具有沉积结构环氧树脂电磁屏蔽材料的制备及表征

文中首先构筑具有三维结构的四针状氧化锌负载银(Ag@T-ZnO)和二维石墨烯纳米片(GNS)的混杂导电网络,随后灌注环氧树脂固化得到具有沉积结构的Ag@T-ZnO/GNS/EP复合材料,系统研究了Ag@T-ZnO和GNS的配比对复合材料屏蔽效能和力学性能的影响。当Ag@T-ZnO和GNS总质量分数为复合材料的20%且二者质量比为9:1时,二者之间的协同作用及独特的沉积导电网络结构赋予了复合材料优异的屏蔽效能和力学性能,在X波段的平均屏蔽效能可以达到83.8 dB,拉伸性能可达到51.6 MPa。为设计制备兼具优异力学性能和屏蔽性能的复合材料提供了新的思路。

Ultra-deep desulfurization by reactive adsorption desulfurization on copper-based catalysts

In this paper,a novel copper-based catalyst for FCC gasoline improving the ability of removal the sulfur and avoiding the loss of the octane number from olefin saturation by reactive adsorption desulfurization(RADS) was investigated.The series of Cu/Zn O-Al_2 O_3 catalysts were characterized by X-ray powder diffraction(XRD),N_2 adsorption analysis and temperature-programmed reduction(TPR) studies,X-ray photoelectron spectroscopy(XPS),scanning electron microscope(SEM) and transmission electron microscopy(TEM).The experiment results showed that the catalysts had an optimum desulfurization ability with copper loading 6 wt%,which the sulfur contents of product decreased less than 10 μg/g and olefin contents decreased from 16.19% to 14.14% for the long period operation.The appropriate Cu loading content could lead to the high active and low apparent activation energy(E_a).Therefore,the Cu-based catalyst may become a novel catalyst for second-generation for reactive adsorption desulfurization,which achieves the high desulfurization active and low olefins saturation to satisfy the upgrading the product.

Tall gastrodis tuber combined with antiepileptic drugs repairs abnormal perfusion foci in focal epilepsy

One hundred patients with focal epilepsy were recruited for the present study and their seizures controlled with antiepileptic drugs. The patients then orally received a capsule of tall gastrodis tuber powder, a traditional Chinese drug, and underwent single photon emission computed tomography, long-term electroencephalogram, and CT/MRI. Blood drug levels were monitored throughout the study. Before treatment with tall gastrodis tuber, 35 of the 100 cases had abnormal CT/MRI scans; 79 cases had abnormal single photon emission computed tomography images; 86 cases had abnormal electroencephalogram; and a total of 146 abnormal perfusion foci were observed across the 100 subjects. After treatment, the number of patients with normal single photon emission computed tomography images increased by 12; normal electroencephalogram was observed in an additional 27 cases and the number of patients with epileptiform discharge decreased by 29 （34% of 86）; the total number of abnormal perfusion foci decreased by 52 （36%） and changes in abnormal loci were visible in 65 patients. These changes indicate that the administration of tall gastrodis tuber in combination with antiepileptic drugs repairs abnormal perfusion foci in patients with focal epilepsy Our results demonstrate that traditional Chinese drugs can repair abnormal perfusion foci and, as such, are a promising new pathway in the treatment of focal epilepsy.

Preparation of a halogen-free P/N/Si flame retardant monomer with reactive siloxy groups and its application in cotton fabrics

