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31.
32.
AbstractA toroidal-shaped differential mobility analyzer (DMA), called toroidal Hanyang-DMA (toroidal Hy-DMA), was developed for particle characterization. The height, width, and weight of the newly developed toroidal Hy-DMA are 8?cm, 14?cm, and 1.2?kg, respectively, indicating that it is much more compact and lighter than the TSI long-DMA; nevertheless, the classifiable particle size range is up to 400?nm. Therefore, the toroidal Hy-DMA can be useful for many applications in a limited space owing to its small size. The performance of the Hy-DMA was evaluated using tandem differential mobility analyzer (TDMA) experiments with two identical Hy-DMAs and numerical simulations using a single-particle tracking analysis in a Lagrangian framework. To simulate particle behaviors, a flow-rate-weighted particle injection method, which is more realistic, was employed, and the proposed particle tracking method can be widely applied to any non-plug flow conditions. The obtained experimental data and numerical results of central particle sizes are consistent with each other. Empirical and numerical transfer functions of the toroidal Hy-DMA were obtained and compared with those of other types of well-known DMAs. It is concluded that the toroidal Hy-DMA has an empirical transmission probability ranging from 0.5 to 0.9 and a sizing resolution ranging from 5.5 to 9.0, which indicates acceptable performance in classifying monodisperse particles within the test size range of 20 to 400?nm.Copyright © 2019 American Association for Aerosol Research 相似文献
33.
Hong-Soo Kim Gun Yong Sung Chong Hee Kim 《Journal of the American Ceramic Society》1992,75(3):587-591
The effect of the cooling rate on the PTCR (positive temperature coefficient of resistivity) characteristics of 0.1 mol% Sb2 O3 -doped BaTiO3 ceramics has been investigated. Resistances both below and above the Curie temperature were increased by slow cooling, which indicated that the resistive layer width at the grain boundary increased as the cooling rate decreased. Concentration profiles of the Ba vacancies as a function of distance from the grain boundary have been simulated by the finite difference method. The inversion temperature of the 0.1 mol% Sb2 O3 -doped BaTiO3 system was determined to be 1160°C from the measured electrical properties and computed concentration profiles. 相似文献
34.
Young Cheol Ryu Tae Gun Kim Guem-Seok Seo Jin Hwan Park Cha Soo Suh Seong-Soo Park Seong-Soo Hong Gun Dae Lee 《Journal of Industrial and Engineering Chemistry》2008,14(2):213-218
The TiO2/substrate pearlescent pigments were prepared by the hydrolysis of TiOCl2 on the substrate followed by a calcinations process. The natural mica (muscovite), synthetic mica (fluorophlogopite) and -alumina flake were selected as the substrates for pearlescent pigments. The effect of substrate on the anatase to rutile (A–R) phase transformation of TiO2 was studied. The A–R phase transformation of TiO2 during the preparation of pearlescent pigments and their proportion in the TiO2 layer have been analyzed by XRD measurements. The phase compositions of TiO2 layer in each pearlescent pigment are quite different depending on the substrates. The TiO2 layer deposited on -alumina has higher rutile fraction than those on the natural and synthetic mica. The XPS analysis showed that the cations originally present in the substrates diffused into the TiO2 layer. The TiO2 layer deposited on -alumina contains Al, while those on the natural and synthetic mica substrates contain Si and K in addition to Al. The metal cations diffusing from the substrate into TiO2 layer might retard the A–R phase transformation of TiO2. The suppressing effect on the A–R transformation of TiO2 by mixed cations seems to be much stronger than that of single cation, resulting in relatively higher rutile fraction in the case of TiO2 layer deposited on -alumina. 相似文献
35.
Sung Ho Oh Jae Gun Han Young Kim Ji Hye Ha Seung Seop Kim Myoung Hoon Jeong Hyang Suk Jeong Na Young Kim Jeong Sub Cho Won Byong Yoon Shin Young Lee Do Hyung Kang Hyeon Yong Lee 《Journal of Bioscience and Bioengineering》2009,108(5):429-434
Autotrophic growth of Porphyridium cruentum under 18:12 h and 12:12 h light:dark cycles showed the maximum cell concentration of 2.1 g-dry wt./L, whereas the specific growth rate, 0.042 (1/h), at 18:6 h is faster than that of 12:12 h, 0.031 (1/h), respectively. The highest lipid accumulation level, 19.3 (%, w/w), was achieved at 12:12 h cycle. Under dark cultivation condition with 10 g/L of glucose, the lipid accumulation in the cell was 10.9 (%, w/w), whereas the heterotrophic growth with glycerol as the carbon resource showed low level of cell concentration and lipid production, compared to that of glucose. The glucose was decided to be a suitable carbon resource for the heterotrophic growth of P. cruentum. The lipids from P. cruentum seemed be feasible for biodiesel production, because over 30% of the lipid was C16–C18:1. The cultivation time and temperature were important factors to increase the maximum cell concentration. Extending the cultivation time helps maintain the maximum cell concentration, and higher lipid accumulation was achieved at 25 °C, compared to 35 °C. The fed-batch cultures showed that, under the light condition, the specific production rate was slightly decreased to 0.4% lipid/g-dry wt./day at the later stage, whereas, under the dark condition, the specific production rate was maintained to be a maximum value of 1.1% lipid/g-dry wt./day, even in the later stage of cultivation. The results indicate that the heterotrophic or 12:12 h cyclic mixotrophic growth of P. cruentum could be used for the production of biodiesel in long-term fed-batch cultivation of P. cruentum. 相似文献
36.
