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231.
Experimental results for a fibre pigtailed 1*16 power splitter based on the radiative approach are reported, together with the results of temperature cycling over the range -40-70 degrees C. A novel technique using variable width waveguides has been used to improve the uniformity of 1*N splitters.<> 相似文献
232.
The authors investigate a fuzzy logic-based video rate control technique which aims to regulate compressed video to a constant transmission rate, without incurring objectionable quality degradation. Conventional fuzzy rule-based control (FRC) does not adequately control the output video quality. Video information is therefore added into the FRC design by incorporating feed-forward scaling factors, derived from scene change features. The performance of this coder has been compared with other approaches measuring buffer occupancy, the number of coded bits per frame and peak signal-to-noise ratio 相似文献
233.
DeCoste JB Glover TG Mogilevsky G Peterson GW Wagner GW 《Langmuir : the ACS journal of surfaces and colloids》2011,27(15):9458-9464
A novel technique for determining the relative accessibility and reactivity of basic surface hydroxyl sites by reacting various zirconium(IV) hydroxide materials with 2,2,2-trifluoroethanol (TFE) and characterizing the resulting material using (19)F magic angle spinning (MAS) nuclear magnetic resonance (NMR) is presented here. Studied here are three zirconium hydroxide samples, two unperturbed commercial materials, and one commercial material that is crushed by a pellet press. Factors, such as the ratio of bridging/terminal hydroxyls, surface area, and pore size distribution, are examined and found to affect the ability of the zirconium(IV) hydroxide to react with TFE. X-ray diffraction, nitrogen isotherms, and (1)H MAS NMR were used to characterize the unperturbed materials, while thermogravitric analysis with gas chromatography and mass spectrometry along with the (19)F MAS NMR were used to characterize the materials that were reacted with TFE. Zirconium hydroxide materials with a high surface area and a low bridging/terminal hydroxyl ratio were found to react TFE in the greatest amounts. 相似文献
234.
Bates CM Strahan JR Santos LJ Mueller BK Bamgbade BO Lee JA Katzenstein JM Ellison CJ Willson CG 《Langmuir : the ACS journal of surfaces and colloids》2011,27(5):2000-2006
The orientation of cylinder-forming poly(styrene-block-methyl methacrylate) [P(S-b-MMA)] was investigated on two sets of polymeric surface treatments: 10 para-substituted polystyrene derivatives with <10 mol % poly(4-vinylbenzyl azide) and a series of poly(styrene-random-4-vinylbenzyl azide) [P(S-r-VBzAz)] copolymers with 5-100 mol % poly(4-vinylbenzyl azide). The copolymers were spin-coated to form thin films and then cross-linked by heating. The resulting films exhibited a range of surface tensions from 21 to 45 dyn/cm. Perpendicular orientation of P(S-b-MMA) cylinders was achieved with poly(p-bromostyrene) and all the [P(S-r-VBzAz)] copolymer surface treatments, most notably the homopolymer of poly(4-vinylbenzyl azide). Films made from these simple copolymers are as effective as random terpolymer alignment layers commonly made from both block monomers and a cross-linkable monomer. 相似文献
235.
The oxidative decomposition mechanism of the lithium battery electrolyte solvent propylene carbonate (PC) with and without PF(6)(-) and ClO(4)(-) anions has been investigated using the density functional theory at the B3LYP/6-311++G(d) level. Calculations were performed in the gas phase (dielectric constant ε = 1) and employing the polarized continuum model with a dielectric constant ε = 20.5 to implicitly account for solvent effects. It has been found that the presence of PF(6)(-) and ClO(4)(-) anions significantly reduces PC oxidation stability, stabilizes the PC-anion oxidation decomposition products, and changes the order of the oxidation decomposition paths. The primary oxidative decomposition products of PC-PF(6)(-) and PC-ClO(4)(-) were CO(2) and acetone radical. Formation of HF and PF(5) was observed upon the initial step of PC-PF(6)(-) oxidation while HClO(4) formed during initial oxidation of PC-ClO(4)(-). The products from the less likely reaction paths included propanal, a polymer with fluorine and fluoro-alkanols for PC-PF(6)(-) decomposition, while acetic acid, carboxylic acid anhydrides, and Cl(-) were found among the decomposition products of PC-ClO(4)(-). The decomposition pathways with the lowest barrier for the oxidized PC-PF(6)(-) and PC-ClO(4)(-) complexes did not result in the incorporation of the fluorine from PF(6)(-) or ClO(4)(-) into the most probable reaction products despite anions and HF being involved in the decomposition mechanism; however, the pathway with the second lowest barrier for the PC-PF(6)(-) oxidative ring-opening resulted in a formation of fluoro-organic compounds, suggesting that these toxic compounds could form at elevated temperatures under oxidizing conditions. 相似文献
236.
A net trans C-N reductive elimination reaction is observed from a macrocyclic aryl-Cu(III) complex, and a mechanistic study of this reaction indicates that coordinating ligands play a role in mediating this unusual transformation. 相似文献
237.
This paper studies stochastic orderings for folded beta distributions. A necessary and sufficient condition for one folded beta random variable to be larger than another in likelihood ratio order is obtained. The work is motivated by the recent results of Porzio and Ragozini on stochastic orderings for folded binomial distributions. Beta distributions are commonly used to model proportions or probabilities, particularly as conjugate distributions for binomial random variables. Stochastic orderings may arise, for instance, in considerations of fairness in coin flips. 相似文献
238.
In this paper, we examine, by dissipative particle dynamics (DPD) simulation, the interactions between nanoparticles and block copolymer bilayer membranes. The bilayer has a hydrophobic core and hydrophilic head groups on both sides of the core. Nanoparticles without or with a grafted homopolymer are considered. For the conditions investigated, the single nanoparticles and small aggregates are located at the interfaces of the membrane, namely the interfaces between the hydrophilic domains of the membrane and the solvent as well as at the interface between the hydrophobic and hydrophilic domains of the membrane. The large aggregates are located in the hydrophilic domains. By increasing the length of the homopolymer grafted on the nanoparticles, the size of the aggregates in the membrane decreases. At relatively short DPD step times, the particles aggregate in the solvent. As the time increases, the single particles and aggregates penetrate into the membrane. 相似文献
239.
The 13C dipolar N.M.R. spectrum of 13CH3 14NO2 has been recorded at 25 K. The principal values of the 13C shielding tensor, obtained by a computer fit of the experimental lineshape, are similar to those found in other 13CH3 groups. 14N quadrupolar parameters and direct dipolar couplings are also reported. In fitting the spectrum we find that an effective trace must be added to the dipolar interaction to account for librational motion. 相似文献
240.
B. K. Mukhopadhyay K. K. Ahlquist V. Gruenman A. Lutz I. I. Kovalevski B. Schulze E. Rieger A. Noll W. Nagel J. Grant A. Abrams P. W. Codwise W. Staedel und J. D. Piper 《Fresenius' Journal of Analytical Chemistry》1936,105(5-6):212-222
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