Preparation and performance of crosslinked poly(arylene ether)s containing azobenzene chromophores

A series of novel poly(arylene ether)s with crosslinked groups and different azobenzene chromophores contents (azo-CPAEs: PAE-allyl20%-azo20%, PAE-allyl20%-azo40%, PAE-allyl20%-azo60%) were synthesized from a new bisfluoro monomer, (2,6-difluorophenyl)-(4-hydroxyphenyl)methanone. Their chemical structures were characterized by means of UV-vis and FI-IR. The thermal properties of the polymers were investigated by TGA and DSC, indicating the polymers had high glass transition temperatures (T_g > 147 °C) and good thermal stability (T_d5 > 360 °C) even when the contents of azobenzene chromophores was high to 60%. And the influence of thermal crosslinking on the performance of PAE-allyl20%-azo20%, a typical one of the series, was investigated. T_g of PAE-allyl20%-azo20% increased with the increase of heating time when heat-treated at 250 °C for 20, 40 and 60 min, indicating the crosslink degree of the polymer increased. After heat-treated for 60 min, T_g of PAE-allyl20%-azo20% increased to 175 °C from 147 °C before thermal crosslinking. Upon irradiation with a 532 nm neodymium doped yttrium aluminum garnet (Nd:YAG) laser beam, the remnant value of the polymer PAE-allyl20%-azo20% before and after the thermal crosslinking were 81 and 96%, respectively, meaning that the PAE-allyl20%-azo20% after thermal crosslink showed more stable photoinduced alignment than that before thermal crosslinking.     

Bioinspired Impact-Resistant and Self-Monitoring Nanofibrous Composites

Lightweight and impact-resistant materials with self-monitoring capability are highly desired for protective applications, but are challenging to be artificially fabricated. Herein, a scalable-manufactured aramid nanofiber (ANF)-based composite combining these key properties is presented. Inspired by the strengthening and toughening mechanisms relying on recoverable interfaces commonly existing in biological composites, mechanically weak but dense hydrogen bonds are introduced into the ANF interfaces to achieve simultaneously enhanced tensile strength (300 MPa), toughness (55 MJ m⁻³), and impact resistance of the nanofibrous composite. The achieved mechanical property combination displays attractive advantages compared with that of most of previously reported nanocomposites. Additionally, the nanofibrous composite is designed with a capability for real-time self-monitoring of its structural safety during both quasi-static tensile and dynamic impact processes, based on the strain/damage-induced resistance variations of a conductive nanowire network inside it. These comprehensive properties enable the present nanofibrous composite with promising potential for protective applications.     

High-temperature phase transition,coordination mechanism and magnetism in multiferroic YMnO<Subscript>3</Subscript> nanopowders

Single phase YMnO₃ nanopowders were successfully synthesized by a modified polyacrylamide gel route at an optimal sintering temperature. High temperature is helpful for further crystallization and the formation of single hexagonal YMnO₃. The process was monitored by X-ray diffraction as well as by X-ray photoelectron spectroscopy, transmission electron microscope, Fourier transform infrared spectrum and magnetic measurements. A mixture of orthorhombic and hexagonal phases was found to exist in the 800?°C, while for the metastable orthorhombic YMnO₃ phase complete conversion to hexagonal phase occurs at 950?°C. In the synthesis process, the coordination mechanisms of EDTA anions and metal ions (Y³⁺ and Mn³⁺) have been discussed on the basis of the experimental and computational results. The synthesis route used in this case has been aggreed to be more convenient for obtaining single hexagonal YMnO₃ phase than by the combination of hydrothermal synthesisand additional thermal treatment or the glycine–nitrate process. The magnetic susceptibility indicates that the anti-ferromagnetic transition temperature increases from 58 to 71 K with increasing sintering temperature from 800 to 950?°C.     

Configurable Integration of On‐Chip Quantum Dot Lasers and Subwavelength Plasmonic Waveguides

The integration of on‐chip dielectric lasers and subwavelength plasmonic waveguides has attracted enormous attention because of the combination of both the advantages of the high performances of the small dielectric lasers and the subwavelength plasmonic waveguides. However, the configurable integration is still a challenge owing to the complexity of the hybrid structures and the damageability of the gain media in the multistep micro/nanofabrications. By employing the dark‐field optical imaging technique with a position uncertainty of about 21 nm and combining the high‐resolution electron beam lithography, the small colloidal quantum dot (CQD) lasers without any damages are accurately aligned with the silver nanowires. As a result, the integration of the CQD lasers and the silver nanowires can be flexibly configured on chips. In the experiment, the tangential coupling, radial coupling, and complex coupling between the high‐performance CQD lasers and the subwavelength silver nanowires are demonstrated. Because of the subwavelength field confinements of the silver nanowires, the deep‐subwavelength coherent sources (multimode, one‐color single‐mode, or two‐color single‐mode) with a mode area of only 0.008λ² are output from these hybrid structures. This configurable on‐chip integration with high flexibility and controllability will greatly facilitate the developments of the complex functional hybrid photonic–plasmonic circuits.     

