加压下液体过热的亚稳态

本文用液滴悬浮法测定了十四种碳氢化合物的加压情况下的过热极限，并经筛选由ｍｖｄＷ方程对过热极限进行了预测，发现两者符合较好。     

Effect of interfacial chemistry on the linear rheology and thermal stability of poly(arylene ether nitrile) nanocomposite films filled with various functionalized graphite nanoplates

Poly(arylene ether nitrile) (PEN) nanocomposites filled with functionalized graphite nanoplates (GNs) were prepared by a simple solution‐ casting method and then characterized by rheometer and thermogravimetric analysis (TGA). This study investigates how the surface treatment of GNs affects the GN dispersion state. The linear rheological test indicated that the 4‐aminophenoxyphthalonitrile‐grafted GN (GN‐CN) presented better dispersion in PEN matrix than purified GN because the corresponding composite showed the lower rheological percolation threshold, which was further confirmed by scanning electron microscopy and solution experiments. The TGA revealed that the presence of 4‐aminophenoxyphthalonitrile‐grafted GN retarded the depolymerization evidently compared with that of purified GN, showing remarkable increase in the temperatures corresponding to a weight loss of 5 wt % (increased by 21°C) and maximum rate of decomposition (increased by 9°C). Both the dispersion state and the surface functionalization of GN are very important to the thermal stability of PEN matrix. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Biochip with integrated pumps for plug-based sequential exchange of solutions

A novel method for exchanging solutions used in biochemical analyses and a device to carry out the exchange are proposed. An array of plugs formed using six injectors was transported in a microflow channel using a main pump located at one end of the main flow channel. The injectors and main pump were operated on the basis of the change in volume caused by the electrolysis of water. Bubbles were produced from working electrodes; these bubbles caused a diaphragm placed below the injectors to inflate and occlude the inlet of the solution reservoir. Increase in the number of bubbles caused the reservoir to inject the solution into the main flow channel in the form of a plug. Each plug was individually transported downstream to the sensing area by the main pump, which was operated in a similar manner to the injector. The device was used for the detection of a tumor marker, α-fetoprotein (AFP). Plugs of necessary solutions were individually transported to the sensing area with immobilized primary antibodies to allow antigen–antibody binding, cleaning, and detection. The fluorescence intensity from the antibodies showed clear dependence on the concentration of AFP. The immobilization of antibodies could also be carried out on-chip.     

Mesophase structure discovered through in-situ X-ray measurement in drawing process of poly(ethylene 2,6-naphthalene dicarboxylate) fiber

The structure development in the continuous laser-heated drawing process of poly(ethylene 2,6-naphthalene dicarboxylate) (PEN) fiber was analyzed by in-situ X-ray diffraction measurement. Because of the rapid and uniform laser heating, and the resultant steady-state nature of the necking-drawing, the structure development after the on-set of necking could be measured in the time resolution of several hundred microseconds. We found for the first time the temporal appearance of meridional (001′) diffraction at several milliseconds after the on-set of necking indicating that the mesophase structure similar to the one reported for poly(ethylene terephthalate) was also formed in the initial stage of fiber structure development of PEN. The d-spacing of the (001′) diffraction 1.230 ± 0.003 nm was shorter than the c-axis lengths of both α and β crystals.     

IPC-80亚、跨、超音速风洞弹丸及飞行器试验测试系统

本文主要介绍亚、跨、超音速风洞基本结构及气动原理,新配置的IPC-80测试系统。论述了弹丸及飞行器气动试验模拟信号处理、变换采样、数字量取真、模型迎角和阀位循环码读取方法,对标模动校作了测试精度考核。     

Factors affecting the oxidative activity of laccase towards biphenyl derivatives in homogeneous aqueous-organic systems

Catalytic oxidation of biphenyl derivatives was investigated using laccase in a homogeneous aqueous-organic system. A thermostable laccase from Trametes sp. showed the highest catalytic activity for the oxidation of 4-hydroxybiphenyl (4-HB) at a reaction temperature of 60 degrees C when dimethylsulfoxide (DMSO) was employed as a co-solvent. Furthermore, the catalytic performance was successfully enhanced by the incorporation of a laccase mediator system (LMS) into the aqueous-DMSO media. The catalytic performance strongly depended on the type of mediator, and the highest activity was observed with 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as mediator, suggesting the importance of the selection of a suitable mediator. It was verified that this mediator system is applicable to the oxidation of several biphenyl derivatives with hydroxyl groups.     

