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김웅수(Woongsoo Kim),송일석(Ilseok Song),신종현(Jonghyun Shin),오천환(Cheonhwan Oh),김은아(Eunah Kim),김극태(Keugtae Kim),김현자(Hyunja Kim),김종수(Kim, Jongsu Kim),최윤호(Yunho Choi) 한국환경보건학회 2017 한국환경보건학회지 Vol.43 No.3
Objectives: The pollution status of heavy metals within the soil was investigated with an aim to establishing a sustainable soil environment within parks and amusement facilities installed in urban areas of Gyeonggi–do Province. Methods: As sampling sites, 14 locations were selected from a city with a number of factories near a residential area, a residential area, and a children s park in a city with mixed green areas. Seven kinds of heavy metals, including Cd, Pb, and Hg, and the pH of soil were analyzed three times by inductively coupled plasma optical emission spectroscopy (ICP-OES) and atomic absorption spectrometer (AAS). Results: In this study, the pH of the samples from the residential park and industrial park showed 5.7-6.5 and 5.9-7.0, respectively. The overall mean concentration (mg/kg) of heavy metals was Zn (132.8), Ni (73.0), Cu (47.4), Pb (35.9), As (4.84), Cd (0.39), and Hg (0.07), indicating that these concentrations of heavy metals were lower than those for the area 1 standard of soil pollution concern criteria. In addition, the sampling sites in the residential area and the industrial area also showed the same tendency for concentration distribution. Conclusions: We found that the soil pollution class (SPC) of some spots were over 200, which are third and fourth classes. In order to manage a sustainable soil environment in a city park, it is suggested that local governments, the management bodies for these parks, need to manage, supervise, and investigate soil pollution and quickly replace contaminated soil.
Kim, Jongsu,Yoon, Hee-Jae,Kim, Suhyun,Wang, Kangkyun,Ishii, Takehiko,Kim, Yong-Rok,Jang, Woo-Dong Royal Society of Chemistry 2009 Journal of materials chemistry Vol.19 No.26
<P>Polymer–metal complex micelles (PMCMs) containing cisplatin (<I>cis</I>-dichlorodiammineplatinum(<SMALL>II</SMALL>), CDDP), an anticancer drug, were prepared by a coordination bond of CDDP to dendrimer phthalocyanine (DPc) and poly(ethylene glycol)-block-poly(<SMALL>L</SMALL>-aspartic acid) (PEG-PLAn; molecular weight of PEG segment = 12 000 g mol<SUP>−1</SUP>; polymerization degrees of aspartic acid segment <I>n</I> = 68, 96). Transmission electron microscopy (TEM) and laser light scattering (LLS) exhibited formation of unimodal PMCM<SUB>68</SUB> and PMCM<SUB>96</SUB> with average sizes of 108 and 135 nm, respectively. PMCMs were very stable in 10 mM phosphate buffer solution (PBS) without NaCl to maintain their shape and size over a month. However, PMCMs slowly released CDDP when they were incubated in physiological saline PBS solution at 37 °C. Upon laser light irradiation, generation of singlet oxygen was detected by photo-luminescence observation. The PMCMs would be effective nano-devices for anticancer drug carriers with sustained drug release and photodynamic therapy (PDT).</P> <P>Graphic Abstract</P><P>Polymer–metal complex micelles (PMCMs) containing an anticancer drug and a dendritic photosensitizer were prepared for sustained drug release and photodynamic therapy. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b904224e'> </P>
Bending Performance of Flexible Organic Thin-Film Transistors With/Without Encapsulation Layer
Oh, Jongsu,Kim, Jin-Ho,Lee, So Young,Kim, Min Su,Kim, Jae Moon,Park, Keechan,Kim, Yong-Sang IEEE 2018 IEEE transactions on device and materials reliabil Vol.18 No.1
<P>Flexible pentacene-based organic thin-film transistors (TFTs) were fabricated and their performance was investigated as a function of the bending radius and the thickness of the polydimethylsiloxane (PDMS) encapsulation layer. The TFTs were fabricated on a flexible polyimide film (film thickness: 75 <TEX>$\mu \text{m}$</TEX>), and encapsulated by a PDMS layer. Degradation of the device performance during application of a tensile bending stress of 3 mm was minimized by utilizing an encapsulation layer thickness of 75 <TEX>$\mu \text{m}$</TEX>, because the mechanical strain on the pentacene layer was almost off-set (tensile strain was applied to the bottom layer of the pentacene, and compressive strain was applied to the top layer of pentacene). At the tensile bending stress of 3 mm, the performance of the non-encapsulated TFT was degraded, whereas the encapsulated device showed great stability. This flexibility and bending stability were enabled by the use of the 75- <TEX>$\mu \text{m}$</TEX> PDMS encapsulation layer, due to the location of the pentacene active layer in the neutral region position. A mechanical reliability test was performed for 120 min with a bending radius of 3 mm, demonstrating that only the device with the 75- <TEX>$\mu \text{m}$</TEX> thick encapsulation layer showed stable device performance over a stress time of 120 min.</P>
MELTING OF THE EUCLIDEAN METRIC TO NEGATIVE SCALAR CURVATURE
Kim, Jongsu Korean Mathematical Society 2013 대한수학회보 Vol.50 No.4
We find a $C^{\infty}$-continuous path of Riemannian metrics $g_t$ on $\mathbb{R}^k$, $k{\geq}3$, for $0{\leq}t{\leq}{\varepsilon}$ for some number ${\varepsilon}$ > 0 with the following property: $g_0$ is the Euclidean metric on $\mathbb{R}^k$, the scalar curvatures of $g_t$ are strictly decreasing in $t$ in the open unit ball and $g_t$ is isometric to the Euclidean metric in the complement of the ball. Furthermore we extend the discussion to the Fubini-Study metric in a similar way.
