Honeycomb‐Like Spherical Cathode Host Constructed from Hollow Metallic and Polar Co9S8 Tubules for Advanced Lithium–Sulfur Batteries

The practical application of lithium‐sulfur (Li‐S) batteries remains remote because of rapid capacity fade caused by the low conductivity of sulfur, dissolution of intermediate lithium polysulfides, severe volumetric expansion, and slow redox kinetics of polysulfide intermediates. Here, to address these obstacles, a new sulfiphilic and highly conductive honeycomb‐like spherical cathode host constructed from hollow metallic and polar Co₉S₈ tubes is designed. Co₉S₈ can effectively bind polar polysulfides for prolonged cycle life, due to the strong chemisorptive capability for immobilizing the polysulfide species. The hollow structure, as the sulfur host, can further prevent polysulfide dissolution and offer sufficient space to accommodate the necessary volume expansion. Well‐aligned tubular arrays provide a conduit for rapid conduction of electrons and Li‐ions. More importantly, the experimental results and theoretical calculations show that Co₉S₈ plays an important catalytic role in improving the electrochemical reaction kinetics. When used as cathode materials for Li–S batteries, the S@Co₉S₈ composite cathode exhibits high capacity and an exceptional stable cycling life demonstrated by tests of 600 cycles at 1 C with a very low capacity decay rate of only ≈0.026% per cycle.     

Multifunctional Phosphorus‐Containing Lewis Acid and Base Passivation Enabling Efficient and Moisture‐Stable Perovskite Solar Cells

Multiple‐cation lead mixed‐halide perovskites (MLMPs) have been recognized as ideal candidates in perovskite solar cells in terms of high efficiency and stability due to decreased open‐circuit voltage loss and suppressed yellow phase formation. However, they still suffer from an unsatisfactory long‐term moisture stability. In this study, phosphorus‐containing Lewis acid and base molecules are employed to improve device efficiency and stability based on their multifunction including recombination reduction, phase segregation suppression, and moisture resistance. The strong fluorine‐containing Lewis acid treatment can achieve a champion PCE of 22.02%. Unencapsulated and encapsulated devices retain 63% and 80% of the initial efficiency after 14 days of aging under 75% and 85% relative humidity, respectively. The better passivation of Lewis acid implies more halide defects than Pb defects at the MLMP surface. This unbalanced defect type results from phase segregation that is the synergistic effect of Cs and halide ion migrations. Identifying defect type based on different passivation effects is beneficial to not only choose suitable passivators to boost the efficiency and slow down the moisture degradation of MLMP solar cells, but also to understand the mechanism of defect‐assisted moisture degradation.     

飞轮系统的符号动力学故障检测方法

为检测飞轮系统的微弱故障,提出一种基于符号动力学的故障检测方法.首先,利用符号动力学算法将飞轮的电流数据进行字符映射,实现信号降噪、数据压缩.其次,利用D阶马尔科夫过程定义电流字符序列的变异过程,且根据字符序列的熵值变化率确立算法的字符个数,并计算字符的概率状态转移矩阵.最后,根据概率状态转移矩阵求解字符概率特征向量,并利用特征向量之间的距离阈值检测飞轮的故障.仿真结果表明:该方法能够根据字符概率特征向量之间的距离区分不同严重程度的飞轮系统故障,实现微弱故障的检测;与扩展卡尔曼滤波算法相比,该方法不需复杂的动力学建模,且仅利用单变量即可实现飞轮的故障检测.此外,利用过程数据,该方法可以快速学习卫星其他部件的行为,并检测故障。     

中空无机微珠填充ABS复合材料的流动性质

应用熔融指数仪，考察了温度、载荷和填料浓度对中空微珠填充ABS复合材料流动性能的影响。结果表明，试样熔体的熔融流动速率(MFR)随着温度或压力的增加而提高，而MFR随中空微珠体积分数的变化则不太明显。     