融合自注意力的关系抽取级联标记框架研究

命名实体识别和关系抽取是自然语言处理和知识图谱构建中两个十分重要的子任务。针对关系抽取过程中容易出现的错误传递和实体共享的缺陷,提出了一种融合自注意力机制的实体关系抽取级联标记框架Att-CasRel,不仅解决了级联错误,还能够解决同一个句子中多个关系三元组共享相同实体的问题。在Bert模型的基础上,使用CMeIE数据集的文本进行再训练得到适用于中文医疗领域的CB-Bert,并在尾实体识别阶段融入自注意力机制来增强头实体编码向量的特征表达,提高了模型的特征提取能力。在CMeIE数据集上的实验结果表明,该标记框架相较于独立抽取的模型以及其他联合抽取模型取得了更好的效果。     

Experimental study on the drainage gas recovery of an environmentally friendly nanofluid in tight gas reservoirs

The efficiency of gas recovery in tight gas reservoirs has been a challenge in the oil and gas industry for the past decade because conventional drainage or water-controlled gas recovery technologies typically have poor performance in low-permeability reservoirs. To solve this problem, self-made nanofluid was introduced to enhance drainage gas recovery in a tight gas reservoir. In this paper, nanofluid was prepared by phase reversal technology for application in a tight gas reservoir. Its thermal, acidic, alkaline, and salty stabilities were systematically investigated by using light transmittance as a shortcut index. At the same time, its biodegradability and biotoxicity were evaluated based on the industry/national standard, and the effectiveness of its drainage gas recovery was studied by dynamic gas–water percolation. The results showed that the self-made nanofluid can be effectively used for drainage gas recovery in tight gas reservoirs. The nanofluid has chemical stability and is environmentally friendly, which fully conforms to the contemporary development trend of the oil and gas industry. The nanofluid can shift the isotonic point of the gas–water relative permeability to the left (its minimum is 1.83% at 6.25 wt.% and maximum is 4.78% at 100 wt.%) and reduce the irreducible water saturation (its minimum is 8.84% at 6.25 wt.% and maximum is 4.28% at 100 wt.%), achieving the purpose of the enhancement of drainage gas recovery. The research results provide technical support for the application of nanofluid to improve the gas production in tight gas reservoirs.     

芦笋猕猴桃复合果酒发酵过程中挥发性香气物质的变化

以芦笋副产物为原料,经榨汁与猕猴桃汁混合,发酵制备芦笋猕猴桃复合果酒,并采用固相微萃取-气相色谱-质谱联用对芦笋猕猴桃复合果酒在发酵前期、中期、后期、后发酵、陈酿期中挥发性香气物质成分进行分析。整个发酵阶段共检测出78种挥发性香气物质,各发酵阶段中含量较高的挥发性香气物质均为酯类和醇类。其中,乙酯含量在总酯所占比例相对较大,分别为54.72%、79.20%、72.92%、76.60%和70.14%。随着发酵的进行,挥发性香气物质种类呈逐渐下降并趋于平稳的趋势,质量浓度呈先上升后下降并趋于平稳的状态。乙酸异戊酯、己酸乙酯、苯乙酸甲酯、辛酸乙酯、苯乙酸乙酯、癸酸乙酯、异戊醇、异丁醇、苯乙醇和2,4-二叔丁基苯酚为整个发酵阶段中共有的挥发性香气物质。采用气味活性值分析法得到13种特征香气物质,己酸乙酯和辛酸乙酯为整个发酵阶段中共有的特征香气物质,其中辛酸乙酯是在各发酵阶段中OAV值最大的化合物。发酵前期的主要特征香气物质为辛酸乙酯、苯乙醛;发酵中期和发酵后期的的主要特征香气物质为辛酸乙酯、己酸乙酯;后发酵和陈酿期的主要特征香气物质为辛酸乙酯、2-甲基丁基乙酸酯。该研究分析了芦笋猕猴桃复合果酒的特征风味,为其产业化开发提供理论参考。     

智能站配置文件规范性分析与整改措施研究

智能变电站配置文件(SCD文件)包含了全部配置信息,其正确性关系到变电站安全稳定运行.根据配置文件规范性检查内容和常见问题,采用基于可追溯技术的配置文件管控措施,解决配置规范性检验难题,以双母接线变电站标准信息流的虚端子连接为例,提出增加虚端子连接准确性的措施,为提升智能变电站配置文件准确性提供参考.     

Dielectric properties and defect mechanisms of (1-<Emphasis Type="Italic">x</Emphasis>)Ba(Fe<Subscript>0.5</Subscript>Nb<Subscript>0.5</Subscript>)O<Subscript>3</Subscript> -<Emphasis Type="Italic">x</Emphasis>BiYbO<Subscript>3</Subscript> ceramics

(1-x)Ba(Fe_0.5Nb_0.5)O₃ -xBiYbO₃ (BFN-xBY) ceramics were prepared by a conventional solid-state reaction method. The dielectric properties and relaxation behavior of BFN-xBY ceramics were analyzed according to dielectric and impedance spectroscopy. Dielectric permittivity of the ceramics increases with increasing temperature below 500 K then remains unchanged up to 700 K, while corresponding loss factor decreases with the increase of temperature below 500 K then increase slowly. Defect compensation mechanism of this system was analyzed in detail. The giant dielectric behavior of the ceramics arises from the internal barrier layer capacitor (IBLC) effect. Polarization effect at insulating grain boundaries between semiconducting grains accompanied by a strong Maxwell-Wagner (MW) relaxation mode. The characteristic of grain boundaries was revealed using impedance spectroscope and the universal dielectric response law.     

microRNA-148b对奶牛乳腺上皮细胞乳蛋白合成的影响

以奶牛乳腺上皮细胞(Dairy cow mammary epithelial cells,DCMECs)为研究模型,探讨microRNA-148b对DCMECs增殖和β-酪蛋白合成的影响.应用脂质体转染技术将miR-148b转染DCMECs,qRT-PCR观测其表达量,采用双荧光素酶实验验证miR-148b与转化生长因...