• 한국결정성장학회지
• /
• 제31권3호
• /
• pp.143-148
• /
• 2021

Alkaline oxygen evolution reaction (OER) electrocatalysts have been widely studied for improving the efficiency and green hydrogen production through electrochemical water splitting. Transition metal-based electrocatalysts have emerged as promising materials that can significantly reduce the hydrogen production costs. Among the available electrocatalysts, transition metal-based layered double hydroxides (LDHs) have demonstrated outstanding OER performance owing to the abundant active sites and favorable adsorption-desorption energies for OER intermediates. Currently, cobalt doped nickel LDHs (NiCo LDHs) are regarded as the benchmark electrocatalyst for alkaline OER, primarily owing to the physicochemical synergetic effects between Ni and Co. We report effects of heat-treatment of the as-grown NiCo LDH on electrocatalytic activities in a temperature range from 250 to 400℃. Electrocatalytic OER properties were analysed by linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). The heat-treatment temperature was found to play a crucial role in catalytic activity. The optimum heat-treatment temperature was discussed with respect to their OER performance.

• 한국분말재료학회지
• /
• 제29권5호
• /
• pp.376-381
• /
• 2022

Tungsten disulfide (WS₂) nanosheets have attracted considerable attention because of their unique optical and electrical properties. Several methods for fabrication of WS₂ nanosheets have been developed. However, methods for mass production of high-quality WS₂ nanosheets remain challenging. In this study, WS₂ nanosheets were fabricated using mechano-chemical ball milling based on the synergetic effects of chemical intercalation and mechanical exfoliation. The ball-milling time was set as a variable for the optimized fabricating process of WS₂ nanosheets. Under the optimized conditions, the WS₂ nanosheets had lateral sizes of 500-600 nm with either a monolayer or bilayer. They also exhibited high crystallinity in the 2H semiconducting phase. Thus, the proposed method can be applied to the exfoliation of other transition metal dichalcogenides using suitable chemical intercalants. It can also be used with high-performance WS₂-based photodiodes and transistors used in practical semiconductor applications.

• Elastomers and Composites
• /
• 제58권2호
• /
• pp.70-80
• /
• 2023

The effect of phenylphosphonic acid (PPOA) on polyurethane (PU) thermal stability was studied through Fourier transform infrared spectroscopy and Thermogravimetric analysis. To synthesize PPOA-modified PUs (PPOA-PUs), polyether-type diols (Mw=62, 106, 190, 419, 605) were chemically modified with PPOA and then reacted with 4,4'-dicyclohexylmethane diisocyanate (H₁₂MDI) and 4,4-diphenylmethane diisocyanate (MDI). During thermal decomposition in air, the PPOA embedded in the PUs formed intumescent phosphocarbonaceous char. Below 400℃, PPOA-H₁₂MDI-PUs were more unstable, as PPOA decomposed at lower temperatures than phenyl groups and aliphatic ethers. Above 550℃, the thermal stability of PUs followed this order: PPOA-MDI-PUs > PPOA-H₁₂MDI-PUs > MDI-PUs > H₁₂MDI-PUs. At 700℃, unmodified PUs had no residue, while the PPOA-MDI-PU residue was 4.4~23.0 wt.% and the PPOA-H₁₂MDI-PU residue was 1.5~17.5 wt.%. The enhanced thermal stability of PPOA-MDI-PUs at high temperatures can be attributed to the synergetic effect of PPOA and phenyl groups on the formation of phosphocarbonaceous char.

• 농업과학연구
• /
• 제50권4호
• /
• pp.759-771
• /
• 2023

Plant growth-promoting rhizobacteria (PGPR) are naturally occurring bacteria that intensively colonize plant roots and are crucial in promoting the crop growth. These beneficial microorganisms have garnered considerable attention as potential bio-inoculants for sustainable agriculture. PGPR directly interacts with plants by providing essential nutrients through nitrogen fixation and phosphate solubilization and accelerating the accessibility of other trace elements such as Cu, Zn, and Fe. Additionally, they produce plant growth-promoting phytohormones, such as indole acetic acids (IAA), indole butyric acids (IBA), gibberellins, and cytokinins.PGPR interacts with plants indirectly by protecting them from diseases and infections by producing antibiotics, siderophores, hydrogen cyanide, and fungal cell wall-degrading enzymes such as glucanases, chitinases, and proteases. Furthermore, PGPR protects plants against abiotic stresses such as drought and salinity by producing 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase and modulating plant stress markers. Bacteria belonging to genera such as Bacillus, Pseudomonas, Burkholderia, Pantoa, and Enterobacter exhibit multiple plant growth-promoting traits, that can enhance plant growth directly, indirectly, or through synergetic effects. This comprehensive review emphasizes how PGPR influences plant growth promotion and presents promising prospects for its application in sustainable agriculture.