基于多微商核函数的SVM话者确认

给出了一种基于多微商核函数(MDK)的结合高斯混合模型(GMM)和支持向量机(SVM)的方法,并应用于SVM文本无关话者确认。从GMM话者语音特征概率分布出发,用多阶微商描述GMM概率分布,将GMM和SVM结合的问题转化为用多阶微商建立SVM话者模型的问题。首先对说话人语音进行基于因子分析的参数域失配补偿,用GMM描述失配补偿后的话者语音特征的概率分布;然后对GMM求多阶微商;最后构建多微商核函数,建立多SVM话者模型。在NIST’01 2min-1min话者确认数据库上的实验表明,基于多微商核函数的SVM话者确认系统性能优于基于失配补偿的GMM系统,也比基于失配补偿的Fisher核函数SVM话者系统和基于失配补偿的Kullback-Leibler(KL)距离SVM话者系统有较大的提高。     

Modeling of velocity distribution among microchannels with triangle manifolds

A model of velocity distribution among microchannels with triangle manifolds is proposed. According to the flow behaviors analyzed by Fluent, the manifolds are divided into several approximate rectangular channels, and then an equivalent simplified resistance network model is developed to establish the relationships between the velocities and pressure drops in microchannels and approximate rectangular channels. The velocity distributions are calculated under two situations, respectively, considering and ignoring singular losses. The outcomes of the present study are compared with Fluent's simulated results to analyze the effects of singular losses on the velocity distributions. It indicates that the proposed model is suitable for the calculation of velocity distribution among microchannels with obtuse angled or right triangle manifolds under low Reynolds numbers. The premise of ignoring singular losses is that the frictional pressure drops are three times larger than the singular pressure drops in each flow loop. The manifold optimization results indicate that the velocity distribution among microchannels with right triangle manifolds is much more uniform than that of the corresponding one with obtuse angled manifolds. © 2009 American Institute of Chemical Engineers AIChE J, 55: 1969–1982, 2009     

Numerical Simulation of Manifold Microchannel Heat Sinks for Thermal Management in a Li-Ion Battery

The microchannel heat sink is an effective technology for the thermal management of Li-ion batteries. The overall performance of two heat sinks with improved thermal management of Li-ion batteries was determined by a numerical simulation model. A manifold microchannel heat sink (MMC) and a traditional microchannel heat sink (TMC) with different aspect ratios of microchannels were developed. Thermal transfer performance and pressure drop characteristics of two heat sinks were compared by Fluent. Results indicate that the temperature uniformity of the TMC is worse than that of the MMC. The total pressure drop of TMC is significantly higher as compared to that of the MMC. Consequently, the MMC has a better overall performance than the TMC.     

Efficient and stable oxidative steam reforming of ethanol for hydrogen production: Effect of in situ dispersion of Ir over Ir/La2O3

La₂O₃-supported Ir catalyst was prepared by wetness impregnation method for the oxidative steam reforming of ethanol (OSRE). Fresh, reduced, and used catalysts were characterized by N₂ adsorption, H₂ chemisorption, XRD, FT-IR, TEM, and XPS. La₂O₃ would transform into hexagonal La₂O₂CO₃ during OSRE, which suppress coking effectively. Reduced Ir metal can interplay with La₂O₂CO₃ to form Ir-doped La₂O₂CO₃. It dynamically forms and decomposes to release active Ir nanoparticles, thereby preventing the catalyst from sintering and affording high dispersion of Ir/La₂O₃ catalysts at elevated temperatures. By introducing ultrasonic-assisted impregnation method during the preparation of a catalyst, the surface Ir concentration was significantly improved, while the in situ dispersion effect inhibited Ir from sintering. The Ir/La₂O₃ catalyst prepared by the ultrasonic-assisted impregnation method is highly active and stable for the OSRE reaction, in which the Ir crystallite size was maintained at 3.2 nm after 100 h on stream at 650 °C and metal loading was high up to 9 wt%.     

兖州矿区矿压对采动裂隙发育及突水的影响

3煤顶板突水是影响矿井安全生产的关键因素,通过从理论和实践上的分析,归纳出了对发育及突水的影响,最后提出了解决问题的办法。     

Preparation of mercaptoacetic acid-capped ZnSe core–shell nanocrystals by hydrothermal method

Mercaptoacetic acid (MMA)-capped ZnSe (ZnSe–MMA) core–shell nanocrystals have been prepared by two-step hydrothermal method using Se and Zn(NO₃)₂ aqueous solution as precursor. The as-prepared ZnSe are zincblende structure with grain size of 4 nm. The MMA-capped ZnSe nanocrystals are more stable and can be preserved long time without oxidation in the air. The ZnSe–MMA core–shell nanocrystals show good absorption for the ultraviolet light.