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        검색결과 115

        2.
        2023.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Lead sulfide ( PbS ) nanocrystals anchored on nitrogen-doped multiwalled carbon nanotubes ( CNx ) have been synthesized employing an environmentally friendly and inexpensive wet chemistry process. CNx∕PbS composites have been examined by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. Theorical ab initio calculations have been developed to determine the samples structural, morphological and optical properties to explain the experimental evidences. The PbS nanoparticles exhibit of 4 nm to 27 nm particle size with a face-centered cubic crystal structure and are homogeneously distributed along the carbon nanotubes. The nitrogen-doped CNTs acts as binding sites for the PbS clusters as ab initio theoretical study suggests.
        4,000원
        3.
        2022.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The bituminous coal was extracted with different industrial solvents like coal tar (CT), heavy cycle oil (HCO) and with their blends to determine the influence of solvent type on the extract yield, composition, thermal behavior, properties such as solubility to toluene and quinoline. The extracts obtained at 380 °C represented pitch-like solid matter with the softening points of 72–127 °C depending on the solvent used. They were characterized using the elemental and group analysis, FTIR spectroscopy, TG-DTG thermogravimetry and liquid chromatography for benzo(a)pyrene concentration. Also, maltene fractions of some extracts were studied by GC–MS. The results showed coal dissolution and the properties of the extracts to differ greatly depending on the solvent used. Coal tar was more favorable solvent for coal dissolution than HCO. Good correlation between the extract aromaticity and the content of the toluene insolubles was observed. The maltene fractions of the extracts obtained with CT and CT blended with HCO consisted mainly of polycyclic aromatics, and that obtained with the HCO contained also large amount of aliphatic compounds. It was found that the amount of the carcinogenic benzo(a) pyrene (BaP) in the toluene soluble fractions of the extracts were different depending on the solvents used for extraction. The remarkable result was that the BaP concentrations in all extracts were much lower than in the solvents used.
        4,000원
        4.
        2021.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The use of recycled materials, such as the fine recycled aggregate made from concrete waste and carbon fiber (CF) product of industrial waste, for the manufacture of conductive recycled mortars (CRM), transforms the mortar base cement normally made with cement:sand in a sustainable multifunctional material, conferring satisfactory mechanical and electrical properties for non-structural uses. This action provides ecological benefits, reducing the use of natural fine aggregates from rivers and the amount of concrete waste deposited in landfills resulting from construction waste. In this investigation the effect of the addition of CF on electrical properties in hardened, wet and dry state, electric percolation in dry state and fluidity of the wet mixture of a cement based CRM was evaluated: fine recycled aggregate: graphite powder, CRM specimens with dimensions of 4 × 4 × 16 cm. were manufactured for 3, 7 and 28 days of age and sand/cement ratios = 1.00, graphite/cement = 1.00, water/cement = 0.60 and CF = 0.1, 0.3, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0% compared to the weight of cement. The results demonstrated the effect of the addition of CF in CRM, reducing fluidity of the mixtures due to the opposition generated by its physical interaction of CF with recycled sand or recycled fine aggregate and graphite powder (GP), in its case, placing the electric percolation percolation at 0.30% and 0.45% of CF for CRM with and without GP, respectively. Increases in electrical conductivity (EC) without the presence of GP are defined by the contact between the CF and the conductive paths formed. In contrast, with the presence of GP, the EC is defined by the contact between the CF and the GP simultaneously, forming conductive routes with greater performance in its EC.
        4,600원
        5.
        2020.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Wood sawdust from an invasive arboreal species, Parkinsonia aculeata, and seeds from a tropical fruit of massive consumption, Pouteria sapota, were used as precursors for the development of activated carbons (ACs) directed to CO2 adsorption. Chemical activation employing KOH as activating agent and pre-established experimental conditions was applied. Main physicochemical properties of the ACs in relation to their CO2 adsorption performance were examined. The ACs developed from the wood sawdust and the seeds presented specific surfaces areas of 770 and 1000 m2 g−1, respectively, with their porosity development resulting essentially microporous (< 2 nm). They also showed a similar content of acidic surface groups, but basic functionalities of the former duplicated those of the latter. Maximum CO2 adsorbed at equilibrium (273 K and 100 kPa) was 5.0 mmol g−1 and 4.4 mmol g−1 for the samples derived from the sawdust and the seeds, respectively. On the other hand, CO2 adsorption capacities mimicking post-combustion conditions, as evaluated from thermogravimetric assays and breakthrough curves obtained in a packed-bed column, were approximately 1 mmol g−1, indicating a good CO2 adsorption performance for both ACs. Nevertheless, those derived from the wood sawdust with a notorious preeminence of micropores (~ 93%), narrower pore size distribution centered around 1 nm, and a higher content of basic functionalities than the ACs obtained from the seeds showed a relatively better performance. The CO2 removal capacity of the activated carbons was not noticeably affected after five CO2 adsorption–desorption cycles, with both samples almost keeping their initial CO2 adsorption capacity.
        4,000원
        6.
