Explosive instability of quasi-phonon triads in antiferromagnet under frequency modulated electromagnetic field

Compensation of nonlinear frequency shift of hybrid magnetoelastic waves (quasi-phonons) in the process of parametric three-boson coupling is studied theoretically and experimentally. The singular frequency modulation of electromagnetic pumping is proposed for the observation of explosive instability of quasi-phonon triads. The explosive supercritical dynamics is simulated theoretically on the basis of strong nonlinear equations of magnetoelastic dynamics and observed in α-Fe₂O₃ magnetoacoustic resonator.     

Neutrinos and explosive nucleosynthesis

Core-collapse supernovae produce a hot protoneutron star that cools emitting huge amounts of neutrinos of all flavors. The interaction of these neutrinos with the outer layers of the protoneutron star produces an outflow of matter whose composition is determined by the luminosities and energies of the emitted neutrinos and antineutrinos. The presence of light nuclei like deuterons and tritons can have a big impact in the average energies of the emitted antineutrinos and consequently in the neutron-richness of the ejected matter. Recent hydrodynamical models show that the ejected matter is in fact proton-rich and constitutes the site of the νp-process where antineutrino absorption reactions catalyze the nucleosynthesis of nuclei with A>64.     

具有对流项的一类非线性椭圆型问题爆炸解的精确渐近行为

设Ω是RN中的有界光滑区域．应用Karamata正规变化理论和摄动方法.构造比较函数．得到了问题的解在边界附近的精确渐近行为和解的唯一性,其中g在无穷远处以指数1 ρ(ρ>0)正规变化．b在Ω内非负非平凡并且允许在边界为0．     

轴线起爆螺旋型爆磁压缩发生器2维简化模型

 应用Maxwell 方程，建立了轴线起爆螺旋型爆磁压缩发生器(AMFCG)的2维简化理论计算模型。利用此模型，得出了AMFCG中简易磁通表达式,并将等效电路方程与磁通表示结合起来。选用3组不同的几何参数，模拟计算了金属爆炸管在爆轰驱动下的径向膨胀过程，给出AMFCG初始电感、输出电流随时间的变化过程，AMFCG内部磁压、爆轰压及磁场随时间的变化情况。     

Effects of Epoxidation and Nitration on Ballistic Properties of FOX‐7 – A DFT Study

1, 1‐Diamino‐2, 2‐dinitroethylene (FOX‐7) has received increasing attention since it was industrialized in the late 1990s. It has lower sensitivity and comparable performance to RDX. This paper presents ballistic properties of FOX‐7, its mono and dinitro derivatives and their epoxide derivatives computationally. The structures were optimized at the B3LYP/6‐31G(d, p) level and the bond lengths were calculated. The calculated data for FOX‐7 are compatible with the literature one. We have investigated the bond dissociation energies of the molecules. Mulliken electro negativities (χ_M) and chemical hardness (η) were reviewed using Frontier Molecular Orbitals at HF/6‐31G(d, p)//B3LYP/6‐31G(d, p) theoretical level. The detonation performance analyses were done using empirical Kamlet‐Jacobs equations. Additionally, power index values were calculated. All the compounds considered in the present article are powerful candidates for high energy materials.     

间接馈电柱-锥级联爆磁压缩发生器数值模拟

 为了研究间接馈电、两级级联柱-锥构型的爆磁压缩发生器的物理特性，发展了描述爆磁压缩物理过程的2维爆轰磁流体力学程序——MFCG（Ⅴ），并用其分析、计算了一系列模型。通过将计算结果与柱-柱构型的结果进行比较，表明了柱-锥构型更有利于功率放大：在同样的输出电流条件下，不仅爆磁压缩的时间缩短，而且输出功率也相应地增加。MFCG（Ⅴ）程序的建立以及相应的数值模拟结果有助于加深对柱-锥构型的爆磁压缩发生器物理过程的认识，并为实验设计提供参考。     

Rapid detection of nitroaromatic and nitramine explosives on chromatographic paper and their reflectometric sensing on PVC tablets

