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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>
Kim, Jongsu,Ko, Hyungwoo,Jeon, Hyunbae,Kang, Myounggon,Shin, Hyungcheol American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.10
<P>In this paper, we extracted the parasitic components and proposed a design guideline for 5 nm node nanowire FET using a technology computer- aided design (TCAD) simulation. The research was performed separately on a normal contact structure and recessed contact structure, which can reduce contact resistance. As a result, the parasitic resistance decreased while parasitic capacitance increased as the source/drain electron concentration increased. For intrinsic delay, devices should be designed with high source/drain concentrations in normal contact structures while optimum source/drain concentrations can be found in recessed structures.</P>
Light Controlled Optical Aharonov-Bohm Oscillations in a Single Quantum Ring
Kim, Heedae,Park, Seongho,Okuyama, Rin,Kyhm, Kwangseuk,Eto, Mikio,Taylor, Robert A.,Nogues, Gilles,Dang, Le Si,Potemski, Marek,Je, Koochul,Kim, Jongsu,Kyhm, Jihoon,Song, Jindong American Chemical Society 2018 NANO LETTERS Vol.18 No.10
<P>We found that optical Aharonov-Bohm oscillations in a single GaAs/GaAlAs quantum ring can be controlled by excitation intensity. With a weak excitation intensity of 1.2 kW cm<SUP>-2</SUP>, the optical Aharonov-Bohm oscillation period of biexcitons was observed to be half that of excitons in accordance with the period expected for a two-exciton Wigner molecule. When the excitation intensity is increased by an order of magnitude (12 kW cm<SUP>-2</SUP>), a gradual deviation of the Wigner molecule condition occurs with decreased oscillation periods and diamagnetic coefficients for both excitons and biexcitons along with a spectral shift. These results suggest that the effective orbit radii and rim widths of electrons and holes in a single quantum ring can be modified by light intensity via photoexcited carriers, which are possibly trapped at interface defects resulting in a local electric field.</P> [FIG OMISSION]</BR>
Ultrathin flexible thin film transistors with CYTOP encapsulation by debonding process
Kim, Jae Moon,Oh, Jongsu,Jung, Kyung-Mo,Park, KeeChan,Jeon, Jae-Hong,Kim, Yong-Sang Institute of Physics 2019 Semiconductor science and technology Vol.34 No.7
<P>We fabricated ultrathin flexible thin film transistors with hydrophobic encapsulation layer by debonding process. In the debonding process, to separate the transistors from the carrier glass in deionized (DI) water, a strong hydrophobic material such as CYTOP was used for encapsulation, thus increasing their resistance to moisture. PVA was used as a release layer and the debonding process was optimized to separate the carrier glass and the transistors. It was confirmed that water penetration into the device can be suppressed effectively when the CYTOP thickness is 800 nm. In addition, the electrical characteristics remained almost constant even in the presence of water for 50 min. The total thickness after debonding process was approximately 2 <I>μ</I>m. Waterproof experiments and debonding process were performed for a simple inverter circuit as well as a discrete device, and the operation and voltage gain of the inverter did not change when water was placed on the device or after debonding process. Finally, the flexibility was measured by transferring the device to a flexible PI substrate. Consequently, it was confirmed that degradation in the electrical properties was slightly up to a bending radius of 2.5 mm.</P>
SOME DOUBLY-WARPED PRODUCT GRADIENT RICCI SOLITONS
Kim, Jongsu Korean Mathematical Society 2016 대한수학회논문집 Vol.31 No.3
In this paper, we study certain doubly-warped products which admit gradient Ricci solitons with harmonic Weyl curvature and non-constant soliton function. The metric is of the form $g=dx^2_1+p(x_1)^2dx^2_2+h(x_1)^2\;{\tilde{g}}$ on ${\mathbb{R}}^2{\times}N$, where $x_1$, $x_2$ are the local coordinates on ${\mathbb{R}}^2$ and ${\tilde{g}}$ is an Einstein metric on the manifold N. We obtained a full description of all the possible local gradient Ricci solitons.
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.