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排序方式: 共有192条查询结果,搜索用时 156 毫秒
21.
N. A. Belov R. Yu. Nikiforov M. V. Bermeshev Yu. P. Yampolskii E. Sh. Finkelshtein 《Petroleum Chemistry》2017,57(11):923-928
Polypentafluorostyrene (PPFS) (M w = 1.7 × 105 Da, M w /M n = 1.6, and Т g = 110°С) has been synthesized by radical polymerization of pentafluorostyrene. The chemical structure of the polymer has been confirmed by 1H and 19F NMR data. The permeability and diffusion coefficients of gases (He, H2, O2, N2, CO2, and CH4) have been measured on a barometric setup. The permeability, diffusion, and solubility coefficients of gases have been shown to increase with the increases in the fluorine content in the repeat unit of the polymer in the polystyrene–poly(p-fluorostyrene)–PPFS series. Such behavior of transport parameters in the polymer series is associated with the growth in the fractional free volume and decrease in the cohesive energy density. The investigated polymers on the basis of styrene and its derivatives including PPFS are located in the middle of clouds of Robeson diagrams for N2/CH4, CO2/CH4, and O2/N2 and are not of interest for their separation. 相似文献
22.
Geints YE Zemlyanov AA Kabanov AM Bykova EE Apeksimov DV Bukin OA Sokolova EB Golik SS Ilyin AA 《Applied optics》2011,50(27):5291-5298
We report on the experiments on the interaction of gigawatt femtosecond laser pulses with suspended millimeter-sized water droplets. The transparent droplets experienced laser-induced breakdown and explosive boiling up and emitted a broadband radiation. This radiation covers the spectral range from 450 to 1100?nm and consists of the spectrum of laser pulse scattered and transformed by the droplet due to self-phase modulation and plasma emission produced in water during photoionization. The droplet emission spectrum showed remarkable broadening at all viewing angles and is maximal in the direction of the laser exit from the droplet. The enlargement of the droplet results in additional spectral spreading of the emitted radiation. The depth and amount of laser pulse spectral self-transformations upon propagation through the water droplet are simulated by means of numerical calculations. 相似文献
23.
Yurii P. Stefanov 《International Journal of Fracture》2004,128(1):345-352
Localized deformation band formation and crack generation in elastic brittle-plastic materials were simulated numerically in various loading conditions. Cracking patterns for a specimen with a failed inclusion and for a damaged layer of a geomedium in shear, as well as for a sandstone specimen in compression, were obtained. To describe deformation, a complex approach was used. According to this approach, in the course of plastic deformation damages are accumulated and govern bulk plastic deformation. Due to damage accumulation, strength decreases and material degradation occurs, while macrocrack opening and material fracture take place only under the action of tensile stresses. 相似文献
24.
25.
Method for reconstructing atmospheric optical parameters from the data of polarization lidar sensing
Inversion of polarization lidar sensing data based on the form of the lidar sensing equation with allowance for contributions from multiple-scattering calls for a priori information on the scattering phase matrix. In the present study the parameters of the Stokes vectors for various propagation media, including those with the scattering phase matrices that vary along the measuring range, are investigated. It is demonstrated that, in spaceborne lidar sensing, a simple parameterization of the multiple-scattering contribution is applicable and the polarization signal's characteristics depend mainly on the lidar and depolarization ratios, whereas differences in the angular dependences of the matrix components are no longer determining factors. An algorithm for simultaneous reconstruction of the profiles of the backscattering coefficient and depolarization and lidar ratios in an inhomogeneous medium is suggested. Specific features of the methods are analyzed for the examples of interpretation of lidar signal profiles calculated by the Monte Carlo method and are measured experimentally. 相似文献
26.
Dmitry A. Alentiev Elena S. Egorova Maxim V. Bermeshev Ludmila E. Starannikova Yuri P. Yampolskii Eugene Sh. Finkelshtein 《Polymer Engineering and Science》2019,59(12):2502-2507
Here, we report the synthesis and the study of gas‐transport properties of crosslinked highly permeable copolymers from Si‐containing norbornene derivatives. The initial high‐molecular‐weight copolymers were prepared via addition copolymerization of 3‐trimethylsilyltricyclo[4.2.1.02,5]non‐7‐ene (TCNSi1) with 3‐triethoxysilyltricyclo[4.2.1.02,5]non‐7‐ene (TCNSiOEt) in good or high yields using a Pd‐catalyst. The obtained copolymers included up to 10 mol% of TCNSiOEt units bearing reactive Si–O–C‐containing substituents. The crosslinking was readily realized by using simple sol–gel chemistry in the presence of Sn‐catalyst. The formed crosslinked copolymers were insoluble in common organic solvents. Permeability coefficients of various gases (He, H2, O2, N2, CO2, CH4, C2H6, C3H8, n‐C4H10) in these copolymers before and after crosslinking were determined and the influence of the incorporated TCNSiOEt units as well as the crosslinking on gas transport properties were established. As a result, it was found that only a small reduction of gas‐permeability was observed when TNCSiOEt units were incorporated into the main chains, and the copolymers were crosslinked. At the same time, the selectivity for C4H10/CH4 pair was increased. The suggested approach has allowed obtaining crosslinked polymers from Si‐containing monomers without a loss of the main membrane characteristics. POLYM. ENG. SCI., 59:2502–2507, 2019. © 2019 Society of Plastics Engineers 相似文献
27.
