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931.
树映射的不稳定流形,非游荡集与拓扑熵 总被引:2,自引:0,他引:2
设f是个端点数为n的树T上的连续自映射.本文得到了f的单侧不稳定流形与拓扑熵的关系,并证明了:(1)如果x∈i=0∞fi(Ω(f))-P(f),那么,x的轨道是无限的;(2)如果f有一组可循环的不动点,那么h(f)≥In2(n-1). 相似文献
932.
V. E. Zapevalov Yu. K. Kalynov A. N. Kuftin S. A. Malygin E. M. Tai 《Radiophysics and Quantum Electronics》1994,37(3):233-236
The parameters of free oscillations in gyrotron resonators with a lowered reflection from the diffractive energy output for the purpose of reducing ohmic heating by rf power loss have been calculated. A gyrotron with such a cavity has been studied experimentally. The gyrotron had an efficiency of more than 45% with an output of 350 to 700 kW when operating in the 3.6-mm H11,3 mode.Institute of Applied Physics, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 3, pp. 381–386, March, 1994. 相似文献
933.
A new series of halogen-containing side chain ferroelectric liquid crystal polymers was synthesized. Mesophases were characterized by differential scanning calorimetry, polarizing optical microscopy, X-ray diffraction and molecular simulation. The behaviour of the liquid crystalline phase was investigated with variation of chiral centres, spacer units and grafted ratios. It was found that the thermal stability and temperature range of the chiral smectic C phase decreased with increasing length of the oligo-oxyethylene spacer, and decreasing mesogenic group content. The bulky substituent attached to the chiral centre reduces molecular packing in smectic liquid crystal phases, which disturbs the orientation of the side chain liquid crystal polymer. Furthermore, the influence of molecular structure on electrooptical properties of FLCPs has been studied by broad band dielectric spectroscopy (from 0.1 to 1 ×10 6 Hz). 相似文献
934.
Wei Yang Hongdian Lu Qilong Tai Zhihua Qiao Yuan Hu Lei Song Richard K. K. Yuen 《先进技术聚合物》2011,22(12):2136-2144
The flame retardancy mechanisms of poly(1,4‐butylene terephthalate) (PBT) containing microencapsulated ammonium polyphosphate (MAPP) and melamine cyanurate (MC) were investigated via pyrolysis analysis (thermogravimetric analysis (TGA), real‐time Fourier transform infrared (FTIR), TG‐IR), cone calorimeter test, combustion tests (limited oxygen index (LOI), UL‐94), and residue analysis (scanning electron microscopy (SEM)). A loading of 20 wt% MC to PBT gave the PBT composites an LOI of 26%, V‐2 classification in UL‐94 test and a high peak heat release rate (HRR) in cone calorimeter test. Adding APP to PBT/MC composites did not improve their flame retardancy. In comparison with the addition of ammonium polyphosphate (APP) to PBT, MAPP with silica gel shell and MAPP with polyurethane shell both promoted the intumescent char‐forming and improved the flame retardancy of PBT through different mechanisms in the presence of MC. These two halogen‐free PBT composites with V‐0 classification according to UL‐94 test were obtained; their LOI were 32 and 33%, respectively. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
935.
936.
The stability, electronic structure, and thermochemical properties of the pure Li(n) and boron-doped Li(n)B (n = 1-8) clusters in both neutral and cationic states are studied using electronic structure methods. The global equilibrium structures are established, and their heats of formation are evaluated using the G3B3 and CCSD(T)/CBS methods based on the density functional theory geometries. Theoretical adiabatic ionization energies (IE(a)) for the Li(n) clusters are in good agreement with experiment: Li(2) (G3B3, 5.21 eV; CCSD(T), 5.14 eV; expt, 5.1127 ± 0.0003 eV), Li(3) (4.16, 4.11, 4.08 ± 0.10), Li(4) (4.76, 4.68, 4.70 ± 0.05), Li(5) (4.11, 4.06, 4.02 ± 0.10), Li(6) (4.46, 4.32, 4.20 ± 0.10), Li(7) (4.07, 3.99, 3.94 ± 0.10), and Li(8) (4.49, 4.31, 4.16 ± 0.10). The Li(4) experimental IE(a) has been revised on the basis of the Franck-Condon simulations. Species Li(5)B, Li(6)B(+), Li(7)B, and Li(8)B(+) exhibit high stability as compared to their neighbors, which can be understood by considering the magic numbers of the phenomenological shell model (PSM). 相似文献
937.
