Microfluidic preparation of surfactant-free ultrafine DAAF with tunable particle size for insensitive initiator explosives

High purity and ultrafine DAAF(u-DAAF)is an emerging insensitive charge in initiators.Although there are many ways to obtain u-DAAF,developing a preparation method with stable operation,accurate control,good quality consistency,equipment miniaturization,and minimum manpower is an inevitable requirement to adapt to the current social technology development trend.Here reported is the microfluidic preparation of u-DAAF with tunable particle size by a passive swirling microreactor.Under the guidance of recrystallization growth kinetics and mixing behavior of fluids in the swirling microreactor,the key parameters(liquid flow rate,explosive concentration and crystallization temperature)were screened and optimized through screening experiments.Under the condition that no surfactant is added and only experimental parameters are controlled,the particle size of recrystallized DAAF can be adjusted from 98 nm to 785 nm,and the corresponding specific surface area is 8.45 m^(2)·g^(-1)to 1.33 m^(2)·g^(-1).In addition,the preparation method has good batch stability,high yield(90.8%-92.6%)and high purity(99.0%-99.4%),indicating a high practical application potential.Electric explosion derived flyer initiation tests demonstrate that the u-DAAF shows an initiation sensitivity much lower than that of the raw DAAF,and comparable to that of the refined DAAF by conventional spraying crystallization method.This study provides an efficient method to fabricate u-DAAF with narrow particle size distribution and high reproducibility as well as a theoretical reference for fabrication of other ultrafine explosives.

Dynamical Properties of Additive Cellular Automata over Finite Abelian Groups

Some dynamical properties were discussed for additive cellular automata(CA)over finite abelian groups.These properties include surjection,ergodicity,sensitivity to initial conditions and positive expansivity.Some necessary and sufficient conditions of determining ergodicity and sensitivity of the above additive CA were presented,respectively.A necessary condition for the positive expansivity of the above additive CA was given.The positive expansivity was proved to be preserved under the shift mappings for the general CA.The discussion was mainly based on the structure theorem of the finite abelian groups and the matrix associated with the global rule of the additive CA over the finite abelian p-groups.

THE IMPACT TORSIONAL BUCKLING OF ELASTIC CYLINDRICAL SHELLS WITH ARBITRARY FORM IMPERFECTION

A perturbation analysis for the impact torsional buckling of imperfective elastic cylindrical shells subjected to a step torque is given The imperfection is supposed to be small and has arbitrary form. It is shown that only the imperfection which has the shape of static torsional buckling mode could influence the critical step torque. Finally a formula is presented for the critical step torque.

The central limit theorem and chaos

Let X be a compact metric space studies some relationships between stochastic and f ： X→ X be a continuous map. This paper and topological properties of dynamical systems. It is shown that if f satisfies the central limit theorem, then f is topologically ergodic and / is sensitively dependent on initial conditions if and only if / is neither minimal nor equicontinuous.

Metal-organic framework templated synthesis of copper azide as the primary explosive with low electrostatic sensitivity and excellent initiation ability

Subject Code:F05With the support by the State Key Laboratory of Explosion Science and Technology,the research team led by Prof.Yang Li(杨利)and Prof.Wang Bo(王博)of Beijing Institute of Technology,applied MOFderived porous carbon materials with well-distributed metal source in the in-situ synthesis of primary explosive(MOFT-CA),which was published in Advanced Materials(2016,28:5837—5843).

Initial Value Sensitivity in Technology Diffusion

Initial value sensitivity in technology diffusion, an important problem for firms＇ decision making such as the timing and target market chosen for new technology or product entering the market, has long been limited by the research methodology and tool. Based on the network extension of Bass model, this paper proposes a stochastic threshold model and uses computer simulation to empirically examine three propositions on initial value sensitivity in technology diffusion process. Our findings suggest that diffusion extent is sensitive to not only the number of initial adopters but also their positions in social network, and the variance of customers＇ initial assessment as well, which can be detailed as follows： （1） the degree of technology diffusion exhibits highly positive relation to initial adopter quantity, in particular, when the quantity of initial adopters is small, diffusion extent is very sensitive; （2） diffusion extent is sensitive to the positions of initial adopters; （3） in addition, the variance of customers＇ initial evaluation displays strong negative relation to the final diffusion degree in that the larger variance, the lower of diffusion extent.

Recent Development of Chaos Theory in Topological Dynamics

We give a summary on the recent development of chaos theory in topological dynamics, focusing on Li-Yorke chaos, Devaney chaos, distributional chaos, positive topological entropy, weakly mixing sets and so on, and their relationships.

Nonlinear Time Series Analysis Since 1990:Some Personal Reflections

I reflect upon the development of nonlinear time series analysis since 1990 by focusing on five major areas of development. These areas include the interface between nonlinear time series analysis and chaos, the nonparametric/semiparametric approach, nonlinear state space modelling, financial time series and nonlinear modelling of panels of time series.