A novel halogen-free phosphorus–nitrogen–silicon flame retardant monomer with reactive siloxy groups,N-(diphenylphosphino)-1,1-diphenyl-N-(3-(triethoxysilyl)propyl) phosphinamine(DPTA) has been synthesized and was applied to the fire-resistant finishing of cotton fabrics. The molecular structure of DPTA has been well characterized by elemental analysis, FTIR,1H NMR, and ^(31)P NMR spectroscopies. The chemically-grafted cotton fabrics, which were treated with 25 wt% DPTA, were obtained and confirmed by attenuated total reflectance Fourier infrared spectroscopy(ATR-FTIR). The flame retardancy and thermal property of the treated samples were investigated by limited oxygen index(LOI), vertical flammability test(VFT), thermogravimetric analysis(TGA) and microscale combustion calorimeter(MCC). It is noted that in vertical flammability test, the treated samples extinguished immediately upon removing the ignition source, whereas the untreated one was completely burned out. Furthermore, TGA and MCC tests revealed that the treated samples produced a high char formation and a low heated release during combustion. The surface morphology of the untreated and treated samples and the char residues after LOI tests were observed by scanning electron microscopy(SEM). Therefore, all the results showed that the treated cotton fabrics with 25 wt% DPTA apparently improved the fireresistant and thermal performances.

一种基于K—means算法的主题数据库规划方法

主题数据库规划一直是信息资源规划领域研究的重点，而实体聚合算法是影响主题数据库规划质量的关键。但是现有的计算实体聚合毖方法很容易陷入聚簇偏置，影响了规划质量。针对这一问题，作者首先计算实体对的亲和毖，然后将实体对的亲和关系看作网页之间的链接关系，使用PageRaxtk算法对实体对重要性排序，进而使用K—means算法迭代来聚合实体。实验结果表明本文提出的方法能够避免聚簇偏置，进而改善了主题数据库规划质量。

Coupling model for unsteady MHD flow of generalized Maxwell fluid with radiation thermal transform＊

This paper introduces a new model for the Fourier law of heat conduction with the time-fractional order to the generalized Maxwell fluid. The flow is influenced by magnetic field, radiation heat, and heat source. A fractional calculus approach is used to establish the constitutive relationship coupling model of a viscoelastic fluid. We use the Laplace transform and solve ordinary differential equations with a matrix form to obtain the velocity and temperature in the Laplace domain. To obtain solutions from the Laplace space back to the original space, the numerical inversion of the Laplace transform is used. According to the results and graphs, a new theory can be constructed. Comparisons of the associated parameters and the corresponding flow and heat transfer characteristics are presented and analyzed in detail.

Numerical Analysis of the Rotational Magnetic Springs for EDS Maglev Train

Different from the traditional railway trains,the combined levitation and guidance EDS maglev train is more likely to rotate after being disturbed.Therefore,the rotational electromagnetic stiffnesses are significant operating parameters for the train.In this paper,the different effects of each translational offset generated in the rotational motion on the corresponding rotational electromagnetic stiffnesses in the EDS maglev train are analyzed and calculated.Firstly,a three-dimensional model of the maglev train is established.Then,based on the space harmonic method and the equivalent circuit of the levitation and guidance circuits,the formulas of rolling,pitching and yawing stiffness are presented.Finally,by comparing with the three-dimensional finite element simulation results,the key translational displacements in the rotational motion which has a great impact on the stiffness are obtained.Hence,the three-dimensional analytical formula can be simplified and the computation can be reduced.In addition,the accuracy of the calculation results is verified by comparing with the experimental data of Yamanashi test line.

数字金融对中小企业融资的影响

中小企业融资困难一直是我国的热点问题,但随着近几年数字金融的发展,中小企业在融资过程中又迎来了新的契机。本文基于对现状进行分析的基础上,探析了中小企业融资困难成因及数字金融的特点,重点阐述了数字金融对中小企业融资的影响,旨在为我国中小企业在新的机遇下健康成长提供合理的建议和帮助。

A Method of Identifying Thunderstorm Clouds in Satellite Cloud Image Based on Clustering

In this paper,the clustering analysis is applied to the satellite image segmentation,and a cloud-based thunderstorm cloud recognition method is proposed in combination with the strong cloud computing power.The method firstly adopts the fuzzy C-means clustering(FCM)to obtain the satellite cloud image segmentation.Secondly,in the cloud image,we dispose the‘high-density connected’pixels in the same cloud clusters and the‘low-density connected’pixels in different cloud clusters.Therefore,we apply the DBSCAN algorithm to the cloud image obtained in the first step to realize cloud cluster knowledge.Finally,using the method of spectral threshold recognition and texture feature recognition in the steps of cloud clusters,thunderstorm cloud clusters are quickly and accurately identified.The experimental results show that cluster analysis has high research and application value in the segmentation processing of meteorological satellite cloud images.

