Chaewon Kim - Academia.edu (original) (raw)

Papers by Chaewon Kim

Yakhak Hoeji, 2017

The antiproliferative and antioxidative properties of novel polyphenolic acid derivatives, struct... more The antiproliferative and antioxidative properties of novel polyphenolic acid derivatives, structurally related with the natural model gallic acids, have been tested in cancer cell lines (MCF-7, Hep3B, RKO) and lipid peroxidation. A new series of methyl 3,4-dialkylcarbonyloxy-5-methoxybenzoate 4a~4e was synthesized by acylation from O-methyl gallicin 3 for search of bioactive compounds. The structures of the synthetic compounds were characterized using 1 H, 13 C NMR and HRMS spectroscopy. Two target compounds (4c, 4d) showed higher potency than propyl gallicin or drumstick-tree (Moringa oleifera Lam.) extracts for inhibiting the growth of cancer cell lines (MCF-7, Hep3B, RKO). The antioxidative properties of 4b among synthetic compounds was similar to the antioxidant propyl gallate and α-tocopherol.

TENCON 2018 - 2018 IEEE Region 10 Conference, 2018

A smart image sensor system with a current-steering digital-to-analog converter (DAC) for autofoc... more A smart image sensor system with a current-steering digital-to-analog converter (DAC) for autofocusing micro-lens driver is presented. Recently, most of smart image sensor systems want to extend the lens focusing distance with high speed motor drive. Thus they need a high-performance current-steering DAC to drive the lens focusing linear motor. In order to satisfy the specifications, DAC needs small chip area, low power consumption, and high speed operation. In this paper, a brick current cell layout technique and a novel digital logic are proposed. The measured results are within ±0.6LSB for INL, and within ±0.5LSB for DNL. Further, the measured SFDR is 79dB at 1.2MHz output frequency with 250MHz clock frequency. It has 45.6mW power dissipation at 3.3V power supply.

Corrosion Science, 2021

Abstract Two alumina-forming Fe-based alloys, duplex FeNiCrAl (alumina-forming duplex stainless s... more Abstract Two alumina-forming Fe-based alloys, duplex FeNiCrAl (alumina-forming duplex stainless steel, ADSS) and ferritic FeCrAl (APM) alloys, were oxidized in steam at 800 °C to 1050 °C for up to 72 h. Formation of spinel oxides on ADSS resulted in larger weight gain than APM, while the highest weight gain was observed at 900 °C. Outer γ- and/or θ-alumina and inner α-alumina were formed on APM, whereas dispersed spinel oxides as well as γ- and α-alumina on ADSS. Similar alumina formation kinetics was observed for both alloys, while transient alumina formation resulted in faster kinetics at 900 °C.

Frontiers in Microbiology, 2021

Autotransporter proteins are widely present in Gram-negative bacteria. They play a pivotal role i... more Autotransporter proteins are widely present in Gram-negative bacteria. They play a pivotal role in processes related to bacterial pathogenesis, including adhesion, invasion, colonization, biofilm formation, and cellular toxicity. Bioinformatics analysis revealed that Orientia tsutsugamushi, the causative agent of scrub typhus, encodes six different autotransporter genes (scaA–scaF). Although four of these genes (scaA, scaC, scaD, and scaE) are present in diverse strains, scaB and scaF have been detected in only a limited number of strains. Previous studies have demonstrated that ScaA and ScaC are involved in the adherence of host cells. However, the putative function of other O. tsutsugamushi Sca proteins has not been studied yet. In this study, we show that scaB is transcribed and expressed on the surface of O. tsutsugamushi Boryong strain. Using a heterologous Escherichia coli expression system, we demonstrated that ScaB-expressing E. coli can successfully mediate adherence to and...

