• Korea-Australia Rheology Journal
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• v.17 no.4
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• pp.165-170
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• 2005

In this study, high intensity ultrasound was employed to induce mechano-chemical degradation during melt mixing of polycarbonate (PC) and a series of styrene-acrylonitrile (SAN) copolymers. It was confirmed that generation of macroradicals of constituent polymers can lead to in-situ copolymer formation by their mutual combination, which should be an efficient path to compatibilize immiscible polymer blends and stabilize their phase morphology in the absence of other chemical agents. Based on the effectiveness of the compatibilization by ultrasound assisted mixing process, we investigated the effects of viscosity ratio of PC and SAN and AN content in SAN on the compatibilization of PC/SAN blends. It was found that effectiveness of compatibilization is optimal when the AN content is in the range of favorable interaction with PC and the viscosity of the matrix is higher than that of the dispersed phase. In addition, changes in the interfacial tension between PC and SAN were assessed by examining relaxation spectra which were obtained from measuring rheological properties of ultrasonically treated blends.

• Journal of the Korean Electrochemical Society
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• v.24 no.1
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• pp.1-6
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• 2021

In this study, new morphology of NCA cathode material for lithium ion batteries was obtained through the electrospinning method. The prepared NCA nanofibers formed a nano-bush structure, and the primary particles were formed on the surface of the nanofibers. The embossing primary particles increased the surface area thus increasing the reactivity of lithium ions. The nano-bush structure could shorten the Li+ diffusion path and improve the Li+ diffusion coefficient. Scanning electron microscopy (SEM) revealed that the synthesized material consisted of nanofibers. The surface area of the nanofibers increased by primary particles was measured using atomic force microscopy (AFM). X-ray diffraction (XRD) analysis was carried out to determine the structure of the NCA nanofibers.

• Clinical and Experimental Reproductive Medicine
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• v.44 no.3
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• pp.132-140
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• 2017

Objective: Correlations between semen parameters and sperm DNA fragmentation index (DFI) were investigated to identify characteristics of sperm without DNA damage that could be used in selecting sperm for intracytoplasmic sperm injection (ICSI). Pregnancy outcomes were compared to determine whether in vitro fertilization (IVF) or ICSI is a better choice for patients who have sperm with a high-DFI. Methods: Semen analysis was carried out in 388 patients who visited our IVF center for the first time to investigate correlations between sperm DFI and semen parameters. In addition, 1,102 IVF cycles in 867 patients were carried out in the present study; 921 cycles in the low-DFI group (DFI < 30%) and 181 cycles in the high-DFI group ($DFI{\geq}30%$). Both the low- and high-DFI groups were subdivided into IVF and ICSI cycle groups. Results: Sperm DFI showed significant inverse correlations with sperm motility (r = -0.435, p< 0.001) and morphology (r = -0.153, p< 0.05). Sperm DFI also showed significant correlations with rapid motility (r = -0.436, p< 0.001), and the kinetic parameters of average-path velocity (r = -0.403) and linearity (r = -0.412). Although there was no significant difference in the pregnancy rates between IVF (48.6%) and ICSI (44.8%) in the low-DFI group, the pregnancy rate of ICSI cycles (44.8%, p< 0.05) was significantly higher than IVF cycles (25.0%) in the high-DFI group. No significant difference was observed in the abortion rates between the low-DFI (52 of 921, 5.6%) and high-DFI groups (7 of 181, 3.8%). Conclusion: ICSI is a better choice than IVF for improving the pregnancy outcomes of patients who have sperm with a high DFI.

• KIEAE Journal
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• v.15 no.2
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• pp.19-26
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• 2015