Peng T Yang Y Liu Y Ma D Hou Z Wang Y 《Chemical communications (Cambridge, England)》2011,47(11):3150-3152
A phosphorescent material (Fppy)(2)Ir(dipba) possessing high PL efficiency in the solid state and superior hole/electron transporting property has acted successfully as an efficient neat phosphorescent emitter as well as an excellent host for high-performance PHOLEDs. 相似文献
938.
Lee S Cho KH Lee CJ Kim GE Na CH In Y No KT 《Journal of chemical information and modeling》2011,51(1):105-114
The solvation free energy density (SFED) model was modified to extend its applicability and predictability. The parametrization process was performed with a large, diverse set of solvation free energies that included highly polar and ionic molecules. The mean absolute error for 1200 solvation free energies of the 379 neutral molecules in 9 organic solvents and water was 0.40 kcal/mol, and for 90 hydration free energies of ions was 1.7 kcal/mol. Overall, the calculated solvation free energies of a wide range of solute functional groups in diverse solvents were consistent with experimental data. 相似文献
939.
Phenytoin (PHT), phenobarbital (PHB), lamotrigine (LTG), and topiramate (TPM) are some of the most widely used antiepileptic
drugs (AEDs). Monitoring of their concentrations in serum is important for the treatment of epilepsy. A reference measurement
procedure (RMP) for certification of PHT, PHB, LTG, and TPM in serum has been developed and critically evaluated. Isotopically
labeled compounds of PHT, PHB, LTG, and TPM are used as internal standards for the four AEDs. The four drugs and their respective
labeled internal standards are simultaneously extracted from serum using solid-phase extraction prior to reversed-phase liquid
chromatography–tandem mass spectrometry (LC-MS/MS). Chromatographic separation was performed using a C18 column. Electrospray ionization (ESI) in the positive ion mode for PHT and LTG, and in the negative ion mode for PHB and
TPM were used. The recovery of AEDs added to serum (accuracy of the extraction method) was evaluated by recovery studies of
measuring the four drugs in spiked samples with known drug levels. The recoveries of the added drugs ranged from 98.6% to
102.0%. The absolute recoveries (extraction efficiencies) of the four drugs with this method ranged from 97% to 100%. Excellent
repeatability was obtained for the four drugs with between-set coefficients of variation (CVs) within 1%. The type B components
estimates are conservatively large and are considerably larger than the type A component. Therefore, we use the usual metrological
expansion factor of 2 to provide an approximate 95% coverage interval. The relative expanded uncertainties for the four AEDs
ranged from 2.3% to 2.4%. This LC-MS/MS RMP for PHT, PHB, LTG, and TPM in serum demonstrating good accuracy and precision
can be used to assess the accuracy of routine methods used in clinical laboratories. 相似文献
940.
In this study, we have investigated experimentally the convection phenomenon of granular matter in a vertical shaker device.
The motions of the granular materials were recorded by a high-speed camera. Image processing technology and a particle tracking
method were employed to measure the convection strength, convection size, and granular temperature. The results show that
the initial bed height, dimensionless vibrating acceleration, and vibrating frequency have significant influence on the convection
mechanism. An interesting finding that occurs with increasing the bed height is the existence of two peaks and one low convection
strength value which occurs due to the growth of the solid-like region. We also find that the two peak and one low values
become greater when higher dimensionless vibrating acceleration is applied to the granular bed. 相似文献