Journal of Women's Health, 2020

Background: Although uterine leiomyoma causes many problems, including infertility, there are few... more Background: Although uterine leiomyoma causes many problems, including infertility, there are few studies that have investigated the epidemiologic characteristics of uterine leiomyoma in South Korea. The aim of this study is to estimate the prevalence and incidence of uterine leiomyoma in South Korea and analyze the treatment trends. Materials and Methods: Women of reproductive age (15-54 years) were selected from the Korean National Health Insurance Service (NHIS) sample cohort dataset, which was collected from 2002 to 2013. Patients with uterine leiomyoma were identified by ICD-10 (International Codes of Disease, 10th Edition) and intervention codes. Prevalence and incidence were calculated from the NHIS cohort dataset and the treatment trends were analyzed for diagnosed patients. Results: The prevalence in overall age groups increased from 0.96% in 2002 to 2.43% in 2013, and the 1-year incidences of all age groups increased. The 26-30 age group showed the highest rate of 1-year incidence increase (2.14-folds, 0.33% in 2003 to 0.70% in 2013). The proportion of myomectomy increased from 22% in 2002 to 49% in 2013, whereas the proportion of hysterectomy decreased from 78% to 45%. Conclusions: The prevalence and incidence of uterine leiomyoma are increasing in South Korea as time progresses, and the rate of incidence increase is higher in younger reproductive women. Overall trends in uterine leiomyoma treatment are shifting to the methods of the saving uterus.

Bulletin of the Korean Chemical Society, 2017

A new series of 3-allylseleno-6-alkylsulfonylpyridazines and 3-allylseleno-6-alkylsulfinylpyridaz... more A new series of 3-allylseleno-6-alkylsulfonylpyridazines and 3-allylseleno-6-alkylsulfinylpyridazines were synthesized from 3,6-dichloropyridazine for anticancer agent development. The inhibitory effects of 3allylseleno-6-alkylsulfonylpyridazines on human cancer cell lines were investigated. The synthesis involved thiolation, oxidation, selenylation, and Se-allylation of alkylthiols. That is, sodium methanethiolate, ethanethiol, propanethiol, butanethiol, pentanethiol, and hexanethiol were inserted into the 6-position of the pyridazine nucleus. These new synthetic compounds exhibited antiproliferative activity against human breast cancer (MCF-7), hepatocarcinoma (Hep3B), and human colon carcinoma (RKO) cells in CCK-8 assays, and are potential candidates for cancer chemotherapy.

Coatings, 2020

A chromium diffusion coating was applied on an oxide dispersion strengthened ferritic-martensitic... more A chromium diffusion coating was applied on an oxide dispersion strengthened ferritic-martensitic (ODS-FM) steel to improve oxidation resistance at high temperature. By carrying out physical vapor deposition followed by inter-diffusion heat treatment, a thin Cr-rich carbide layer was produced on the ODS-FM steel. Both the as-received and surface-modified specimens were oxidation-tested at 650 °C in air and steam environments for 500 h. The surface-modified specimens showed improved oxidation resistance in both environments. In an air environment, both conditions exhibited a thin and continuous chromia layer, but the formation of Cr2O3 and (Mn, Cr)3O4 nodules resulted in greater weight gain for the as-received specimen. In a steam environment, weight gain increased for both the as-received and surface-modified specimen. Especially, the as-received specimen showed much greater weight gain with the formation of a thick oxide layer consisted of outer Fe-rich oxide and inner (Fe, Cr, Mn)...

Oxidation of Metals, 2019

Model alloys based on Alloy 617 were fabricated with modified minor alloying elements for improve... more Model alloys based on Alloy 617 were fabricated with modified minor alloying elements for improvement in oxidation resistance in high-temperature steam environments. Model alloys were grouped as one with Ti and Al and the other without. Mn content was varied from 0 to 2 wt% for the alloys within each group. The alloys were subjected to oxidation testing in steam at 900 °C for up to 1000 h. Alloys with Ti and Al showed high weight gains due to fast oxide growth on top of grain boundaries and internal oxidation. Mn addition caused formation of Mn-rich spinels and contributed somewhat to weight gain. On the other hand, for the alloys without Ti and Al, Mn content greater than 0.5 wt% prevented oxide spallation. Tensile properties were not significantly affected by the minor alloying element modifications, and one of the model alloys exhibited comparable creep rupture life to Alloy 617.

Journal of the Korean Ceramic Society, 2016

Benzothienobenzothiophene (C 8-BTBT) is a soluble organic small molecule material with high cryst... more Benzothienobenzothiophene (C 8-BTBT) is a soluble organic small molecule material with high crystallinity resulting from its strong self-organizing properties. In addition, the high mobility and easy fabrication of C 8-BTBT make it very attractive in terms of organic thin-film transistors. In this work, we made C 8-BTBT thin films by using the zone-casting method; we also used an organic solvent to treat the devices with solvent vapor annealing to improve the electrical properties. As a result, we confirmed improved mobility, threshold voltage, and subthreshold swing after solvent vapor annealing. To prove the effect of solvent vapor annealing, we used the simultaneous extraction model to extract the contact resistance from the current-voltage curve. We confirmed that the electrical properties improved with decreasing contact resistance.

