Insensitive energetic microspheres DAAF/RDX fabricated by facile molecular self-assembly

Insensitive energetic materials are promising in the defense weapons field.However,energetic materials still suffer from great challenges and the concern about their safety limits their utilization.In this work,insensitive energetic explosive 3,30-diamino-4,40-azoxyfurazan/hexahydro-1,3,5-trinitro-1,3,5-triazine(DAAF/RDX)microspheres were fabricated by self-assembly method.Rod-like DAAF/RDX was prepared by mechanical ball milling for comparison.DAAF/RDX composites with different mass ratios(90:10,80:20,and 70:30)were obtained.The morphologies and structures of as-obtained DAAF/RDX composites were characterized by scanning electron microscopy(SEM),powder x-ray diffraction(PXRD)and fourier transform infrared spectroscopy(FT-IR).The results showed that DAAF/RDX microspheres exhibited regular shaped microspheres with sizes from 0.5 to 1.2 mm.There was no crystal transition during the modification process.The thermal properties of as-obtained materials were then evaluated by differential scanning calorimetry(DSC)and materials studio software.DAAF/RDX microspheres showed an advanced decomposition peak temperature compared with rod-like DAAF/RDX.The binding energy and peak temperature values at zeroβ_(i)(T_(P0))of DAAF/RDX(90:10)increased by 36.77 kJ/mol,1.6℃,and 58.11 kJ/mol,12.3℃compared to DAAF/RDX(80:20)and DAAF/RDX(70:30),indicating the better thermal stability of DAAF/RDX(90:10).The characteristic drop height(H_(50))of DAAF/RDX(higher than 100 cm)composites was higher than that of raw RDX(25 cm),suggesting significant improvements in mechanical safety.The preparation of DAAF/RDX microspheres is promising for the desensitization of RDX and useful for the formation of other materials and future wide applications.

Sequential Monte Carlo Method Toward Online RUL Assessment with Applications

Online assessment of remaining useful life(RUL) of a system or device has been widely studied for performance reliability, production safety, system conditional maintenance, and decision in remanufacturing engineering. However,there is no consistency framework to solve the RUL recursive estimation for the complex degenerate systems/device.In this paper, state space model(SSM) with Bayesian online estimation expounded from Markov chain Monte Carlo(MCMC) to Sequential Monte Carlo(SMC) algorithm is presented in order to derive the optimal Bayesian estimation.In the context of nonlinear & non-Gaussian dynamic systems, SMC(also named particle filter, PF) is quite capable of performing filtering and RUL assessment recursively. The underlying deterioration of a system/device is seen as a stochastic process with continuous, nonreversible degrading. The state of the deterioration tendency is filtered and predicted with updating observations through the SMC procedure. The corresponding remaining useful life of the system/device is estimated based on the state degradation and a predefined threshold of the failure with two-sided criterion. The paper presents an application on a milling machine for cutter tool RUL assessment by applying the above proposed methodology. The example shows the promising results and the effectiveness of SSM and SMC online assessment of RUL.

Production of Active Compounds in Medicinal Plants:From Plant Tissue Culture to Biosynthesis

Over past decades plant tissue culture has emerged as an alternative of whole plant cultivation in the production of valuable secondary metabolites.Adventitious roots culture of Panax ginseng and Echinacea purpure has reached the scale of 1-10 kL.Some molecular biological techniques,such as transgenic technology and genetic stability are increasingly used in the studies on plant tissue cultures.The studies on elicitors have deepened into the induction mechanism,including signal molecules,functional genes,and so on.More and more biological elicitors,such as A.niger and yeast are used to increase the active compounds in plant tissue cultures.We also discussed the application of synthetic biology in the studies on biosynthesis of artemisinin,paclitaxel,and tanshinon.The studies on active ingredients biosynthesis of medicinal plants provide unprecedented possibilities to achieve mass production of active ingredients.Plant tissue cultures can not only produce active ingredients but also as experimental materials for biosynthesis.In order to improve the contents of active compounds in medicinal plants,following aspects could be carried out gene interference or gene silencing,gene overexpression,combination with chemical synthesis,application of elicitors,and site-directed mutagenesis of the key enzymes.

Self-sensing tribological coating with phosphor particles for wear indicator

Monitoring of coating health was achieved by embedding sensor materials(MAl_(2)O_(4):Eu^(2+),Dy^(3+),M=Sr,Ba)in tribological coating.When the luminescence disappears under ultraviolet(UV)light,it means that the functional coating is worn out and that recoating is needed.In this work,four types of alloy(Cu-14Al-X,Cu,Cu-Al,Al)composite coatings were investigated by vacuum pres sure-as sis ted sintering method.The composite coatings with different copper-aluminium alloy matrixes were compared by phase composition,microstructure,luminescence properties and tribological performance.The results indicate that the Cu-14Al-X matrix composite coating shows not only good resistance to wear but also exhibits strong green light emitting under ultraviolet(UV)light.It is the best wear-resistant self-sensitive coating which has potential industrial value.When the coating wore or broke,the emitting intensity will decrease or disappear.

Viscosity and surface tension of CaF_(2)-CaO-Al_(2)O_(3)-based slag with varying SiO_(2) and B_(2)O_(3) contents for ESR of rotor steel

The effect of SiO_(2) and B_(2)O_(3) on viscosity and surface tension of CaF_(2)-CaO-Al_(2)O_(3)-MgO-SiO_(2)-B_(2)O_(3) slag designed for electroslag remelting of rotor steel was investigated.The viscosity of the slag melts increases with increasing the SiO_(2) content from 0.37 to 8.03 mass%,and the viscous activation energy increases from 54.21 to 58.49 kJ/mol.Increasing B_(2)O_(3) content of the slag from 0 to 3.62 mass%exhibits a similar effect on the viscosity,and the activation energy increases from 47.30 to 55.71 kJ/mol.The increase in the viscosity and activation energy for viscous flow of slag is attributed to the enhanced polymerization degree of slag melts network with increasing either SiO_(2) or B_(2)O_(3) content.The surface tension of slag melts decreases with increasing temperature.The surface tension of slag melts decreases with increasing either SiO_(2) or B_(2)O_(3) content,which is originated from the increase in the polymerization degree and the decrease in the CaO content of the slag.