Synthesis and fluorescent investigations of VBL-based waterborne polyurethane dye

Fluorescent brightening agent VBL-based waterborne polyurethane dye (VBL-WPU) was synthesized by incorporation of VBL into waterborne polyurethane chains. The expected structure of polymeric fluorescent brightening agent was confirmed by FT-IR and UV-vis spectra. The molecular weight, average particle sizes and the contents of VBL segments in VBL-WPU were investigated. This polymeric dye exhibited intriguing optical behaviors. The absorption and emission maxima of VBL-WPU showed obviously hypsochromic shift in comparison with those of VBL. The fluorescence intensity of the polymer was prominently enhanced comparing with VBL because of the changes of micro-circumstance of VBL. Furthermore, the fluorescence of VBL-WPU was not sensitive to hydroquinone quencher.     

Synthesis and characterization of highly ordered BiFeO3 multiferroic nanowire arrays

We report the synthesis and characterization of multiferroic BiFeO₃ (BFO) nanowires. The perovskite BFO nanowires with diameters about 60 nm and lengths about 10 μm were fabricated by means of the sol-gel method utilizing nanochannel alumina templates with post annealing at 700 °C. The microstructure of the BFO nanowires was investigated by means of x-ray diffraction and transmission electron microscopy, and the ferroelectric characteristic of BFO nanowires were demonstrated.     

简捷微波合成多角星形氧化锌

Using Zn(acac)₂ as precursor, ethylenediamine as base, distilled water as solvent, multigonal(octagonal and above) star-shaped ZnO microcrystals with high purity and even particle size have been prepared in domestic microwave oven by low heating for 8 min. The obtained powder was characterized by XRD, FESEM and TEM. The individual star-shaped ZnO microcrystal was composed of some hexagonal nanocones with diameters of 100～500 nm and lengths of 0.6～1 μm growing along c axis. The room temperature PL spectrum showed a strong broad yellow emission with peak located at 564 nm. The deep-level involved in the yellow luminescence is attributed to interstitial oxygen.     

Compact images of spaces with a weaker metric topology

If X is a space that can be mapped onto a metric space by a one-to-one mapping, then X is said to have a weaker metric topology. In this paper, we give characterizations of sequence-covering compact images and sequentially-quotient compact images of spaces with a weaker metric topology. The main results are that (1) Y is a sequence-covering compact image of a space with a weaker metric topology if and only if Y has a sequence of point-finite cs-covers such that for each y ∈ Y. (2) Y is a sequentially-quotient compact image of a space with a weaker metric topology if and only if Y has a sequence of point-finite cs*-covers such that for each y ∈ Y. Supported by the NNSF(10471084) of China.     

Maximizing lifetime of a wireless sensor network via joint optimizing sink placement and sensor-to-sink routing

Wireless sensor networks typically contain hundreds of sensors. The sensors collect data and relay it to sinks through single hop or multiple hop paths. Sink deployment significantly influences the performance of a network. Since the energy capacity of each sensor is limited, optimizing sink deployment and sensor-to-sink routing is crucial. In this paper, this problem is modeled as a mixed integer optimization problem. Then, a novel layer-based diffusion particle swarm optimization method is proposed to solve this large-scaled optimization problem. In particular, two sensor-to-sink binding algorithms are combined as inner layer optimization to evaluate the fitness values of the solutions. Compared to existing methods that the sinks are selected from candidate positions, our method can achieve better performance since they can be placed freely within a geometrical plane. Several numerical examples are used to validate and demonstrate the performance of our method. The reported numerical results show that our method is superior to those existing. Furthermore, our method has good scalability which can be used to deploy a large-scaled sensor network.     

轴对称压差系统的自相似解

考察了二维压差系统的轴对称活塞均匀膨胀而产生的自相似流动.在轴对称和自相似假设下,该问题可以简化为一个自治的非线性常微分方程组的自由边值问题.通过对常微分方程组的积分曲线性质的详细分析,建立该自由边值问题正光滑解的整体存在性.     

