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101.
Hoo Kun Lee Kwan Sik Chun Hyun Soo Park Jong Hyun Cho 《Korean Journal of Chemical Engineering》1989,6(4):294-299
A mathematical model for an absorption of nitrogen oxides into water in packed column was developed based on the mass-transfer
coefficient in packed column and the chemical reaction accompanying NO
x
absorption produces HNO3 and HNO2 in the liquid phase. The subsequent dissociation of HNO2 in the liquid-phase results in the formation of HNO3 and NO gas, and then this NO gas follows to be oxidized by O2 in air. The important factors influenced on the absorption of NO
x
are the oxidation state of NO gas and the partial pressure of nitrogen oxides in the gas. The efficiency of NO
x
absorption increases with the increase of the partial pressure of NO
x
. The most critical value for using the model is the constant of
.The selection of 11×10−4kg·mol/atm·m2·sec for
resonable for this model. 相似文献
102.
Y. J. Cho P. S. Song C. G. Lee Y. Kang S. D. Kim L. T. Fan 《Chemical Engineering Communications》2005,192(3):257-271
Liquid dispersion in the radial direction was investigated in the riser of a viscous liquid-solid fluidized bed 0.102 m in diameter and 3.5 m in height. Pressure fluctuations in the riser were also measured and analyzed to examine the behavior of fluidized particles. Effects of liquid velocity (0.15-0.45 m/s), solid circulation rate (2-8 kg/m2s), particle size (1-3 mm), and liquid viscosity (0.96-38 mPas) on pressure fluctuations and the liquid radial dispersion coefficient were determined. The infinite space model was employed to obtain the radial dispersion coefficient from the radial concentration profiles of the tracer. The pressure fluctuations were analyzed by means of autocorrelation coefficient as well as power spectral density function. The dominant frequency obtained from the autocorrelation coefficient or power spectral density function of pressure fluctuations decreases with increasing liquid viscosity or liquid velocity, but it increases with increasing particle size. The liquid radial dispersion coefficient decreases with increasing liquid velocity or viscosity, but it increases as the solid circulation rate or particle size increases. The liquid radial dispersion coefficient is related closely to the resultant behavior of fluidized particles. The radial dispersion coefficient has been well correlated with operating variables in terms of dimensionless groups. 相似文献
103.
In a previous study, CETP inhibitory peptide (3 kDa) was isolated from hog plasma. The peptide, synthesized chemically according
to the amino acid sequence of the 3-kDa peptide (designated P28), showed CETP inhibitory activity both in vitro and in vivo [Cho et al. (1998) Biochim. Biophys. Acta 1391, 133–144]. We report herein further unique features of P28 when it was associated with the cholesteryl ester (CE)-donor and-acceptor lipoproteins. Lipoprotein substrates with P28 present in both HDL (as a CE-donor) and LDL (as a CE-acceptor) served as poor substrates, with CE-transfer activity decreased
up to 60% compared to normal substrates without P28. P28 was found to be located in HDL fractions of hog plasma and showed the same electromobility as that visualized by PAGE on
7% polyacrylamide gel under nondenaturing conditions. Addition of apolipoprotein A-1 (apoA-1) or apoB antibody to a normal
CE-transfer mixture did not alter CE-transfer activity. However, addition of apoA-1 or −B antibody to a CETP-inhibition mixture
decreased the inhibitory activity of P28 by ca. 20%. Western blot analysis revealed that P28 was associated only with human and hog HDL among several lipoproteins purified from human, hog, and rabbit. CFTP-inhibition
assays with various lipoprotein substrates revealed that P28 exhibited substrate-specific inhibitory activity. The inhibitory activity of P28 was highly dependent on the type of lipoprotein substrate (whether CE-donor or-acceptor); P28 inhibited CE transfer from HDL to LDL, but it did not inhibit CE transfer from HDL to HDL. 相似文献
104.