基于外场辅助制备聚合物基电磁屏蔽复合材料

通讯技术不断升级以及移动设备的快速发展极大改善了人们生活,但也带来了电磁干扰和信息安全问题.因此,亟需开发高性能电磁屏蔽材料来抑制电磁辐射和阻止信息泄露.研究发现,在外力作用下填料的自取向行为有助于实现聚合物基复合材料电磁屏蔽性能的提升,因此如何在聚合物基体中构筑有效的填料取向结构正成为电磁屏蔽材料研究的热点.本文首先关注外场诱导复合材料内导电网络的构建策略.随后,梳理了利用外场诱导无机填料取向制备聚合物基电磁屏蔽复合材料的研究进展,其中外场包括温度场、静电场、重力场、机械力场和磁场.值得注意的是,基于外场诱导制备的独特结构与电磁波之间的特殊响应关系通过精选的案例被进一步剖析.最后,提出外场辅助制备聚合物基电磁屏蔽复合材料各自亟待解决的关键科学和技术问题,并对未来的发展方向进行了理性预测.本文讨论的方法和提出的策略有望为高性能聚合物基电磁屏蔽复合材料的创新设计提供一些指导意见.

Polydopamine/polyethyleneimine co-crosslinked graphene oxide for the enhanced tribological performance of epoxy resin coatings

To enhance the wear resistance of graphene oxide(GO)nano-filled epoxy resin(EP)coatings with ex-cellent dispersion,GO were modified using a co-crosslinking strategy between polydopamine(PDA)and polyethyleneimine(PEI)through an environmentally friendly,simple and low-cost process.High-density amino-branched PEI and highly adhesive PDA formed covalent bond cross-links with GO(PDA/PEI-GO)through the Michael addition and Schiffbase reactions.With the introduction of amino active sites,the PDA self-polymerization reaction time was significantly shorted from 24 to 6 h.The covalently cross-linked network increased the lamellar spacing of GO and enhanced the interfacial bonds between the PDA/PEI-GO lamellae and EP matrix.Due to the improved dispersion and surface activity of GO,the PDA/PEI-GO nano-filled EP coating exhibited excellent wear resistance.Reciprocating friction with GCr15 stainless steel ball,the average friction coefficient and wear rate of the coating were reduced by 31.9%and 62.7%,respectively,compared to the pure EP coating.In addition,the wear mechanism of the PDA/PEI-GO/EP coating changed from adhesive and fatigue wear to abrasive wear,and it maintained good wear resistance by forming a GO lubrication transfer film on the counterpart surface.Therefore,this study may provide a new strategy for improving the dispersion of graphene in wear-resistant polymer materials for practical applications.

Transient Chemical Activation of Covalent Bonds for Healing of Kinetically Stable and Multifunctional Organohydrogels

It remains a great challenge to balance the kinetic stability and intrinsic healing ability of polymer materials.Here,we present an efficient strategy of using a synthetic reaction cycle to regulate the intrinsic healing ability of thermodynamically stable and kinetically inert multifunctional organohydrogels.By combining a double decomposition reaction with spontaneous energy dissipation,we can construct the simplest synthetic reaction cycle that can induce a transient out-of-equilibrium state for achieving the healing of organohydrogels with kinetically locked acylhydrazone bonds.In addition to balancing kinetic stability and healing ability,the synthetic reaction cycle also enables the polymer materials to have high tolerance to organic solvents,high ionic strength,high and low temperatures,and other harsh conditions.Therefore,the kinetically stable and healable organohydrogels remain mechanically flexible and electrically conductive even down to−40°C and are readily recyclable.The integration of chemical networks into healable polymers may provide novel,versatile materials for building next-generation electronic devices.

