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91.
Park JS Seo JH Koo JR Seo BM Lee KH Yoon SS Kim YK 《Journal of nanoscience and nanotechnology》2011,11(5):4488-4491
We have demonstrated a highly efficient blue phosphorescent organic light emitting diodes (PHOLED) using iridium (111) bis[(4,6-di-fluoropheny)-pyridinato-N,C2] picolinate doped in double emitting layers (D-EML), N,N-dicarbazolyl-3,5-benzene (mCP) and p-bis (triphenylsilyly)benzene (UGH2). D-EML layers were employed to broaden the exciton formation zone and confine excitons. The optimized blue PHOLEDs having mCP/UGH2 as D-EML with a thickness of 200/100 A, exhibited a peak external quantum efficiency of 11.44%, power efficiency of 16.8 Im/W, luminous efficiency of 23.14 cd/A, and Commission Internationale de l'Eclairage coordinates of (0.17, 0.33). 相似文献
92.
Ja Hun Kwak Donghai Mei Charles H. F. Peden Roger Rousseau János Szanyi 《Catalysis Letters》2011,141(5):649-655
Abstract
Temperature programmed desorption (TPD) of ethanol, as well as ethanol and methanol dehydration reactions were studied on γ-Al2O3 in order to identify the active catalytic sites for alcohol dehydration reactions. Two high temperature (>473 K) desorption features were observed following ethanol adsorption. Samples calcined at T ≤ 473 K displayed a desorption feature in the 523–533 K temperature range, while those calcined at T ≥ 673 K showed a single desorption feature at 498 K. These two high temperature desorption features correspond to the exclusive formation of ethylene on the Lewis (498 K) and Br?nsted acidic (~525 K) sites. The amount of ethylene formed under conditions where the competition between water and ethanol for adsorption sites is minimized is identical over the two surfaces. Furthermore, a nearly 1-to-1 correlation between the number of under-coordinated Al3+ ions on the (100) facets of γ-Al2O3 and the number of ethylene molecules formed in the ethanol TPD experiments on samples calcined at T ≥ 673 K was found. Titration of the penta-coordinate Al3+ sites on the (100) facets of γ-Al2O3 by BaO completely eliminated the methanol dehydration reaction activity. These results demonstrate that in alcohol dehydration reactions on γ-Al2O3, the (100) facets are the active catalytic surfaces. The observed activities can be linked to the same Al3+ ions on both hydrated and dehydrated surfaces: penta-coordinate Al3+ ions (Lewis acid sites), and their corresponding –OH groups (Br?nsted acid sites), depending on the calcination temperature. 相似文献93.
Measurements of the surface tension of aqueous solution of mixtures of sodium dodecyl sulfate (SDDS) with methanol and ethanol
in SDDS concentration range from 10−5 to 10−2 M and mixtures of sodium hexadecyl sulfonate (SHS) with methanol and ethanol at SHS concentration from 10−5 to 8 × 10−4 M and for methanol and ethanol from 0 to 21.1 and, 11.97 M, respectively, were carried out at 293 K. Moreover, the surface
tension of aqueous solution mixtures of SDDS with propanol in the concentration range from 0 to 6.67 M taken from the literature
was also considered. The results obtained indicate that it is possible to describe the relationship between the surface tension
and molar concentration or molar fraction of alcohol by Szyszkowski and Connors equations. However, the Fainerman and Miller
equation allows us to predict the isotherm of the surfactant tension at constant anionic surfactants concentration at which
their molecules are present in the solution in the monomeric form if the molar area of surfactants and alcohols can be determined.
Based on the surface tension isotherms, the Gibbs surface excess of anionic surfactants and alcohols concentration at water–air
interface was determined and then recalculated for Guggenheim-Adam surface excess concentration of these substrates, and next
the molar fraction of alcohols and surfactants in the surface layer was determined. These molar fractions were discussed with
regard to surfactant and alcohol standard free energy of adsorption at the water–air interface determined from Langmuir and
Aronson and Rosen equations. The standard free energy of adsorption determined in these ways was compared to that deduced
on the basis of pC20 and Lifshitz van der Waals-components of the anionic surfactant and alcohol tails. 相似文献
94.
先用聚丙烯酸对电气石进行表面改性,再以不同的配比加入到LDPE中制备复合薄膜,并测试其力学性能、透湿及透气性能。结果表明:聚丙烯酸用量为1.0%时,电气石表面改性效果最佳;改性后的电气石添加量为6%时薄,膜的综合性能最好。 相似文献
95.
96.