• 한국축산식품학회지
• /
• 제38권1호
• /
• pp.88-98
• /
• 2018

In this study, we isolated and characterized a bacteriocin-producing strain and two bacteriophages (P4, A3), showing antimicrobial effects against Clostridium perfringens, from chicken and swine feces by the spot-on-the lawn antagonism method. The selected strain was identified as Streptococcus hyointestinalis by 16S rRNA gene sequencing. The bacteriocin from the isolated strain exhibited strong inhibitory activity against four strains of C. perfringens and all the tested strains of Listeria monocytogenes, and the bacteriocin were highly heat- and pH-stable even at pH 2, pH 10 and $121^{\circ}C$ for 15 min. We also evaluated the combined effects of the isolated bacteriocin and phages. Combining the phage treatments and bacteriocin resulted in a synergetic effect compared with the phage or the bacteriocin alone. In addition, during the probiotic test, the bacteriocin-producing S. hyointestinalis B19 strain reduced the population of C. perfringens significantly. Treatment with S. hyointestinalis B19 and a cocktail of lytic bacteriophages eradicated the C. perfringens KCTC $3269^T$, completely. Consequently, the isolated bacteriocin and bacteriophages represent candidates for effective biocontrol of C. perfringens, and bacteriocin-producing S. hyointestinalis B19 is a potential probiotic candidate for use in domestic animals.

• 콘크리트학회논문집
• /
• 제23권4호
• /
• pp.441-448
• /
• 2011

이 연구에서는 실리카퓸 및 수축 저감제, 팽창재, 고성능 감수제의 혼입을 변수로 한 초고성능 시멘트 복합체(UHPCC)의 초기 수축 거동을 평가하기 위하여 화학수축 및 자기수축 실험을 수행하고, 응결 측정 결과와 비교하여 UHPCC의 자기건조 시작 시점에 대하여 분석하였다. 실험 결과, 실리카퓸 및 수축 저감제는 초기 화학수축을 증가시키는 경향을 보였으며, 고성능 감수제는 시멘트와 배합수의 수화 반응을 지연시키고 화학수축을 저감시키는 것으로 나타났다. 수축 저감제와 팽창재를 조합하여 적용한 경우 약 49%의 자기수축 저감 효과를 보였으며, 팽창재는 경화를 촉진 시키는 것으로 나타났다. 또한 UHPCC는 다수의 섬유 혼입과 낮은 물-결합재비에 의해 초결 이전부터 자기건조 현상이 발생하는 것으로 나타났다.

• 한국정밀공학회지
• /
• 제29권1호
• /
• pp.19-24
• /
• 2012

We demonstrate the desert beetle back mimicking hybrid superhydrophilic/superhydrophobic patterned surface by using the combination method of colloidal lithography and gravure offset printing for nano and micro patterning, respectively. The two methods are cost-effective and industrially available techniques compared to the other nano/micro patterning methods. To verify the water collecting function of the hybrid surface, the water condensation behavior is investigated on the chilled surface in ambient temperature and high humidity. Due to the synergetic effect of drop and film wise condensation, the hybrid superhydrophobic/superhydrophilic surface shows the higher efficiency than one of single wettability surfaces. The work is underway to get the good patterns of hybrid surfaces for water collecting from the dew or fog.

