• Journal of Powder Materials
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• v.25 no.2
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• pp.120-125
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• 2018

Boron nitride nanotubes (BNNTs) are receiving great attention because of their unusual material properties, such as high thermal conductivity, mechanical strength, and electrical resistance. However, high-throughput and high-efficiency synthesis of BNNTs has been hindered due to the high boiling point of boron (${\sim}4000^{\circ}C$) and weak interaction between boron and nitrogen. Although, hydrogen-catalyzed plasma synthesis has shown potential for scalable synthesis of BNNTs, the direct use of $H_2$ gas as a precursor material is not strongly recommended, as it is extremely flammable. In the present study, BNNTs have been synthesized using radio-frequency inductively coupled thermal plasma (RF-ITP) catalyzed by solid-state ammonium chloride ($NH_4Cl$), a safe catalyst materials for BNNT synthesis. Similar to BNNTs synthesized from h-BN (hexagonal boron nitride) + $H_2$, successful fabrication of BNNTs synthesized from $h-BN+NH_4Cl$ is confirmed by their sheet-like properties, FE-SEM images, and XRD analysis. In addition, improved dispersion properties in aqueous solution are found in BNNTs synthesized from $h-BN+NH_4Cl$.

• Korean Journal of Agricultural Science
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• v.41 no.3
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• pp.187-191
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• 2014

The cultivation area and use of genetically modified (GM) crops have been increased continuously over the world. Concerns about the potential risks of GM crops are also increasing. Safe management for the development and production of GM crops is required according to Living Modified Organism Act in Korea. Planning about the methods, duration, and frequency of environmental monitoring is also required for commercial use of GM crops. GM Zoysia japonica Steud. (event name: JG21) expressing resistance to glufosinate-ammonium has been generated previously. By using gamma ray treatment to JG21 we also developed male sterility and dwarf Z. japonica (event name: JG21-MS). The objective of this study was to establish the monitoring system for environment release of JG21-MS. In this study we extracted RNA from JG21 and JG21-MS and conducted RAPD (random amplified polymorphic DNA) method to distinguish JG21 and JG21-MS.

• Physical Therapy Rehabilitation Science
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• v.9 no.1
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• pp.18-24
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• 2020

Objective: The purpose of this study was to compare the activities of the abdominal muscles according to trunk stabilization exercises using Swiss ball in normal individuals. Design: Cross-sectional study. Methods: Ten healthy university students participated in this study. The subjects were required to complete the following three exercise positions: Exercise position 1, sitting on a Swiss ball and lifting the legs; Exercise position 2, pushing to a plank position from an ending position; and Exercise position 3, push-up posture with the legs on a Swiss ball. Changes in the trunk muscle activities were estimated using Biometric electromyography (EMG). Activities of the dominant side internal oblique muscle (IOM) and external oblique muscle (EOM) were estimated in all participants. The maximal voluntary isometric contraction (MVIC %) was measured to standardize the EMG signals for the IOM and EOM during maximum resistance when sitting up with each shoulder pointing towards the contralateral pelvis with knees bent and both arms crossed on the chest for 5 seconds. Results: There was a significant difference in the activity of the internal and external oblique muscles between Exercises 1 and 2 and Exercises 1 and 3 (p<0.05). Furthermore, the IOM/EOM activity ratio was the greatest during Exercise 3 and the smallest during Exercise 1. IOM and EOM activities were the greatest during Exercise 2 with greater EOM activity. Conclusions: In future studies, it will be necessary to investigate muscle activities by supplementing the above-mentioned limitations during the stabilization exercise. The results of this study may be used as a basis for controlling the intensity and frequency of exercise while prescribing trunk stabilization exercises.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.31 no.2
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• pp.156-161
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• 1986

Silage productivity and resistance to rice black streaked dwarf virus (RSDV) of six Korean-improved and six US introduced corn genotypes were tested in the southern part of Korea. There was a negative correlation between culm length retarded by RBSDV and coefficients of variance of culm length. Frequency distribution of culm length could be classified as three genotypic groups according to the type of distribution and percentage of RBSDV diseased plants. There were negative correlations between percent RBSDV diseased plants at harvest and culm length, percent ear bearing plants, silage yield, or ear yield, but percent RBSDV diseased plants did not related to the ear/silage ratio and stover yield. Silage yield of Pioneer XCF38 was highest, but that of Suweon 89 and NC 6131 was lowest. However, there was not signi-ficant difference in silage yield among the remaining genotypes. Pioneer XCF38, Suweon 89, and Jinjuok were quite resistant to RBSDV, but Suweon 19, Kwangok, Hoengseongok, Jecheonok, and Pioneer 3424 were susceptible and NC 6131 was most susceptible to RBSDV. Although Jinjuok and Suweon 89 were resistant to RBSDV, silage yield was not high because of early senescence of leaves after silkillg.

