Papers by Author: Jae Chang Kim

Abstract: After the 9∙11 terrorism and America-Iraq war, apprehension of mass destruction weapons such as bio-chemical agents calls for much more sensitive sensors which can detect toxic gases. In this study, semiconductor gas sensors based on tin oxide were examined to detect chemical agent simulants: dimethyl-methyl-phosponate (DMMP), di(propylene glycol) methyl ether (DPGME), acetonitrile, and dichloromethane. DMMP((CH3O)3), DPGME(C7H16O3), acetonitrile(CH3CN), and dichloromethane(CH2Cl2) gases are the simulants of nerve agent-sarin, vesicant agent-HN(N(CH2CH2Cl)3), blood agent-AC(HCN), and choking agent-CG(COCl2) gases, repectively. The SnO2 powder was prepared by a coprecipitation method from the mixture of tin chloride and zinc acetate dihydrate. Zinc oxide was doped into SnO2 from 1 wt% to 4 wt% to improve its reliability and sensitivity. To fabricate a thick film, powders were made into paste with organic binder of ethyl cellulose and screen-printed on the alumina substrate. The phase development and morphology of ZnO-doped SnO2 film were investigated by XRD (X-ray diffraction analysis), BET (surface and pore size analyzer), and SEM (scanning electron microscope). The gas sensing characteristics for target gases were examined with a flow-type measurement system. The concentrations of simulants were controlled from 500 ppb to 1500 ppb, and working temperatures were regulated from 250  to 400 .

Abstract: In this work, we propose integral photography using bi-convex variable focusing lens arrays (hereafter will be abbreviated as bi-convex VFLA-IP) to obtain wider viewing angle and faster response time and the enhanced depth without decreasing resolution of integrated image. We designed a bi-convex lens structure to apply to 3-dimensional moving pictures. We fabricated twodimensional bi-convex liquid crystal lens arrays using lithography. The response time and the focal lengths of the lens array are measured. Applied voltage to the cell alters the effective refractive index of the liquid crystal layer and results in a change of the focal length. From the results of measuring electro-optic properties of the fabricated cell, we discovered that synchronized elemental image array for real or virtual mode can be integrated in front of or behind the lens array without decreasing resolution by adjusting the focal length.