• Journal of the Korean Vacuum Society
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• v.21 no.4
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• pp.205-211
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• 2012

We investigated the optical and hydrophobic properties of the deposited silver (Ag) zinc oxide (ZnO) nanorods (NRs) on flexible indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates (i.e., ITO/PET). The ZnO NRs were grown by an electrochemical deposition using a sputtered ZnO seed layer and the Ag was deposited by using a thermal evaporator. For comparison, the same fabrication process was carried out on the bare ITO/PET without ZnO NRAs. Due to the discrete surface of ZnO NRs, the deposited Ag was formed as nano-scale particles, while the Ag became film-like for bare ITO/PET. In order to control the size and amount of Ag particles, the Ag deposition time was changed from 100 to 600 s. When the deposition time was increased, the Ag particles became larger and denser, and the absorptance was increased. This enhanced absorptance may be due to the localized surface plasmon resonance of Ag particles. Furthermore, the relatively high hydrophobicity was observed for the deposited Ag on the ZnO NRs/ITO/PET. These improved optical and surface properties are expected to be useful for flexible photovoltaic and optoelectronic devices.

• Polymer(Korea)
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• v.37 no.3
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• pp.332-341
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• 2013

H-shaped amphiphilic pentablock copolymers $(PSt)_2-b-PCL-b-PEO-b-PCL-b-(PSt)_2$ was synthesized via chemoenzymatic method by combining enzyme-catalyzed ring-opening polymerization (eROP) of ${\varepsilon}$-caprolactone (${\varepsilon}$-CL) and atom transfer radical polymerization (ATRP) of styrene. By this process, we obtained copolymers with controlled molecular weight and low polydispersity. The structure and composition of the obtained copolymers were characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC) and infrared spectroscopy analysis (IR). The crystallization behavior of the copolymers was analyzed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The crystallization behavior of the H-shaped block copolymers demonstrated a PCL dominate crystallization. The self-assembly behavior of the copolymers was investigated in aqueous media. The hydrodynamic diameters of the copolymer micelles in aqueous solution were measured by dynamic light scattering (DLS). The morphology of the copolymer micelles was observed by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The hydrodynamic diameters of spherical micelles declined gradually with the increase of the hydrophobic chain lengths of the copolymers. The critical micelle concentration (CMC) values were determined from fluorescence emission, and it was found that the CMCs decreased with an increase of PSt hydrophobic block lengths.

• Journal of the Korean Vacuum Society
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• v.9 no.4
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• pp.382-388
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• 2000

Hydrogenated amorphous carbon (a-C:H) films were fabricated by electron cyclotron resonance plasma-enhanced chemical vapor deposition. The bonding structure of carbon and hydrogen in the a-C:H films has been investigated by varying the deposition conditions such as ECR power, gas composition of methane and hydrogen, deposition time, and negative DC self bias voltage. The bonding characteristics of the a-C:H thin film were analyzed using FTIR spectroscopy. The IR absorption peaks of the film were observed in the range of $2800\sim3000 \textrm{cm}^{-1}$. The atomic bonding structure of a-C:H film consisted of $sp^3$ and $sp^2$ bonding, most of which is composed of $sp^3$ bonding. The structure of the a-C:H films changed from $CH_3$ bonding to $CH_2$ or CH bonding as deposition time increased. We also found that the amount of dehydrogenation in a-C:H films was increased as the bias voltage increased.

• International Journal of Fluid Machinery and Systems
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• v.4 no.1
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• pp.179-190
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• 2011

