Clustering and combustion of dilute aluminum particle clouds in a post-detonation flow field

A hybrid two-phase numerical methodology is used to investigate the flow-field subsequent to the detonation of a spherical charge of TNT with an ambient distribution of a dilute cloud of aluminum particles. The interaction of the particle cloud with the contact surface results in Rayleigh–Taylor instability, which grows in time and gives rise to a mixing layer where the detonation products mix with the air and afterburn. At early times, the ambient particles get engulfed into the detonation products and ignite. Subsequently, they catch up with the Rayleigh–Taylor structures, and the vortex rings around the hydrodynamic structures cause transverse dispersion that results in the clustering of particles. Then, the particles leave the mixing layer and quench, yet preserve their hydrodynamic foot print. Preferential heating and combustion of particles occurs due to clustering. A higher initial mass loading in the ambient cloud results in larger clusters due to stronger/larger vortex rings around the hydrodynamic structures. A larger particle size results in the formation of fewer and degenerate clusters when the initial width of the cloud is larger. A theoretical model is used to predict the bubble amplitudes, and are in good accordance with the simulation results. Overall, this study has provided some useful insights on the explosive dispersal of dilute aluminum particle clouds and the gas dynamics of the flow field in the mixing layer.     

Environmental monitoring approaches used during bioremediation of soils contaminated with hazardous explosive chemicals

Defense sites are contaminated with explosives, which are released during manufacturing, firing, testing and training operations; loading, assembly and packing activities; and demilitarization operations. Explosive chemicals are hazardous in nature. Contamination of the soil and the underlying groundwater by explosives pose serious threat to human and animal health and the eco-system. Bioremediation is an eco-friendly technology as it exploits nature’s own agents- the microbes in degrading the contaminant of interest. This waste treatment technology has been extensively studied for degrading the explosive pollutant. Environmental monitoring, a process of systematic collection of data and analysis is essential in performance evaluation of any waste treatment system. This paper gives a comprehensive overview on the environmental monitoring approaches used during bioremediation of explosives contaminated soil. Biogeochemical factors viz., presence and survivability of microbes, bioavailability of the contaminant, pH, temperature, moisture content, redox conditions, presence/addition of substrate and nutrients and presence of intermediates/co-contaminants in the soil environment that are reported to affect the bioremediation of explosives are highlighted. Details on physical, chemical and biological parameters monitored during bioremediation are included. Advancements in instrumental techniques are evolving rapidly and its application in bioremediation approaches promise an enhanced understanding of the mineralization of explosive in the soil environment. Recent developments in application of advanced analytical instrumentation techniques, future research insights with recommendations, which will illuminate the selection of appropriate monitoring tool for evaluating bioremediation are also summarized.     

半线性椭圆型问题爆炸解的存在性与渐近行为

设Ω是RN（N≥3）中的C2有界区域,f是单调非减的非负连续可微函数满足f＇（a）∫a∞1/f（s）ds≤C0,　a>0.应用一种新型的非线性变换w（x）=∫u（x）∞　ds/f（s）将爆炸解问题△u=k（x）f（u）,u>0,x∈Ω,u|　Ω=∞转化成等价的带奇异项的Dirichlet问题,不仅得到了爆炸解问题解的最小爆炸速度,而且揭示了两类典型非线性爆炸解问题基本上是相同的.应用摄动方法,上下解方法得到了爆炸解的存在性.特别允许非线性项的系数不仅在Ω的内部子区域恒为零而且在Ω上可适当无界.随后再应用摄动方法,将所得结果推广到无界区域,得到了整体爆炸解的存在性以及在无穷远附近的最小爆炸速度（有关文献参见[1-33]）.     

分段表面放电沉积效率研究

利用一种结构紧凑的分段表面放电辐射源模块，详细研究了在不同电压、电容、气压实验条件下回路等效电阻、等效电感及放电能量沉积效率的变化规律，利用四分幅相机拍摄获得了不同实验条件下的放电等离子体通道图像，分析讨论了放电等离子体运动对放电能量沉积效率的影响，提出了提高能量放电沉积效率的有效途径。     

带对流项的非线性椭圆型问题爆炸解的存在性与渐近行为

设Ω是RN（N≥3）中的C2有界区域,对带负对流项的情形,对更广泛的非线性项,构造一种新型的非线性变换将爆炸解问题,转化成等价的带奇异项的Dirichlet问题,应用极大值原理得到了爆炸解问题解的最小爆炸速度.应用三种摄动方法,结合上下解方法、二阶椭圆型偏微分方程的估计理论得到了爆炸解的存在性.特别允许非线性项的系数不仅在Ω的内部子区域恒为零而且在Ω上可适当无界.随后再应用摄动方法,将所得结果推广到RN,得到了整体爆炸解的存在性以及在无穷远附近的最小爆炸速度.而对带正对流项的情形,对更广泛的非线性项,构造爆炸上下解u和u在Ω上满足u≤u,得到了爆炸解u的存在性且在Ω上满足u≤u≤u.     