        2019.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        One- and two-dimensional carbon nanomaterials were tested as adsorbents for the elimination of two anionic dyes, reactive red 2 and methyl orange, and the cationic dye methylene blue from aqueous solutions under the same conditions. Carbon nanomaterials performed well in the removal of dyes. Surface oxygenated groups in the nanomaterials improved the cationic dyes’ adsorption, but not the adsorption of the anionic dye. The interactions between nanomaterials and dyes were verified by infrared and Raman spectroscopy. The pseudo-second order kinetic model was better fitted to the kinetic experimental data than the Elovich and pseudo-first order models. The equilibrium adsorption data were best fitted by the Langmuir model. The dimensions and morphology of the carbon nanomaterials play an important role in the adsorption of the three dyes. The main mechanism of adsorption of anionic dyes is by the interactions of the aromatic rings of the dye structures and π delocalized electrons on carbon nanostructures; the adsorption of cationic dye is mainly due to electrostatic interactions.
        4,300원
        8.
        2018.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Most commercially available detonation nanodiamonds (DNDs) require further processing to qualify for use in biomedical applications, as they often contain many impurities and exhibit poor dispersibility in aqueous media. In this work, DNDs are modified to improve purity and impart a high colloidal stability to the particles. The dispersive and adsorption properties of modified DNDs are evaluated in terms of the suitability of DNDs as carriers for non-steroidal anti-inflammatory drugs (NSAIDs) in transdermal delivery. The study of adsorption on strongly positively and strongly negatively charged DNDs showed their high loading capacity for NSAIDs, and a pronounced relationship between the drugs and the particles’ charges. Experiments on long-term desorption carried out with DND/NSAID complexes indicate that the nanoparticles exert a sustained effect on the drug release process.
        4,000원
        16.
        2017.10 구독 인증기관·개인회원 무료
        Nueva Ecija is a landlocked province in Central Luzon region that is composed of 27 municipalities and 5 cities. It is a province that is rich with biodiversity on its north and east borders, which exhibit a shared ecosystem with the Caraballo mountain range in the north and the Sierra Madre mountain range in the east. Its main economic activity is farming where rice is the main crop. Part of the Sierra Madre mountain range traverses its towns of Bongabon, Laur, Rizal and Pantabangan where most of the locals perform agro – forestry activities as a means of generating income for their families. Due to the accumulation of farm residues as a result of intensive agro-forestry activities, mushroom pharming becomes a very viable agribusiness undertaking in the area. Our research team initiated the establishment of database by tracking the mushroom production activities in the province. Similarly, the prevailing climatic condition in the geographical area and the type of agro-forestry wastes have been tracked. Wastes as a result of intensive agro – forestry activities are being generated which the locals oftentimes burned in the field that posed hazard to the environment. In order to discourage this practice, our research team generated technologies on mushroom pharming using rice straw as the main substrate. The promotion of mushroom pharming is based on the suitability of mushroom species to grow in climatic conditions that prevail in the specific geographical area in the province. As a result of its collaborative research undertakings, the Center for Tropical Mushroom Research and Development of the Central Luzon State University in collaboration with the Laboratory of Forest Products Chemistry of Tokyo University of Agriculture and the Nikken Sohonsha Corporation encouraged the adoption of medicinal mushroom production technologies on rice straw – based formulation. With oyster mushroom (Pleurotus spp) as the most widely cultivated mushroom among the mushroom growers in the province, other ligninolytic mushrooms such as lacquered mushroom (Ganoderma) and wood ear mushroom (Auricularia spp.) are grown by the locals. Similarly, leaf – litter degrading mushrooms such as paddy straw mushroom (Volvariella volvacea) are also being cultivated in the province. However, some mushroom growers in the province adopt sawdust – based mushroom production technology which is not economically appropriate in the province due to the scarcity of its availability compared to rice straw. Majority of the mushroom growers in the province adopt the rice straw – based mushroom technology. Moreover, high value mushroom – based products other than the fresh mushrooms are already in the local market.
        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
        19.
        2016.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We report the characterization of a massive (mp = 3:91:4Mjup) microlensing planet (OGLE- 2015-BLG-0954Lb) orbiting an M dwarf host (M = 0:33  0:12M ) at a distance toward the Galactic bulge of 0:6+0:4 􀀀0:2 kpc, which is extremely nearby by microlensing standards. The planet-host projected separation is a?  1:2AU. The characterization was made possible by the wide- eld (4 deg2) high cadence (􀀀 = 6 hr􀀀1) monitoring of the Korea Microlensing Telescope Network (KMTNet), which had two of its three telescopes in commissioning operations at the time of the planetary anomaly. The source crossing time t = 16 min is among the shortest ever published. The high-cadence, wide- eld observations that are the hallmark of KMTNet are the only way to routinely capture such short crossings. High-cadence resolution of short caustic crossings will preferentially lead to mass and distance measurements for the lens. This is because the short crossing time typically implies a nearby lens, which enables the measurement of additional e ects (bright lens and/or microlens parallax). When combined with the measured crossing time, these e ects can yield planet/host masses and distance.
        4,000원
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