CARD资源发现架构在无线传感网络中的性能研究

(西北工业大学计算机学院,陕西西安,710072)【摘要】CARD架构适用于大规模、高查询率、每次查询的数据传输量较小的Ad-hoc网络,它的核心目标是降低网络资源发现能耗,延长网络生命周期。文章首先介绍了CARD架构的结构;然后,建立了该架构的数学模型,该模型以无线传感器网络为目标场景,并推导出CARD架构的能耗和查询成功率与各个参数之间的函数关系;最后,根据该模型对CARD架构的能耗和查询成功率进行了理论分析,为CARD架构的参数选择提供了可靠的依据,并为对架构的进一步优化打下了坚实基础。     

Role of support in reforming of CH4 with CO2 over Rh catalysts

The reforming of CH₄ with CO₂ over supported Rh catalysts has been studied over a range of temperatures (550–1000 K). A significant effect of the support on the catalytic activity was observed, where the order was Rh/Al₂O₃>Rh/TiO₂>Rh/SiO₂. The catalytic activity of Rh/SiO₂ was promoted markedly by physical mixing of Rh/SiO₂ with metal oxides such as Al₂O₃, TiO₂, and MgO, indicating a synergetic effect. The role of the metal oxides used as the support and the physical mixture may be ascribed to the promotion in dissociation of CO₂ on the surface of Rh, since the CH₄ + CO₂ reaction is first order in the pressure of CO₂, suggesting that CO₂ dissociation is the rate-determining step. The possible model of the synergetic effect was proposed.     

Study on chemical structures of poly (tetrafluoroethylene-co-perfluoroalkylvinylether) by soft-EB irradiation in solid and molten state

Poly (tetrafluoroethylene-co-perfluoroalkylvinylether) (PFA) was irradiated by soft electron beam (soft-EB) under nitrogen gas atmosphere in solid-state and its molten state, respectively. The changes of thermal property and chemical structures of irradiated PFA in solid-state and molten state were studied by differential scanning calorimetric analysis (DSC) and solid-state ¹⁹F magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. By DSC analysis, the melting temperature shifted to lower temperatures, and crystallinity decreased with increasing soft-EB dose. By solid-state ¹⁹F MAS NMR spectroscopy, the new signals was observed and the detected new signals in irradiated PFA at 315 °C and at 30 °C were due to the tertiary carbon group with branching site (Y-type crosslinking site), perfluoro-propylene site and chain end methylene groups, respectively.Moreover, the molar ratio of perfluoroalkylvinylether (FAVE) structure to -CF₂- units decreased with increasing dose.     

水中非合作运动磁性目标跟踪及参数估计

针对水中非合作运动磁性目标的跟踪及参数估计问题,提出了一种基于Hopfield神经网络和磁梯度张量定位结合粒子滤波的方法对磁性目标进行跟踪,利用Hopfield神经网络和磁梯度张量定位为粒子滤波算法提供一部分更加优化的粒子,以增加粒子滤波算法中粒子的多样性,能够有效克服粒子退化现象,同时保证动态跟踪的速度和精度,并解决了远场磁定位中信噪比下降的问题.通过模拟仿真和磁性船模磁定位实验验证了算法的有效性,该算法可用于空中磁探潜和港口磁防御以及一般的UXO探测和定位问题,具有一定的军事和民用意义.