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Poly(p-phenylene terephthalamide) (PPTA) is one kind of lyotropic liquid crystal polymer. Kevlar fibers performed from PPTA are widely used in many fields due to their superior mechanical properties resulting from their highly oriented macromolecular structure. However, the “infusible and insoluble” characteristic of PPTA gives rise to its poor processability, which limits its scope of application. The strong interactions and orientation characteristic of aromatic amide segments make PPTA attractive in the field of self-assembly. Chemical derivation has proved an effective way to modify the molecular structure of PPTA to improve its solubility and amphiphilicity, which resulted in different liquid crystal behaviors or supramolecular aggregates, but the modification of PPTA is usually complex and difficult. Alternatively, higher-order all-PPTA structures have also been realized through the controllable hierarchical self-assembly of PPTA from the polymerization process to the formation of macroscopic products. This review briefly summarizes the self-assembly methods of PPTA-based materials in recent years, and focuses on the polymerization-induced PPTA nanofibers which can be further fabricated into different macroscopic architectures when other self-assembly methods are combined. This monomer-started hierarchical self-assembly strategy evokes the feasible processing of PPTA, and enriches the diversity of product, which is expected to be expanded to other liquid crystal polymers.

Knowledge graphs are usually constructed to describe the various concepts that exist in real world as well as the relationships between them. There are many knowledge graphs in specific fields, but they usually pay more attention on text or structured data, ignoring the image vision information, and cannot play an adequate role in the emerging visualization applications. Aiming at this issue, we design a method that integrates image vision information and text information derived from Wikimedia Commons to construct a domain-specific multi-modal knowledge graph, taking the metallic materials domain as an example to illustrate the method. The text description of each image is regarded as its context semantic to acquire the image's context semantic labels based on the DBpedia resource. Furthermore, we adopt deep neural network model instead of simple visual descriptors to acquire the image's visual semantic labels using the concepts from WordNet. In order to fuse the visual semantic labels and context semantic labels, a path-based concept extension and fusion strategy is proposed based on the conceptual hierarchies of WordNet and DBpedia to obtain the effective extension concepts as well as the links between them, increasing the scale of the knowledge graph and enhancing the correlation between images. The experimental results show that the maximum extension level has a significant impact on the quality of the generated domain knowledge graph, and the best extension level number is respectively determined for both DBpedia and WordNet. In addition, the results of this paper are compared with IMGpedia to further show the effectiveness of the proposed method.

We use the quadrature method to show the existence and multiplicity of positive solutions of the boundary value problems involving one-dimensional p-Laplacian u′t|p−2u′t′+λfut=0, t∈0,1, u(0)=u(1)=0, where p∈(1,2], λ∈(0,∞) is a parameter, f∈C1([0,r),[0,∞)) for some constant r>0, f(s)>0 in (0,r), and lims→r-(r-s)p-1f(s)=+∞.

The direct synthesis of polymer microspheres modified by aramid nanofibers (ANFs) is an interesting challenge. This work describes a simple aqueous process to prepare polystyrene (PS)/ANF composite microspheres, where the specific ANF network was "dressed" on PS. ANF was derived from the copolymerization of terephthaloyl chloride, p-phenylene diamine, and methoxypolyethylene glycol and could be dispersed in water stably. We applied the as-synthesized ANF as a Pickering emulsifier in the o/w emulsion of styrene monomer. Radical polymerization was subsequently initiated in the Pickering emulsion system. The combination of ANF with polymer spheres was revealed by scanning electron microscopy (SEM) and thermal gravity analysis. The role of ANF in the monomer emulsion as well as in the polymerization was studied through SEM, optical microscopy, optical stability analyzer, and pulse nuclear magnetic resonance combined with the polymerization kinetic analysis. Moreover, we investigated the effects of other synthesis parameters, such as monomer type, monomer content, pH value, and salt concentration. [ABSTRACT FROM AUTHOR]

The yields of 85Krm, 87Kr and 88Kr of neutron-induced fission of 239Pu are important nuclear parameters. They have a moderate half-life, are β- decay and emission γ-rays with a certain probability, so it is appropriate to use γ-ray spectrum method to determine their yield. At present, there are few experimental data with large deviation abroad and no experimental results have been reported in China. The yield measurements of 85Krm, 87Kr and 88Kr of thermal-neutron-induced fission of 239Pu were carried out based on the irradiation of plutonium target by Xi’an Pulsed Reactor rabbit system. The purified plutonium solution was then titrated and dried to prepare the silica-encapsulated plutonium target. Three kinds of measurement experiments were designed: γ-ray nondestructive method for the relative yield of 88Kr and 99Mo, gas-solid separation method for 85Krm, 87Kr and 88Kr and γ-ray nondestructive method for the relative yield of 85Krm, 87Kr and 88Kr. After the target irradiation and cooling, the fission products were measured by the above-mentioned methods. The efficiency of the three kinds of experimental samples was calibrated by the equivalent efficiency curve method. The plan source of organic glass package was used to equate the efficiency calibration of quartz tube source, and the plan source of stainless steel package with the same thickness and material as the measuring source was used to equate the efficiency calibration of 50 mL gas source. By Monte Carlo simulation, the suitable equivalent position was selected, and the efficiency value was fine corrected (less than 0.8%). The uranium target was prepared in the same way of plutonium target. The relative yields of 85Krm, 87Kr and 88Kr of 235U fission induced by thermal neutron measured by gas-solid separation after irradiation are consistent with the recommended values of the evaluation database, which indicates that the release rates of 85Krm, 87Kr and 88Kr in the plutonium target are the same. After modified by the influence of non-primary neutron field and non-primary isotope, the fission yields of 85Krm, 87Kr and 88Kr were obtained based on the measured relative yield with reference product 99Mo and the yield of 99Mo given by ENDF/BⅧ.0 evaluation database. The measured yields are (0.559±0.020)%, (0.992±0.034)% and (1.264±0.037)%, respectively, which are consistent with the evaluation value of the database and the uncertainty is significantly reduced compared with other literature value. In this paper, the retrieval and deduction methods of γ-ray energy peak interference ratio in measurement are universal, but the uncertainty of theoretical yield may be added. The experimental method in this paper can also provide reference for the measurement of fission product yield at different neutron energy points.