Influence of Solid Rocket Motor Slag on the Space Debris Environment

The resulting slag particles from solid rocket motor( SRM) firings are an important component of space debris environment. Slag sizes as large as 1 cm have been witnessed in ground tests,and comparable sizes have been also estimated via observations of sub-orbital tail-off events. We achieve slag initial data based on MASTER slag model and SRM historical launch data,and propagate slag long-term orbital evolution taking into account the zonal harmonics J2,atmospheric drag,solar radiation pressure and luni-solar attraction to discuss the slag size distribution and orbital characteristics. Finally,future slag debris environment is evaluated based on two different launch rate assumptions. The result shows that current launch frequency will make the slag population sustain growth and the population will not decrease at once even if there are no more launches in the future.

System scan of the multiplicity correlation between forward and backward rapidities in relativistic heavy-ion collisions using a multi-phase transport model

A systematic study on forward–backward(FB)multiplicity correlations from large systems to small ones through a multi-phase transport model(AMPT)has been performed and the phenomenon that correlation strength increases with centrality can be explained by taking the distribution of events as the superposition of a series of Gaussian distributions.It is also found that correlations in the η−ϕ plane can imply the shape of the event.Furthermore,long-range correlations originate from the fluctuations associated with the source information.FB correlations allow us to decouple long-range correlations from short-range correlations,and may provide a chance to investigate the α-clustering structure in initial colliding light nuclei as well.It seems the tetrahedron ^(16)O+^(16)O collision gives a more uniform and symmetrical fireball,that emits the final particles more isotropically or independently in the longitudinal direction,indicating that the forward-backward multiplicity correlation could be used to identify the pattern of α-clustered ^(16)O in future experiments.

Structure and Morphology of Poly(ε-caprolactone)Heterogeneous Shish-Kebab Structure Induced by Poly(lactic acid)Nanofibers

In recent years,the hybrid shish-kebab structure with excellent physical properties and functionalities has attracted much attention because it provides a way of blending nanofibers with different properties into polymer matrix in a regular arrangement.It is often not easy to induce the formation of the hierarchically ordered structure for the semi-crystalline polymer in heterogeneous shish-kebab structure.A poly(lactic acid)(PLA)/poly(ε-caprolactone)(PCL)heterogeneous shish-kebab structure,i.e.,the PCL crystals periodically crystallized onto PLA nanofibers,was successfully created and the interfacial crystal morphology of the PLA/PCL heterogeneous shish-kebab structure was observed using scanning electron microscopy and atomic force microscopy.NaOH aqueous solution was applied to modify the surface of the PLA nanofibers to produce adsorption sites and carboxyl groups.The total reflectance Fourier transform infrared spectroscopy(ATR-FTIR)and X-ray diffraction(XRD)results demonstrated that the formation of the heterogeneous shish-kebab structure was mainly due to the hydrogen bonding interaction between the kebab and shish interface,and the growth process of the kebab crystals also promoted the crystallization of the shish fibers.This heterogeneous nanostructure of biodegradable polymers will have great applications in tissue engineering and regenerative medicine.