Gun Joo Jung Sung Ki Song Young Chull Ahn Geun Sug Oh Young Bin Im 《Journal of Mechanical Science and Technology》2011,25(2):503-512
This research has investigated physical variables affecting indoor thermal comfort and subjective responses of thermal comfort
of students in a university in Korea in which the weather is oceanic temperate climate, and has been performed to contribute
to the research fields of Sustainable Thermal Standard and Adaptive Thermal Comfort (ATC). This research is based on the ISO
7730-2005 standard and the ATC theories and 4 main variables of PMV such as dry bulb temperature (Ta), relative humidity (RH),
black bulb temperature (Tg), and air velocity (Va) are measured once a week during two regular semesters. A clothing insulation,
a thermal sensation vote (TSV), an acceptability of thermal environment, and a preference for cooling and heating are investigated
at the same time using a questionnaire. This study was carried out for 26 weeks during the spring season, from March to June
2009, and the autumn season, from September to December 2009. The main achievements of this study are as follows. Monthly
Mean Outdoor Temperature (MMOT) and Operative Temperature (OT) in the classroom during research periods are 7.4∼23.3°C and
17.5∼29.0°C, respectively. The acceptability ratio of thermal environment shows over 80% when the range of OT in the classroom
is 17∼25°C, and the range can be applicable to operative index of heating and cooling of classroom. The mean TSV of respondents
is almost “neutral (0)” when the PMV in the classroom moves to “neutral (0)” and “slightly cool (−1)”, and the TSV is almost
“+1.5” when the PMV moves to “slightly warm (+1)”. The acceptability ratio of thermal environment is slightly different from
ASHRAE Standard 55-2004. So it is necessary to more investigate standard range of acceptability of thermal environment in
oceanic temperate climate region using much more databases. 相似文献
37.
Sang Soo Lee Hyun Jong Kim Kyung Taek Jung Hak Soo Kim Yong Gun Shul 《Korean Journal of Chemical Engineering》2001,18(6):914-918
Iron or tungsten-doped nano TiO2 were successfully synthesized from TiCl4. All of the samples showed anatase phase of TiO2. For the iron-doped TiO2, Iron ion was well dispersed in the TiO2 lattice. However, tungsten-doped TiO2 formed 12-tungstate with anatase TiO2. As the concentration of tungsten increased, 12-tungstate disappeared. The photocatalytic oxidation of acetaldehyde was evaluated
to examine the photocatalytic characteristics of metal-doped TiO2. Because of the surface containing metal oxide or metal precursors at high concentration metal ion, increasing the concentration
of W or Fe ion decreased the reactivity. The reaction rate was drastically increased after 300 °C heat treatment. Furthermore,
the photocatalytic activity of iron- or tungsten-doped TiO2 was higher than that of synthesized pure TiO2 and commercial TiO2. 相似文献
38.
A new ambient drying process that is simple, effective, and reproducible has been developed to synthesize low- k SiO2 aerogel thin films for intermetal dielectric (IMD) materials. The SiO2 aerogel films having a thickness of 9500 Å, a high porosity of 79.5%, and a low dielectric constant of 2.0 were obtained by a new ambient drying process using n -heptane as a drying solvent. 相似文献
39.
In this paper, we present a 600‐V reverse conducting insulated gate bipolar transistor (RC‐IGBT) for soft and hard switching applications, such as general purpose inverters. The newly developed RC‐IGBT uses the deep reactive‐ion etching trench technology without the thin wafer process technology. Therefore, a freewheeling diode (FWD) is monolithically integrated in an IGBT chip. The proposed RC‐IGBT operates as an IGBT in forward conducting mode and as an FWD in reverse conducting mode. Also, to avoid the destructive failure of the gate oxide under the surge current and abnormal conditions, a protective Zener diode is successfully integrated in the gate electrode without compromising the operation performance of the IGBT. 相似文献
40.
Gyoo Gun Lim Ju Young Kang Jae Kyu Lee Dae Chul Lee 《Electronic Commerce Research and Applications》2011,10(6):637
Comparison shopping allows customers to reduce time and effort when searching for product information and prices. However, traditional comparison sites mainly compare product prices without using precise information on delivery cost. To overcome this limitation, we adopted a rule-based comparison shopping framework using the eXtensible Rule Markup Language (XRML) architecture, which computes the exact personalized delivery cost at comparison sites. The prototype ConsiderD, which was developed for this purpose, computes the exact delivery costs considering the shipping rules, destination, delivery speed, and shipping rates. The XRML architecture effectively maintains the consistency of formal rules with the original Web pages. To demonstrate the performance of rule-based comparisons, we conducted an experiment on the purchase of books based on real-world data from five leading online bookstores. This experiment shows that rule-based comparison can significantly outperform data-based comparison in terms of the total cost of product and delivery. We also found that the comparison of delivery cost is very important because the variance of delivery cost can be as big as the variance of book prices itself. 相似文献