Jae K Kim

Metasurfaces have attracted great attention due to their ability to manipulate the phase, amplitude, and polarization of light in a compact form. Tunable metasurfaces have been investigated recently through the integration with mechanically moving components and electrically tunable elements. Two interesting applications, in particular, are to vary the focal point of metalenses and to switch between holographic images. We present the recent progress on tunable metasurfaces focused on metalenses

A unique porous polymeric film was prepared by drying a ternary polymer solution: a polystyrene (PS), polyethylene glycol (PEG), and toluene solution. Highly ordered micropores, ranging from 5 to 12 mum in diameter, were formed on the film surface, and the rim of each micropore was surrounded by a ring of PEG. The effects of the weight ratio of the polymer blend and molecular weight of the polymer (PEG) on the porous structure were investigated. Based on in situ visual observation and light scat

Predicting the degree of sickness is an imperative goal to guarantee viewing safety when watching virtual reality (VR) contents. Ideally, such predictive models should be explained in terms of the human visual system (HVS). When viewing VR contents using a head mounted display (HMD), there is a conflict between user's actual motion and visually perceived motion. This results in an unnatural visual-vestibular sensory mismatch that causes side effects such as onset of nausea, oculomotor, disorient

A periodic striping pattern with microscale pore size is observed on the surface of thin films prepared by spin-casting from a polystyrene (PS) and polyethylene glycol (PEG) blend solution. The pattern is created by the convection generated by thermal gradients in the solution between the substrate and film solution during solvent evaporation, the radial flow of the spin-coated solution, and the primary and secondary phase separation of the PS and PEG solutions. The formation mechanism of the pe

Abstract We prepared a polymeric membrane with a fine porous structure from polystyrene (PS), poly(ethylene glycol) (PEG), and solvent solutions by exploiting the phase separation induced in the course of dry casting. To determine the effect of the drying rate and phase separation on the developed porous structure, six different solvents, including toluene, chlorobenzene, tetrahydrofuran, methyl ethyl ketone, 1,4‐dioxane, and chloroform, were used. The pore size and density drastically changed w

Knowledge sharing is an important research area in knowledge management. This study broadens the perspective on knowledge sharing by investigating an individual’s behavior type as a cooperator, reciprocator, and free rider toward knowledge contribution. In this study, we view shared knowledge in a community of practice as a public good and adopt a theory of reciprocity to explain how different cooperative types affect knowledge contribution. In the perspective of shared knowledge as a public goo

Both principal component regression (PCR) and partial least squares regression (PLSR) have been commonly used to predict neurochemical concentrations from measurements of fast-scan cyclic voltammetry (FSCV). However, a comparison of the accuracy of the above methods for FSCV analysis is yet to be demonstrated. In this work, we compare the concentration estimation performance of PCR and PLSR in an analysis of FSCV data. Using conventional FSCV, we recorded in vitro background-subtracted cyclic vo

We examined the atomic layer deposition (ALD) of silicon dioxide thin films on a silicon wafer by alternating exposures to tetrakis(ethylamino)silane [Si(NHC2H5)4] and O3. The growth kinetics of silicon oxide films was examined at substrate temperatures ranging from 325 to 514 degrees C. The deposition was governed by a self-limiting surface reaction, and the growth rate at 478 degrees C was saturated at 0.17 nm/cycle for Si(NHC2H5)4 exposures of 2 x 10(6) L (1 L = 10(-6) Torr x s). The films de

The liquid−liquid equilibrium for the quaternary system toluene + water + propionic acid + ethyl acetate was measured at 25 °C and atmospheric pressure. Binodal curves, tie lines, a distribution curve, and a selectivity curve for the quaternary system have been determined in order to investigate the effect of using binary solvents toluene and ethyl acetate on extracting propionic acid from aqueous solution. In addition, these experimental tie-line data were also compared with the values predicte

Modern efforts on digitizing electronic books focus on preserving authentic spatial representation of the original sources. The new format requires new tools to help users to access, process, and make sense of digital information. This paper presents an approach which assists users of these new spatial sources by giving them a combination of annotation and social navigation support. This approach is currently fully implemented and under evaluation in a classroom study

Among the various methods used for glass edge sealing, this study uses microwaves to seal glass edges. Through basic experiments, the main process conditions for edge sealing of glass were derived, and the experimental plan and analysis were carried out using the Box-Behnken method of response-surface analysis based on 3 factors and 3 levels. The step height which influences sealing was set as a response variable. If the step height becomes too large, the glass can be damaged, and if the step he

The variation of the c-axis conductivity of a multilayer graphene (MLG) as a function of H2 pressure from vacuum to 20 bar has been investigated. MLG was connected to the electrodes vertically using a wet transfer process. After exposure to H2 gas pressure up to 20 bar, the chemisorption of dissociated atomic hydrogen on MLG affects its electrical and structural properties. The formation of C-H bonds causes a decoupling of graphene layers, and then interferes with charge transfer through the out