关于梯黑(35/65)炸药体胀规律的研究

本文依据有壳梯黑(35/65)装药部件的贮存检测数据,应用统计回归分析,拟合出该装药的密度下降规律,以及年均体膨胀率,发现该装药在贮存过程中的体积长大确是一个不容忽视的问题,特别是当具有坚固外壳时,这种体胀率会转化成内应力,所以必须给予充分的重视。     

A Stress Self-Adaptive Structure to Suppress the Chemo-mechanical Degradation for High Rate and Ultralong Cycle Life Sodium Ion Batteries

Transition-metal phosphides (TMPs) as typical conversion-type anode materials demonstrate extraordinary theoretical charge storage capacity for sodium ion batteries, but the unavoidable volume expansion and irreversible capacity loss upon cycling represent their long-standing limitations. Herein we report a stress self-adaptive structure with ultrafine FeP nanodots embedded in dense carbon microplates skeleton (FeP@CMS) via the spatial confinement of carbon quantum dots (CQDs). Such an architecture delivers a record high specific capacity (778 mAh g⁻¹ at 0.05 A g⁻¹) and ultra-long cycle stability (87.6 % capacity retention after 10 000 cycles at 20 A g⁻¹), which outperform the state-of-the-art literature. We decode the fundamental reasons for this unprecedented performance, that such an architecture allows the spontaneous stress transfer from FeP nanodots to the surrounding carbon matrix, thus overcomes the intrinsic chemo-mechanical degradation of metal phosphides.     

基于多尺度滤波和线检测算子的视网膜血管检测

视网膜血管分割在眼底图像分析中具有重要作用。结合多尺度Hessian矩阵滤波和线检测算子,提出了一种有效的血管检测方法。首先利用多尺度Hessian矩阵的特征值构建血管相似性函数,实现血管增强;然后采用改进的线检测算子,提取反映血管测度的特征;最后采用SVM实现血管检测。实验结果表明,该方法只需要较少的训练样本即可达到与其他方法相当的准确率,且在灵敏性上具有更好的性能。     

Highly Robust Palladium(II) α‐Diimine Catalysts for Slow‐Chain‐Walking Polymerization of Ethylene and Copolymerization with Methyl Acrylate

A series of sterically demanding α‐diimine ligands bearing electron‐donating and electron‐withdrawing substituents were synthesized by an improved synthetic procedure in high yield. Subsequently, the corresponding Pd complexes were prepared and isolated by column chromatography. These Pd complexes demonstrated unique properties in ethylene polymerization, including high thermal stability and high activity, thus generating polyethylene with a high molecular weight and very low branching density. Similar properties were observed for ethylene/methyl acrylate copolymerization. Because of the high molecular weight and low branching density, the generated polyethylene and ethylene/methyl acrylate copolymer were semicrystalline solids. The (co)polymers had unique microstructures originating from the unique slow‐chain‐walking activity of these Pd complexes.     

Effect of synthesis route on the morphologies of silver nanostructures by galvanic displacement reaction

The present study is concerned with the preparation of Ag nanostructures by reduction of AgNO₃ with zinc foil by galvanic displacement reaction. The results confirm that the synthesis route has a direct influence on the morphologies of Ag nanostructures. In addition, the effect of synthesis conditions, including the concentration of AgNO₃ aqueous solutions and reaction time, are investigated. X-ray diffraction (XRD), filed emission scanning electron microscope (SEM) and UV-vis spectra are used to characterize the obtained products. A reasonable formation process of Ag nanostructures is proposed based on the characterization results.     

含硅氢键聚二硅氧烷/聚醚共混聚合物电解质 I. 离子电导率研究

首次采用新型有机硅聚合物——侧链含一半硅氢键的羟基封端聚二硅氧烷(PSEMH)与聚氧乙烯醚(PEO)作为基质, 通过溶液浇铸法制备了PEO-PSEMH-LiClO4全固态共混聚合物电解质膜. 交流阻抗谱实验测定结果表明PSEMH与PEO共混作为聚合物电解质的基质可以显著提高共混聚合物电解质的离子电导率. PSEMH含量为25%, O/Li＋为12∶1时, 共混聚合物电解质具有最大离子电导率2.7×10－5 S•cm－1 (28 ℃). PSEMH的引入一方面可以显著地抑制PEO的结晶性能, 另一方面PSEMH分子链节中的二硅醚氧原子与Li＋间具有配位作用, 且参与了共混聚合物电解质锂离子迁移运动.     

有机硅合成新方法

有机硅材料作为一类具有独特优异性能的新材料,已成为化学和材料领域的重点研究方向之一。本文综述了近年来国内外有机硅合成的新方法,主要包括炔基-叠氮环加成反应、巯基-双键反应和胺-烯迈克尔加成反应等,重点介绍各种合成方法的优势及在制备新型功能化的有机硅化合物、有机硅聚合物及有机硅弹性体等中的应用,并对未来有机硅合成方法的发展方向进行了展望。     

Improved quadratic isogeometric element simulation of one-dimensional elastic wave propagation with central difference method

Two improved isogeometric quadratic elements and the central difference scheme are used to formulate the solution procedures of transient wave propagation problems. In the proposed procedures, the lumped matrices corresponding to the isogeometric elements are obtained. The stability conditions of the solution procedures are also acquired. The dispersion analysis is conducted to obtain the optimal Courant-Friedrichs-Lewy (CFL) number or time-step sizes corresponding to the spatial isogeometric elements. The dispersion analysis shows that the isogeometric quadratic element of the fourth-order dispersion error (called the isogeometric analysis (IGA)-f quadratic element) provides far more desirable numerical dissipation/dispersion than the element of the second-order dispersion error (called the IGA-s quadratic element) when appropriate time-step sizes are selected. The numerical simulations of one-dimensional (1D) transient wave propagation problems demonstrate the effectiveness of the proposed solution procedures.     

Fluorescence‐Tuned Polyhedral Oligomeric Silsesquioxane‐Based Porous Polymers

Two series of new polyhedral oligomeric silsesquioxane (POSS)‐based fluorescent hybrid porous polymers, HPP‐1 and HPP‐2 , have been prepared by the Heck reaction of octavinylsilsesquioxane with 2,2′,7,7′‐tetrabromo‐9,9′‐spirobifluorene and 1,3,6,8‐tetrabromopyrene, respectively. Three sets of reaction conditions were employed to assess their effect on fluorescence. These materials exhibit tunable fluorescence from nearly no fluorescence to bright fluorescence both in the solid state and dispersed in ethanol under UV light irradiation by simply altering the reaction conditions. We speculated that the difference may be attributable to the fluorescence quenching induced by Et₃N, P(o‐CH₃Ph)₃, and their hydrogen bromide salts employed in the reactions. This finding could give valuable suggestions for the construction of porous polymers with tunable/controllable fluorescence, especially those prepared by Heck and Sonogashira reactions in which these quenchers are used as organic bases or co‐catalysts. In addition, the porosities can also be tuned, but different trends in porosity have been found in these two series of polymers, which suggests that various factors should be carefully considered in the preparation of porous polymers with tunable/controllable porosity. Furthermore, HPP‐1 c showed moderate CO₂ uptake and fluorescence that was efficiently quenched by nitroaromatic explosives, thereby indicating that these materials could be utilized as solid absorbents for the capture and storage of CO₂ and as sensing agents for the detection of explosives.     

Synthesis and electrochemical properties of PbLi2Ti6O14 for lithium ion battery applications

Journal of Solid State Electrochemistry - Lead lithium titanium oxide with the composition PbLi2Ti6O14 has been successfully synthesized by the rheological phase reaction method and exhibited...