• Journal of Ginseng Research
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• v.45 no.1
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• pp.149-155
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• 2021

Background: We have reported that internal deletions in the nef, gag, and pol genes in HIV-1-infected patients are induced in those treated with Korean Red Ginseng (KRG). KRG delays the development of resistance mutations to antiretroviral drugs. Methods: The vif-vpr genes over 26 years in 20 hemophiliacs infected with HIV-1 from a single source were sequenced to investigate whether vif-vpr genes were affected by KRG and KRG plus highly active antiretroviral therapy (ART) (hereafter called GCT) and compared the results with our previous data. Results: A significantly higher number of in-frame small deletions were found in the vif-vpr genes of KRG-treated patients than at the baseline, in control patients, and in ART-alone patients (p < 0.001). These were significantly reduced in GCT patients (p < 0.05). In contrast, sequences harboring a premature stop codon (SC) were more significant in GCT patients (10.1%) than in KRG-alone patients, control (p < 0.01), and ART-alone patients (p = 0.078 for peripheral blood mononuclear cells). The proportion of SC in Vpr was similar to that in Vif, whereas the proportion of sequences revealing SC in the env-nef genes was significantly lower than that in the pol-vif-vpr genes (p < 0.01). The genetic distance was 1.8 times higher in the sequences harboring SC than in the sequences without SC (p < 0.001). Q135P in the vif gene is significantly associated with rapid progression to AIDS (p < 0.01). Conclusion: Our data show that KRG might induce sD in the vif-vpr genes and that vif-vpr genes are similarly affected by lethal mutations.

• Current Photovoltaic Research
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• v.12 no.2
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• pp.37-40
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• 2024

One of the current innovation trends in the solar industry is the increase in the size of silicon wafers. As the wafer size increases, the series resistance of the module rises, highlighting the need for research on methods for cutting and bonding solar cells. Among these, the Infrared (IR) laser scribing technique has been extensively researched. However, there is still insufficient optimization research regarding the thermal damage caused by lasers on the Transparent Conductive Oxide (TCO) layer of Heterojunction (HJT) solar cells. Therefore, in this study, we systematically varied conditions such as IR laser scribing speed, frequency, power, and the number of scribes to investigate their impact on the performance of cut cells under each condition. Additionally, we conducted a comparative analysis of thermal damage effects on the TCO layer based on varying scribing depths.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.5 s.335
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• pp.1-8
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• 2005

A RC parallel gate model is used to consider gate distributed effect that affects RF MOSFET performance, and extraction formula based on $Y_{11}$-parameters are used to extract model parameters directly from measured S-parameters. Better agreement between measured and modeled S-parameters in the frequency range beyond 10 GHz is achieved by using the RC parallel model than conventional Rg one, demonstrating the accuracy of the RC model and extraction technique. Using these extraction methods, gate voltage dependent curves of RC gate model parameters are newly extracted, and these parameter data will greatly contribute to developing a RF nonlinear gate model.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.784-788
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• 1999

In this work, we analyzed the viscoelastic characteristics of electrochemically polymerized polypyrrole(PPy) thin film in various electrolyte solutions, $Na_2SO_4,\;Na_2CO_3$ and SDS + $NaClO_4$, using QCA. The characteristics of redox reaction of electrochemically polymerized PPy thin film for 180 sec in each electrolyte, was investigated in 0.1 M $NaClO_4$ electrolyte solution by cyclic voltammetry method. We used one side of quartz crystal electrode as a working electrode and measured the resonant frequency, resonant resistance and current as analytical parameters. As the results, we suggest that electrochemically polymerized PPy thin film in various electrolyte solutions shows tendency changing from elastic characteristics to viscoelastic one in the order of $ClO_4{^{-}}\;+\;DS^-,\;SO_4{^{-2}}$ and $CO_3{^{-2}}$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.11
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• pp.949-955
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• 2009

In this study, we investigated the effects of Cr dopant (1.0 at% $Cr_2O_3$ sintered at $1000^{\circ}C$ for 1 h in air) on the bulk trap (i.e. defect) and interface state levels of ZnO using dielectric functions ($Z^*$, $M^*$, $Y^*$, $\varepsilon^*$, and $tan{\delta}$), admittance spectroscopy (AS), and impedance-modulus spectroscopy (IS & MS). For the identification of the bulk trap levels, we examine the zero-biased admittance spectroscopy and dielectric functions as a function of frequency and temperature. Impedance and electric modulus spectroscopy is a powerful technique to characterize grain boundaries of electronic ceramic materials as well. As a result, three kinds of bulk defect trap levels were found below the conduction band edge of ZnO in 1.0 at% Cr-doped ZnO (Cr-ZnO) as 0.11 eV, 0.21 eV, and 0.31 eV. The overlapped defect levels ($Zn^{..}_i$ and $V^{\cdot}_0$) in admittance spectra were successfully separated by the combination of dielectric function such as $M^*$, $\varepsilon^*$, and $tan{\delta}$. In Cr-ZnO, the interfacial state level was about 1.17 eV by IS and MS. Also we measured the resistance ($R_{gb}$) and capacitance ($C_{gb}$) of grain boundaries with temperature using impedance-modulus spectroscopy. It have discussed about the stability and homogeneity of grain boundaries using distribution parameter ($\alpha$) simulated with the Z"-logf plots with temperature.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.12
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• pp.1310-1315
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• 2006

This study examines algae removal and reduction using ultrasonic. Experiments were carried out on frequency: 28 kHz single-wave, 40 kHz multi-wave; intensity: 10, 15, 20, 25, 30 W/L; algae concentration: 500, 1000, 1700/ml; exposure time: 1, 3, 5, 7, 10, 15, 20 min. Also, We investigated algae removal and reduction in single cistern where raw water including algae was directly exposed to ultrasonic and in the double cisterns located in 4 cm from ultrasonic vibrator. The algae type used in this study was Melosira genus of Bacillariophceae. The Bacillariophceae is the representative algae which causes blockage of filter basin. Because of its resistance against oxidizers, it flows into the filter basin after sterilization. As a result of this study, the form of Bacillariophceae was completely destroyed and dissolved after the application of ultrasonic waves unlike the sterilization using oxidizers. Removal efficiency of algae using ultrasonic waves increased in proportion to intensity and exposure time of ultrasonic waves, and in double cisterns is better than single cistern.