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901.
Weon Gyu Shin Chaolong Qi Jing Wang Heinz Fissan David Y.H. Pui 《Journal of aerosol science》2009,40(5):463-468
We investigated the dependence of unipolar diffusion charging of nanoparticles on the dielectric constant of the particle material experimentally. The examined nanoparticles (10–200 nm) cover a wide range of dielectric constant but have almost the same spherical or compact morphology. Measurements of both intrinsic charged fraction and mean charge per particle show very small differences among different materials. The level of the small difference is consistent with the estimation by Fuchs’ [(1963). On the stationary charge distribution on aerosol particles in bipolar ionic atmosphere. Geofisica Pura e Applicata, 56, 185–193] theory. 相似文献
902.
Yo-Han Cho Kyunghee Lee Kyunghoon Kim Kwang Hyun Baik Jinhan Cho Jihyun Kim Kyusoon Shin Joona Bang 《Korean Journal of Chemical Engineering》2009,26(1):277-280
We demonstrate that the nanoscopic block copolymer patterns on GaN can enhance light extraction efficiency of GaN-based light
emitting diodes. Nanoporous patterns were fabricated on a bare GaN substrate via self-assembly of poly(styrene-b-methyl methacrylate) block copolymers from which PMMA microdomains were selectively removed later on. A bare GaN surface
was treated with a photo-crosslinkable thin layer of poly(styrene-r-methyl methacrylate) random copolymers to tune the cylindrical microdomain orientations. The nanoporous block copolymer thin
film was controlled to be thicker than its typical repeat period in bulk by incorporating PMMA homopolymer into block copolymer.
Consequently, the light extraction efficiency in photoluminescence spectra could be tuned with the thickness of nanopatterned
thin film on GaN.
This paper is dedicated to Professor Chul Soo Lee on the occasion of his retirement from Korea University. 相似文献
903.
Surfactant systems show highly non-ideal phase behavior because of the inter-association and intra-association hydrogen bond.
We present a lattice fluid equation of state that combines the multi-fluid nonrandom lattice fluid model with modified Veytsman
statistics for intra+inter molecular association to calculate phase behavior for mixture containing surfactant systems. The
literatureresults fitted to this model show good accordance for mixtures containing nonionic surfactant systems.
This article is dedicated to Professor Chul Soo Lee in commemoration of his retirement from Department of Chemical and Biological
Engineering of Korea University. 相似文献
904.
Seung Won Choi Dong Myeong Shin Joo Sung Lee Ju Min Kim Hyun Wook Jung Jae Chun Hyun 《Korean Journal of Chemical Engineering》2009,26(1):26-31
The sensitivity of two-dimensional isothermal film casting processes to ongoing sinusoidal disturbances has been investigated
by using the frequency response method with transient simulation techniques. Amplitude ratios of state variables such as cross-sectional
area, film width and film thickness at the take-up position with respect to a sinusoidal disturbance show resonant peaks along
the frequency domain. Effects of operating conditions, such as drawdown ratio and aspect ratio, on the process sensitivity
have been examined. Increasing drawdown ratio and decreasing aspect ratio make the system more sensitive to disturbances.
Also, the dichotomous behavior in the sensitivity analysis using viscoelastic Phan-Thien and Tanner fluids has been elucidated.
This frequency response method can be a useful tool to optimally design process systems for better processability and product
quality.
This article is dedicated to Professor Chul Soo Lee in commemoration of his retirement from Department of Chemical and Biological
Engineering of Korea University. 相似文献
905.
The preparation and microwave dielectric properties of ZnAl2O4-based glass–ceramic composites were investigated. Using zinc borosilicate (ZBS) glass and Al2O3, glass–ZnAl2O4 composites with high quality factor was successfully prepared at temperatures below 950 °C. The linear shrinkage for 50 vol% ZBS glass–ZnAl2O4 composite showed a steep increase up to 650 °C and a plateau between 700 °C and 950 °C, implying that one-stage densification process occurred. The crystallization of ZnAl2O4 was observed above 700 °C and an insufficient densification occurred due to the consumption of the glass. As the sintering temperature increased, the quality factor (Q × f0) showed an increase with an S-type curve whereas the dielectric constant was almost constant. The formation of ZnAl2O4 might correspond to the increase of Q × f0; a high value of 17,757 GHz (1415 at 12.6 GHz) was obtained for the specimen sintered at 900 °C. 相似文献
906.
