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991.
G. I. Rusu A. Airinei Viorica Hamciuc G. G. Rusu Petronela Râmbu Mihaela Diciu 《Journal of Macromolecular Science: Physics》2013,52(2):238-253
Polysulfone (PSF)-polydimethylsiloxane (PDMS) block copolymers (PSF-b-PDMS) with various compositions were prepared by condensing chloro-terminated polysulfone oligomers with α, ω -dihydrogensilyl-polydimethylsiloxane in refluxing chlorobenzene solution in the presence of urea as a hydrogen chloride acceptor. The temperature dependences of the electrical conductivity and thermoelectric power (Seebeck coefficient) of copolymers were studied using thin films deposited from a dimethylformamide solution (spin coating method) onto glass substrates. It was established that the various copolymers showed typical semiconducting properties. Some correlations between these properties (activation energy, ratio of carrier mobilities, etc) and molecular structure of the copolymers were found. A model based on band gap representation was found to be suitable for explanation of the electronic transport mechanism through the studied copolymers in thin films. The study of the transmission and absorption spectra (in the spectral range from 300 nm to 1400 nm) evidenced that the indirect allowed optical transitions were predominant. The values of the optical energy band gap (ranged between 1.50 eV and 1.70 eV) are in agreement with values of width of the forbidden band calculated from the temperature dependence of the electrical conductivity. 相似文献
992.
Michal Ilavsk Karel Bouchal Helena Valentovä František Lednick Antonín Sikora Josef Baldrian 《Journal of Macromolecular Science: Physics》2013,52(5):645-666
Synthesis of the liquid crystalline (LC) diol 6,6′-[ethylenebis(l,4-phenylene-oxy)]-dihexanol (I) is described. The structure of polyurethanes prepared from diol I and 4,4′-methylenedi(phenyl isocyanate) (MDI), 4,4′-methylenedi(cyclohexyl isocyanate) (HMDI), or 2(4)-methyl-l,3-phenylene diisocyanate (TDI) at 1:1 molar ratios of isocyanate and hydroxy groups is studied by dynamic mechanical spectroscopy, differential scanning calorimetry (DSC), polarizing microscopy, and x-ray scattering. The polymer prepared from HMDI and the diol (I/HMDI) shows, on cooling, thermal behavior typical of amorphous polymers. A frequency-temperature superposition could be applied to the mechanical data, and the horizontal shift factor satisfied the Williams-Landel-Ferry (WLF) equation. A more-complex thermal behavior was found for I/HMDI polymer during subsequent heating; above 70°C, the formation of an ordered structure takes place, and this structure melts at about 120°C. Complex thermal behavior is exhibited by I/TDI polymer. On cooling its melt, the polymer forms a nematic phase at about 80°C, which freezes into the LC glassy state. On heating, the mesophase melts, and. subsequently, a better-ordered smectic phase is formed at 95°C, which melts at 120°C. This structure buildup is accompanied by a rapid increase in storage modulus G′, and the sample shows thermorheologically complex mechanical behavior. The polymer formed from the diol and MDI (I/MDI) exhibits a most-complex thermal behavior. On cooling and heating, four transitions can be detected in its thermal mechanical behavior, and the structure of the polymer is strongly dependent on its thermal history. 相似文献
993.
La2+xMnGe2+y (I) and Ce2+xMnGe2+y (II) are prepared by arc‐melting of the elements in molar ratios of 2:1:2 followed by annealing (sealed silica tubes, 800 °C, 2 weeks). 相似文献
994.
Yu. A. D’yakova E. I. Suvorova Andrei S. Orekhov Anton S. Orekhov A. S. Alekseev R. V. Gainutdinov V. V. Klechkovskaya E. Yu. Tereschenko N. V. Tkachenko H. Lemmetyinen L. A. Feigin M. V. Kovalchuk 《Crystallography Reports》2013,58(6):927-933
The structure of porphyrin-fullerene dyad ZnDHD6ee monolayers formed on the surface of aqueous subphase in a Langmuir trough and transferred onto solid substrates has been studied. The data obtained are interpreted using simulation of the structure of isolated molecules and their packing in monolayer and modeling of diffraction patterns from molecular aggregates having different sizes and degrees of order. Experiments on the formation of condensed ZnDHD6ee monolayers are described. The structure of these monolayers on a water surface is analyzed using π-A isotherms. The structure of the monolayers transferred onto solid substrates is investigated by electron diffraction and atomic force microscopy. The unit-cell parameters of two-dimensional domains, which are characteristic of molecular packing in monolayers and deposited films, are determined. Domains are found to be organized into a texture (the molecular axes are oriented by the [001] direction perpendicular to the substrate). The monolayers contain a limited number of small 3D domains. 相似文献
995.
