Current Issue : October - December Volume : 2020 Issue Number : 4 Articles : 5 Articles
This work is aimed at studying asymmetric (BaTiO3..........
Unexpected pressure rise may occur in the end-burning grain solid rocket motor. It is generally believed that this phenomenon is\ncaused by the nonparallel layer combustion of the burning surface, resulting in the increase of burning rate along the inhibitor. In\norder to explain the cause of this phenomenon, the experimental investigation on four different end configurations were carried out.\nBased on the X-ray real-time radiography (RTR) technique, a new method for determining the dynamic burning rate of propellant\nand obtaining the real-time end-burning profile was developed. From the real-time images of the burning surface, it is found that\nthere was a phenomenon of nonuniform burning surface displacement in the end-burning grain solid rocket motor. Through image\nprocessing, the real-time burning rate of grain center line and the real-time cone angle are obtained. Based on the analysis of the\nreal-time burning rate at different positions of the end surface, the end face cone burning process in the motor working process\nis obtained. The closer to the shell, the higher the burning rate of the propellant. Considering the actual structure of this endburning\ngrain motor, it is speculated that the main cause of the cone burning of the grain may be due to the heat conduction of\nthe metal wall. By adjusting the initial shape of the grain end surface, the operating pressure of the combustion chamber can be\nbasically unchanged, so as to meet the mission requirements. The results show that the method can measure the burning rate of\nsolid propellant in real time and provide support for the study of nonuniform combustion of solid propellant....
The pore geometry and topology properties of pore space in rocks are significant for a better\nunderstanding of the complex hydrologic and elastic properties. However, geometry and topology\ninformation about the sandstone pore structures is not fully available. In this study, we obtained the\ntopological and geometrical pore parameters from a representative elementary volume (REV) for\nfluid flow in sandstone samples. For comparison, eight types of sandstones with various porosities\nwere studied based on the X-ray micro-computed tomography technique. In this study, the REV\nsize was selected based on the parameters from the respective pore network models (PNM), not just\nthe porosity. Our analysis indicates that despite different porosity, all the sandstone samples have\nhighly triangular-shaped pores and a high degree of pore structural isotropy. The high porosity group\nsandstones exhibit wider ranges of pore sizes than the low porosity group sandstones. Compared to the\nhigh porosity group sandstones, the low porosity group sandstones samples showing a higher global\naspect ratio, indicating some pores exist in the form of bottlenecks. The pore topological properties of\ndifferent sandstones show a high dependence of the porosity. The high porosity group sandstones\nobtain large coordination numbers, large connectivity densities and low tortuosities. The results from\nthis study will help better understand the complex pore structure and the fluid flow in sandstone....
Unconventional rocks such as tight sandstone and shale usually develop multiscale complex pore structures, with dimensions ranging\nfrom nanometers to millimeters, and the full range can be difficult to characterize for natural samples. In this paper, we developed a\nnew hybrid digital rock construction approach to mimic the pore space of tight sandstone by combining X-ray CT scanning and\nmultiple-point geostatistics algorithm (MPGA). First, a three-dimensional macropore digital rock describing the macroscopic pore\nstructure of tight sandstone was constructed by micro-CTscanning. Then, high-resolution scanning electron microscopy (SEM) was\nperformed on the tight sandstone sample, and the three-dimensional micropore digital rock was reconstructed by MPGA. Finally, the\nmacropore digital rock and the micropore digital rock were superimposed into the full-pore digital rock. In addition, the nuclear\nmagnetic resonance (NMR) response of digital rocks is simulated using a random walk method, and seepage simulation was\nperformed by the lattice Boltzmann method (LBM). The results show that the full-pore digital rock has the same anisotropy and good\nconnectivity as the actual rock. The porosity, NMR response, and permeability are in good agreement with the experimental values....
X-ray radiotherapy is a common method of treating cancerous tumors or other malignant\nlesions. The side effects of this treatment, however, can be deleterious to patient quality of life\nif critical tissues are affected. To potentially lower the effective doses of radiation and negative\nside-effects, new classes of nanoparticles are being developed to enhance reactive oxygen species\nproduction during irradiation. This report presents the synthesis and radiotherapeutic efficacy\nevaluation of a new nanoparticle formulation designed for this purpose, composed of a CaF2 core,\nmesoporous silica shell, and polyethylene glycol coating. The construct was additionally doped with\nTb and Eu during the CaF2 core synthesis to prepare nanoparticles (NPs) with X-ray luminescent\nproperties for potential application in fluorescence imaging. The mesoporous silica shell was added\nto provide the opportunity for small molecule loading, and the polyethylene glycol coating was\nadded to impart aqueous solubility and biocompatibility. The potential of these nanomaterials to\nact as radiosensitizers for enhancing X-ray radiotherapy was supported by reactive oxygen species\ngeneration assays. Further, in vitro experiments indicate biocompatibility and enhanced cellular\ndamage during X-ray radiotherapy....
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