Shin-Tae Bae Hyunho Shin Hyun Suk Jung Kug Sun Hong 《Journal of the American Ceramic Society》2009,92(11):2512-2516
By carbothermally reducing a TiO2 core–sucrose shell precursor, titanium carbide mesoporous nanoparticles with a very high specific surface area (147 m2 /g at 1500°C) have been prepared. The high specific surface area results from the mesoporous nature of the produced nanoparticles with two types of pores: the one with a pore diameter of about 20 nm and the other with <4 nm. 相似文献
907.
In-Sun Cho Shin Tae Bae Dong Kyun Yim Dong Wan Kim Kug Sun Hong 《Journal of the American Ceramic Society》2009,92(2):506-510
CaNb2 O6 nanoparticles with a size range of 30–50 nm were synthesized by heat treatment at 600°C after a solvothermal process and their optical and photocatalytic properties were investigated. The prepared powders were characterized by X-ray powder diffractometer, field-emission scanning electron microscope, transmission electron microscope, UV-Vis diffuse reflectance spectroscopy, Fluorescence spectroscopy, and Raman spectroscopy. Compared with a powder of the same material prepared by a solid-state reaction (SS) method, the nanoparticles exhibited a higher Brunauer–Emmett–Teller (BET) surface area, more efficient light absorption, and enhanced photocatalytic activity for producing H2 from pure water under UV irradiation. The photoluminescence spectra revealed that a radiative recombination process is dominant in the powder prepared by the SS method (strong blue emission at 300 K) under UV light irradiation, while no obvious emission was observed in the nanoparticles. This decrease of the radiative recombination as well as the higher optical absorption ability and higher BET surface area resulting from the reduced dimensionality led to enhanced photocatalytic activity of the nanoparticles. 相似文献
908.
Application of membrane filtration has been significantly expanded throughout the world in two decades. A project was launched to facilitate the application of membrane filtration in drinking water plants in Korea in 2004. Five pilot plants each with a capacity of 500 m3/d were installed in a Gueui Drinking Water Plant. The Han River water was a main raw water source for the plants. Key parameters of the raw water were examined. The raw water characteristics are tremendously varied with seasons and rain fall, especially in terms of turbidity and algae numbers. The operation of pretreatment was of substantial importance due to the variation of the raw water. Coagulation and powdered activated carbon adsorption were performed as pretreatment options of microfiltration. The coagulant doses were optimized with increasing turbidity compared to the conventionally used operational manual. PAC adsorption was applied to overcome fouling by high algae numbers. The addition of PAC relieved the aggravation of fouling. However, the PAC addition could not stop the undergoing fouling. A set of laboratory experiments showed that the removal of floc aggregates after coagulation and PAC was critical to maintain high water flux in the membrane system. 相似文献
909.
Use of biosurfactant to remediate phenanthrene-contaminated soil by the combined solubilization-biodegradation process 总被引:1,自引:0,他引:1
The applicability of the combined solubilization-biodegradation process was examined using soil-packed column. In the solubilization step, 50 pore volumes of 150 mg/l biosurfactants solution was injected and the percentage removal of phenanthrene (mg) was 17.3% and 9.5% from soil with pH 5 and 7, respectively. The highest solubility was detected at pH 5 and this result confirmed that adjusting the pH of the biosurfactants solution injected could enhance the solubility of phenanthrene. Following this, soil samples were completely transferred to batches and incubated for 10 weeks to monitor phenanthrene degradation. The phenanthrene concentration in the soil samples decreased significantly during the biodegradation step in all soil samples, except for the soil sample that was flushed with biosurfactants solution with pH 4. This indicated that the degradation of contaminants by specific species might not be affected by the residual biosurfactants following application of the solubilization process. Moreover, these results suggested that the biosurfactant-enhanced flushing process could be developed as a useful technology with no negative effects on subsurface environments and could be combined with the biodegradation process to increase the removal efficiency. 相似文献