Investigation of a root zone heating system for greenhouse seedling and its effects on micro-environment

Under the extremely cold climatic condition,crops have to survive severe heat stress conditions,even if they are being kept in greenhouses.In the winter and spring of North China,the air and soil temperature is low inside the greenhouse,and when using a traditional heating system,the energy consumption is high.This paper reports on a study of different design solutions for a root zone heating system based on a kind of low temperature radiation material.Root zone heating systems offer increasing crop quality and productivity.A novel type of heat preservation and root zone heating system was applied in greenhouse seedling.And through multiple experiments,the effect of the root zone heating system on the ambient environment and seedbed surface was studied,and the heat preservation effect and heating uniformity were discussed.Results show that single-layer film covering on the root zone heating system can make the average temperature at night increase 1°C.And the average seedbed surface and substrate temperature can increase 11.3°C and 5.2°C,respectively.In conclusion,the root zone heating system can effectively improve the environmental temperature of seedling and the uniformity of heating is high,which provides a strong guarantee for high-quality seedling cultivation.

Energetic particles’fluxes and dose in the Radiation Gene Box measured by space radiation detector onboard SJ-10 satellite

Background To evaluate the hazard of space radiation posing to the tissues,it is important to obtain exact fluxes of different radiation particles.The Radiation Gene Box(RGB)onboard SJ-10 spacecraft was an instrument designed to investigate the effects of space environment on the mESCs and drosophila.To derive the dose received by the tissues inside the RGB,the Space Radiation Detector(SRD)was installed inside it.Purpose The SRD was designed to derive the fluxes of electron,proton,hellion and gamma rays around it.If the type of the particles,the energies,the fluxes and the conversion coefficients are known,the dose received by the tissues could be evaluated.Methods The SRDwas designed as a △E-E solid-state telescope.By measuring the energy deposited in the three subdetectors,the particles’type and their energies could be discriminated.The data of SRDwere divided into 15 bins by the types of particles and their energy ranges.Results The gamma ray flux was higher than any other particle flux inside the RGB,and the electron was the most intense charge particle,while the helium ion was the most harmful radiation to the cells inside the RGB.Conclusion The dose rate inside the Radiation Gene Box was much higher than in the ground,but the integral dose of 12 days inside the RGB was about 2.13 mSv.It seemed unlikely to have obvious biological effects on the tissues of mice and drosophila.

Molecular Switches and Multiple Logic Gates Based on 4-（2-Pyridylazo）resorcinol

A simple-structured 4-（2-pyridylazo）resorcinol （PAR） system presents interesting properties with dual fluorescent outputs. Modulated by solution pH two kinds of reversible switch behaviors, ＂ON-OFF＂ and ＂OFF-ON＂, were realized with the PAR system. Stimulated by different combination of external stimulus, such as metal ions, UV ir- radiation and solution pH, the PAR system could perform multiple logic functions including three inputs AND, two inputs INHIBIT and combinatorial ＂NOR/AND＂ in parallel. The operation of the designed system is very simple and detected with a high sensitive fluorescent signal.

Result of proton beam energy calibration of GECAM satellite charged particle detector

Purpose A charged particle detector(CPD)is one of two main detectors on the GECAM satellite.It was designed to detect charged particles.Electrons and protons are space’s mainly charged particles.So,a research on the proton detection ability of a CPD and deriving the energy response to charged particles of the CPD in the two designed operating modes is important.Method The proton calibration tests of the CPD under diferent working modes were carried out at the Heavy Ion Research Facility in Lanzhou.Result and conclusion Through testing and analysis,it was concluded that when CPD works in semi-component mode,it can detect the maximum energy,and when working in full-component mode,it can provide better energy resolution.