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31.
《Tetrahedron: Asymmetry》2005,16(15):2649-2651
The antipode of the antitumor marine metabolite harzialactone A was synthesized from l-malic acid via a very efficient route in 40% overall yield involving only two chromatographic separations. 相似文献
32.
《Radiation Physics and Chemistry》2007,76(2):275-279
Dissipative energy losses accompanying growth of the Ps bubble are calculated using the Navier–Stokes equation. This allows to demonstrate a fulfilling of the total energy balance in this process. It is in favor of the adopted approach. 相似文献
33.
ZHU Li-ping~ YANG Xiao-yan~ YU Zhou~ LIU Xiang-rong~ School of Finance Statist. East China Normal Univ. Shanghai China. Dept.of Statist. Zhejiang Univ.of Finance Economics Hangzhou China. 《高校应用数学学报(英文版)》2008,23(1):107-112
The single-index model with monotonic link function is investigated. Firstly, it is showed that the link function h(.) can be viewed by a graphic method. That is, the plot with the fitted response y on the horizontal axis and the observed y on the vertical axis can be used to visualize the link function. It is pointed out that this graphic approach is also applicable even when the link function is not monotonic. Note that many existing nonparametric smoothers can also be used to assess h(.). Therefore, the I-spline approximation of the link function via maximizing the covariance function with a penalty function is investigated in the present work. The consistency of the criterion is constructed. A small simulation is carried out to evidence the efficiency of the approach proposed in the paper. 相似文献
34.
PiLing 《高校应用数学学报(英文版)》2004,19(4):417-428
Using Picard‘s theorem and the l.eray-Schauder fixed point theorem to reinvestigate the area-preserving convex curve flow in the plane which is considered as a coupled system and thus different from the setting handled by Gage. 相似文献
35.
X. Chen L. Canova A. Malvache A. Jullien R. Lopez-Martens C. Durfee D. Papadopoulos F. Druon 《Applied physics. B, Lasers and optics》2010,99(1-2):149-157
We report the routine generation of sub-5-fs laser pulses with 1-mJ energy and stable carrier–envelope phase at 1-kHz repetition rate, obtained by compressing the multi-mJ output from a phase-locked Ti:sapphire amplifier in a rare-gas-filled hollow fiber. The dual-stage amplifier features a hybrid transmission grating/chirped mirror compressor providing 2.2-mJ, 26-fs pulses at 1 kHz with standard phase deviation of 190 mrad rms. We demonstrate hour-long phase stability without feedback control of grating position or rigorous control of the laser environment, simply by using small pulse stretching factors in the amplifier, which minimize the beam pathway in the compressor. The amplifier also integrates a versatile AOPDF (acousto-optic programmable dispersive filter) for closed-loop spectral phase optimization. The various factors influencing the overall phase stability of the system are discussed in detail. Using the optimized output, 1-mJ, 4.5-fs pulses are generated by seeding the neon gas filled hollow fiber with a circularly polarized input beam. A standard phase deviation of 230 mrad after the HCF is obtained by direct f-to-2f detection and slow-loop feedback to the oscillator locking electronics without any additional spectral broadening. 相似文献
36.
《Journal of magnetism and magnetic materials》2002,248(2):158-163
The temperature dependence of magnetization is analysed for R2Fe17C via the two-sublattice molecular field theory. The molecular field coefficients nFF, nRF and nRR are obtained, by which TC was calculated. Using the least-squares method, the fitted-form of HR(T) varying with temperature for each compound is presented. The results are analysed. In addition, the parameters F=MFe2(0)nFF/TC was calculated for each R2Fe17C. By F, some phenomena different from the normal view were explained. 相似文献
37.
《Tetrahedron: Asymmetry》2003,14(5):549-554
Asymmetric syntheses of the syn- and anti-stereoisomers of N-Boc statine, based on the stereodivergent reduction of a single sulfoxide 5, derived from N-Boc-l-leucine, are reported. 相似文献
38.
《Communications in Nonlinear Science & Numerical Simulation》2014,19(8):2874-2882
In this paper, the effect of spatial frequencies distributions on the oscillation death in a ring of coupled nonidentical oscillators is studied. We find that the rearrangement of the spatial frequencies may deform the domain of oscillation death and give rise to a ragged oscillation death in some parameter spaces. The usual critical curves with shape V in the parameter space of frequency-mismatch vs coupling-strength may become the shape W (or even shape WV). This phenomenon has been not only numerically observed in coupled nonidentical nonlinear systems, but also well supported by our theoretical analysis. 相似文献
39.
Organic–inorganic hybrid material of formula (C4H3SC2H4NH3)2[PbI4] was synthesized and studied by X-ray diffraction, Infrared absorption, Raman scattering, UV–Visible absorption and photoluminescence measurements. The molecule crystallizes as an organic–inorganic two-dimensional (2D) structure built up from infinite PbI6 octahedra surrounded by organic cations. Such a structure may be regarded as quantum wells system in which the inorganic layers act as semiconductor wells and the organic cations act as insulator barriers. Room temperature IR and Raman spectra were recorded in the 520–3500 and 10–3500 cm−1 frequency range, respectively. Optical absorption measurements performed on thin films of (C4H3SC2H4NH3)2[PbI4] revealed three distinct bands at 2.4, 2.66 and 3.25 eV. We also report DFT calculations of the electric dipole moments (μ), polarizability (α), the static first hyperpolarizability (β) and HOMO–LUMO analysis of the title compound investigated by GAUSSIAN 09 package. The calculated static first Hyperpolarizability is equal to 11.46 × 10−31 esu. 相似文献
40.
For the first time, the energy diffusion approximation is confronted at the percent level with the exact numerical modeling of thermal decay of a metastable state. This model is useful in many branches of natural sciences: e.g. in biology, nuclear physics, chemistry, etc. The exact (within the statistical errors about 2%) quasistationary decay rates result from the Langevin equations for the coordinate and conjugated momentum. For the energy (or action) diffusion approach, a Langevin-type equation for the action is constructed, validated, and solved numerically. The comparison of these two approaches is performed for four potentials (two of which are anharmonic) in a wide range of two dimensionless scaling parameters: i) the governing parameter G reflecting how high is the barrier with respect to the temperature and ii) the damping parameter φ expressing the friction strength. It turns out that the energy diffusion approach produces the rate which comes into 50%-agreement with the exact one only at φ < 0.02. Thus, we quantify, for the first time by our knowledge, the condition φ ≪ 1 known in the literature. 相似文献