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        검색결과 1,093

        41.
        2022.03 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Zintl phase Mg3Sb2 is a promising thermoelectric material in medium to high temperature range due to its low band gap energy and characteristic electron-crystal phonon-glass behavior. P-type Mg3Sb2 has conventionally exhibited lower thermoelectric properties compared to its n-type counterparts, which have poor electrical conductivity. To address these problems, a small amount of Sn doping was considered in this alloy system. P-type Mg3Sb2 was synthesized by controlled melting, pulverizing, and subsequent vacuum hot pressing (VHP) method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate phases and microstructure development during the process. Single phase Mg3Sb2 was successfully formed when 16 at.% of Mg was excessively added to the system. Nominal compositions of Mg3.8Sb2-xSnx (0 ≤ x ≤ 0.008) were considered in this study. Thermoelectric properties were evaluated in terms of Seebeck coefficient, electrical conductivity, and thermal conductivity. A peak ZT value ≈ 0.32 was found for the specimen Mg3.8Sb1.994Sn0.006 at 873 K, showing an improved ZT value compared to intrinsic one. Transport properties were also evaluated and discussed.
        4,000원
        42.
        2021.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The aims of this study were to measure the ultrasonographic biometry of genitalia of the indigenous rams and observe the relationship of biometry on semen parameters. The epididymal volume was significantly reduced (p < 0.01) after semen collection compared with before collection for both left and right part in all rams. The cumulative results showed that although there was no significant difference in length, width and volume of epididymis between before and after semen collection, however the values were lower after collection. The epididymal length was significantly correlated with epididymal volume (p < 0.01), semen motility (p < 0.05) and semen morphology (p < 0.01). Epididymal width was only significantly correlated with epididymal volume (p < 0.01) not with the semen parameters. Epididymal volume had a significant correlation only with semen morphology (p < 0.01).The scrotal circumference had the significant correlation with semen density, mass activity, concentration and motility (p < 0.01). The epididymis had the similar or slightly increased echogenicity as compared to the normal testis. During whole study, some white spots were found on testis which did not affect the semen quantity and quality. Significant variation was observed only for semen concentration and motility among the rams (p < 0.05). The overall normal morphology was 90.5 ± 4.6% with highest percentage of coiled tail abnormalities.
        4,000원
        43.
        2021.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Although personality and culture have been employed as independent predictors of emotion regulation, less is known about the interplay between them. Thus, the present study tests their interaction by focusing on the match between personality (public self-consciousness) and culture (valuing independence vs. interdependence) in modulating an emotion regulation strategy, namely, emotion suppression, on Facebook. Furthermore, relationship concern related to the expression of positive and negative emotions on Facebook is explored as a potential underlying mechanism. An online survey on Facebook users in the United States (n = 320) and South Korea (n = 336) was conducted through two professional survey companies. The results revealed that the positive association between public self-consciousness and emotion suppression was stronger among respondents who value interdependence (vs. independence), which led to a significant interaction between the two predictors. Furthermore, public self-consciousness was associated with emotion suppression through relationship concern for the expression of positive, but not negative, emotions. Furthermore, this mediated relationship was stronger among respondents who value interdependence (vs. independence). Lastly, the study discussed the importance of exploring the interplay between personality and culture and the implication of dialectic emotions.
        4,900원
        48.
        2021.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Sensing of volatile organic compounds (VOCs) is a growing research topic because of the concern about their hazard for the environment and health. Furan is a VOC produced during food processing, and it has been classified as a risk molecule for human health and a possible biomarker of prostate cancer. The use of carbon nanotubes for VOCs sensing systems design could be a good alternative. In this work, a theoretical evaluation of the interactions between furan and zigzag single-wall carbon nanotubes takes into account different positions and orientations of the furan molecule, within a density-functional theory first-principles approach. The van der Waals interactions are considered using different exchange-correlation functionals (BH,C09, DRSLL and KBM). The results indicate that vdW-functionals do not significantly affect geometry; however, the binding energy and the distance between furan and nanotube are strongly dependent on the selected exchange-correlation functional. On the other hand, the effects of single and double vacancies on carbon nanotube are considered. It was found that the redistribution of charge around the single-vacancy affects the bandgap, magnetic moment, and binding energy of the complex, while furan interaction with a double-vacancy does not considerably change the electronic structure of the system. Our results suggest that to induce changes in the electronic properties of carbon nanotubes by furan, it is necessary to change the nanotube surface, for example, by means of structural defects.
