排序方式: 共有149条查询结果,搜索用时 15 毫秒
11.
The reaction between C3H8 and N2O over steam-activated FeMFI zeolites leads to high yields towards propene (24%) and propionaldehyde (6%) at 773-798 K. 相似文献
12.
We study the theory of lovely pairs of geometric structures, in particular o-minimal structures. We use the pairs to isolate a class of geometric structures called weakly locally modular which generalizes the class of linear structures in the settings of SU-rank one theories and o-minimal theories. For o-minimal theories, we use the Peterzil-Starchenko trichotomy theorem to characterize for a sufficiently general point, the local geometry around it in terms of the thorn U-rank of its type inside a lovely pair. 相似文献
13.
The structural properties of a-Al2O3/Ge, a-Al2O3/In0.5Ga0.5As and a-Al2O3/In0.5Al0.5As/InGaAs interfaces were investigated by density-functional theory (DFT) molecular dynamics (MD) simulations. Realistic a-Al2O3 samples were generated using a hybrid classical-DFT MD “melt and quench” approach. The interfaces were formed by annealing at 700 K/800 K and 1100 K with subsequent cooling and relaxation. The a-Al2O3/Ge interface demonstrates pronounced interface intermixing and interface bonding exclusively through Al–O–Ge bonds generating high interface polarity. In contrast, the a-Al2O3/InGaAs interface has no intermixing, Al–As and O–In/Ga bonding, low interface polarity due to nearly compensating interface dipoles, and low substrate deformation. The a-Al2O3/InAlAs interface demonstrated mild intermixing with some substrate Al atoms being adsorbed into the oxide, mixed Al–As/O and O–Al/In bonding, medium interface polarity, and medium substrate deformation. The simulated results demonstrate strong correlation to experimental measurements and illustrate the role of weak bonding in generating an unpinned interface for metal oxide/semiconductor interfaces. 相似文献
14.
Bishop SR Clemens JB Chagarov EA Shen J Kummel AC 《The Journal of chemical physics》2010,133(19):194702
Ordered, low coverage to monolayer, high-κ oxide adsorption on group III rich InAs(0 0 1)-(4×2) and In(0.53)Ga(0.47)As(0 0 1)-(4×2) was modeled via density functional theory (DFT). Initial adsorption of HfO(2) and ZrO(2) was found to remove dangling bonds on the clean surface. At full monolayer coverage, the oxide-semiconductor bonds restore the substrate surface atoms to a more bulklike bonding structure via covalent bonding, with the potential for an unpinned interface. DFT models of ordered HfO(2)/In(0.53)Ga(0.47)As(0 0 1)-(4×2) show it fully unpins the Fermi level. 相似文献
15.
Clemens JB Chagarov EA Holland M Droopad R Shen J Kummel AC 《The Journal of chemical physics》2010,133(15):154704
The reaction of trimethyl aluminum on the group III rich reconstructions of InAs(0 0 1) and In(0.53)Ga(0.47)As(0?0?1) is observed with scanning tunneling microscopy/spectroscopy. At high coverage, a self-terminated ordered overlayer is observed that provides the monolayer nucleation density required for subnanometer thick transistor gate oxide scaling and removes the surface Fermi level pinning that is present on the clean InGaAs surface. Density functional theory simulations confirm that an adsorbate-induced reconstruction is the basis of the monolayer nucleation density and passivation. 相似文献
16.
Koech PK Polikarpov E Rainbolt JE Cosimbescu L Swensen JS Von Ruden AL Padmaperuma AB 《Organic letters》2010,12(23):5534-5537
We studied the influence of a pyridine moiety versus a phenyl moiety when introduced in the molecular design of an ambipolar host. These pyridine-based host materials for organic light-emitting diodes (OLEDs) were synthesized in three to five steps from commercially available starting materials. The isomeric hosts have similar HOMO/LUMO energies; however, data from OLEDs fabricated using the above host materials demonstrate that small structural modification of the host results in significant changes in its carrier-transporting characteristics. 相似文献
17.
We study the theory of the structure induced by parameter free formulas on a “dense” algebraically independent subset of a model of a geometric theory T. We show that while being a trivial geometric theory, inherits most of the model theoretic complexity of T related to stability, simplicity, rosiness, the NIP and the NTP2. In particular, we show that T is strongly minimal, supersimple of SU‐rank 1, has the NIP or the NTP2 exactly when has these properties. We show that if T is superrosy of thorn rank 1, then so is , and that the converse holds if T satisfies acl = dcl. 相似文献
18.
Evgueni Kassianov 《Journal of Quantitative Spectroscopy & Radiative Transfer》2003,77(4):373-393
A two-part paper describes the statistical treatment of solar radiative transfer in multilayer broken clouds. The proposed approach is a logical development of the statistical ones originally suggested for a single-layer broken clouds. This first part introduces a new statistically inhomogeneous Markovian model that allows one to properly account for different combinations of the random and maximum overlap of broken clouds at distinct vertical layers. The statistically inhomogeneous Markovian model and the stochastic radiative transfer equation have been used to derive equations for the mean radiance of solar radiation. It was demonstrated that in extreme cases the obtained equations agree with corresponding equations previously derived for (i) the statistically homogeneous broken clouds and (ii) the vertically inhomogeneous overcast clouds. 相似文献
19.
The Ullmann coupling of 1 (R = H) gives a 2:1 mixture of diastereomers 2 (R = H) in 81% yield that are easily separated by silica gel chromatography. This procedure avoids the generally cumbersome and sometimes difficult resolution step with DBTA. Similar Ullmann couplings and separation of the corresponding diastereomers are employed with other derivatives of 1 (R = OtBu, iPr, Ph, and mesityl) ultimately affording a new series of 3,3′-disubsituted-MeO-BIPHEP derivatives. The use of these new derivatives in palladium-catalyzed asymmetric Heck reaction, Pd-catalyzed polyene cyclizations and rhodium-catalyzed hydrogenations is also reported. 相似文献
20.
Evgueni Doubtsov 《Proceedings of the American Mathematical Society》2007,135(2):393-395
It is shown that the invariant subspace of the Bergman space of the unit disc, generated by a finite union of Hardy interpolation sequences, is complemented in .