进入酸中 ,从理论分析和实验中得出了磷矿中的 n(F) / n(Al)是影响铝进入磷酸中的关键因素 ,并发现当矿中 n(F) / n(Al)为 3时 ,进入酸中的铝离子最少     

纳米银与纳米铜混合焊膏用于电子封装低温烧结连接

文中提出将纳米银焊膏与纳米铜焊膏按照一定比例进行混合,研究其烧结特性及其用于低温烧结连接镀银的铜块.结果表明,多元醇法制得的纳米银+纳米铜混合焊膏具有良好的防氧化特性;在5 MPa压力并保温5 min条件下,摩尔比例为1:1的混合焊膏在烧结温度为250℃时,接头抗剪强度最大并达到22 MPa.随混合焊膏中纳米银颗粒含量增加,接头强度逐渐增大;纯纳米铜颗粒焊膏的接头抗剪强度为15 MPa,纯纳米银焊膏的接头强度可到达56 MPa.     

Metal-carbonate formation from ammonia solution by addition of metal salts—An effective method for CO2 capture from landfill gas (LFG)

The absorption of CO₂ from LFG in different weight concentration ammonia solution and metal salts (Zinc and Barium) is investigated in this study. Addition of metal salts results in useful metal carbonates when LFG is passed through the solution. Barium salts show a better potential of removing CO₂ as compared to Zinc salts. Addition of Barium salts to ammonia solution results in a new absorbent as no study has been focused on it till date. Also metal salts are added to alkaline wastewater which not only decreases the pH of the wastewater but also useful metal carbonates are obtained from wastewater when LFG is passed through it. Different parameters like CO₂ loading, reaction rate and change in pH are investigated. Formation of carbonates is proved by using SEM and XRD analysis. Raman spectroscopy was performed on the discarded liquid after removal of carbonates to understand the formation of bicarbonates, carbonates and carbamates.     

二组份表面活性剂水溶液的表面行为的研究

本文测定了25℃时不同浓度下C_(12)H_(25)(OC_2H_4)_4OH、C_(12)H_(25)(OC_2H_4)_8OH水溶液及其混合水溶液的表面张力,误差为±0.3mN·m~(-1)。 根据物理漠型导出表面张力与浓度的关联式,计算值与实验值之间的平均标偏为0.3mN·m~(-1)。 用表面热力学方法求得表面层中不同表面活性剂分予间的作用参数β=-0.3584,由此反算出表面相摩尔分数,比Rosen的计算方法好。还能在胶束形成之前的整个实验浓度范围内,只需本体相浓度和表面张力数据,可算得表面相摩尔分数和表面过剩量。