硫磺粉尘爆炸特性研究

为研究硫磺粉尘爆炸危险性,采用哈特曼管式爆炸测试装置与20 L球爆炸测试装置对常温常压下不同粒径的硫磺粉尘爆炸特性参数进行了测试和评估,得到了不同粒径硫磺粉尘的最小点火能、爆炸下限质量浓度和爆炸指数,根据实验结果对硫磺粉尘危险性进行了分级。结果表明,70~850 μm不同粒径的硫磺粉尘最小点火能在0.144~125 mJ,且随着粒径的减小而降低;45~375 μm不同粒径的硫磺粉尘爆炸极限质量浓度在15~20 g/m3,且随着粉尘粒径的减小而降低;45~375 μm不同粒径的硫磺粉尘最大爆炸指数在34.46~39.87 MPa·m/s,且随着粒径的减小而增大,其粉尘爆炸危险性等级为St3。     

混合图元加密系统研究

针对目前图像加密技术效率不高或安全性较弱的问题,在对混合图元加密基本原理阐述的基础上,提出了一种混合图元加密系统,建立了系统的数学模型和结构模型,并详细分析了系统的加密效率和安全性。从理论上对混合图元加密算法进行了较为深入的探讨。最后,对系统研究成果进行了概括,对尚待解决的问题进行了描述和展望。     

Measurements of minimum ignition energy in premixed laminar methane/air flow by using laser induced spark

Reducing engine pollutant emissions and fuel consumption is an important challenge. Lean-burning engines are a promising development; however, such engines require high-energy ignition systems for typical working conditions (equivalence ratio, Φ < 0.7). Laser-induced ignition is envisaged as a way to obtain high-energy ignition as a result of progress that has been made in laser beam technology in terms of stability, size, and energy. This study investigated the minimum energy necessary to ignite a laminar premixed methane air mixture experimentally. A parametrical study was performed to characterize the effects of the flow velocity, equivalence ratio, and lens focal length on the minimum energy required for ignition. Experiments were conducted using a premixed laminar CH₄/air burner. Laser-induced breakdown was achieved by focusing a 532-nm nanosecond pulse from a Q-switched Nd:YAG laser with an anti-reflection-coated lens. Mixture ignition and the early stages of flame propagation were studied using a high speed Schlieren technique. Despite the stochastic characteristic of the laser breakdown phenomena, good reproducibility in the minimum energy required for the ignition measurements was observed. The cases in which the CH₄/Air mixture flow ignites are defined as those with a laminar flame front propagation visible in the Schlieren images 10 ms after the energy deposition. The same minimum ignition energy (MIE) versus equivalence ratio (Φ) type of curves were obtained with a laser-induced spark and with a spark plug. Due to the threshold of energy required to obtain breakdown and the stochastic character of the energy absorption by the spark, a constant value was obtained (corresponding to the breakdown threshold) when the minimum ignition energy was lower than the breakdown threshold. As already noticed by several authors, MIE values higher than those observed using spark plugs were obtained. However, these differences tended to disappear at the lean and rich fuel limits.     

面向企业信息化市场的客户需求分析

系统分析了企业信息化市场构成及其特点，对企业信息化市场客户需求分析方法进行了研究，确立了需求分析基础信息，构建了客户产品需求分析框架，并结合CAPP产品，阐述了具体应用。     

基于ET-GM-PHD的机动多扩展目标跟踪算法

针对原始扩展目标高斯混合概率假设密度（Extended Target Gaussian Mixture Probability Hypothesis Density,ET-GM-PHD）滤波算法不能解决机动目标跟踪问题,在高斯混合概率假设密度（Gaussian Mixture Probability Hypothesis Density,GM-PHD）滤波框架下,引入修正的输入估计算法（Modified Input Estimation,MIE）,可以有效地处理多扩展目标的机动问题。此外,提出的算法虽然可以实现对未知数目的多机动扩展目标进行跟踪,但无法获得各个目标的航迹。针对此问题,进一步引入高斯分量标记方法,有效地将多机动扩展目标的航迹进行准确关联,获取各个目标的航迹。实验结果表明,提出的算法在弱机动扩展目标跟踪中具有较好的跟踪性能,同时能够有效地估计多扩展目标的航迹。     

装配工艺对工程机械维修质量的影响

针对目前工程机械修理技术现状，介绍装配工艺对工程机械维修质量的影响，提出装配工艺完好率划分状况，以期提高装配工艺质量，进而提高工程机械维修质量。     

面向企业的工业工程实践论

分析了企业在工业工程实践中存在的问题，提出了推行工业工程的策略和途径。     

电磁散射问题中的频域有限元算法

有限元法作为一种十分有效的数值方法,不仅适用于求解不规则的几何形状和边界条件,而且能计算解决复杂介质问题。首先推导了有限元应用于散射问题的变分公式,然后介绍了电磁散射算法。为验证有限元散射程序的准确性和对任意散射体的适应性,还完成了MIE级数解析求解球体散射问题的算法用于与数值结果对比。通过针对三种不同散射体与现有典型算例的比较,证明了有限元散射算法的有效性。     

Effects of hydrogen on combustion characteristics of methane in air

The explosion process of multi-component gas mixture is extremely complex and may cause serious disaster effects. The safety issue concerning explosion of multi-component gas mixture is urgent to be investigated on account of its wide range of applications. In current work, series of experiments were performed in a 20 L spherical explosion vessel at initial conditions of 1 atm and 293 K, involving methane–hydrogen/air mixtures. The proportion of hydrogen in fuels varied from 0% to 100%. It was observed that peak temperature is always behind the peak pressure in arrival time whatever the fuel equivalence is. Experimental values of peak overpressure are lower than adiabatic ones due to heat loss. It was also founded that the hydrogen addition can raise explosion pressure and temperature in experiment but slightly decrease that in adiabatic condition, and both the increase in experiment and the decrease in adiabatic show a linear correlation versus the proportion of hydrogen. Hence the deviation between the experimental results and the adiabatic results decreases as the hydrogen proportion rises. Moreover, the positive effect of hydrogen addition on (dp/dt)_max is very slight at low hydrogen proportion, while the effect becomes much more pronounced at higher hydrogen contents, showing an exponential growth. For each fuel composition throughout all experiments, the peak overpressure, peak temperature and (dp/dt)_max concerning fuel equivalence ratios of 0.6, 1 and 1.5 follow a same rule: Ф = 1 is the highest, followed by Ф = 1.5 and Ф = 0.6. Finally, the MIEs of gaseous methane–hydrogen/air mixtures at a fuel equivalence ratio of 1.5 were measured as a function of hydrogen proportion. It shows a sharp decrease as the fraction of hydrogen in fuel rises, from 118 mJ for methane–air to 0.12 mJ for hydrogen–air. It is also observed that the MIE of multi-component gas mixtures can be approximately figured as the linear weighted sum of the MIE of each component; the weighting factor is respectively the volume fraction of each component. This can be considered as a universal method to obtain the MIE for a specific multi-component gas.