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A Hybrid Algorithm for Online Location Update using Feature Point Detection for Portable Devices
( Jibum Kim ),( Inbin Kim ),( Namgu Kwon ),( Heemin Park ),( Jinseok Chae ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.2
We propose a cost-efficient hybrid algorithm for online location updates that efficiently combines feature point detection with the online trajectory-based sampling algorithm. Our algorithm is designed to minimize the average trajectory error with the minimal number of sample points. The algorithm is composed of 3 steps. First, we choose corner points from the map as sample points because they will most likely cause fewer trajectory errors. By employing the online trajectory sampling algorithm as the second step, our algorithm detects several missing and important sample points to prevent unwanted trajectory errors. The final step improves cost efficiency by eliminating redundant sample points on straight paths. We evaluate the proposed algorithm with real GPS trajectory data for various bus routes and compare our algorithm with the existing one. Simulation results show that our algorithm decreases the average trajectory error 28% compared to the existing one. In terms of cost efficiency, simulation results show that our algorithm is 29% more cost efficient than the existing one with real GPS trajectory data.
Juhyun Lee,Seokyoon Shin,Sejin Kwon,Woochool Jang,Hyeongsu Choi,Hyunwoo Park,Namgue Lee,전형탁 한양대학교 세라믹연구소 2021 Journal of Ceramic Processing Research Vol.22 No.3
Among various thin film encapsulation (TFE) methods, thin films prepared by atomic layer deposition (ALD) have been shownto provide superior protection against the permeation of moisture and oxygen. This technique has numerous of advantagessuch as excellent uniformity, precise thickness control, and strong adhesion. Therefore, with ozone-based ALD, we conductedthe influence of the thickness of aluminum oxide (Al2O3) on moisture barrier properties. From the results of an electricalcalcium test, Al2O3 had two distinctly different permeation regimes. Between 10 and 25 nm of Al2O3 thickness, the water vaportransmission rate (WVTR) decreased exponentially from 6.3 × 10−3 to 1.0 × 10−4 g m−2 day−1 (1/60 times). In contrast, asthickness increased from 25 to 100 nm, the WVTR values decreased by only two-thirds, from 1.0 × 10−4 to 6.6 × 10−5 g·m−2·day−1. Tobetter understand the change from an exponential to a sub-exponential regime, defect density and refractive index of Al2O3were measured. The thickness dependence on defect density and refractive index was analogous with one of moisture barrierperformance. These results confirmed the existence of a critical thickness at which the WVTR decreased drastically.
Sangwoo Kim,방재훈,최명식,Wansik Oum,Ali Mirzaei,Namgue Lee,Hyouk‑Chon Kwon,Dohyung Lee,Hyeongtag Jeon,Sang Sub Kim,Hyoun Woo Kim 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.3
We report the gas-sensing properties of pristine and SnS2functionalized TeO2nanowires (NWs). TeO2NWs were synthesizedby a vapor–liquid–solid growth method, and SnS2functionalization was performed using an atomic layer depositiontechnique followed by thermal treatment. Structural and morphological analyses verified the formation of pristine and SnS2functionalized TeO2NWs with desired composition, phase, and morphology. Interestingly, sensing results showed that thepristine TeO2NW gas sensor had better sensing properties relative to the SnS2functionalized TeO2NW gas sensor. Anunderlying sensing mechanism is explained in detail, and reasons for the decrease of sensing performance with the SnS2functionalized TeO2NW sensor was attributed to the coverage of TeO2surface by the SnS2nanoparticles.