• 생약학회지
• /
• 제12권1호
• /
• pp.31-43
• /
• 1981

In order to determine the effect of Oryeongsan reputed to have diuretic action since Han Dynasty and possible synergetic action of Dianthi Semen, Polygonum avicularis Herba, Kochiae Fructus and Akebiae Lignum, herbs with similar reputation, when added to the above prescription, their decoction powders were solved into distilled water and injected into rabbits through the ear vein. Upon the treatment, the excretion of sodium, potassium and chloride ion together with urine volume was kinetically determined. At the same time the clearance of plasma creatinine and sodium ion was determined and the following results were obtained. Every experimental group demonstrated diuretic action, though feable, of relatively long duration. The diuretic mechanism in the case of Oryeongsan made up by mixing the seperate extracts of individual components and Oryeongsan(A) plus Dianthi Semen was found to be inhibitory effect of renal tubular reabsorption in contrast to the case of Oryeongsan(A) plus Polygonum avicularis Herba, Kochiae Fructus or Akebiae Lignum in which case the diuretic mechanism was found to be glomerular vascular dilatation. The urinary excretion of potassium ion was increased in the case of Oryeongsan(A) plus Dianthi Semen, Kochiae Fructus of Akebiae Lignum whereas in the other cases no similar change was registered. The diuretic action was most remarkable in the case of Oryeongsan(A) plus Polygonum avicularis Herba followed by Oryeongsan(A) plus Kochiae Fructus, Oryeongsan(A) plus Dianthi Semen, extract mixture of individual component of Oryeongsan, Oryeongsan(A) and Oryeongsan(A) plus Akebiae Lignum decreasing order. The duration of diuretic action was found to be 90 minutes in the case of Oryeongsan and mixture of individual component of Oryeongsan, and 60 minutes in the case of Oryeongsan(A) plus Dianthi Semen, Kochiae Fructus or Akebiae Lignum in contrast to the case of Oryeongsan(A) plus Polygonum avicularis Herba which lasted up to 120 minutes.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
• /
• pp.669-669
• /
• 2013

Hierarchical N doped TiO2 nanostructured catalyst with micro, meso and macro porosity have been synthesized by a facile self-formation route using ammonia and titanium isopropoxide precursor. The samples were calcined in different calcination temperature ranging from $300^{\circ}C$ to $800^{\circ}C$ at slow heating rate ($5^{\circ}C$/min) and designated as NHPT-300 to NHPT-800. $TiO_2$ nanostructured catalyst have been characterized by physico-chemical and spectroscopy methods to explore the structural, electronic and optical properties. UV-Vis diffuse reflectance spectra confirmed the red shift and band gap narrowing due to the doping of N species in TiO2 nanoporous catalyst. Hierarchical macro porosity with fibrous channel patterning was observed (confirmed from FESEM) and well preserved even after calcination at $800^{\circ}C$, indicating the thermal stability. BET results showed that micro and mesoporosity was lost after $500^{\circ}C$ calcination. The photocatalytic activity has been evaluated for methanol oxidation to formaldehyde in visible light. The enhanced photocatalytic activity is attributed to combined synergetic effect of N doping for visible light absorption, micro and mesoporosity for increase of effective surface area and light harvestation, and hierarchical macroporous fibrous structure for multiple reflection and effective charge transfer.

• 패션비즈니스
• /
• 제22권4호
• /
• pp.59-75
• /
• 2018

The purpose of this study was to investigate the relations and differences in Korean national image, Korean wave (Hanryu) interest, and Korean beauty service satisfaction of Korean, Chinese, and Vietnamese living in Korea and to lay the foundations for the export of various contents, especially beauty services, through the enhancement of Korea's national image. The present study was conducted from $10^{th}$ June to $10^{th}$ August 2017, by presenting 523 questionnaires to Koreans living in Seoul and another metropolitan area, and to Chinese and Vietnamese students studying in different Korean language Institutes in Seoul and other areas' universities. The basic questionnaire items were analyzed based on frequency analysis. The data on the national image, Korean wave interest, and Korean beauty service satisfaction were reduced by the factor analysis. The effects of each items were analyzed by regression. The differences in three factors were analyzed by ANOVA, and the differences were calculated by mean values. Consequently, it was observed that three factors are mutually affected each other. Therefore, it is necessary to establish a synergetic relationship between the individual factors. In addition, the individual items exhibited higher mean value in Vietnam, China, and Korea in a descending order. This indicates that Koreans are more likely to de-evaluate their cultures than others. Therefore, Koreans should be aware of the excellence of their culture and try to spread Korean culture and technology to the rest of the world with pride.