        4,000원
        51.
        2021.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The discharge of dye-containing industrial effluents such as methylene blue (MB) in water bodies has resulted in severe aquatic and human life problems. In addition to this factor, there is the accumulation of banana peel wastes, which can generate ecological damage. Thus, this research purpose a different method from the literature using the banana peel waste (BP) to produce activated carbon (ACBP) by NaOH activation followed by pyrolysis at 400 °C to remove methylene blue (MB). The material was characterized by TGA, XRD, SEM, BET, and FTIR. The influence of dye concentration (10, 25, 50, 100, 250, and 500 mg L−1) was investigated. ACBP presented a well-developed pore structure with a predominance of mesopores and macropores. This morphological structure directly influences the MB removal capacity. The highest efficiency for dye removal was in the MB initial concentration of 25 mg L−1, sorbent of 0.03 g, and contact time of 60 min, which were 99.8%. The adsorption isotherms were well defined by Langmuir, Freundlich, and Temkin isotherm models. The Langmuir model represented the best fit of experimental data for ACBP with a maximum adsorption capacity of 232.5 mg g−1. This adsorbent showed a comparatively high performance to some previous works. So, the banana peel waste is an efficient resource for producing activated carbon and the adsorption of methylene blue.
        4,600원
        52.
        2021.08 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Zintl compound Mg3Sb2 is a promising candidate for efficient thermoelectric material due to its small band gap energy and characteristic electron-crystal phonon-glass behavior. Furthermore, this compound enables fine tuning of carrier concentration via chemical doping for optimizing thermoelectric performance. In this study, nominal compositions of Mg3.8Sb2-xTex (0 ≤ x ≤ 0.03) are synthesized through controlled melting and subsequent vacuum hot pressing method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) are carried out to investigate phase development and surface morphology during the process. It should be noted that 16 at. % of excessive Mg must be added to the system to compensate for the loss of Mg during melting process. Herein, thermoelectric properties such as Seebeck coefficient, electrical conductivity, and thermal conductivity are evaluated from low to high temperature regimes. The results show that Te substitution at Sb sites effectively tunes the majority carriers from holes to electrons, resulting in a transition from p to n-type. At 873 K, a peak ZT value of 0.27 is found for the specimen Mg3.8Sb1.99Te0.01, indicating an improved ZT value over the intrinsic value.
        4,000원
        53.
        2021.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        We report the comparative study of electronic and optical properties of (6,1) SWCNT from GGA and DFT-1/2 methods. (6,1) SWCNT is a low-bandgap semiconductor, which falls within ( n1 − n2)/3≠ integer. The calculated bandgaps are 0.371 eV and 0.462 eV from GGA and DFT-1/2, respectively. Thus, DFT-1/2 enhanced the electronic bandgap by 24.52%. From both GGA and DFT-1/2 approaches (6,1) SWCNT exhibits an indirect bandgap along Γ − Δ symmetry. However, the percentage change in direct–indirect bandgap is negligibly small, i.e., 4.1% and 3.7% from GGA and DFT-1/2, respectively. The refractive index measured along x-axis ( n x ) approaches unity, indicating transparent behaviour, while that along z-axis ( n z ) goes as high as ∼3.82 for photon energy 0.0 − 0.15 eV, exhibiting opaque behaviour. Again, the value of n z drops below unity at photon energy ∼0.18 eV and again approaches ∼ 1 for higher energy ranges. The optical absorption is highly anisotropic and active within the infrared region.
        4,000원
        54.
        2021.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Recent years have witnessed remarkable development in the field of nanotechnology and it has been affirmed that carbonbased nanomaterials have wide applications in agriculture, industrial, biomedical and environmental sectors. Due to distinctive physicochemical properties of the carbon nanotubes (CNTs), they have been extensively utilized in plant science as a growth promoter, and thus, could be a boon for biomass production of agricultural products. Studies suggest that CNTs help increase the plant’s ability to absorb water and essential nutrients, thereby increasing growth. Apart from this, CNTs have been scrutinized for their utilization in genetic engineering for the delivery of genes, proteins or drugs. However, the literature discloses mixed effects of CNTs exposure on plants like in inducing oxidative stress by generating reactive oxygen species (ROS). Moreover, studies concerning CNTs interaction with plant system is at a nascent stage and needs further investigations to explore the mechanisms influencing the growth and toxicity in plants. Therefore, this review attempts to highlight the current literature on CNTs (including both single walled and multi walled) exposure on plants. It also explores unresolved challenges, as well as recommendations to ensure sustainable development of CNTs while minimizing any possible adverse health impacts.