Purpose: Maximizing human comfort in design of medical environments depends immensely on specialized architects particularly critical care design; the study proposes Evidence-Based Design as an apparent analog to Evidence-Based Medicine. Healthcare facility designs are substantially based on the findings of study in an effort to design environments that augment care by improving patient safety and being therapeutic. On SPSS (Statistical Package for Social Science) t-test is applied to simulate two independent variables of PDR (Pre Design-Research) and POE (Post- Occupancy Evaluation). PDR is conducted on relatively new hospital Hallym University Dongtan Sacred Heart Hospital to analyse visibility from researchers' point of view, here the ICU is arranged in I-Shape. POE is applied on Dongguk University Ilsan Hospital to simulate walking on LogWare where two NS are designed based on L- Shape and Seoul St. Mary's Hospital, The Catholic University of Korea where five NS are functional for ICU Intensive Care Unit, Surgical Intensive Care Unit (SICU), Medical Intensive Care Unit (MICU), Critical Care Unit (CCU), Korean Oriental Medical Care Unit which are mostly arranged in U-Shape, and walking pattern is recognized to be in a zigzag path. Method: T-Test is applied on two dependent communication variables: walkability and visibility, with confidence interval of 95%. This study systematically analyses the Nurse Station (NS) typo-morphology, and simulates nurse horizontal circulation, by computing round route visits to patient's bed, then estimating minimum round route on LogWare stop sequence software. The visual connectivity is measured on depth map graphs. Hence the aim is to reduce staff stress and fatigue for better patients care by minimizing staff horizontal travel time and to facilitate nurse walk path and support space distribution by increasing effectiveness in delivering care. Result: Applying visibility graph and isovist field on space syntax on I- Shape, L- Shape and U- Shape ICU (SICU, MICU and CCU) configuration, I-shape facilitated 20% more patients in linear view as they stir to rise from their beds from nurse station compared to U-shape. In conclusion, it was proved that U-Shape supply minimum walking and maximum visibility; and L shape provides just visibility as the nurse is at pivot. I shape provides panoramic view from the Nurse Station but very rigorous walking.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.49.2-49.2
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• 2017

Star forming dwarf galaxies in various environments are attractive objects for investigating the environmental effects on chemical evolution of dwarf galaxies. Using SDSS DR7 spectroscopic data and GALEX ultraviolet (UV) imaging data, we study the chemical properties of star forming dwarf galaxies in various environments of the Virgo cluster, Ursa Major group, and field. We derived gas-phase abundance, galaxy mass, and UV specific star formation rate (sSFR) of subsample, early-type (ETD) and late-type star forming dwarf (LTD) galaxies, which are divided by visually classified galaxy morphology. We found no O/H enhancement of LTDs in cluster and group environments compared to the field, implying no environmental dependence of the mass-metallicity relation for LTDs. LTDs in the Virgo cluster and Ursa Major group have similar sSFR at a given galaxy mass, but they exhibit systematically lower sSFR than those in isolated field environment. We suggest that LTDs in the Virgo cluster are an infalling population that was recently accreted from the outside of the cluster. We found that ETDs in the Virgo cluster and Ursa Major group exhibit enhanced O/H compared to those in the field. However, no distinct difference of N/O of galaxies between different environments. The chemically evolved ETDs in the Virgo cluster and Ursa Major group also show similar mass-sSFR relation, but systematically lower sSFR at a fixed galaxy mass compared to the field counterparts. We suggest that ETDs in the Virgo cluster and Ursa Major group have evolved under the similar local environments. We also discuss the evolutionary path of ETDs and LTDs with respect to the environmental effects of ram pressure stripping and galaxy interaction/merging.

• Atmosphere
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• v.23 no.3
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• pp.321-329
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• 2013

This study examines the effect of aerosols on the vertical invigoration of continental stratiform clouds, using a dataset of Atmospheric Radiation Measurement (ARM) Intensive Operational Period (IOP, March 2000) at the Southern Great Plains (SGP) site. To provide further support to our observation-based findings, the weather research and forecasting (WRF) sensitivity simulations with changing cloud condensation nuclei (CCN) concentrations have been carried out for the golden episode over SGP. First, cross correlation between observed aerosol scattering coefficient and cloud liquid water path (LWP) with a 160-minutes lag is the highest of r = 0.83 for the selected episode, which may be attributable to cloud vertical invigoration induced by an increase in aerosol loading. Modeled cloud fractions in a control run are well matched with the observation in the perspective of cloud morphology and lasting period. It is also found through a simple sensitivity with a change in CCN that aerosol invigoration (AIV) effect on stratiform cloud organization is attributable to a change in the cloud microphysics as well as dynamics such as the corresponding modification of cloud number concentrations, drop size, and latent heating rate, etc. This study suggests a possible cloud vertical invigoration even in the continental stratiform clouds due to aerosol enhancement in spite of a limited analysis based on a few observed continental cloud cases.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.53-53
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• 2011

