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101.
The fold and lateral surfaces of chain-folded lamellae of poly(bisphenol-A-co-etheroctane), containing both aliphatic CH2 and aromatic segments, were investigated by time-of-flight secondary ion mass spectrometry (ToF-SIMS). At low and high crystallization temperatures, the surfaces of the polymer films were shown to consist mainly of edge-on and flat-on lamellae, respectively. Surfaces with a mixture of edge-on and flat-on lamellae were produced at intermediate temperatures. The edge-on and flat-on lamellae were identified by using ions that recognize the flexible and rigid segments of the polymer. Ion images produced using selected ions that are related to the edge-on or flat-on orientation can be used to identify the location of these lamellae on the polymer surface. Our results indicate that ToF-SIMS can be used to detect different lamellar orientations at the surfaces of semi-crystalline polymers. 相似文献
102.
A New Approach for Visual Cryptography 总被引:1,自引:0,他引:1
Visual cryptography is to encrypt a secret image into some shares (transparencies) such that any qualified subset of the shares can recover the secret visually. The conventional definition requires that the revealed secret images are always darker than the backgrounds. We observed that this is not necessary, in particular, for the textual images.In this paper, we proposed an improved definition for visual cryptography based on our observation, in which the revealed images may be darker or lighter than the backgrounds. We studied properties and obtained bounds for visual cryptography schemes based on the new definition. We proposed methods to construct visual cryptography schemes based on the new definition. The experiments showed that visual cryptography schemes based on our definition indeed have better pixel expansion in average. 相似文献
103.
A facile one-pot procedure for copper-catalyzed PhI(OAc)2-mediated asymmetric alkene aziridination had been developed. Commercially available PhI(OAc)2 and sulfonamides were used to generate the nitrene precursors (PhINR) in situ for olefin aziridination. This one-pot procedure had been optimized using 4-nitrobenzenesulfonamide as the nitrene source. With 5 mol % of the chiral copper catalyst, these conditions afforded 94% yield of the isolated product with 75% ee. We had also developed a simple and rapid method to monitor the rate of this one-pot aziridination. 相似文献
104.
负载型钼系催化剂广泛用于加氢脱硫、抗硫甲烷化及部分氧化等,其加氢脱硫活性与低温氧的表面吸附量成正比,活性组分受载体性质的影响。超细粒子是近年来兴起的新型催化材料,由于其表面及体积效应,导致其特殊的表面吸附性能。以超临界法合成NiO/Al_2O_3、Fe_2O_3/SiO_2等超细催化剂已有报道,但该法对MoO_3/Al_2O_3的合成尚未见报道。本文以MoO_3/Al_2O_3超临界法合成超细粒子催化剂,根据超细催化剂分散性与粒径的关系选择了活性与钼表面分散性有依赖关系的临氢重整反应为探针,研究了超细MoO_3/Al_2O_3催化剂的性质。 相似文献
105.
Sub-Doppler optical-optical double-resonance excitation spectra of BaF were recorded using two single-mode cw dye lasers. In the 30 000-cm?1 region, the electronic states observed were E2Σ+ and F2Π. The latter had been previously assigned as the “F2Σ+” state by Fowler [Phys. Rev.59, 645–652 (1941)]. The (3, 0) and (4, 0) bands of the E2Σ+-B2Σ+ transition and the (1, 0) and (2, 0) bands of the F2Π-B2Σ+ transition were rotationally analyzed. The molecular constants suggest inferences about the dominant atomic orbital character of the Rydberg molecular orbitals responsible for the E2Σ+ and F2Π electronic states. A new electronic state, the , is predicted. The molecular parameters obtained (in cm?1, 1σ uncertainty in parentheses) are
3 | 29 767.32(1) | 1 | 29 997.29(1) | |
3 | 522.841(27) | 1 | 522.553(2) | |
0.22990(22) | 0.22931(8) | |||
0.00113(14) | 0.00108(2) | |||
1 | 56.9840(12) | |||
1 | ?0.02426(6) | |||
3 | ?0.17367(46) |