Metals and Materials International, 2018

As a catalytic support for passive autocatalytic recombiner in nuclear power plants, anodic alumi... more As a catalytic support for passive autocatalytic recombiner in nuclear power plants, anodic alumina layer was formed on stainless steel 304 by applying either Al or NiAl diffusion coatings on 304SS, followed by anodization and calcination. The anodic alumina had porous and nano-fibrous morphology and showed comparable hydrogen conversion ratio as the conventional wash-coated catalytic support. Integrity of catalytic supports was evaluated by steam oxidation test at 900 °C for 100 h. The wash-coated catalytic support exhibited oxide breakaway and Fe-oxide formation. On the other hand, α-alumina was formed on anodized catalytic support with Al or NiAl diffusion layers, which showed good adherence to the underlying metal substrate.

Journal of Nuclear Materials, 2018

Abstract High aluminum content (>5 wt.%) duplex stainless steels were developed as accident-to... more Abstract High aluminum content (>5 wt.%) duplex stainless steels were developed as accident-tolerant fuel (ATF) cladding materials for light water reactors. A set of model alumina-forming duplex stainless steel (ADSS) alloys with a nominal composition range of Fe-(18–21)Ni-(16–21)Cr-(5–6)Al were prepared and tested for corrosion resistance in both 1200 °C steam and simulated pressurized water reactor (PWR) operating conditions. The performance and properties of the ADSS alloys were compared to those of the austenitic (310 S) and ferritic (FeCrAl-APM) stainless steels. The results showed that the ADSS alloys possessed good corrosion resistances in both conditions, and better tensile properties. The applicability of the ADSS alloys as ATF cladding materials was discussed in view of their corrosion resistance, irradiation resistance, and embrittlement.

Progress in Natural Science: Materials International, 2018

The oxidation behavior of three high-strength FeCrAl alloys was investigated in supercritical car... more The oxidation behavior of three high-strength FeCrAl alloys was investigated in supercritical carbon dioxide environment at 650°C. After exposure for 500 h, the weight gains of the FeCrAl alloys gradually decreased with increasing Al content. The oxide scales are primarily composed of α-Al 2 O 3 and spinel oxides. With increasing Al content, the amount of α-Al 2 O 3 increases and the C content decreased in the oxide scale and sub-scale matrix. Moreover, larger (Nb,Mo)C carbides formed in the sub-scale matrix and their number decreased with the increase of Al content.

Nanoscale, 2018

Quasi-2D perovskite phases are controlled by excess cations and zinc oxide (ZnO) nanoparticles, i... more Quasi-2D perovskite phases are controlled by excess cations and zinc oxide (ZnO) nanoparticles, improving the light-emitting performance and device stability.

$Research paper thumbnail of 400 °C aging embrittlement of FeCrAl alloys: Microstructure and fracture behavior$

Materials Science and Engineering: A, 2018

Two commercial advanced powder-metallurgical FeCrAl alloys with nominal composition of Fe-22Cr-6A... more Two commercial advanced powder-metallurgical FeCrAl alloys with nominal composition of Fe-22Cr-6Al (APM) and Fe-21Cr-5Al-3Mo (APMT) were aged at 400 °C up to 4828 h. In the as-received condition, both alloys had similar amount of Al-rich particles, while there were more Si-rich particles in APMT. In the aged condition, APMT was more susceptible to the aging embrittlement than APM, showing a complete cleavage fracture in tensile tests. During aging, areal fraction and size of Si-rich particles were not affected for both alloys, but the growth of oxygen-free Al-rich particles was observed for APMT. Meanwhile, Fe-Cr phase separation was not observed in both alloys after 4828 h aging at 400 °C. Instead, fracture surface observation revealed that the severe aging embrittlement of APMT could be correlated to the growth of large Al-rich particles, which acted as crack initiation sites leading to the cleavage fracture.