Kim, Hee Dae,Okuyama, Rin,Kyhm, Kwangseuk,Eto, Mikio,Taylor, Robert A.,Nicolet, Aurelien L.,Potemski, Marek,Nogues, Gilles,Dang, Le Si,Je, Ku-Chul,Kim, Jongsu,Kyhm, Ji-Hoon,Yoen, Kyu Hyoek,Lee, Eun Hy American Chemical Society 2016 Nano letters Vol.16 No.1
<P>The Aharonov-Bohm effect in ring structures in the presence of electronic correlation and disorder is an open issue. We report novel oscillations of a strongly correlated exciton pair, similar to a Wigner molecule, in a single nanoquantum ring, where the emission energy changes abruptly at the transition magnetic field with a fractional oscillation period compared to that of the exciton, a so-called fractional optical Aharonov-Bohm oscillation. We have also observed modulated optical Aharonov-Bohm oscillations of an electron-hole pair and an anticrossing of the photoluminescence spectrum at the transition magnetic field, which are associated with disorder effects such as localization, built-in electric field, and impurities.</P>
Temperature dependence of the radiative recombination time in laterally coupled GaAs quantum dots
Kim, Heedae,Murayama, Akihiro,Kim, Jongsu,Song, Jindong Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.457 No.-
<P><B>Abstract</B></P> <P>We performed temperature dependent photoluminescence measurements of exciton states in GaAs laterally coupled quantum dots. The temperature dependence of the radiative decay time was used to investigate the density of states to study the intra-relaxation of thermally excited exciton states. We analyzed the density of states in laterally coupled quantum dots by observing the radiative decay time of exciton states as a function of temperature, where the decay time of exciton photoluminescence was calibrated with respect to photoluminescence intensity to extract the radiative decay time. In the case of laterally coupled quantum dots, a one-dimensional structure can be formed by elongation along the direction of coupling between two quantum dots. However, this assumption is not valid when the size in the uncoupled direction is comparable to that in the coupled direction. From experimental measurements, the power order of the temperature dependence was found to be 0.8, which corresponds to a quasi-one-dimensional system (∼T<SUP>α=0.8</SUP>), which is in between a two-dimensional (α = 1) and a one-dimensional (α = 0.5) density of states. This is due to several factors including a large size along the uncoupled direction, an extended wave function owing to optical coupling, and the presence of dark states.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The dimensionality of laterally coupled quantum dots is reported based on the measurement of temperature dependent radiative decay time. </LI> <LI> A quasi-one-dimensional density of states is observed with respect to the power order of the temperature dependence. </LI> <LI> Time-integrated photoluminescence spectral intensities are measured at various temperatures in laterally coupled quantum dots. </LI> </UL> </P>
Performance Analysis of a Convolutional Interleaver under Mobile Satellite Fading Channel
Jongsu Lee,Sangseob Song,Sooyoung Kim,Heewook Kim,Do Seob Ahn 대한전자공학회 2008 ICEIC:International Conference on Electronics, Inf Vol.1 No.1
This paper describes the design and simulation results of a convolutional interleaver by burst errors under the mobile satellite fading channel. We investigate a personal mobile satellite system using turbo codes. An efficient interleaver effectively randomizes burst errors due to long term fading, and thus it can highly enhance the BER performance at the decoder output. We designe and presente two types of convolutional interleavers by trading off between the performance enhancementand the time delay. The systematic approach presented in this paper can be easily adjusted to other systems, and thus can be used to design efficient interleavers.
Ultrasonic vibration micro-shaping using single PZT actuator-embedded tool holder
Jongsu Kim,이주형,강봉철 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.7
In this study, we suggest a novel tool holder design for simple and cost-effective ultrasonic vibration shaping to provide improvements such as low cutting force, smooth chip exhaust, and better surface quality in the cutting performance. An ultrasonic vibration tool actuated by a single actuator, which was designed by asymmetrically installing a single PZT actuator inside a cylindrical tool holder, generated the synchronized two-axis ultrasonic vibration motion on the tool tip along the cutting and thrust directions. By conducting dynamic structural analysis and simulating the tool tip movement trajectory using finite element method, the resonance mode, amplitude, and frequency of the model were optimized to achieve the vibration characteristics required for precision micro-shaping processes. According to the experimental evaluations, the vibration of the tool holder was characterized by a resonance mode of 24 kHz. The cutting performance of the tool was evaluated by comparing the cutting force, machined surface, and chip shape with those using a non-vibration micro-shaping tool. The cutting force was reduced more than 90 %, and the machined shape and chip exhaust were improved compared with that in conventional shaping processes.