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Lee, Sooheyong,Wi, Haeng Sub,Jo, Wonhyuk,Cho, Yong Chan,Lee, Hyun Hwi,Jeong, Se-Young,Kim, Yong-Il,Lee, Geun Woo National Academy of Sciences 2016 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.113 No.48
<P>Solution studies have proposed that crystal nucleation can take more complex pathways than previously expected in classical nucleation theory, such as formation of prenucleation clusters or densified amorphous/liquid phases. These findings show that it is possible to separate fluctuations in the different order parameters governing crystal nucleation, that is, density and structure. However, a direct observation of the multipathways from aqueous solutions remains a great challenge because heterogeneous nucleation sites, such as container walls, can prevent these paths. Here, we demonstrate the existence of multiple pathways of nucleation in highly supersaturated aqueous KH2PO4 (KDP) solution using the combination of a containerless device (electrostatic levitation), and in situ micro-Raman and synchrotron X-ray scattering. Specifically, we find that, at an unprecedentedly deep level of supersaturation, a high-concentration KDP solution first transforms into a metastable crystal before reaching stability at room temperature. However, a low-concentration solution, with different local structures, directly transforms into the stable crystal phase. These apparent multiple pathways of crystallization depend on the degree of supersaturation.</P>
Encapsulation of CdSe Nanoparticles inside Liposome Suspended in Aqueous Solution
김성진,박혁규,Haeng Sub Wi,양호순,김기범,Kyuyong Lee,Sang Min Kim 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.III
We studied the encapsulation of CdSe nanoparticles inside liposomes suspended in aqueous solution. A mixed solution of CdSe nanoparticles and asolectin lipid molecules was dried and hydrated with phosphate buffer saline (PBS). We observed large liposomes with CdSe nanoparticles, which exist in two different states. In one state, nanoparticles exist as micelle state inside the liposome. In the other state, nanoparticles are locally encapsulated in the lipid bilayer of the liposome. To our knowledge, the encapsulation of CdSe nanoparticles in the lipid bilayer of a liposome has never been reported so far.
Lee, Sooheyong,Jo, Wonhyuk,Wi, Haeng Sub,Gutt, C,Lee, Geun Woo Optical Society of America 2014 Optics express Vol.22 No.18
<P>We report an alternate light scattering approach to measure intermediate scattering function and structures of colloidal suspension by using two-pulse speckle contrast correlation analysis. By systematically controlling time-delays between two laser pulses incident on the sample, we are able to monitor transient evolution of coherent diffraction pattern, from which particle dynamics at different length and time scales are obtained simultaneously. Our result demonstrates the feasibility of utilizing a megapixel detector to achieve sufficient data statistics in a short amount of time while enabling microsecond time-resolution. Ultimately, this method provides means to measure high-speed dynamics well beyond the time response limit of a large area two-dimensional (2D) detector.</P>
Effects of the disaccharide concentration and the extrusion speed on the size of unilamella vesicles
신동명,서정아,Jin-Gun Kim,Si-In Kim,이규용,Haeng Sub Wi,권현정,박혁규,김형국,황윤회 한국물리학회 2011 Current Applied Physics Vol.11 No.6
We investigated the effects of the concentration of disaccharides (trehalose, maltose, and sucrose) and the extrusion speed on the mean size of the unilamella vesicles (ULVs) by using the photon correlation spectroscopy (PCS). We found that the mean diameters of ULVs prepared in the solution with the same disaccharide concentration and the same extrusion speed were quite different. In the case of trehalose,the mean diameter of ULVs decreased as the disaccharide concentration decreased and the extrusion speed increased. Based on those findings, we could fabricate the uniform sized ULVs in different disaccharide solutions with the same concentration by controlling the extrusion speed.
태양조명시스템을 위한 저가형 태양광 추적 임베디드시스템 개발
김형우(Hyoung-Woo Kim),신병한(Byung-Han Sheen),위행섭(Haeng-Sub Wi),최준영(Joon-Young Choi) 한국정보기술학회 2016 한국정보기술학회논문지 Vol.14 No.1
We develop a low-cost solar tracking embedded system to improve the light-collecting efficiency of sun light systems. The driving part of the solar tracker is designed in the structure of inclination-dependent 2-axis that enables less initial production cost and easy maintenance. The embedded system hardware consists of two motor drivers to control the 2-axis movements independently, a GPS module to calculate the sun position, gyro-sensor, highperformance DSP, and additional communication interfaces for the configuration of real-time operation and the manual control. For the software of the solar tracking embedded system, we employ the mathematical formula-based tracking method using GPS data instead of the sensor-based tracking method using high-cost light sensors or hall sensors. The solar tracking performance of the developed embedded system is demonstrated by the experimental results that the normal location of light-collecting panel tracks the solar position within an error range of 0.03 degree.
태양광 추적 장치의 성능 향상을 위한 블루투스 기반 제어시스템 개발
김세준(Se-Jun Kim),김형우(Hyoung-Woo Kim),신병한(Byung-Han Shin),위행섭(Haeng-Sub Wi),남기곤(Kigon Nam),최준영(Joon-Young Choi) 한국정보기술학회 2016 한국정보기술학회논문지 Vol.14 No.9
We develop a bluetooth-based control system for the performance improvement of sunlight tracker, which improves the degradation of sunlight tracking performance by various physical factors occured during the installation of sunlight tracker. By using the mobile platform based on Android OS, the master part is developed to send and receive actuator control signal, correlation command signal, and current status information. In order to track the sun’s position automatically or manually, the slave part is constructed by the horizontal shaft drive-dependent 2-axis actuator together with GPS, gyrosensor, and bluetooth module. We conduct various experiments of sunlight tracker controlled by the designed control system for the performance evaluation. From the experiment results, we demonstrate that the sunlight tracker tracks the solar position within an error range of 0.05 degree.