Changyong Choi Su Young Chae Tai‐Hyoung Kim Jung Keon Kweon Chong Su Cho Mi‐Kyeong Jang Jae‐Woon Nah 《应用聚合物科学杂志》2006,99(6):3520-3527
Diblock copolymers with different poly(ε‐caprolactone) (PCL) block lengths were synthesized by ring‐opening polymerization of ε‐caprolactone in the presence of monomethoxy poly(ethylene glycol) (mPEG‐OH, MW 2000) as initiator. The self‐aggregation behaviors and microscopic characteristics of the diblock copolymer self‐aggregates, prepared by the diafiltration method, were investigated by using 1H NMR, dynamic light scattering (DLS), and fluorescence spectroscopy. The PEG–PCL block copolymers formed the self‐aggregate in an aqueous environment by intra‐ and/or intermolecular association between hydrophobic PCL chains. The critical aggregation concentrations of the block copolymer self‐aggregate became lower with increasing hydrophobic PCL block length. On the other hand, reverse trends of mean hydrodynamic diameters were measured by DLS owing to the increasing bulkiness of the hydrophobic chains and hydrophobic interaction between the PCL microdomains. The partition equilibrium constants (Kv) of pyrene, measured by fluorescence spectroscopy, revealed that the inner core hydrophobicity of the nanoparticles increased with increasing PCL chain length. The aggregation number of PCL chain per one hydrophobic microdomain, investigated by the fluorescence quenching method using cetylpyridinium chloride as a quencher, revealed that 4–20 block copolymer chains were needed to form a hydrophobic microdomain, depending on PCL block length. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3520–3527, 2006 相似文献
105.
Autoxidation of ethyl eicosapentaenoate and docosahexaenoate 总被引:2,自引:0,他引:2
Soon-Yeong Cho Kazuo Miyashita Teruo Miyazawa Kenshiro Fujimoto Takashi Kaneda 《Journal of the American Oil Chemists' Society》1987,64(6):876-879
The extent of oxidation of ethyl esters of eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) was compared quantitatively
with that of ethyl linoleate (Lo) and ethyl linolenate (Ln) by oxygen uptake and formation of conjugated diene, hydroperoxide
and secondary oxidation products. EPA and DHA esters were oxidized rapidly even at 5 C in the dark after an induction period
of 3–4 days, while the induction periods of Ln and Lo esters were 20 days and more than 60 days, respectively. Oxygen uptake
of EPA and DHA esters after the induction period was 5.2 and 8.5 times faster than that of ethyl Ln, respectively. Hydroperoxides
of EPA and DHA esters are much less stable than those of ethyl Lo. The peroxide value is not necessarily a good indication
of oxidation in these polyenoic acids because a considerable amount of secondary products is formed at the early stage of
oxidation. Polymers were found to be major secondary products in these polyenoic esters. 相似文献
106.
Oxidative coupling of methane (OCM) was carried out over Na+-ZrO2-Cl /A1[2O3 catalysts in a temperature range from 1023 to 1123 K. The catalysts were prepared by impregnating the α- or γ-Al2O3 supports with sodium carbonate and/or zirconyl chloride. The OCM activity was examined using the catalysts prepared by three
different preparation procedures. The best catalyst was the one prepared by subsequent impregnation of sodium carbonate-preimpregnated
γ-Al2O3 with a mixed solution of sodium carbonate and zirconyl chloride. It was found that preimpregnated sodium played an important
role in reducing the combustion activity of the γ-Al2O3. The catalyst with an optimal composition showed the highest C2 selectivity and yield of 40.8% and 15.1%, respectively. From the X-ray diffraction analysis it was found that tetragonal
ZrO2 was formed and that NaCl existed in the catalysts with relatively high sodium contents. 相似文献
107.
