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        검색결과 96

        1.
        2023.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this research, in order to increase the oxidation resistance of graphite, kaolin and alumina powder with different ratios (26A-74S, 49A-51S, 72A-28S) and slurry method were used to create an aluminosilicate coating on the graphite substrate. In order to reduce the difference in the coefficients of thermal expansion of graphite with aluminosilicate coating, aluminum metaphosphate coating as an interlayer was prepared on the surface of graphite by cathodic electrochemical treatment. The isothermal oxidation test of the samples was carried out in air at a temperature of 1250 °C for 1, 3 and 5 h. The microstructure, chemical composition, and phase components of the coating were, respectively, analyzed by scanning electron microscope equipped with an energy-dispersive spectrometer and X-ray diffraction. The results indicated that, by increasing the withdrawal speed of the samples in slurry method, the amount of changes in the weight of the samples has increased and therefore had a direct effect on oxidation. In addition, it was approved that, at high-temperature oxidation, AlPO4 glass phase forms on aluminum metaphosphate interlayer which retards graphite oxidation. Along with aluminum metaphosphate, aluminosilicate coating also produces a glass phase which fills and seals the voids on the surface which prevents the oxygen to reach the surface of graphite. The created double-layer coating including an interlayer of aluminum metaphosphate + slurry coating prepared with the ratio of 26A-74S as the optimal coating in this research was able to increase the oxidation resistance of graphite by 73% at a temperature of 1250 °C.
        4,600원
        2.
        2023.05 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The rapid synthesis techniques and interesting multidisciplinary applications make carbon nanodots (CNDs) stand out from semiconductor quantum dots. Moreover, CNDs derived from green precursors have gained more importance beyond chemically derived CNDs due to sustainable synthesis opportunities. However, the presence of molecular impurities or intermediates or fluorophores was neglected during the entire process. Herein, we illustrate the sustainable synthesis of CNDs from Hemigraphis alternata plant leaves with extended carbonization procedure (3 and 9 min) along with simultaneous ethylene glycol and diethyl ether solvent treatment method for the successful removal of interfering fluorophores. To unravel the distinction between purified CNDs (P-CNDs) and organic fluorescent carbon nanostructures (org-FCNs), we carried out photophysical, structural, and morphological studies. A quantum yield (QY) of 69 and 42% was observed for crude org-FCNs, and crude P-CNDs; however after purification, QY of 1% and absence of one component from the fluorescent decays curve suggest the removal of fluorophores. Further, HR-TEM and DLS studies showed the quasi-spherical amorphous particles having < 10 nm particle size for P-CNDs. Besides, in vitro biocompatibility investigation and cellular uptake assay (1–100 μg/mL) against the MDA-MB 468 cell lines proves the ≥ 95% cell viability and good internalization for both org-FCNs and P-CNDs. Hence, our study shows the presence of fluorophore impurities in plant-derived CNDs, the removal and resemblance in biocompatibility properties. Hence, this information can be considered during the synthesis and isolation of CNDs. Simple and effective removal of impurities to harvest pure carbon nanodots (CNDs) through solvent-based selective separation method, and revelation of the cocktail flourphores similar to biocompatible blue fluorescent CNDs were studied.
        4,900원
        3.
        2021.09 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Legacy waste from the decommissioned A-1 nuclear power plant in the Slovak Republic is scheduled for immobilisation within a tailored alkali borosilicate glass formulation, as part of ongoing site cleanup. The aqueous durability and characterisation of a simulant glass wasteform for Chrompik III legacy waste, was investigated, including dissolution experiments up to 112 days (90°C, ASTM Type 1 water). The wasteform was an amorphous, light green glassy product, with no observed phase separation or crystalline inclusions. Aqueous leach testing revealed a suitably durable product over the timescale investigated, comparing positively to other simulant nuclear waste glasses and vitreous products tested under similar conditions. Iron and titanium rich precipitates were observed to form at the surface of monolithic samples during leaching, with the formation of an alkali deficient alteration layer behind these at later ages. Overall this glass appears to perform well, and in line with expectations for this chemistry, although longer-term testing would be required to predict overall durability. This work will contribute to developing confidence in the disposability of vitrified Chrompik legacy wastes.
        4,600원
        4.