The swirling flow developing in Francis turbine draft tube under part load operation leads to pressure fluctuations usually in the range of 0.2 to 0.4 times the runner rotational frequency resulting from the so-called vortex breakdown. For low cavitation number, the flow features a cavitation vortex rope animated with precession motion. Under given conditions, these pressure fluctuations may lead to undesirable pressure fluctuations in the entire hydraulic system and also produce active power oscillations. For the upper part load range, between 0.7 and 0.85 times the best efficiency discharge, pressure fluctuations may appear in a higher frequency range of 2 to 4 times the runner rotational speed and feature modulations with vortex rope precession. It has been pointed out that for this particular operating point, the vortex rope features elliptical cross section and is animated of a self-rotation. This paper presents an experimental investigation focusing on this peculiar phenomenon, defined as the upper part load vortex rope. The experimental investigation is carried out on a high specific speed Francis turbine scale model installed on a test rig of the EPFL Laboratory for Hydraulic Machines. The selected operating point corresponds to a discharge of 0.83 times the best efficiency discharge. Observations of the cavitation vortex carried out with high speed camera have been recorded and synchronized with pressure fluctuations measurements at the draft tube cone. First, the vortex rope self rotation frequency is evidenced and the related frequency is deduced. Then, the influence of the sigma cavitation number on vortex rope shape and pressure fluctuations is presented. The waterfall diagram of the pressure fluctuations evidences resonance effects with the hydraulic circuit. The influence of outlet bubble cavitation and air injection is also investigated for low cavitation number. The time evolution of the vortex rope volume is compared with pressure fluctuations time evolution using image processing. Finally, the influence of the Froude number on the vortex rope shape and the associated pressure fluctuations is analyzed by varying the rotational speed.

• Anxiety and mood
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• v.14 no.2
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• pp.63-70
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• 2018

It has been suggested that aberrant self-referential processing (SRP) is one of the important components of the explanatory models of social anxiety disorder (SAD). The default mode network (DMN), which reflects intrinsic brain functions, is known to play a critical role in SRP. Recently, resting state functional magnetic resonance imaging (fMRI) research on the functional connectivity in the brain network has gained greater attention as a tool to elucidate the neurobiological basis of various psychiatric disorders. We reviewed resting state fMRI studies that investigated the resting state functional connectivity (RSFC) of the DMN in SAD. Despite of the heterogeneity of the analytic methods and occasional negative findings, most studies consistently reported abnormalities of RSFC within the DMN, suggesting that the DMN may be significant neural correlates of aberrant SRP in SAD. Also, changes in RSFC of the DMN are associated with clinical improvements of therapeutic interventions. Moreover, emerging findings provide the basis for potential use of RSFC as a complementary method in diagnosis of SAD. Ongoing and future research to investigate RSFC of the DMN could broaden our understanding regarding the neurobiological basis of SAD, and contribute to the development of novel treatments for SAD.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.3
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• pp.303-307
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• 2022

Magnetoelectric (ME) properties of 3-0 type particulate composites have been investigated with respect to application features for reliable magnetic sensitivity and magnetically-induced output voltage. In order to figure out the magnetoelectric characteristics in the ME composites, frequency dependent ME responses were studied from [0.948 Na_0.5K_0.5NbO₃-0.052 LiSbO₃]-[Co_1-xZn_xFe₂O₄] (NKNLS)/Co_1-xZn_xFe₂O₄ (CZFO, x=0, 0.1, and 0.2). As a result, the maximal α_ME of 23.15 mV/cm·Oe was achieved from the NKNLS-CZFO (x_Zn = 0.1) composites at resonance frequency of 315 kHz and H_dc = 0 Oe. From the frequency dependent ME responses, it is clearly described that the self-biased ME composites can be used for applications as both magnetic sensors and energy harvesters, respectively.

• Journal of Korean Medicine Rehabilitation
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• v.33 no.1
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• pp.97-108
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• 2023

The purpose of this study is to investigate the effectiveness of integrative Korean medicine treatment for patients who were diagnosed as acute fracture on pelvis. The patients were treated by Korean medicine as conservative management including acupuncture, pharmacopuncture, herbal medication and cupping for hospitalization periods. Numerical rating scale (NRS), EuroQol-5 dimensions (EQ-5D), Oswestry disability index (ODI), patient global impression of change (PGIC), self-walking distance and the changes of symptoms were measured to assess patients' improvement. NRS, ODI scores and EQ-5D definitely improved on 4 patients of 5 cases. NRS decreased from 6~7 to 3~5, ODI scores decreased from 62~75.11 to 40~52 and EQ-5D increased from 0.013~0.331 to 0.47~0.773. PGIC and self-walking distance were also enhanced after treatments. In conclusion, this study suggests that integrative Korean medicine could be effective treatment for acute pelvic fracture.