The influence of organo-modified sepiolite on the flame-retardant and thermal properties of intumescent flame-retardant polylactide composites

Polylactide (PLA) composites based on intumescent flame-retardant (IFR) and organo-modified sepiolite (OSEP) were prepared via direct melt compounding. The uniform dispersion of OSEP in the PLA matrix was observed by TEM, but some agglomerates still existed at the high loading. Tensile results showed that high loading of the conventional IFR led to a reduction in tensile strength of PLA composites; however, replacing a portion of the IFR with modified sepiolite in the PLA matrix improved this result. The thermal degradation temperature of the PLA/IFR/OSEP composites determined by thermogravimetric analysis was lower than that of neat PLA, as a consequence of the catalyzed carbonization induced by the addition of IFR and OSEP. The formulation with 13 mass% IFR and 2 mass% OSEP exhibited the highest LOI value of 32 vol% and also reached UL-94 V-0 rating in the vertical burning tests. Furthermore, the co-addition of IFR and OSEP gave rise to a significant reduction in peak heat release rate (PHRR) and total heat release (THR) of PLA composites during combustion, particularly in the case of PLA/IFR13/OSEP2 (82% reduction in PHRR and 69% in THR). The excellent fire resistance of PLA/IFR13/OSEP2 could be attributed to that IFR catalyzed carbonization of PLA to form the char, while OSEP resulted in further stabilization in the charred layers.     

Investigation of thermal decomposition of polymer nanocomposites with different char residues

The pyrolysis process of polypropylene (PP), PP‐based nanoclay composites, acrylonitrile‐butadiene‐styrene (ABS), and ABS/metal hydroxide nanorods (MHR)/grapheme nanosheets (GNS) composites in a cone calorimeter test was simulated with a recently developed numerical codes, the Federal Aviation Administration ThermaKin. First, the heat release rate (HRR) and the surface temperature as a function of time were compared with experiment data. With reasonable input parameters, the pyrolysis behaviors were predicted reasonably. Subsequently, the influence of the properties of char residue on the HRR was discussed. The char residue of PP/nanoclay acted as a heat transfer barrier, while the char layer of ABS/MHR/GNS acted as a mass transfer barrier. Finally, the sensitivity of the residue characteristic parameters to the model output was discussed. Copyright © 2015 John Wiley & Sons, Ltd.     

Molecular simulations of host-guest interactions between zeolite framework STW and its organic structure-directing agents

Zeolites have been widely applied in many chemical processes owing to their featured microporous framework structures. Organic structure-directing agents (OSDAs) play an important role during of the formation of zeolite frameworks via non-bonding host-guest interactions. Understanding these interactions is crucial to the design of OSDAs and the synthesis of target zeolites. Here, we report a molecular simulation study in the host-guest interactions between zeolite framework STW and 21 alkylated imidazolium and pyrazolium cations that have been used as the OSDAs for the synthesis of STW-type zeolites. We find that OSDAs that have successfully directed the formation of STW exhibit stronger host-guest interactions than unsuccessful ones. Furthermore, we find all successful OSDAs possess relatively more negative atomic charges on nitrogen atoms and smaller dipole moments. According to this finding, we have designed seven new alkylated imidazolium and pyrazolium cations that may be suitable for zeolite STW, and verified their structure-directing capability by molecular simulation calculations.     

ITER纵场的电磁分析与电源系统的概念设计

进行了ITER纵场磁体电源系统的概念设计.首先,对ITER主机基于循环对称算法,借助ANSYS软件进行了电磁的分析,然后根据电磁分析得到的结果,设计了ITER纵场磁体电源的拓扑结构,分析了整流器的输出电压波形;其次,基于电磁分析的结果,设计了ITER纵场磁体失超保护系统,并计算了磁体失超保护电路中的关键部件-电容和电阻...