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71.
In this paper we derive a general analytical solution for a monocentric lens system and present a global optimization method combining sequential design for global optimization and an expected improvement algorithm for global optimization for the design and analysis of a layered monocentric lens system, which provides an “intelligent” way to search the optimization space based on accumulated experience. We then apply these methods to an example of monocentric lens design, and explore the improvement in system performance obtained through increasing the system volume. 相似文献
72.
Nanometer-sized diamond grains are commonly found in primitive chondritic meteorites, but their origin is puzzling. Using evidence from atomistic simulation, we establish a mechanism by which nanodiamonds form abundantly in space in a two-stage process involving condensation of vapor to form carbon onions followed by transformation to nanodiamond in an energetic impact. This nonequilibrium process is consistent with common environments in space and invokes the fewest assumptions of any proposed model. Accordingly, our model can explain nanodiamond formation in both presolar and solar environments. The model provides an attractive framework for understanding noble gas incorporation and explains all key features of meteoritic nanodiamond, including size, shape, and polytype. By understanding the creation of nanodiamonds, new opportunities arise for their exploitation as a powerful astrophysical probe. 相似文献
73.
The role of water adsorption on Ti-rich SrTiO3(001) surface reconstructions is studied. Density functional calculations with hybrid functionals of numerous adsorption configurations indicate that the relative stability of the different reconstructions is strongly altered by the addition of water, with all the reconstructions having comparable energy for half-monolayer coverage, most with a fair degree of hydrogen bonding. This strongly suggests that which reconstruction is observed depends upon a competition between the kinetics of ordering and dehydration. X-ray photoelectron spectra are consistent with the theoretical predictions for the dehydration of the 2 × 1 and c(4 × 2) reconstructions. 相似文献
74.
Density functional theory-based simulations of scanning tunneling micrographs were used for comparison to published experimental images of reconstructed SrTiO3(001) surfaces. It was found that the addition of dissociatively adsorbed H2O to the presently accepted structural solution of the 2 × 1 reconstruction is more consistent with the experimental data. A proposed model for the c(4 × 4) reconstruction, based on the hydrated 2 × 1 structure, agrees well with experiment and is consistent with a formation process consisting of the simple dehydration of a wet 2 × 1 structure. 相似文献
75.
S Loser H Miyauchi JW Hennek J Smith C Huang A Facchetti TJ Marks 《Chemical communications (Cambridge, England)》2012,48(68):8511-8513
A solution-processed small molecule utilizing a novel 4,9-bis(2-ethylhexyloxy)naphtho[1,2-b:5,6-b']dithiophene "zig-zag" core (zNDT) exhibits high hole mobility, upshifted frontier MO energies, and enhanced photovoltaic cell short-circuit currents, fill-factors, and power conversion efficiencies (4.7%) versus the linear NDT isomer. 相似文献
76.
Becerra-Toledo AE Marshall MS Castell MR Marks LD 《The Journal of chemical physics》2012,136(21):214701
Density functional theory is used to simulate high-bias, constant-current scanning tunneling micrographs for direct comparison with experimental images. Coupled to previous spectroscopic data, these simulations are used to determine the atomic structure of Ti-rich nanostructures on strontium titanate (001) surfaces. These nanostructures have three consecutive TiO(x) surface layers and exploit the distinctive structural motif of the c(4 × 2) reconstruction as their main building block. A structural model of a characteristic triline defect is also proposed. 相似文献
77.
E. A. Marks E. I. Burmakin B. D. Antonov G. Sh. Shekhtman 《Russian Journal of Electrochemistry》2000,36(5):516-521
Solid solutions based on rubidium pyrophosphate are synthesized in the Rb4 -2xMxP2O7 systems (M = Ca, Sr, Ba, Pb). The temperature and concentration dependences of their rubidium-cation conductivity are investigated.
The X-ray data for the low and high-temperature forms of Rb4P2O7 and also for solid solutions based on it are reported. The effect exerted by modifying cation M2+ on electrical properties of synthesized solid solutions is considered 相似文献
78.
Christine Mousty Arielle Lepellec Serge Cosnier Andres Novoa Robert S. Marks 《Electrochemistry communications》2001,3(12):727-732
We describe herein, the creation of an organic phase enzyme electrode (OPEE) via avidin–biotin interactions built over an electrogenerated polymer. Multilayered polyphenol oxidase (PPO) assemblies were transferred into an organic solvent (chloroform) for the catechol detection at −0.2 V. In conjunction with an alginate gel, as a hydrophilic additive, the biosensor performance was widely enhanced. The effects of biotinylated polypyrrole film and alginate gel on the diffusion process through the biosensor coating are studied by rotating disk electrode experiments carried out in chloroform with hydroquinone as electroactive permeant. 相似文献
79.
80.