• The Korean journal of internal medicine
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• v.39 no.3
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• pp.430-438
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• 2024

Background/Aims: A poor prognostic factor for Crohn's disease (CD) includes perianal fistulizing disease, including perianal fistula and/or perianal abscess. Currently, a tool to assess perianal symptoms in patients with CD remains nonexistent. This study aimed to develop a perianal fistulizing disease self-screening questionnaire for patients with CD. Methods: This prospective pilot study was conducted at three tertiary referral centers between January 2019 and May 2020. We formulated questions on perianal symptoms, including tenesmus, anal discharge, bleeding, pain, and heat. A 4-point Likert scale was used to rate each question. Patients with CD completed a questionnaire and underwent pelvic magnetic resonance imaging (MRI). Results: Overall, 93 patients were enrolled, with 51 (54.8%) diagnosed with perianal fistulizing disease, as determined by pelvic MRI. The Spearman correlation findings demonstrated that anal pain (p = 0.450, p < 0.001) and anal discharge (p = 0.556, p < 0.001) were the symptoms that most significantly correlated with perianal disease. For anal pain and discharge, the area under the receiver operating characteristic curve of the scores was significantly higher than that of the combined score for all five symptoms (0.855 vs. 0.794, DeLong's test p = 0.04). For the two symptoms combined, the sensitivity, specificity, and positive predictive and negative predictive values were 88.2, 73.8, 80.4, and 83.8%, respectively, with 81.7% accuracy for detecting perianal fistulizing disease. Conclusions: This study indicates that simple questions regarding anal pain and discharge can help accurately identify the presence of perianal fistulizing disease in patients with CD.

• Macromolecular Research
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• v.17 no.5
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• pp.301-306
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• 2009

This work has demonstrated that a novel amphiphilic poly(epichlorohydrine)-graft-polystyrene (PECH-g-PS) copolymer at 34:66 wt% was synthesized via atom transfer radical polymerization (ATRP) of styrene using PECH as a macroinitiator. The structure of the graft copolymer was characterized by nuclear magnetic resonance ($^1H$ NMR) and FTIR spectroscopy, demonstrating that the "grafting from" method using ATRP was successful. The self-assembled graft copolymer was used as a template film for the in-situ growth of silver nanoparticles from $AgCF_3SO_3$ precursor under UV irradiation. The in situ formation of silver nanoparticles with 6-8 nm in average size in the solid state template film was confirmed by transmission electron microscopy (TEM), UV-visible spectroscopy and wide angle X-ray scattering (WAXS). Differential scanning calorimetry (DSC) also displayed the selective incorporation and the in situ formation of silver nanoparticles within the hydrophilic PECH domains, probably due to stronger interaction of the silvers with the ether oxygens of PECH backbone than that with hydrophobic PS side chains.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.305-310
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• 2007

This paper presents a damper system design in torque converter to minimize the vibration in powertrain of automatic transmission vehicle. The lock-up clutch in torque converter makes engine and transmission connected directly. When the lock-up clutch is engaged the torque fluctuation of engine is attenuated by the damper system. This function decides the vehicle power-train dynamic characteristics. At first, the dynamic hysteresis effect with any self and surface to surface contact problems of the damper springs in the damper system for torque converter is analyzed by using FEM. It is shown that these simulation results have a good design reference to energy dissipation operating by damper system in torque converter. And, to calculate dynamic characteristics, the vehicle model is structured by using $AMESim^{(R)}$?? that is a common use program. The vehicle model shows the frequency response of vehicle by changing the stiffness of damper spring, and these results lead the most suitable stiffness of spring. Also, new damper system is analyzed resonance frequency variation and is compared with prior damper.