基于差示扫描量热法的火工品材料选型研究

通过综合分析差示扫描量热法(DSC)图谱及动力学数据,进行火工品中药剂外包覆材料的选型研究。采用DSC测试炸药与不同涂敷层材料在不同升温速率的热性质,利用Ozawa法和DSC曲线对比法,对几种涂敷层材料进行分析。炸药与丙烯酸清漆混合后,DSC曲线表观性征、峰温以及反应的活化能变化最小;炸药与快速固化剂混合后,峰温及活化能变化影响居中,DSC曲线表观性征在升温速率大时有较大变化;炸药与硅橡胶混合后,DSC曲线表观性征、峰温以及反应的活化能变化最大。从而确定丙烯酸清漆为最合适的炸药包覆材料。     

A new route to Explosive Percolation

The biased link occupation rule in the Achlioptas process (AP) discourages the large clusters from growing much ahead of others and encourages faster growth of clusters which lag behind. In this paper we propose a model where this tendency is sharply reflected in the Gamma distribution of the cluster sizes, unlike the power law distribution in AP. In this model single edges between pairs of clusters of sizes s_i and s_j are occupied with a probability ∝(s_is_j)^α. The parameter α is continuously tunable over the entire real axis. Numerical studies indicate that for α<α_c the transition is first order, α_c=0 for a square lattice and α_c=−1/2 for random graphs. In the limits of α=−∞,+∞ this model coincides with models well established in the literature.     

有应用前景的低感高能炸药研究进展

概述了有应用前景的高能低感炸药的研究成果,从改善现有高能炸药晶体品质和合成新的高能低感炸药方面,总结了大幅度降低炸药冲击波感度的研究现状。     

基于光纤布拉格光栅的浇注炸药固化温度监测

首次采用光纤Bragg光栅实时测量浇注炸药在固化成型过程中固化剂与粘结剂的反应放热量。为了实时、准确的测量出浇注炸药在固化过程中的温度值,设计了基于光纤布拉格光栅的组网式温度监测系统。鉴于炸药成分的危险性、以及浇注炸药固化过程时间长、对条件要求恒温的特殊性,直接的实时监测一直未找到合适的测量方法。近年来,光纤布拉格光栅由于其优越的特点,在通信和传感领域得到广泛应用。利用光纤光栅与温度之间的线性关系,将采集的光栅反射波长值换算为温度实时显示。通过波分复用技术在两根光纤上写入7个光栅点同时测量,多点分布式测量可以将炸药内部温度的分布趋势显示出来。封装的光栅传感器采用90°弯曲设计,不仅改进了传感器与跳线的连接,同时有利于装入烘箱内。Origin软件将txt数据绘制成曲线图形式,将固化过程温度的变化直观明了的显示出来。结果表明,该方法操作简单,精确度高,满足炸药固化过程中对温度的测试需求。     

Structure and properties of detonation waves of heterogeneous explosives from the point of view of the hot spots mechanism

It is assumed that the chemical reaction of a detonation transformation, that is, burning, arises first in separate hot spots originated by the explosive compression behind or within the detonation wave front due to heterogeneity of charges, instability of the detonation wave, etc. Then the burning spreads around into the bulk of the explosive and is completed in the Chapman–Jouguet plane, where the detonation product velocity relative to the detonation front is equal to the sound velocity. A simple analytical method proposed early by the authors is used to calculate the expression for the detonation transformation time, from which it follows that there are at least two nondimensional numbers defining the possibility of the realization of the mechanism mentioned above. The first one is the Frank-Kamenetskii number, that is, the relation of the characteristic time of the cooling of the hot spot to the adiabatic induction period at some characteristic temperature of the hot spot. The hot spot mechanism is realized if the Frank-Kamenetskii number is greater than the critical one that determines the minimum possible size of hot spots capable of ignition. The second number is the relation of the detonation transformation time in the presence of hot spots to the reaction time in accordance with classical mechanism. The hot spot mechanism at detonation is realized if this number is less than unity. By means of the numbers proposed, some interpretations of available experimental data concerning the detonation process are given.