Papers by Author: Kwang Rae Lee

Abstract: A membrane permeable to water vapor was prepared and used for dehumidification of air. At a given feed flow rate, the permeation ratios were almost independent to relative humidities of feed stream; The permeation ratios were about 45%, 60%, and 25% at feed flow rate of 50, 70, and 90cc/min, respectively. Permeation ratio might also be enhanced with increasing feed flow rate. However, the permeation ratio (about 25%) at a feed flow rate of 90cc/min was much less than at 50cc/min (about 45%) and 70cc/min (about 60%). This phenomenon might be explained that a water film does form at surface of membrane because the amount of water vapor contained in feed stream of 90cc/min was much more than the permeate through the membrane.

Abstract: The nano-size PbTiO3 particles were prepared by sol-gel method and the effects of processing variables such as concentration of sol solution, catalyst, concentration of catalyst, calcination temperature and calcination process on particle size of PbTiO3 were analyzed. The condition for preparation of sol solution from the precursor is very critical to the size of PbTiO3 particle. At certain experimental conditions, the particles of 129nm, 213nm and 343nm were obtained. However, the particle size of commercialized PbTiO3 powder was 5㎛(5,000nm). The prepared nano-size PbTiO3 powder adsorbed more acetic acid and formic acid than the commercialized one; 1.5 times for acetic acid and 1.2 times for formic acid. Formic acid was preferentially adsorbed than acetic acid.