        2021.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Even in an era where 8-meter class telescopes are common, small telescopes are considered very valuable research facilities since they are available for rapid follow-up or long term monitoring observations. To maximize the usefulness of small telescopes in Korea, we established the SomangNet, a network of 0.4{1.0 m class optical telescopes operated by Korean institutions, in 2020. Here, we give an overview of the project, describing the current participating telescopes, its scienti c scope and operation mode, and the prospects for future activities. SomangNet currently includes 10 telescopes that are located in Australia, USA, and Chile as well as in Korea. The operation of many of these telescopes currently relies on operators, and we plan to upgrade them for remote or robotic operation. The latest SomangNet science projects include monitoring and follow-up observational studies of galaxies, supernovae, active galactic nuclei, symbiotic stars, solar system objects, neutrino/gravitational-wave sources, and exoplanets.
        4,600원
        7.
        2019.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Comparisons between bare carbon (CPs) and nitrogen-doped carbon nanoparticles (N-CPs) synthesised using hydrothermal reaction are carried out. It was found that hydrothermal reaction of citric acid yields graphene-like sheets, while the nitrogen doping using ethylenediamine resulted in amorphous polymeric ball-like hydrocarbons devoid of any aromatic rings. Although the Fourier transform infrared spectroscopy, Raman spectroscopy and nuclear magnetic resonance spectroscopy indicate the presence of carbon–carbon double bonds (C=C), and the ground states of both materials are very deep (> 7.8 eV) as measured by ultraviolet photoelectron spectroscopy. This indicates the conjugation is very short. This is supported by the fact that both materials are UV blue emitting peaking at 375 nm probably originating from C=C.
        4,000원
        11.
        2018.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this study, an empirical relationship between the energy band gap of multi-walled carbon nanotubes (MWCNTs) and synthesis parameters in a chemical vapor deposition (CVD) reactor using factorial design of experiment was established. A bimetallic (Fe-Ni) catalyst supported on CaCO3 was synthesized via wet impregnation technique and used for MWCNT growth. The effects of synthesis parameters such as temperature, time, acetylene flow rate, and argon carrier gas flow rate on the MWCNTs energy gap, yield, and aspect ratio were investigated. The as-prepared supported bimetallic catalyst and the MWCNTs were characterized for their morphologies, microstructures, elemental composition, thermal profiles and surface areas by high-resolution scanning electron microscope, high resolution transmission electron microscope, energy dispersive X-ray spectroscopy, thermal gravimetry analysis and Brunauer-Emmett-Teller. A regression model was developed to establish the relationship between band gap energy, MWCNTs yield and aspect ratio. The results revealed that the optimum conditions to obtain high yield and quality MWCNTs of 159.9% were: temperature (700ºC), time (55 min), argon flow rate (230.37 mL min–1) and acetylene flow rate (150 mL min–1) respectively. The developed regression models demonstrated that the estimated values for the three response variables; energy gap, yield and aspect ratio, were 0.246 eV, 557.64 and 0.82. The regression models showed that the energy band gap, yield, and aspect ratio of the MWCNTs were largely influenced by the synthesis parameters and can be controlled in a CVD reactor.
        4,000원
        12.
        2018.12 구독 인증기관 무료, 개인회원 유료
        In late 1950’s, the beginning of container revolution has started a new paradigm shift in maritime industry worldwide. This new paradigm has become a major reason for seaport systems to prepare their physical capacity, space availability, multi-modalism, transport connectivity via regionalisation. However, in early 2010’s the introduction of industrial revolution 4.0 (IR4.0) which starts the era of immersive digitalization proved that seaport systems need to be prepared to face pattern of unstable magnitudes in dynamic maritime trade. Therefore, this paper analyses key components required for Malaysian seaport system to be aligned with the key requirements in IR4.0. By employing document analysis, this research analyses the challenges faced by Malaysian seaport system as well as suggests strategies to muddle through the key requirements of IR4.0. The findings from this research indicate that Malaysian seaport system need to be improved by enforcing skill-based education system, flexibility in labour structure, development in skill and competence level as well as improvement in infrastructure suitability. The findings from this research also reflect significant strategies to improve seaport system in the era of IR4.0 including enhancing requirements for intermodal terminals, improving preparation for seaport alliances, developing mechanism for interoperability, improving utilisation of intra and interregional economic development as well as scrutinising safety and security.
        4,800원
        13.
