Synthesis and characterization of crystallizable aliphatic thermoplastic poly(ester urethane) elastomers through a non-isocyanate route

A simple non-isocyanate route is developed for synthesizing crystallizable aliphatic thermoplastic poly(ester urethane) elastomers(TPEURs) with good thermal and mechanical properties. Three prepolymers of1,6-bis(hydroxyethyloxycarbonylamino) hexane(BHCH), i.e. Pre PBHCHs, were prepared through the self-transurethane polycondensation of BHCH. A poly(butylene adipate) prepolymer(Pre PBA) with terminal HO― groups was prepared and used as a polyester glycol. A series of TPEURs were prepared by the co-polycondensation of the Pre PBHCHs with Pre PBA at 170 ℃ under a reduced pressure of 399 Pa. The TPEURs were characterized by gel permeation chromatography, FTIR,1H-NMR, differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray diffraction, atomic force microscopy, and tensile test. The TPEURs exhibited M_n up to 23300 g/mol, M_w up to 51100 g/mol, Tg ranging from-33.8 ℃ to-3.1 ℃, T_m from 94.3 ℃ to 111.9 ℃, initial decomposition temperature over 274.7 ℃, tensile strength up to18.8 MPa with a strain at break of 450.0%, and resilience up to 77.5%. TPU elastomers with good crystallization and mechanical properties were obtained through a non-isocyanate route.     

2015年全国研究生数学建模竞赛F题综述

叙述了2015年全国研究生数学建模竞赛F题"旅游路线规划问题"的命题背景和目的,分析了本赛题的建模及求解思路,对评阅中发现的问题进行了综述,最后叙述了本赛题还需继续思考的问题.     

高温超导变压器在电网中的应用

随着高温超导带材性能的不断提高,高温超导变压器在电力系统中的应用可以有效提高系统效率。在广泛调研的基础上,分析了高温超导变压器的关键技术以及目前的技术瓶颈。在此基础上,结合近几年来国内外对高温超导变压器的研究进展,对高温超导变压器的应用前景进行了分析,并给出了高温超导变压器的发展路线。     

测量薄凸透镜光学参量的简便方法

本文从薄凸透镜的反射成象原理出发,定性地解释了为什么物光经透镜后表面反射形成的倒立等大的实象时,其物距、象距都小于透镜焦距;介绍了逆向光路的计算方法.最后,通过薄凸透镜的反射成象原理和逆向光路的计算,推导出测量薄凸透镜的光学参量的简便方法.     

Precipitate synthesis of BaMoO4 and BaWO4 nanoparticles at room temperature and their photoluminescence properties

The uniform BaMoO₄ and BaWO₄ nanoparticles (NPs) have been successfully synthesized by solution route – the direct precipitation of Ba(NO₃)₂ and Na₂MO₄ (M = Mo and W) in ethylene glycol under 24 h stirring. The XRD patterns and SEM images proved that the products were tetragonal structured BaMoO₄ and BaWO₄ with uniform round nanoparticles. Shape, average particle size and particle-size distribution of products were analyzed by TEM – showing the round nanoparticles with the average size of 31.52 ± 4.65 nm for BaMoO₄, and 59.77 ± 9.61 nm for BaWO₄. The room temperature photoluminescence (PL) indicated that the products have strong blue emission centered at 441 nm – excited with 280 nm wavelength for BaMoO₄ NPs, and strong violet emission centered 378 nm – excited with 344 nm wavelength for BaWO₄ NPs. These PL behaviors attributed the existence of intrinsic transitions in the [MO₄]^2-$[{\text{MO}}_4{]}^{2-}$ (M = Mo and W) tetrahedrons of their crystal lattices.     

Calotropis procera mediated one pot green synthesis of Cupric oxide nanoparticles (CuO‐NPs) for adsorptive removal of Cr(VI) from aqueous solutions

The present study deals with the synthesis of CuO‐NPs via green route and investigated its application for removal of Cr(VI) from aqueous solutions. The experimental parameters were optimized through Box–Behnken Design (BBD) of response surface methodology for the optimum response. The adsorption equilibrium data was well fitted to Freundlich isotherm model and the kinetics was explained through pseudo‐second‐order kinetic model. The overall process was feasible, spontaneous and exothermic. Linear approach for analysing the isotherm as well as kinetic parameters was found more appropriate than the non‐linear approach. The adsorbent was successfully regenerated and reused up to five consecutive cycles without significant loss in removal capacity. The experimental results exhibited that CuO‐NPs can be a good alternative for Cr(VI) removal from aqueous solutions.     

B2C电子商务仓库拣货路径优化策略应用研究

当前国内B2C电子商务仓库多为人至物的拣货模式,拣货作业成为其核心作业之一,占据仓库大量时间成本和资金成本,拣货路径优化成为企业亟需解决的问题。本文基于TSP对拣货路径进行建模,利用蚁群算法、模拟退火算法和禁忌搜索对该NP-hard问题进行求解,并同当前企业普遍采用的S型启发式策略进行对比,拣货时间节约13.35%。进一步得出当拣货品数量较少时应采用模拟退火算法求解,而当拣货品数量较大时采用蚁群算法仅进行一次迭代,则可以实现短时间得到相对较优的解。所得结果已应用于某大型电子商务企业,效果明显。     

General synthesis of metal sulfides nanocrystallines via a simple polyol route

In this report, a simple and easy polyol route for synthesizing many binary metal sulfides nanocrystallines is demonstrated. Powder X-ray electron diffraction and energy-dispersive X-ray spectrum are applied to investigate the crystallinity and composition of the nanoscale materials. The resulting particle size and morphology are examined by transmission electron microscopy, and the possible mechanism is also briefly discussed.     

基于累积前景理论的石油管道路径方案优选

建立以一种基于前景理论的石油管道输送路径方案优选方法.首先依据决策者对各个属性的期望,将具有清晰数、区间数和语义短语三种形式的决策矩阵转化成为前景决策矩阵.其次,再利用主客观赋权偏差最小的思想,构建组合赋权模型,计算各个属性的权重;然后,根据决策者对待收益和损失的不同风险态度,计算各个方案的累积前景值.最后,以石化某油田外输管道路径方案问题为实例,介绍了该方法的决策流程,为解决同类工程方案优选问题提供了一种新的途径.     

Nanocrystalline CaTiO3 prepared by soft-chemical route

Nanocrystalline CaTiO₃ has been synthesized by using soft-chemical route. X-ray diffraction study indicates that as-prepared powders were amorphous in nature and formation of CaTiO₃ phase starts at about 773 K. Phase formation saturates at around 1023 K and it remains orthorhombic up to 1400 K. Microstructure analysis by the Rietveld method revealed that the CaTiO₃ crystal size varies from 22.9 to 49.3 nm, while the annealing temperature varies from 773 to 1023 K. The variation of DC resistivity with temperature in the range 400–560 K shows a polaronic behavior in this system.