Journal of Korean Society of Environmental Engineers, 2018

This study was conducted to suggest the hydraulic modification for improving evenness of inlet fl... more This study was conducted to suggest the hydraulic modification for improving evenness of inlet flow distribution into the manifold pipe having a structure in which the treated water flows in parallel arranged membrane modules using CFD (Computational Fluid Dynamics) simulation and experiment. From a result of CFD simulation, it was confirmed that the standard deviation of the inlet flows into each membrane module from the manifold pipe was reduced by about 76% by installing other orifice pipe inside header pipe (double piping header). In addition, the experimental results showed that the coefficient of variation was reduced by 50% in the case of double piping header compared to the case of single piping header. Consequently, the design concept of doubling header pipe with rough internal pipe is much effective to improve the evenness of the flow distribution rate in parallel arranged membrane modules.

Bulletin of the Korean Chemical Society, 2014

Advanced Functional Materials, 2017

In article number 1605593, Cheol Seong Hwang, Mi Jung Lee, and co-workers demonstrate a new type ... more In article number 1605593, Cheol Seong Hwang, Mi Jung Lee, and co-workers demonstrate a new type of wearable electronic device in which resistive switching memory devices are woven into an electronic textile using a loom, which is similar to weaving normal cloth. Aluminumcoated threads with native aluminum oxide and carbon are chosen for bipolar resistive switching reactions at the interface to create conducting pathways upon applied bias.

Journal of Nanoscience and Nanotechnology, 2016

Transparent conductive films (TCFs) are indispensable components for various optoelectronic devic... more Transparent conductive films (TCFs) are indispensable components for various optoelectronic devices. Recently, the development of flexible TCFs has received attention for applications in flexible and wearable electronics. In this work, we developed silver nanowires (Ag NWs) with a mesh pattern to obtain the optical and electrical properties, as well as flexibility, required for touch screen panels (TSPs). The Ag NW grid pattern was achieved using photolithography by employing a titanium adhesion layer between Ag NWs and substrates to attain a uniform and stable pattern. The transmittance and sheet resistance of patterned Ag NWs were 95% and 88 / , respectively, and the NWs showed good stability against bending operations for up to 2,000 bending cycles. Moreover, this fabrication process has the advantage of low cost and can be applied to a large-scale devices using a solution process.

Bulletin of the Korean Chemical Society, 2015

A new series of 3-alkylseleno-6-alkylaminopyridazines, 3-alkylseleno-6-alkyliminopyridazines, and... more A new series of 3-alkylseleno-6-alkylaminopyridazines, 3-alkylseleno-6-alkyliminopyridazines, and 3-alkylseleno-6-dialkylaminopyridazines was synthesized from 3,6-dichloropyridazine for development of new anticancer agents. The process involves the selenylation, Se-alkylation, and aralkylamination (or imination). The alkylamines such as ethylamine and the dialkylamines such as dipropylamine were introduced into the 3-position of the pyridazine ring. These new compounds showed antiproliferative activities against breast cancer (MCF-7) and hepatocellular carcinoma (Hep3B) cells in CCK-8 assays and could be promising candidates for chemotherapy of carcinomas.

Electronic Materials Letters, 2015

Although flexibility and transparency are considered advantages of organic electronic devices alo... more Although flexibility and transparency are considered advantages of organic electronic devices along with low processing cost and the possibility of large-area production, high operating voltages and metallic contacts are obstacles to their application in real electronic products. In this work, flexible and transparent organic complementary inverters that can be operated with low voltage were fabricated on a plastic substrate. Two different air-stable organic semiconductors, fluorinated copper phthalocyanine and pentacene, are used for n-type and p-type transistors, respectively. An ITO gate electrode was deposited by sputtering, and a hybrid dielectric layer with a thin Al2O3 layer and self-assembled monolayers (SAMs) was fabricated to reduce the operation voltage. To confirm the properties of the hybrid dielectric layer, the capacitance and gate leakage current were measured. Then, source and drain electrodes were formed from gold or ITO specifically for fully transparent devices. For the ITO electrodes, a MoO3 interlayer was incorporated between the pentacene and ITO to reduce the contact resistance caused by mismatch of workfunction. Finally, we evaluated the low-voltage operation of the flexible organic inverters and the fully transparent device through transmittance measurement.