H2/air autoignition: The nature and interaction of the developing explosive modes

Appropriate algorithmic tools are employed for the analysis of the explosive modes developing during the autoignition of homogeneous mixtures. The ability of these tools to provide significant physical understanding is demonstrated in the case of the homogeneous ignition of a stoichiometric H₂/air mixture, modelled by two different chemical kinetics mechanisms. It is shown that the ignition process evolves in two stages. The first stage is characterised by the development of two explosive timescales (one fast and one slow), that lead the system away from equilibrium. As the end of the first stage is approached, the two explosive timescales converge, they merge and then they disappear. In the second stage only dissipative timescales develop, which drive the system all the way to equilibrium. It is shown that throughout the first stage the fast explosive timescale is generated by chain reactions. The slow explosive timescale is initially generated by an initiation reaction that produces the radicals required for the start-up of the fast mode, while later on it is generated by reactions that are responsible for the heat released. These findings are validated with sensitivity analysis results for the ignition delay time and are employed in order to clarify the discrepancies in the solution provided by the two different chemical kinetics mechanisms considered.     

Ultrasound aided smooth dispensing for high viscoelastic epoxy in microelectronic packaging

Epoxy dispensing is one of the most critical processes in microelectronic packaging. However, due its high viscoelasticity, dispensing of epoxy is extremely difficult, and a lower viscoelasticity epoxy is desired to improve the process. In this paper, a novel method is proposed to achieve a lowered viscoelastic epoxy by using ultrasound. The viscoelasticity and molecular structures of the epoxies were compared and analyzed before and after experimentation. Different factors of the ultrasonic process, including power, processing time and ultrasonic energy, were studied in this study. It is found that elasticity is more sensitive to ultrasonic processing while viscosity is little affected. Further, large power and long processing time can minimize the viscoelasticity to ideal values. Due to the reduced loss modulus and storage modulus after ultrasonic processing, smooth dispensing is demonstrated for the processed epoxy. The subsequently color temperature experiments show that ultrasonic processing will not affect LED’s lighting. It is clear that the ultrasonic processing will have good potential to aide smooth dispensing for high viscoelastic epoxy in electronic industry.     

Sensitivity of run-to-detonation distance in practical explosives

The dynamics of detonation in a granular explosive following a piston impact is examined computationally for a two-phase model. Different choices are considered for equations of state and reaction rate. Of special interest is the behaviour of the run-to-detonation distance as a function of the initial porosity of the explosive, for which new experimental information has recently become available. It is found that this response can vary both qualitatively and quantitatively depending upon the constitutive input to the model. Computations based upon up-to-date equation-of-state and reaction-rate information for the explosive PBX-9501 show that the response of the run-to-detonation distance as a function of the initial porosity is in the shape of an inverted U, which is in qualitative agreement with the latest experiments. Mechanisms responsible for this behaviour are identified.     

Validation of an analytical method using UPLC–MS/MS to quantify four bioactive components in rat plasma and its application to pharmacokinetic study of traditional and dispensing granules decoction of Ziziphi Spinosae Semen

A rapid and sensitive UPLC–MS/MS method was established for the simultaneous quantification of 6′′′-feruloylspinosin, spinosin, jujuboside A, and jujuboside B in rat plasma after the oral administration of traditional and dispensing granules (DG) decoction of Ziziphi Spinosae Semen (ZSS). The four components were separated using 0.1% formic acid and acetonitrile as a mobile phase by gradient elution at a flow rate of 0.3 mL/min equipped with a C₁₈ column (2.1 × 50 mm, 1.7 μm particle size, Acquity BEH C₁₈). The mass spectrometer was operated under multiple reaction monitoring mode. An aliquot of 100 μL rat plasma was deproteinized by 300 μL methanol. The supernatant was injected into the UPLC–MS/MS system for analysis. The calibration curves displayed good linearity. The intra-day and inter-day precisions (RSD) were less than 7.3%. The accuracies ranged from −1.3 to 6.1%. The extraction recoveries ranged from 95.8 to 101.9%, and the matrix effects were satisfactory. For DG, half-life values (t_1/2) of 6′′′-feruloylspinosin and C_max of jujuboside A were elevated remarkably. MRT_0–t of jujuboside B was significantly increased. No significant variation was observed for the pharmacokinetic parameters of spinosin. The results could provide a scientific basis for the clinical application of traditional and DG decoction of ZSS.     

激光引爆PETN炸药的数值模拟

本文在以为反应流体动力学方程组的能量方程中加入激光源项，分别计算了透明玻璃窗口和镀铝窗口复盖下PETN炸药激光引爆的临界参数和炸药表面的温度和压力。结果表明，这两种窗口情况下，炸药起爆都是热机制。     

控制断裂能量与爆破效果的分形分析

定向断裂爆破与普通光爆、预裂相比，爆破效果明显提高，爆破能量利用更为合理。文中根据爆破断裂的分形研究，阐述了控制断裂爆破改进周边成形质量，提高爆炸能量利用率的力学机制。     

激波与火焰的相互作用过程

基于带化学反应的Navier Stokes方程和有关的热力学和反应动力学数据,利用改进的VLS格式,对甲烷 空气混合物中激波与火焰的相互作用进行了数值模拟。根据计算结果,讨论了激波掠过火焰时的变形、分叉和发展,以及激波作用下火焰的失稳、变形、破碎和相应的带旋涡的流场。     

乳化炸药配方设计的数学模型研究

根据炸药爆炸反应的热化学 ,建立了乳化炸药配方设计的数学模型 ,利用数学模型讨论了不同含量的硝酸铵、硝酸钠、水、乳化剂Span 80和油相材料对乳化炸药的热化学参数 (爆热和比容 )的影响。结果表明 :(1)硝酸铵的含量增加 ,乳化炸药的爆热和比容提高 ;硝酸钠的最佳含量为 7%～ 9% ;水的最佳含量为 9%～ 10 % ;乳化剂的最佳用量为 1.5 %～ 2 %。 (2 )油相材料的用量满足整体乳化炸药为零氧平衡即可。     

爆炸复合板边界效应研究

认为引起边界效应的主要因素不仅有炸药和基、复板边界稀疏的影响，而且尚受复板反弹拉伸的作用。设计了不等面积复合板爆炸焊接工艺，超声探伤结果表明，复合板的边界效应极小，满足工程需要。