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1.
Byeong-Seon Shin Sang-Yun Lim Suk-Jin Choung 《Korean Journal of Chemical Engineering》1994,11(4):254-260
As an attempt to improve the catalytic activity at higher reaction temperatures between 300-450°C, various mole ratios of
WO3 were added to V2O5/TiO2 catalytic systems. And also, in order to suggest a new mixed oxide catalyst system for simultaneous removal of NOx and SOx, from stationary sources, MoO3-V2O5/TiO2catalysts were prepared by a conventional impregnation method together with a newly introduced method of surface fixation
(non-aqueous solution method). In case of WO3 addition, at higher reaction temperature range (300–450°C), WO3 and WO3-V2O5/TiO2 catalysts showed significant high conversion in NO reduction with NH3 while V2O5/TiO2 catalyst showed a significant change in selectivity mainly due to the excess side reaction of NH3 oxidation. This difference in selectivity due to NH3 oxidation at high temperature is supposed to be associated with the difference in values of surface excess oxygen between
WO3 and V2O5 on titania. The surface acidities of tested catalysts were relatively well correlated with the % conversion of NO at 400°C.
In case of MoO3 addition, the catalytic activity for the simultaneous removal of NOx and SOx were quite enhanced by the addition of MoO3 into V2O5/TiO2 catalysts. The enhanced activities were responsible for the formation of Mo=O bond on the intermediate species produced by
solid solutions on MoO3-V2O5/TiO2 (aqueous). However, in the case of MoO3-V2O5/TiO2 (non-aqueous), the exact source of active site was not able to detect in IR spectra in spite of more enhanced activity was
obtained in this study. After SO2 contact, VOSO4 is newly formed on the surface of catalyst, which supposed to be associated with the activity enhancement. 相似文献
2.
Machine Learning - Covariance estimation for high-dimensional datasets is a fundamental problem in machine learning, and has numerous applications. In these high-dimensional settings the number of... 相似文献
3.
Yeonjung Han Yonggun Park Jun-Ho Park Sang-Yun Yang Chang-Deuk Eom 《Drying Technology》2016,34(13):1613-1620
This work focused on the shrinkage and drying stress of red pine (Pinus densiflora) wood during kiln drying and investigated transverse shrinkage and moisture changes in thin specimens using digital image analysis and near-infrared spectroscopy, respectively. The effect of specimen thickness, which ranged from 1 to 10?mm on shrinkage, was analyzed under drying conditions with restrained stresses. The shrinkage due to moisture content was presented in the form of an exponential function and a linear function above and below the fiber saturation point, respectively. A shorter existence of the moisture gradient increased the transverse shrinkage. The tangential and radial shrinkage at the tissue level in 30-µm (longitudinal) thick slices was measured and compared with the shrinkage of above specimens with difference thicknesses. The transverse shrinkage of 1-mm-thick specimen is similar to the shrinkage measured using 30-µm-thick slice. 相似文献
4.
Direct incorporation of vanadium into three-dimensional KIT-6: 1. Optimization of synthesis conditions 总被引:1,自引:0,他引:1
Balasamy Rabindran Jermy Sang-Yun Kim Kanattukara Vijayan Bineesh Manickam Selvaraj Dae-Won Park 《Korean Journal of Chemical Engineering》2009,26(5):1235-1240
Three dimensional (3-D) cubic KIT-6 with directly incorporated vanadium was hydrothermally synthesized by using Pluronic P123
and n-butanol as the structure-directing mixture, tetraethyl orthosilicate (TEOS) as the silica source and NH4VO3 as the vanadium source. The molar composition was varied in the range of 0.017 P123/0.08–2.4 V/1.0–2.0 TEOS/1.31–1.70 BuOH/1.83–3.00
HCl/195 H2O. The orderness of mesopore structure was estimated by X-ray diffraction, N2 adsorption, and TEM analysis. The effects of the amount of HCl, TEOS and BuOH on the structure of KIT-6 were discussed. The
time and temperature for the synthesis of KIT-6 were also optimized. The amount of vanadium content influenced the framework
structure and crystallinity of the Ia3d phase significantly. 相似文献
5.
Balasamy Rabindran Jermy Sang-Yun Kim Kanattukara Vijayan Bineesh Manickam Selvaraj Seung-Kug Song Jong-Woo Ryu Dae-Won Park 《Korean Journal of Chemical Engineering》2009,26(5):1241-1245
The direct incorporation of vanadium into the three-dimensional (3-D) cubic Ia3d mesostructure designated as V-KIT-6 was prepared,
and the material obtained therein showed a very high specific surface area of ∼1,000 m2/g with tunable pore diameters in a narrow distribution of sizes, ∼5.7 to 6.0 nm. The coordination and nature of the V sites
in V-KIT-6 were characterized by 51V-spin-echo NMR analysis. It shows that after calcination, the V4+ species are totally oxidized to the V5+ state with 4- and 6-coordinated V-O environments in a highly dispersed state with much less crystalline V2O5 formation. The calcined V-KIT-6 materials showed excellent catalytic activity in the direct oxidation of styrene using tert-butyl
hydroperoxide (TBHP) as an oxidant. 相似文献
6.