As the dimension of Cu interconnects has continued to reduce, its resistivity is expected to increase at the nanoscale due to increased surface and grain boundary scattering of electrons. To suppress increase of the resistivity in nanoscale interconnects, alloying Cu with other metal elements such as Al, Mn, and Ag is being considered to increase the mean free path of the drifting electrons. The formation of Al alloy with a slight amount of Cu broadly studied in the past. The study of Cu alloy including a very small Al fraction, by contrast, recently began. The formation of Cu-Al alloy is limited in wet chemical bath and was mainly conducted for fundamental studies by sputtering or evaporation system. However, these deposition methods have a limitation in production environment due to poor step coverage in nanoscale Cu metallization. In this work, gap-filling of Cu-Al alloy was conducted by cyclic MOCVD (metal organic chemical vapor deposition), followed by thermal annealing for alloying, which prevented an unwanted chemical reaction between Cu and Al precursors. To achieve filling the Cu-Al alloy into sub-100nm trench without overhang and void formation, furthermore, hydrogen plasma pretreatment of the trench pattern with Ru barrier layer was conducted in order to suppress of Cu nucleation and growth near the entrance area of the nano-scale trench by minimizing adsorption of metal precursors. As a result, superconformal gap-fill of Cu-Al alloy could be achieved successfully in the high aspect ration nanoscale trenches. Examined morphology, microstructure, chemical composition, and electrical properties of superfilled Cu-Al alloy will be discussed in detail.

• Korean Journal of Materials Research
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• v.28 no.5
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• pp.261-267
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• 2018

Hydrothermal synthesis of highly crystalline $TiO_2$ nanorods is a well-developed technique and the nanorods have been widely used as the template for growth of various core-shell nanorod structures. Magneli/CdS core-shell nanorod structures are fabricated for the photoelectrochemical cell (PEC) electrode to achieve enhanced carrier transport along the metallic magneli phase nanorod template. However, the long and thin $TiO_2$ nanorods may form a high resistance path to the electrons transferred from the CdS layer. $TiO_2$ nanorods synthesized are reduced to magneli phases, $TixO_{2x-1}$, by heat treatment in a hydrogen environment. Two types of magneli phase nanorods of $Ti_4O_7$ and $Ti_3O_5$ are synthesized. Structural morphology and X-ray diffraction analyses are carried out. CdS nano-films are deposited on the magneli nanorods for the main light absorption layer to form a photoanode, and the PEC performance is measured under simulated sunlight irradiation and compared with the conventional $TiO_2/CdS$ core-shell nanorod electrode. A higher photocurrent is observed from the stand-alone $Ti_3O_5/CdS$ core-shell nanorod structure in which the nanorods are grown on both sides of the seed layer.

• Current Photovoltaic Research
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• v.2 no.3
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• pp.88-94
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• 2014

The structural, optical and electrical properties of sputter-deposited CIGS films were directly influenced by the sputtering process parameters such as substrate temperature, working pressure, RF power and distance between target and substrate. CIGS thin films deposited by using a quaternary target revealed to be Se deficient due to Se low vapor pressure. This Se deficiency affected the overall stoichiometry of the films, causing the films to be Cu-rich. Current tends to pass through the Cu-Se channels which act as the shunting path increasing the film conductivity. The crystal structure of CIGS thin films depends on the substrate orientation due to the influence of surface morphology, grain size and stress of Mo substrate. The excess of Cu was removed from the CIGS films by KCN treatment, achieving a suitable Cu concentration (referred as Cu-poor) for the fabrication of solar cell. Due to high Cu concentrations on the CIGS film surface induced by Cu-Se phases after CIGS film deposition, KCN treatment proved to be necessary for the fabrication of high efficiency solar cells. Also during KCN treatment, dislocation density and lattice parameter decreased as excess Cu was removed, resulting in increase of bandgap and the decrease of conductivity of CIGS films. It was revealed that Cu-Se secondary phase could be removed by KCN wet etching of CIGS films, allowing the fabrication of high efficiency absorber layer.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.73-73
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• 2009

In this sutdy, a new class ACA(Anisotropic Conductive Adhesive) with low-melting-point alloy(LMPA) and self-organized interconnection method were developed. This developed self-organized interconnection method are achieved by the flow, melting, coalescence and wetting characteristics of the LMPA fillers in ACA. In order to observe self-interconnection characteristic, the QFP($14{\times}14{\times}2.7mm$ size and 1mm lead pitch) was used. Thermal characteristic of the ACA and temperature-dependant viscosity characteristics of the polymer were observed by differential scanning calorimetry(DSC) and torsional parallel rheometer, respectively. A electrical and mechanical characteristics of QFP bonding were measured using multimeter and pull tester, respectively. Wetting and coalescence characteristics of LMPA filler particles and morphology of conduction path were observed by microfocus X-ray inspection systems and cross-sectional optical microscope. As a result, the developed self-organized interconnection method has a good electrical characteristic($2.41m{\Omega}$) and bonding strength(17.19N) by metallurgical interconnection of molten solder particles in ACA.