Yangkun He Gerhard H. Fecher Chenguang Fu Yu Pan Kaustuv Manna Johannes Kroder Ajay Jha Xiao Wang Zhiwei Hu Stefano Agrestini Javier Herrero-Martín Manuel Valvidares Yurii Skourski Walter Schnelle Plamen Stamenov Horst Borrmann Liu Hao Tjeng Rudolf Schaefer Stuart S. P. Parkin John Michael D. Coey Claudia Felser 《Advanced materials (Deerfield Beach, Fla.)》2020,32(45):2004331
The development of high-density magnetic recording media is limited by superparamagnetism in very small ferromagnetic crystals. Hard magnetic materials with strong perpendicular anisotropy offer stability and high recording density. To overcome the difficulty of writing media with a large coercivity, heat-assisted magnetic recording was developed, rapidly heating the media to the Curie temperature Tc before writing, followed by rapid cooling. Requirements are a suitable Tc, coupled with anisotropic thermal conductivity and hard magnetic properties. Here, Rh2CoSb is introduced as a new hard magnet with potential for thin-film magnetic recording. A magnetocrystalline anisotropy of 3.6 MJ m−3 is combined with a saturation magnetization of μ0Ms = 0.52 T at 2 K (2.2 MJ m−3 and 0.44 T at room temperature). The magnetic hardness parameter of 3.7 at room temperature is the highest observed for any rare-earth-free hard magnet. The anisotropy is related to an unquenched orbital moment of 0.42 μB on Co, which is hybridized with neighboring Rh atoms with a large spin–orbit interaction. Moreover, the pronounced temperature dependence of the anisotropy that follows from its Tc of 450 K, together with a thermal conductivity of 20 W m−1 K−1, make Rh2CoSb a candidate for the development of heat-assisted writing with a recording density in excess of 10 Tb in.−2. 相似文献
28.
Dirk H. Ortgies Francisco J. Teran Uéslen Rocha Leonor de la Cueva Gorka Salas David Cabrera Alexander S. Vanetsev Mihkel Rähn Väino Sammelselg Yurii V. Orlovskii Daniel Jaque 《Advanced functional materials》2018,28(11)
Magnetic nanoparticles (M:NPs) are unique agents for in vivo thermal therapies due to their multimodal capacity for efficient heat generation under optical and/or magnetic excitation. Nevertheless, their transfer from laboratory to the clinic is hampered by the absence of thermal feedback and by the influence that external conditions (e.g., agglomeration and biological matrix interactions) have on their heating efficiency. Overcoming these limitations requires, first, the implementation of strategies providing thermal sensing to M:NPs in order to obtain in situ thermal feedback during thermal therapies. At the same time, M:NPs should be modified so that their heating efficiency will be maintained independently of the environment and the added capability for thermometry. In this work, optomagnetic hybrid nanostructures (OMHSs) that simultaneously satisfy these two conditions are presented. Polymeric encapsulation of M:NPs with neodymium‐doped nanoparticles results in a hybrid structure capable of subtissue thermal feedback while making the heating efficiency of M:NPs independent of the medium. The potential application of the OMHSs herein developed for fully controlled thermal therapies is demonstrated by an ex vivo endoscope‐assisted controlled intracoronary heating experiment. 相似文献
29.
An organometallic approach was used to functionalize multiwalled carbon nanotubes with n-butyllithium. This procedure was repeated two more times to achieve a higher degree of multiwalled carbon nanotube functionalization. The functionalized nanotubes have been characterized by Fourier transform infrared and Raman spectroscopy, thermogravimetrical analysis, scanning electron microscopy and sedimentation studies. It was possible to form stable suspensions of the functionalized nanotubes in tetrahydrofuran and they were used to make nanotube polymer composites. The mechanical properties of these new nanotube polymer composites were tested and they were found to show an increase of up to 25% in their Young's moduli and up to 50% in their tensile strength over pure polystyrene. 相似文献
30.
Hernandez Y Nicolosi V Lotya M Blighe FM Sun Z De S McGovern IT Holland B Byrne M Gun'Ko YK Boland JJ Niraj P Duesberg G Krishnamurthy S Goodhue R Hutchison J Scardaci V Ferrari AC Coleman JN 《Nature nanotechnology》2008,3(9):563-568
Fully exploiting the properties of graphene will require a method for the mass production of this remarkable material. Two main routes are possible: large-scale growth or large-scale exfoliation. Here, we demonstrate graphene dispersions with concentrations up to approximately 0.01 mg ml(-1), produced by dispersion and exfoliation of graphite in organic solvents such as N-methyl-pyrrolidone. This is possible because the energy required to exfoliate graphene is balanced by the solvent-graphene interaction for solvents whose surface energies match that of graphene. We confirm the presence of individual graphene sheets by Raman spectroscopy, transmission electron microscopy and electron diffraction. Our method results in a monolayer yield of approximately 1 wt%, which could potentially be improved to 7-12 wt% with further processing. The absence of defects or oxides is confirmed by X-ray photoelectron, infrared and Raman spectroscopies. We are able to produce semi-transparent conducting films and conducting composites. Solution processing of graphene opens up a range of potential large-area applications, from device and sensor fabrication to liquid-phase chemistry. 相似文献