使用振动样品磁强计(VSM)对两种金刚石的磁性进行测量,测量数据显示两者的磁化强度相差8倍之多.用该样品制作锯片进行切割试验,结果表明:用磁化强度大的金刚石制作的锯片的切割速度比磁化强度小的慢了17.1%.金刚石内部磁性大,是金刚石内部杂质多,导致了金刚石晶格结构的畸变,影响了金刚石的冲击强度,从而使用金刚石制作的锯片的切割速度变慢. 相似文献
97.
The rapid introduction of wavelength division multiplexing (WDM) technology in long distance fiber optic communication networks which has been observed in the recent years has been driven by line economy. Not merely the ability to overcome fiber scarcity, but also the savings associated with the replacement of many electronic regenerators by fewer optical amplifiers, have motivated the carriers to employ WDM. These arguments do not often apply to optical networking in metropolitan areas because transmission distances are short. For this reason, metro-WDM has been deployed in a few rare cases only, though it has been widely discussed by a broad scientific and industrial community. In this paper, an advanced operational concept for all optical transport networks in the metropolitan area is introduced. It focuses on node economy, i.e., the technical concepts to provide gigabit services access to the transport network at minimum cost, characterized by the following basic features: protocol independence, monitoring, protection and fast bandwidth provisioning. 相似文献
98.
Contact angles were measured in the following systems: quartz/water droplet/saturated vapor of water + n-alkane and quartz/water droplet/saturated vapor of n-alkane. The alkanes tested were from hexane to pentadecane. In both systems non-smooth changes of contact angle as a function of the chain length were observed. These changes are similar to the zeta-potential changes measured previously for two different samples of quartz in the quartz/n-alkana/water system. On the basis of the results and calculations it is suggested that the observed non-smooth changes of contact angle are due to similar changes in film pressures of the water and n-alkanes. 相似文献
99.
Byung June Choi Bumsoo Kim Sung Moon Jin Ja Choon Koo Wan Kyun Chung Hyouk Ryeol Choi Hyungpil Moon 《Intelligent Service Robotics》2010,3(2):99-113
We propose a precise position error compensation and low-cost relative localization method in structured environments using
magnetic landmarks and hall sensors. The proposed methodology can solve the problem of fine localization as well as global
localization by tacking landmarks or by utilizing various patterns of magnetic landmark arrangement. In this paper, we consider
two patterns of implanted permanent magnets on the surface, namely, at each vertex of regular triangles or rectangles on a
flat surface. We show that the rectangular configuration of the permanent magnetic bars is better for a robust localization
under sensor noise. For the experiments, permanent magnet sets in rectangular configuration are placed on the floor as landmarks
at regular intervals, and magnetic hall sensors are installed at the bottom of a mobile robot. In our implementation, the
accuracy after the error compensation is less than 1 mm in the position and less than 1° in the orientation. Due to the low
cost and accuracy of the proposed methodology, it would be one of the practical solutions to the pose error correction of
a mobile robot in structured environments. 相似文献
100.
Selective catalytic reduction (SCR) of NOx with ammonia using metal-exchanged molecular sieves with a chabazite structure has recently been commercialized on diesel vehicles. One of the commercialized catalysts, i.e., Cu-SSZ-13, has received much attention for both practical and fundamental studies. For the latter, the particularly well-defined structure of this zeolite is allowing long-standing issues of the catalytically active site for SCR in metal-exchanged zeolites to be addressed. In this review, recent progress is summarized with a focus on two areas. First, the technical significance of Cu-SSZ-13 as compared to other Cu ion-exchanged zeolites (e.g., Cu-ZSM-5 and Cu-beta) is highlighted. Specifically, the much enhanced hydrothermal stability for Cu-SSZ-13 compared to other zeolite catalysts is addressed via performance measurements and catalyst characterization using several techniques. The enhanced stability of Cu-SSZ-13 is rationalized in terms of the unique small pore structure of this zeolite catalyst. Second, the fundamentals of the catalytically active center; i.e., the chemical nature and locations within the SSZ-13 framework are presented with an emphasis on understanding structure–function relationships. For the SCR reaction, traditional kinetic studies are complicated by intra-crystalline diffusion limitations. However, a major side reaction, nonselective ammonia oxidation by oxygen, does not suffer from mass-transfer limitations at relatively low temperatures due to significantly lower reaction rates. This allows structure–function relationships that are rather well understood in terms of Cu ion locations and redox properties. Finally, some aspects of the SCR reaction mechanism are addressed on the basis of in situ spectroscopic studies. 相似文献