Abstract: In last two decades, rapid development in the field of terahertz (THz) technology has opened new possibilities for creating innovative imaging and sensing systems. Although the applications of THz technology in different sectors constantly increase, the construction industry lags behind them. The aim of this article is to review the current applications of THz spectroscopy in research and industry related to construction and building materials, along with the key drawbacks of technology and recommendations for future use. The review concludes that THz spectroscopy and imaging have promising potential and provide many opportunities for applications in construction and building materials characterization. 相似文献
996.
Ramona Anton 《偏微分方程通讯》2013,38(10):1862-1889
We prove wellposedness of the Cauchy problem for the cubic nonlinear Schrödinger equation with Dirichlet boundary conditions and radial data on 3D balls. The main argument is based on a bilinear eigenfunction estimate and the use of X s, b spaces. The last part presents a first attempt to study the non radial case. We prove bilinear estimates for the linear Schrödinger flow with particular initial data. 相似文献
997.
Anton Arnold 《偏微分方程通讯》2013,38(3-4):473-506
ABSTRACT. This paper is concerned with the relaxation-time von Neumann- Poisson (or quantum Liouville-Poisson) equation in three spatial dimensions which describes the self-consistent time evolution of an open quantum me- chanical system that includes some relaxation mechanism. This model and the equivalent relaxation-time Wigner-Poisson system play an important role in the simulation of quantum semiconductor devices. For initial density matrices with finite kinetic energy, we prove that this problem, formulated in the space of Hermitian trace class operators, admits a unique global strong solution. A key ingredient for our analysis is a new generalization of the Lieb-Thirring inequality for density matrix operators. 相似文献
998.
Anton S. Zakharov 《代数通讯》2013,41(5):2285-2298
999.
Anatoly I. Neishtadt Alexey A. Vasiliev Anton V. Artemyev 《Regular and Chaotic Dynamics》2013,18(6):686-696
We study the dynamics of a nonlinear pendulum under a periodic force with small amplitude and slowly decreasing frequency. It is well known that when the frequency of the external force passes through the value of the frequency of the unperturbed pendulum’s oscillations, the pendulum can be captured into resonance. The captured pendulum oscillates in such a way that the resonance is preserved, and the amplitude of the oscillations accordingly grows. We consider this problem in the frames of a standard Hamiltonian approach to resonant phenomena in slow-fast Hamiltonian systems developed earlier, and evaluate the probability of capture into resonance. If the system passes through resonance at small enough initial amplitudes of the pendulum, the capture occurs with necessity (so-called autoresonance). In general, the probability of capture varies between one and zero, depending on the initial amplitude. We demonstrate that a pendulum captured at small values of its amplitude escapes from resonance in the domain of oscillations close to the separatrix of the pendulum, and evaluate the amplitude of the oscillations at the escape. 相似文献
1000.
Martin Benedikt Daniel Watzenig Anton Hofer 《Mathematical and Computer Modelling of Dynamical Systems: Methods, Tools and Applications in Engineering and Related Sciences》2013,19(5):451-470
Concerning non-iterative co-simulation, stepwise extrapolation of coupling signals is required to solve an overall system of interconnected subsystems. Each extrapolation is some kind of estimation and is directly associated with an estimation error. The introduced disturbance depends significantly on the macro-step size, i.e. the coupling step size, and influences the entire system behaviour. In addition, for synchronization purposes, sampling of the coupling signals can cause aliasing. Instead of analysing the coupling effects in the time domain, as it is commonly practised, we concentrate on a model-based approach to gain more insight into the coupling process. In this work, we consider commonly used polynomial extrapolation techniques and analyse them in the frequency domain. Based on this system-oriented point of view of the coupling process, a relation between the coupling signals and the macro-step size is available. In accordance to the dynamics of the interconnected subsystems, the model-based relation is used to select the most critical parameter, i.e. the macro-step size. Besides a ‘rule of thumb’ for meaningful step-size selection, a co-simulation benchmark example describing a two degree of freedom (2-DOF) mechanical system is used to demonstrate the advantages of modelling and the efficiency of the proposed method. 相似文献