Choi, Hyeongsu,Lee, Jeongsu,Shin, Seokyoon,Lee, Juhyun,Lee, Seungjin,Park, Hyunwoo,Kwon, Sejin,Lee, Namgue,Bang, Minwook,Lee, Seung-Beck,Jeon, Hyeongtag IOP Pub 2018 Nanotechnology Vol.29 No.21
<P>Representative tin sulfide compounds, tin monosulfide (SnS) and tin disulfide (SnS<SUB>2</SUB>) are strong candidates for future nanoelectronic devices, based on non-toxicity, low cost, unique structures and optoelectronic properties. However, it is insufficient for synthesizing of tin sulfide thin films using vapor phase deposition method which is capable of fabricating reproducible device and securing high quality films, and their device characteristics. In this study, we obtained highly crystalline SnS thin films by atomic layer deposition and obtained highly crystalline SnS<SUB>2</SUB> thin films by phase transition of the SnS thin films. The SnS thin film was transformed into SnS<SUB>2</SUB> thin film by annealing at 450 °C for 1 h in H<SUB>2</SUB>S atmosphere. This phase transition was confirmed by x-ray diffractometer and x-ray photoelectron spectroscopy, and we studied the cause of the phase transition. We then compared the film characteristics of these two tin sulfide thin films and their switching device characteristics. SnS and SnS<SUB>2</SUB> thin films had optical bandgaps of 1.35 and 2.70 eV, and absorption coefficients of about 10<SUP>5</SUP> and 10<SUP>4</SUP> cm<SUP>−1</SUP> in the visible region, respectively. In addition, SnS and SnS<SUB>2</SUB> thin films exhibited p-type and n-type semiconductor characteristics. In the images of high resolution-transmission electron microscopy, SnS and SnS<SUB>2</SUB> directly showed a highly crystalline orthorhombic and hexagonal layered structure. The field effect transistors of SnS and SnS<SUB>2</SUB> thin films exhibited on–off drain current ratios of 8.8 and 2.1 × 10<SUP>3</SUP> and mobilities of 0.21 and 0.014 cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP>, respectively. This difference in switching device characteristics mainly depends on the carrier concentration because it contributes to off-state conductance and mobility. The major carrier concentrations of the SnS and SnS<SUB>2</SUB> thin films were 6.0?×?10<SUP>16</SUP> and 8.7?×?10<SUP>13</SUP> cm<SUP>−3</SUP>, respectively, in this experiment.</P>
Effect of ozone concentration on atomic layer deposited tin oxide
Park, Hyunwoo,Park, Joohyun,Shin, Seokyoon,Ham, Giyul,Choi, Hyeongsu,Lee, Seungjin,Lee, Namgue,Kwon, Sejin,Bang, Minwook,Lee, Juhyun,Kim, Bumsik,Jeon, Hyeongtag American Institute of Physics 2018 Journal of Vacuum Science & Technology. A Vol.36 No.5
Kinetics and equilibrium partitioning of dissolved BTEX in PDMS and POM sheets
Nam, G. U.,Bonifacio, R. G.,Kwon, J. H.,Hong, Y. Springer Science + Business Media 2016 Environmental Science and Pollution Research Vol.23 No.18
<P>Passive sampling of volatile organic chemicals from soil and groundwater is primarily important in assessing the status of environmental contamination. A group of low molecular weight pollutants usually found in petroleum fuels, benzene, toluene, ethylbenzene, and xylenes (BTEX) was studied for its kinetics and equilibrium partitioning with single-phase passive samplers using polydimethylsiloxane (PDMS) and polyoxymethylene (POM) as sorbing phase. PDMS (1 mm) and POM (0.076 mm) sheets were used for sorption of BTEX and concentrations were analyzed using GC-FID. The equilibrium absorption and desorption of PDMS in water was achieved after 120 min while POM sheets absorbed up to 35 days and desorbed in 7 days. The kinetic rate constants in PDMS is higher than in POM up to 3 orders of magnitude. Logarithms of partition coefficient were determined to be in the range of 1.6-2.8 for PDMS and 2.1-3.1 for POM. The results indicate that POM is a stronger sorbent for BTEX and has slower equilibration time than PDMS. The partitioning process for both polymers was found to be enthalpy-driven by measurement of K-d values at varying temperatures. K-d values increase at low temperature and high ionic strength conditions. Presence of other gasoline components, as well as dissolved organic matter, did not significantly affect equilibrium partitioning. A good 1:1 correlation between the measured and the predicted concentrations was established on testing the potential application of the constructed PDMS sampler on natural soils and artificial soils spiked with gasoline-contaminated water.</P>