Four oil absorbents based on styrene–butadiene (SBR)—pure SBR (PS), 4‐tert‐butylstyrene–SBR (PBS), EPDM–SBR network (PES), and 4‐tert‐butylstyrene‐EPDM‐SBR (PBES)—were produced from crosslinking polymerization of uncured styrene–butadiene rubber (SBR), 4‐tert‐butylstyrene (tBS), and ethylene–propylene–diene terpolymer (EPDM). The reaction took place in toluene using benzoyl peroxide (BPO) as an initiator. Uncured SBR was used as both a prepolymer and a crosslink agent in this work, and the crosslinked polymer was identified by IR spectroscopy. The oil absorbency of the crosslinked polymer was evaluated with ASTM method F726‐81. The order of maximum oil absorbency was PBES > PBS > PES > PS. The maximum values of oil absorbency of PBES and PBS were 74.0 and 69.5 g/g, respectively. Gel fractions and swelling kinetic constants, however, had opposite sequences. The swelling kinetic constant of PS evaluated by an experimental equation was 49.97 × 10?2 h?1. The gel strength parameter, S, the relaxation exponent, n, and the fractal dimension, df, of the crosslinked polymer at the pseudo‐critical gel state were determined from oscillatory shear measurements by a dynamic rheometer. The morphologies and light resistance properties of the crosslinked polymers were observed, respectively, with a scanning electron microscope (SEM) and a color difference meter. 相似文献
108.
Chul-Kun Cho Kil Sang Chang Timothy S. Cale 《Korean Journal of Chemical Engineering》1993,10(4):195-202
Magnetic crystallite thermometry has been used to measure the average nickel crystallite temperature in packed bed reactors
during ethane hydrogenolysis, an exothermic reaction. The technique is based on the temperature dependence of the magnetic
moment of dispersed nickel catalysts. Measurement of the average catalyst temperature is very useful for reactor control because
of its shorter time constant compared with exit fluid temperature. Bed temperature control based on the exit fluid temperature,
which has often been used as a control variable, is too slow to protect thermal runaway of the bed. The advantage of short
time constant by measuring the average catalyst temperature has been incorporated with enhanced feedback control system to
control the bed temperature and prevent the thermal runaway of the catalyst bed. An enhanced feedback control structure with
supervisory action performed better than the classical proportional-integral control in runaway prevention when the two control
schemes were compared with each other on the basis of the trippoint (incipient thermal runaway). 相似文献
109.
Jin Sung Choi Sang Hyuk Im Min Young Song O Ok Park Hansol Cho Jin Taek Hwang 《应用聚合物科学杂志》2005,95(5):1100-1104
A gradient refractive index rod was successfully prepared by a new fabrication method using laminar shear mixing, and a graded index polymer optical fiber that satisfied IEEE1394b was obtained from the method. To fabricate the gradient refractive index rod, a liquid monomer mixture with a relatively low refractive index was placed in a prepared cylindrical glass reactor and a transparent polymer rod with a higher refractive index was introduced at the center of the reactor. The reactor and the polymer rod were then rotated concurrently with a small rotating speed difference to generate a Couette flow in the liquid phase. The centrifugal force generated by rotation and the polymer diffusion into the liquid monomer mixture developed a graded concentration profile in a radial direction. The Couette flow could reduce the concentration fluctuation in a tangential direction. In addition, the graded index profile could be controlled by the copolymer composition of the rod and its diameter. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1100–1104, 2005 相似文献
110.
To understand the smart (i.e., good memory) characteristics of hybrid composites of carbon fibers (CFs) and glass fibers (GFs) with epoxy resin as a matrix, the changes in the electrical resistance of composites with tension and on bending were investigated. The electrical resistance behavior of composites under tension changed with the composition of the CF/GF, as well as with the applied strain. The fractional electrical resistance increased slowly with increasing strain within a relatively low strain region. However, with further loading it increased stepwise with the strain according to the fracture of the CF layers. The strain sensitivity of the samples increased with increasing CF weight percentage, and the samples incorporating more than 40 wt % CF showed a strain sensitivity higher than 1.54 for a single CF. The changes in the fractional electrical resistance with bending were not so dominant as those with tension. This difference was attributed to the action of two cancelling effects, which are the increasing and decreasing fractional electrical resistance due to tension and compression with bending, respectively. On recovery from a large applied bending, the fractional electrical resistance decreased slowly with unloading because of the increase of contacts between the fibers that resulted from the reorganization of ruptured CFs during the recovery. Even the composites incorporating a relatively small CF content showed an irreversible electrical resistance with both tension and bending. However, the strain sensitivity being larger with tension than with bending is ascribed to the difference in their mechanical behaviors. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2447–2453, 2002 相似文献