        4,000원
        57.
        2021.01 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Background/Aim: Endoscopic retrograde cholangiopancreatography (ERCP) training requires varying degrees of staff assistance regarding operation of the fluoroscopy machine via a foot pedal. Efficiency is important to acquire during this training due to radiation risks. In this study, we evaluate the effect of controlling endoscopy and fluoroscopy unit on duct cannulation rates (CRs) and total fluoroscopy time (FT) for fellows in training. Methods: 204 patients undergoing ERCP were randomized to one of two groups: 1) “Endoscopist Driven” group in which the endoscopist controlled the foot pedal for fluoroscopy, and 2) “Assistant Driven” group in which attending or fellow controlled the foot pedal while the other team member controlled the endoscope. Various measures including selective duct CR and total FT were recorded. Results: There was no significant difference in mean procedure duration between the two groups (32 minutes vs. 33 minutes, p=0.70). There was also no statistically significant difference in CR (83.7% vs. 77.4%, p=0.25) or FT (3.27 minutes vs. 3.54 minutes, p=0.48). Conclusions: ERCP is a technically challenging procedure which requires extensive supervision. This study demonstrates that CR and FT are not affected by who controls the fluoroscopy.
        4,000원
        58.
        2020.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Nickel nanopowders are obtained by the spark discharge method, which is based on the evaporation of the electrode surface under the action of the discharge current, followed by vapor condensation and the formation of nanoparticles. Nickel electrodes with a purity of 99.99% are used to synthesize the nickel nanoparticles in the setup. Nitrogen is used as the carrier gas with a purity of 99.998%. XRD, TEM, and EDX analyses of the nanopowders are performed. Moreover, HRTEM images with measured interplanar spacings are obtained. In the nickel nanopowder samples, a phase of approximately 90 wt% with an expanded crystal lattice of 6.5% on average is found. The results indicate an unusual process of nickel nanoparticle formation when the spark discharge method is employed.
        3,000원
        59.
        2020.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The present study was conducted in a goat farm for pregnancy diagnosis by using vaginal cytology and B-mode real time ultrasound using 5 MHz probe by transabdominal method. Seventeen pregnant does were used for this study. The objective of the study was to determine the earliest day of pregnancy and describe the chronological characteristics of pregnancy from day 22 to day 40 for vaginal cytology and day 25 to day 60 for ultrasonography of gestation. The differences among the average percentage of cell value in different age of pregnancy were significant (p < 0.05). The average percentage of intermediate cells (81.12%) was also significantly (p < 0.05) higher than superficial (9.41%), keratinized (7.10%) and neutrophil (2.61%) on 22-40th days of pregnancy. In case of real time B-mode ultrasonography, the gestational sac was observed only in three does out of seventeen (17.6 %) at 25-30 days whereas the placentomes and heart beat of the foetus were first detected at 31-35 days in six does (35.3%). The foetal leg buds were first visualized at 36-40 days in four does (23.5%) whereas the foetal vertebral column was first observed at 36-40 days of gestation in only three does (17.6%). In conclusion, vaginal cytology and trans-abdominal ultrasonography can be used for detection of early pregnancy in does.
        4,000원
        60.
        2020.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We report the discovery of a giant exoplanet in the microlensing event OGLE-2017-BLG-1049, with a planet―host star mass ratio of q = 9.53 ± 0.39 × 10-3 and a caustic crossing feature in Korea Microlensing Telescope Network (KMTNet) observations. The caustic crossing feature yields an angular Einstein radius of θE = 0.52 ± 0.11 mas. However, the microlens parallax is not measured because the time scale of the event, tE ≃ 29 days, is too short. Thus, we perform a Bayesian analysis to estimate physical quantities of the lens system. We fi nd that the lens system has a star with mass Mh = 0.55+0.36 -0.29 M⊙ hosting a giant planet with Mp = 5.53+3.62 -2.87 MJup, at a distance of DL = 5.67+1.11 -1.52 kpc. The projected star{planet separation is aㅗ = 3.92+1.10 -1.32 au. This means that the planet is located beyond the snow line of the host. The relative lens{source proper motion is μrel ~ 7 mas yr-1, thus the lens and source will be separated from each other within 10 years. After this, it will be possible to measure the flux of the host star with 30 meter class telescopes and to determine its mass.
        4,000원
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