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61.
This Paper investigates the sensitivity to frequency-selective fading of different modulation techniques commonly used in digital radio systems. The modulation methods considered are phase-shift-keying (M ary PSK), nonoffset and offset quadrature amplitude modulation (M -ary QAM), and quadrature partial response signaling (QPRS). The performances of these methods during multipath fading are compared on the basis of the "signatures" calculated for idealized systems. Results are presented from which the relative outage probability was determined, assuming a propagation channel with frequency-selective Rician fading. 相似文献
62.
The addition of acetates and nitrates for the synthesis of single-wall carbon nanotubes via laser ablation was explored. Targets containing nominal amounts of acetates or nitrates in addition to Ni and Co catalysts were compared to a standard target containing only Ni and Co at temperatures ranging from 1000 to 1200 °C. The as produced web-like soot was characterized by transmission electron microscopy, Raman spectroscopy and optical absorption spectroscopy. All samples showed a linear increase in SWCNT mean diameter with temperature; however, the rate of mean diameter change with temperature differed for the various targets, more so at lower temperatures. The addition of nitrates improved the SWCNT relative yield over all the temperatures used, whereas the inclusion of acetates improved the relative yield only at lower temperatures. The above results were discussed and analyzed according to the porous structure of the targets resulting from the decomposition of the acetates and nitrates and consequential thermal diffusion changes. 相似文献
63.
Several theories for modelling fracture and slow growth of a crack in wood have been developed. The various models may be differentiated by the specifically regarded stress levels, failure mechanisms and averaging procedures. This paper deals with the application of viscoelastic fracture mechanics models to predict delayed failure of a timber element in bending. Simulations are compared to experimental results of bending tests carried out on LVL (Laminated Veneer Lumber) notched beams. This analysis emphasizes the influence of the geometry and of the size of the beam as well as of the damage area on the delayed failure. 相似文献
64.
65.
The alkali metals Cs and Rb are the only surfaces which are not wetted by superfluid
4
He below a certain temperature. In our experiments, using the photoelectron tunneling method, we can highly resolve the growth of the non-wetting thin-film state of
4
He on a quench-condensed Cs surface. It turns out that far from coexistence there is little adsorption of helium. In contrast, close to coexistence a rapid growth up to two monolayers of helium is observed, but the surface is still non-wet under the usual convention. 相似文献
66.
Valentin Magn Florent Blanchard Angela Marinetti Arnaud Voituriez Xavier Guinchard 《Advanced Synthesis \u0026amp; Catalysis》2016,358(21):3355-3361
N‐Propargyl‐ and N‐homoallenyl‐2‐bromo‐β‐tryptamines undergo gold(I)‐catalyzed dearomatizing cyclizations to afford 2‐bromospiroindolenines that are in situ hydrolyzed to furnish spirooxindoles in a one‐pot process. Tryptophane derivatives (R2=CO2Et) led upon cyclization to chiral spirooxindoles in excellent diastereoselectivities.
67.
Núria Parera Pera Dr. Hilbert M. Branderhorst Dr. Raymond Kooij Caroline Maierhofer Dr. Marjolein van der Kaaden Rob M. J. Liskamp Prof. Dr. Valentin Wittmann Prof. Dr. Rob Ruijtenbeek Dr. Roland J. Pieters Dr. 《Chembiochem : a European journal of chemical biology》2010,11(13):1896-1904
Multivalency is an important phenomenon in protein–carbohydrate interactions. In order to evaluate glycodendrimers as multivalent inhibitors of carbohydrate binding proteins, we displayed them on a microarray surface. Valencies were varied from 1 to 8, and corrections were made for the valencies so that all surfaces contained the same amount of the sugar ligand. Five different carbohydrates were attached to the dendrimers. A series of fluorescent lectins was evaluated, and for each of them a binding profile was obtained from a single experiment showing both the specificity of the lectin for a certain sugar and whether it prefers multivalent ligands or not. Very distinct binding patterns were seen for the various lectins. The results were rationalized with respect to the interbinding distances of the lectins. 相似文献
68.
69.
Cristina Elena Ciomaga Mirela Airimioaei Valentin Nica Luminita M. Hrib Ovidiu F. Caltun Alexandra R. Iordan Carmen Galassi Liliana Mitoseriu Mircea N. Palamaru 《Journal of the European Ceramic Society》2012,32(12):3325-3337
Magnetoelectric composites of xNiFe2O4–(1 ? x)Pb(Zr,Ti)O3 with x = 2, 5, 10, 20, 30% were prepared by citrate–nitrate combustion using PZT-based template powders. In order to ensure a better connectivity of dissimilar phases, we have used chemical methods for preparation in situ composites, followed by adequate sintering procedure. The structural, microstructural and functional properties of di-phase magnetoelectric composites of NiFe2O4–PZT are reported. The XRD analysis is demonstrating the synthesis of pure ferrite phase directly on the ferroelectric templates. An excellent mixing was obtained in the composite powders, as proved by a detailed SEM analysis.The magnetic and dielectric behaviors of the ceramic composites vary with the ratio of the two phases. The dielectric behavior is greatly influenced by the magnetic phase. The magnetoelectric (ME) coefficient was measured as a function of applied DC magnetic field. The maximum ME coefficient (dE/dH) varies from 0.0011 mV/(cm Oe) to 0.5 mV/(cm Oe) with increasing of NF addition. 相似文献
70.
The temperature dependence has been determined for the wetting by molten aluminum of materials based on aluminum oxide (polycor and corundum). A temperature range has been identified in which the wetting increases significantly. There is no effect on the wetting characteristics of these oxide materials from the addition to the aluminum of up to 25% silicon, 33% copper, or 6% nickel. 相似文献