Rapid and inexpensive sensing of explosive traces in soil and post-blast debris for environmental and criminological purposes with optical sensors has recently gained importance. The developed sensing method for nitro-aromatic and nitramine-based explosives is based on dropping an acetone solution of the analyte to an adsorbent surface, letting the solvent to dry, spraying an analytical reagent to produce a persistent spot, and indirectly measuring its reflectance by means of a miniature spectrometer. This method proved to be useful for on-site determination of nitro-aromatics (trinitrotoluene (TNT), 2,4,6-trinitrophenylmethylnitramine (tetryl) and dinitrotoluene (DNT)) and nitramines (1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)) pre-adsorbed on a poly vinyl chloride (PVC) surface, with the use of different spray reagents for each group of explosives producing different colors. The calibration equations of the tested compounds as reflectance vs. concentration showed excellent linearity (correlation coefficient: 0.998-0.999). The linear quantification interval in terms of absolute quantity of analyte was 0.1-0.5 μg. The developed method was successfully tested for the analysis of military explosives Comp B and Octol, and was validated against high performance liquid chromatography (HPLC). The reflectometric sensing method could also be used for qualitative identification of the nitrated explosives on a chromatographic paper. The reagent-impregnated paper could also serve as sensor, enabling semi-quantitative determinations of TNT and tetryl.     

太阳爆发日珥内双向喷流事件的紫外光谱研究

太阳双向喷流事件是过渡区重要的小尺度现象之一。双向喷流事件的光谱特征是强的展宽和非高斯形状。当双向喷流事件发生时,光谱像的红、蓝两翼分别或者同时明显增强,其相应的多普勒速度可达100 km·s-1以上。双向喷流事件的平均尺度约1 800 km, 寿命约60 s。双向喷流事件出现在磁对消区附近,且其速度与当地的阿尔芬速度相当,普遍认为其产生机制为小尺度快速磁重联。对其系统、全面地研究始于SOHO时代。SOHO/SUMER具有高时空和谱分辨率、宽的谱线覆盖,其观测的光谱数据为探究双向喷流事件提供了有力的光谱学诊断工具。双向喷流事件及其他过渡区小尺度现象的相互联系已被广泛研究,但双向喷流事件与日珥及其精细结构的关系研究还很少。文章通过SOHO/SUMER的Si Ⅲ谱线的定点观测,再现了爆发日珥演化的强度﹑多普勒速度和宽度演化图。通过Si Ⅲ谱线分析,找出宽度大于三个标准偏差的Si Ⅲ谱线,然后进行视像筛选出双向喷流事件,最终在爆发日珥中诊断出多个双向喷流事件,且大多数的双向喷流事件以准周期20 min重复出现在爆发日珥的中心区域。通过讨论,认为日珥中心磁流管之间的磁重联导致了双向喷流事件的重复出现,双向喷流事件产生的高速等离子体流可能是日面物质抛射的一部分,或是跟随日面物质抛射的太阳风的一部分。     

Estimation of spinodals from the density profile of the vapor–liquid interface

An extension of a recently proposed method for the calculation of the spinodals in pure fluid systems from the interfacial properties is elaborated, which requires the density profile as only input. The foundation of this approach is the so-called Fuchs-transformation which gives an estimate for the tangential pressure profile from the density profile. Using molecular dynamics simulation data for argon and carbon dioxide as well as lattice Boltzmann simulation data for the argon-like Shan–Chen fluid, the accuracy of the approach is analyzed. The Fuchs-transformation is qualitative, however it is possible to estimate the temperature–density projection of the spinodal. Depending on the underlying correlation function for the interfacial density profile reasonable results are obtained for the liquid and the vapor spinodal. The advantage of this method is that equilibrium data can be used to estimate the spinodal which is experimentally impossible to access because it is a highly non-equilibrium property. In the final consequence of this approach only the coexistence vapor and liquid densities are required to estimate the temperature–density projection of the spinodals.     

四苯乙烯的合成、表征及在爆炸物检测中的应用 ——介绍一个大学化学综合实验

因具有聚集诱导发光特性、螺旋桨结构的四苯乙烯及其衍生物,在有机光电材料、荧光传感和生物成像等领域表现出优异的荧光性能。本实验以二苯甲酮为原料,利用McMurry偶联反应合成四苯乙烯。采用萃取、干燥和柱层析等手段对产物进行分离和纯化,通过熔点测定、核磁共振氢谱、核磁共振碳谱和质谱对其结构进行表征后,使用苦味酸作为模型化合物,利用荧光光谱测定其对爆炸物的荧光检测极限。本实验寓科研热点于实验教学中,不仅提高了学生的实验操作技能,而且有助于学生了解具有聚集诱导发光性能的四苯乙烯及其衍生物的研究现状和应用前景,激发了学生的科研兴趣和创新意识。