Rapid Bonding of Ti3SiC2 and Ti3AlC2 by Pulsed Electrical Current Heating

Inspired by pressure resistance welding of metallic materials, herein we describe how two MAX phases—Ti₃SiC₂ and Ti₃AlC₂—were successfully joined by a rapid electric current heating method in a pulsed electric current sintering furnace. No welding agent was employed and the total processing time was less than 6 min. When the bulk temperature of the joint couple exceeded 1070°C, good joints, with shear strength above 50 MPa, were achieved in both homo‐ and heterojunction joints.     

The use of environmental scanning electron microscopy for imaging the microstructure of gels for profile control and water shutoff treatments

The use of gel systems as profile control and water shutoff agents has become a wide practice in recent years for oil recovery applications. But few systematic studies have been carried out on the microstructure of gels. In this study, environmental scanning electron microscopy (ESEM) was employed to investigate the microstructure of gels in their natural state. It was directly observed that a three‐dimensional network structure formed in chromium or zirconium crosslinked polymer gels is the same as organic/ inorganic crosslinked gels. However, there is a dense flat structure in phenol resin crosslinked polymer gels or phenolic resin gels. The differences between the microstructures can be attributed to the different crosslinking sites and crosslinking density, and this affect the gel's stability at reservoir temperatures. In addition, this paper also introduced the crosslinking mechanism and macro‐morphology of the bulk gels. It can contribute to a better understanding of the gel's microstructure. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39946.     

One-Pot Synthesis,Crystal Structure,and Thermal Decomposition Behavior of 1,1ʹ-Diamino-4,4ʹ,5,5ʹ-Tetranitro-2,2ʹ-Biimidazole

1,1?-Diamino-4,4?,5,5?-tetranitro-2,2?-biimidazole (DATNBI) was synthesized, by employing one-pot facile method, from 4,4?,5,5?-tetranitro-2,2?-biimidazole. The crystal structure was determined by X-ray diffraction for the first time. DATNBI crystallized in monoclinic system P2₁/c, with a crystal density of 1.934 g cm^?3 at 293(2) K and 2.019 g cm^?3 at 130(2) K, respectively. Its crystal parameters at 293 K are a = 4.8833(15) Å, b = 6.960(2) Å, c = 6.928(4) Å, α = γ = 90°, β = 93.418(6)°, V = 591.1(3) ?³, Z = 2, μ = 0.178 mm^?1, and F(000) = 348. The thermal stability and non-isothermal kinetics of DATNBI were studied by differential scanning calorimeter (DSC) with heating rates of 5, 10, 15, and 20 K min^?1. The apparent activation energy (E_a) at the first decomposition peak calculated by Kissinger, Ozawa, and Starink equations were 85.50, 89.67, and 86.10 kJ mol^?1, respectively. For the second peak, these were 116.49, 119.82, and 117.45 kJ mol^?1, respectively, with individual pre-exponential factors lnA = 18.40 s^?1 and lnA = 25.11 s^?1. The thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) analysis of thermal decomposition products reveals that the main decomposition gas products are H₂O, N₂O, CO₂, and NO₂. Based on the new crystalline densities, the detonation velocity and pressure predicted by EXPLO5 are 9062 m s^?1 and 36.4 GPa, respectively.     

Dearomatization of Indole Derivatives via Palladium‐Catalyzed C?H Bond Functionalization of Pyrroles: Convenient Construction of Spiroindolenines

An intramolecular palladium(II)‐catalyzed dearomative arylation reaction of indoles via C H bond functionalization was developed, providing access to structurally novel spiroindolenines with moderate to good yields. A one‐pot process for the synthesis of spiroindoline derivatives was also realized.

     

Pharmacokinetic Comparison of Berberine in Rat Plasma after Oral Administration of Berberine Hydrochloride in Normal and Post Inflammation Irritable Bowel Syndrome Rats

In the present study, post inflammation irritable bowel syndrome (PI-IBS) rats were firstly established by intracolonic instillation of acetic acid with restraint stress. Then the pharmacokinetics of berberine in the rat plasma were compared after oral administration of berberine hydrochloride (25 mg/kg) to normal rats and PI-IBS rats. Quantification of berberine in the rat plasma was achieved by using a sensitive and rapid UPLC-MS/MS method. Plasma samples were collected at 15 different points in time and the pharmacokinetic parameters were analyzed by WinNonlin software. Compared with the normal group, area under the plasma concentration vs. time curve from zero to last sampling time (AUC_0–t) and total body clearance (CL/F) in the model group significantly increased or decreased, (2039.49 ± 492.24 vs. 2763.43 ± 203.14; 4999.34 ± 1198.79 vs. 3270.57 ± 58.32) respectively. The results indicated that the pharmacokinetic process of berberine could be altered in PI-IBS pathological conditions.     

中国服装企业库存问题的分析与探讨

从库存的概念及成因入手,分析了我国各类服装企业库存现状及产生原因,并提出解决我国服装企业库存问题的方法及建议.有效的库存能确保物畅其流,提高周转率,提高经济效益.     

复杂环境下深基坑内旧地下室的拆除设计与施工

针对周边环境复杂的深基坑内既有地下结构的大范围拆除施工,在综合考虑周边环境的情况下,提出了相应的地下室拆除设计方案与施工关键技术.相关施工方案在减小基坑变形的同时,也减少了对周边环境的影响,总结的施工经验可为类似工程提供借鉴.     

基于改进EMD和LS-SVM的刀具磨损状态识别

针对经验模态分解(empirical mode decomposition, EMD)的端点效应、停止准则和虚假分量作了改进处理, 通过对仿真信号的对比验证证明了改进方法的可行性.采集切削加工中的声发射(acoustic emission, AE)信号并对AE信号运用改进EMD方法分解为若干个固有模态函数(intrinsic mode function, IMF)分量, 利用IMF分量和原始信号的相关系数作为判断依据, 剔除分解中产生的虚假分量, 然后提取IMF分量的归一化能量值并将其作为特征向量.将提取的特征向量分为2组:一组用于对最小二乘支持向量机(least squares support vector machine, LS-SVM)训练;另一组用于识别刀具磨损状态.实验结果表明该方法可有效地表征刀具的磨损状态.     

中国能源生产的累计㶲需求分析

以㶲理论为基础, 结合基于投入产出方法的清单计算模型, 计算了我国能源生产的累计㶲需求, 对不同能源产品的累计㶲需求进行了对比, 并分析了高次生产的㶲消耗在累计㶲需求中的比例.结果表明:供应1MJ的各能源产品, 电力的累计㶲需求最高, 为3.4MJ;其次为炼油产品、焦炭等其他二次能源, 为1.55~1.63MJ;初级化石能源最低, 为1.18~1.23 MJ.与基于流程的清单计算模型相比, 基于投入产出方法的清单计算模型更适用于分析能源系统.