坚硬顶板下巷道锚网索喷联合支护技术实践

干河煤矿+80水平三采区皮带巷上部赋存坚硬岩层,围岩压力较大;针对坚硬顶板条件,拟定以强主动支护为主的对策,即采用锚网索喷联合支护技术;应用表明,该巷道围岩变形量不大,验证了该支护技术安全可靠。     

Addressing amorphization and transgranular fracture of B4C through Si doping and TiB2 microparticle reinforcing

Over the last two decades, many studies have contributed to improving our understanding of the brittle failure mechanisms of boron carbide and provided a road map for inhibiting the underlying mechanisms and improving the mechanical response of boron carbide. This paper provides a review of the design and processing approaches utilized to address the amorphization and transgranular fracture of boron carbide, which are mainly based on what we have found through 9 years of work in the field of boron carbides as armor ceramics.     

Distinct dispersion stability of various TiO2 nanopowders using ammonium polyacrylate as dispersant

The dispersion stabilities of three titania (TiO₂) nanopowders with different particle sizes and surface chemistries in aqueous suspensions containing a common water-based dispersant, ammonium polyacrylate (PAA-NH₄), have been investigated and compared. According to adsorption isotherm and Fourier transform infrared spectroscopy analyses, the adsorption conformations of PAA-NH₄ are distinct for the different TiO₂ nanopowders. In addition, PAA-NH₄ exhibited the greatest adsorption affinity to the larger, hydrophilic TiO₂ nanopowder and the least affinity to smaller, hydrophobic nanopowder. From sedimentation and rheological results, the dispersion stability of the larger, hydrophilic TiO₂ nanopowder was demonstrated to be the greatest. Based on thermodynamic and kinetic calculations for the stabilization energies, the larger, hydrophilic TiO₂ nanopowder was also shown to be the best-stabilized powder, although it settles faster than the smaller, hydrophilic TiO₂ nanopowder; this is due to the greater affection of sedimentation flux on the larger nanopowder. In contrast, the hydrophobic TiO₂ nanopowder formed a gel-like structure in the aqueous suspension when the solid content was greater than 10 wt%, which is attributed to polymer bridging between PAA-NH₄-adsorbed TiO₂ nanoparticles.     

Core–shell porphyrin·multi-walled carbon nanotube hybrids linked by multiple hydrogen bonds: nanostructure and electronic communication

In this paper, multiple hydrogen bonding interaction of ureidopyrimidinone (UPM) was employed as the linking bridge for the formation of a novel porphyrin·multi-walled carbon nanotube (MWNT) hybrid, which was then used to fabricate a layer-by-layer (LbL) film composed of porphyrin-UPM·MWNT-UPM. Both in the assembled hybrid and the LbL film, porphyrin was closely attached to the surface of the MWNT under the strong multiple hydrogen bonding interaction, forming the core–shell structure. In addition, strong electronic communication was observed between porphyrin and MWNT. The hydrogen bonding association behavior between porphyrin-UPM and MWNT-UPM was attentively analyzed by UV–Vis spectra, fluorescent spectra and transmission electron microscope experiments. It was found that the hydrogen bonding interactions were crucial for the formation of the supramolecular hybrid and the LbL film as well as the occurrence of interfacial electronic communication. This result indicated that the introduction of strong noncovalent bonding interaction between donor and acceptor is an appropriate way to control the material structure and facilitate the interfacial electronic communication in the hybrids which lay the groundwork for their application in electrochemical sensors or photovoltaic devices.     

A simple permanent deformation model of rockfill materials

Existing experimental results have shown that using a semi-log linear relationship between the permanent volumetric strain and cyclic number underestimates the volumetric deformation of rockfill materials with a large cyclic number, and that the error increases with the confining pressure. The existing permanent deformation models are not suitable for the seismic safety analysis of high dams during strong earthquakes. In this study, a series of large-scale triaxial cyclic loading tests of rockfill materials were performed, and a new permanent deformation model of rockfill materials was developed and validated with three kinds of rockfill materials. The results show that the proposed model can properly reflect the general features of the permanent deformation of rockfill materials. The main features of the model are as follows: (1) relations between the cyclic number and permanent volumetric/shear strain are described by hyperbolic functions, which can avoid underestimating the volumetric deformation occurring during strong earthquakes; (2) the model can capture the effect of the mean effective stress on the permanent volumetric strain, with greater confining pressure correlating to greater permanent volumetric deformation, and the permanent volumetric strain under low confining pressure near the dam crest can be well represented; and (3) the model can reflect the effect of the consolidation stress ratio on the permanent shear strain.     

Analysis and improvement of the influence of sample shape on Pu measurement results

ABSTRACT

The analysis method of Fast Neutron Multiplicity Counting (FNMC) plays an increasingly important role in the measurement of nuclear material properties. Based on the assumption of point model, fast neutron multiplicity measurement equation is derived which can be used to measure the mass of Pu sample. However, the deviation of the simulated measurement of 1 kg Pu sample reaches 16.6% and increases with mass. Because nonpoint source samples of different shapes do not fully satify the hypothesis. To correct this deviation, a set of fast neutron multiplicity counters was built by Geant4 to simulate and study the mass attribute of Pu samples.The cylindrical sources of different shapes and different masses were simulated, the self-multiplication factor and α coefficient were corrected.And the corresponding third-order polynomial fitting equation was obtained, the goodness of fit was greater than 0.970. In the same way, the spherical and spherical shell source samples in the mass range of 0–5 kg were analyzed, the corrected mass deviation of samples was less than 10% in this interval. The results show that the combination of the fast neutron multiplicity counter and parameter correction can accurately measure the sample mass attribute.     

球坐标系下中子输运方程泄漏项的简便推导

采用一种恰当的方法，简便地推导出中子输运方程泄漏项在球坐标系下的表达式，该方法避免直接寻求二面角与中子飞行距离之间的复杂微分关系，转而寻求二面角与其他平面角之间的几何关系，再利用其他平面角与中子飞行距离之间的微分关系（通常是已知的或比较容易推导得到），便可间接推导出中子输运方程泄漏项在球坐标系下的表达式。该方法与传统方法推导得到的表达式完全一致，且推导过程直观、物理图像清晰。      

Rotatable Aggregation‐Induced‐Emission/Aggregation‐Caused‐Quenching Ratio Strategy for Real‐Time Tracking Nanoparticle Dynamics

Real‐time tracking of the dynamics change of self‐assembled nanostructures in physiological environments is crucial to improving their delivery efficiency and therapeutic effects. However, such tracking is impeded by the complex biological microenvironment leading to inhomogeneous distribution. A rotatable fluorescent ratio strategy is introduced that integrates aggregation‐induced emission (AIE) and aggregation‐caused quenching (ACQ) into one nanostructured system, termed AIE and ACQ fluorescence ratio (AAR). Following this strategy, an advanced probe, PEG^5k‐TPE₄‐ICGD₄ (PTI), is developed to track the dynamics change. The extremely sharp fluorescent changes (up to 4008‐fold) in AAR allowed for the clear distinguishing and localization of the intact state and diverse dissociated states. The spatiotemporal distribution and structural dynamics of the PTI micelles can be tracked, quantitatively analyzed in living cells and animal tissue by the real‐time ratio map, and be used to monitor other responsive nanoplatforms. With this method, the dynamics of nanoparticle in different organelles are able to be investigated and validated by transmission electron microscopy. This novel strategy is generally applicable to many self‐assembled nanostructures for understanding delivery mechanism in living systems, ultimately to enhance their performance in biomedical applications.