We present a tutorial introduction to the multi-rotor unmanned aerial vehicles, often simply referred as drones. We first explain typical configuration, components and construction of the drones. We then provide basic kinematic and dynamic modeling of drones and their principle of flight. Some representative motion control techniques are then presented, which take into account the issue of under-actuation of the drones. State estimation problem of the drones, that is crucial for their proper flying, yet, should be done only by using onboard sensors and their sensor fusion, is explained. Some emerging research directions requiring capability beyond typical drones are also mentioned. 相似文献
7.
Sang-Yun Jeon Ha-Ni Im Bhupendra Singh Jin-Ha Hwang Sun-Ju Song 《Ceramics International》2013,39(4):3893-3899
A bilayer configuration of mixed ion-electron conducting La2NiO4+δ and oxygen-ion conducting Gd0.1Ce0.9O1.95 (LNO/GDC10) was proposed for hydrogen production by water-splitting and its properties were measured as a function of temperature, reducing gas CO content and water vapor pressure during the hydrogen production by water-splitting. The hydrogen production flux increased with increasing water vapor pressure and oxygen chemical potential to a maximum of 0.12 cm3 (STP)/min-cm2 with 23.25% CO/76.75% CO2 (40 sccm)/balance He (60 sccm) gas mixture on the oxygen-permeate side and wet N2 (pH2O=0.49 atm) on the oxidizing side at 900 °C. The stability of the bilayer membrane was tested in a very low oxygen partial pressure (pO2) on the oxygen-permeate side. The presence of GDC10 on the oxygen-permeate side of the bilayer prevented the direct exposure of LNO to very low pO2 and thus protected it from decomposition, even at pO2≈10?15 atm. 相似文献
8.
Seong-Yeon?YooEmail author Dong-Seong?Park Min-Ho?Chung Sang-Yun?Lee 《Journal of Mechanical Science and Technology》2002,16(1):109-115
Vortex generators are fabricated on the fin surface of a fin-tube heat exchanger to augment the convective heat transfer. In addition to horseshoe vortices formed naturally around the tube of the fin-tube heat exchanger, longitudinal vortices are artificially created on the fin surface by vortex generators. The purpose of this study is to investigate the local heat transfer phenomena in the fin-tube heat exchangers with and without vortex generators, and to evaluate the effect of vortices on the heat transfer enhancement. Naphthalene sublimation technique is employed to measure local mass transfer coefficients, then analogy equation between heat and mass transfer is used to calculate heat transfer coefficients. Experiments are performed for the model of fin-circular tube heat exchangers with and without vortex generators, and of fin-flat tube heat exchangers with and without vortex generators. Average heat transfer coefficients of fin-flat tube heat exchanger without vortex generator are much lower than those of fin-circular tube heat exchanger. On the other hand, fin-flat tube heat exchanger with vortex generators has much higher heat transfer value than conventional fin-circular tube heat exchanger. At the same time, pressure losses for four types of heat exchanger is measured and compared. 相似文献
9.
In order to investigate effects of an electron donor in propylene polymerization (in gas and slurry phase reactions each)
by using a 3rd generation Ziegler-Natta catalyst, the catalytic activities were measured before and after the addition of
an electron donor. And physical properties of produced polymer were estimated. Polymerization rate was decreased with increasing
EB/A1 mole ratio because atactic sites on catalyst were selectively poisoned by the addition of the electron donor, and consequently
total number of active sites were diminished. It was found that the overall reaction order was the 2nd order, and a reaction
rate form was suggested by using a CO inhibition technique. Catalyst deactivation was due to the formation of dense isotactic
polypropylene on the catalyst at the beginning of polymerization so that monomers had the difficulties in diffusion into catalyst
surface through the dense polymer. From the measurements of polymer physical properties, probability of active site transitions
from atactic→low isotactic→high isotactic sites could be considered, which may be due to the formation of a complex between
co-catalyst and electron donor. 相似文献
10.
Balasamy Rabindran Jermy Dal-Rae Cho Kanattukara Vijayan Bineesh Sang-Yun Kim Dae-Won Park 《Microporous and mesoporous materials》2008,115(3):281-292
The direct synthesis of three-dimensional (3-D) cubic V-KIT-6 was prepared using a Pluronic P123 triblock copolymer as the structure directing agent and n-butanol as the co-surfactant. The material obtained therein showed a very high specific surface area 1000 m2/g with pore diameters that could be tuned within a narrow size distribution of 5.7–6.0 nm. After calcination, Raman and UV–vis analysis revealed the presence of V5+ species in a highly dispersed state with much less crystalline V2O5 formation. 51V-NMR analysis showed that the vanadium species interacted directly with the silica framework in an almost symmetrical tetrahedral environment. NH3-TPD analysis for V-KIT-6 showed a wide distribution of acid sites at temperatures ranging from 200 to 800 °C. The calcined V-KIT-6 materials showed excellent catalytic activity in the direct oxidation of cyclohexane using dilute aqueous H2O2 as the oxidant. 相似文献