        2018.07 구독 인증기관·개인회원 무료
        In nowadays consumption-based society, products (e.g. food and electronic products) are often thrown away before they are sufficiently used. The aversive consequence of such a lifestyle is becoming more alarming. There is an urgent need for a change in people’s consumption style. How can we make people correct their existing wasteful consumption behaviors and act responsibly? In fact, feelings very often can influence people’s behavior and judgments (Schwarz, 1990), even though the feelings are aroused by irrelevant sources - incidental emotion (Garg, Inman, & Mittal, 2005; Lerner & Keltner, 2000; Schwarz & Clore, 1983). Feelings of guilt and shame are known as moral emotions which are the guidance to ethical behaviors (Tangney, 1991, 2003). Although there is a significant overlapping between these two emotions, they also differ in several important aspects. One critical difference lies in the way the transgressor makes attributions (Niedenthal, Tangney, & Gavanski 1994). A transgressor who attributes the wrongdoing to a specific behavior (i.e. “I’ve done something bad”) is more likely to experience guilt while a transgressor who makes attribution to the global self (i.e. “I’m a terrible person”) is more likely to experience shame (Tracy & Robins, 2004). Given these fundamental differences, we speculate that a guilt-laden consumer is more likely to correct his or her wrongdoing (i.e. wastage) by taking reparative actions to minimize waste but a shame-laden consumer may possibly give up doing so. Findings from an experimental study (N=90) largely support this prediction. Undergraduate students who were made to feel shame were less likely to participate in a recycling campaign organized by the university than the students in the control condition. They reported a lower intention to use recycling facilities provided. On the other hand, participants who were made to feel guilt reported a marginally higher intention to participate in the campaign than the control participants. These preliminary findings suggest that emotional experience derived from other life domains might determine responsible consumption behaviors. Shame, which is commonly regarded as a moral emotion, may not necessarily make people more responsible consumers. The mechanism that underlies this effect may warrant further investigation.
        15.
        2017.04 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We investigate two abnormal CME-Storm pairs that occurred on 2014 September 10 - 12 and 2015 March 15 - 17, respectively. The first one was a moderate geomagnetic storm (Dstmin  -75 nT) driven by the X1.6 high speed flare-associated CME (1267 km s−1) in AR 12158 (N14E02) near solar disk center. The other was a very intense geomagnetic storm (Dstmin  -223 nT) caused by a CME with moderate speed (719 km s−1) and associated with a filament eruption accompanied by a weak flare (C9.1) in AR 12297 (S17W38). Both CMEs have large direction parameters facing the Earth and southward magnetic field orientation in their solar source region. In this study, we inspect the structure of Interplanetary Flux Ropes (IFRs) at the Earth estimated by using the torus fitting technique assuming self-similar expansion. As results, we find that the moderate storm on 2014 September 12 was caused by small-scale southward magnetic fields in the sheath region ahead of the IFR. The Earth traversed the portion of the IFR where only the northward fields are observed. Meanwhile, in case of the 2015 March 17 storm, our IFR analysis revealed that the Earth passed the very portion where only the southward magnetic fields are observed throughout the passage. The resultant southward magnetic field with long- duration is the main cause of the intense storm. We suggest that 3D magnetic field geometry of an IFR at the IFR-Earth encounter is important and the strength of a geomagnetic storm is strongly affected by the relative location of the Earth with respect to the IFR structure.
        4,200원
        16.
        2017.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        We built a 8 μm selected sample of galaxies in the NEP-AKARI eld by defining 4 redshift bins with the four AKARI bands at 11, 15, 18 and 24 microns (0:15 < z < 0:49, 0:75 < z < 1:34, 1:34 < z < 1:7 and 1:7 < z < 2:05) . Our sample contains 4079 sources, 599 are securely detected with Herschel/PACS. Also adding ultraviolet (UV) data from GALEX, we fit the spectral energy distributions using the physically motivated code CIGALE to extract the star formation rate, stellar mass, dust attenuation and the AGN contribution to the total infrared luminosity (LIR). We discuss the impact of the adopted attenuation curve and that of the wavelength coverage to estimate these physical parameters. We focus on galaxies with a luminosity close the characteristic L* IR in the different redshift bins to study the evolution with redshift of the dust attenuation in these galaxies.
        4,000원
        17.
        2017.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The recent updates of the North Ecliptic Pole deep (0.5 deg2, NEP-Deep) multi-wavelength survey covering from X-ray to radio-wave is presented. The NEP-Deep provides us with several thousands of 15 μm or 18 μm selected galaxies, which is the largest sample ever made at these wavelengths. A continuous filter coverage in the mid-infrared wavelength (7, 9, 11, 15, 18, and 24 μm) is unique and vital to diagnose the contributions from starbursts and AGNs in the galaxies out to z=2. The new goal of the project is to resolve the nature of the cosmic star formation history at the violent epoch (e.g. z=1{2), and to find a clue to understand its decline from z=1 to present universe by utilizing the unique power of the multiwavelength survey. The progress in this context is brie y mentioned.
        4,000원
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