검색결과

검색조건
좁혀보기
검색필터
결과 내 재검색

간행물

    분야

      발행연도

      -

        검색결과 1,440

        41.
        2023.11 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The legal status of Biodiversity Beyond National Jurisdiction (BBNJ) has been regulated through the High Seas Treaty as a common heritage of humankind. However, there still exist problems related to overlapping areas above the Extended Continental Shelf (ECS). In such areas, a significant continental shelf would fall within national jurisdiction, whereas the water column would be under the regime of the high seas, and BBNJ would be the common heritage of humankind. We argue that, in order to address the overlapping of areas within the superjacent waters in the ECS, a given sui generis status is required, so that the coastal state has a sovereign right to conserve the BBNJ in these areas. This study concludes that the sui generis arrangement should be implemented in the context of an overlapping ECS and its water column. The efforts of the Indonesian government to extend the continental shelf beyond 200 nautical miles constitute an important step in preserving natural resources for future generations.
        5,200원
        43.
        2023.11 구독 인증기관·개인회원 무료
        Most of the C-14 produced is in the organic form, generated as methane (14CH4), methanol (14CH3OH), formaldehyde (14CH2O), and formic acid (14CO2H2). When analyzing C-14, it is transformed into the form of 14CO2, and its concentration is determined using LSC. Typical examples include the wet oxidation method, the combustion or Pyrolysis. The wet oxidation method uses strong acids and involves repeated operations, which generates large amounts of acid waste and secondary radioactive waste. The combustion method uses high temperatures, which requires an oxygen device. Pyrolysis also requires high temperature in a vacuum and catalysts. Catalysts are expensive because they are platinum-based. To compensate for these shortcomings, a C-14 analysis method using UV irradiation was developed. In this study, 100 mL of distilled water mixed with formic acid (CO2H2), potassium persulfate (K2S2O8), and silver nitrate (AgNO3) was irradiated with a 320-390 nm UV lamp to conduct a CO2 production reaction experiment. The UV range was measured using a photometer (UV Power puck II). The beaker was made of quartz in 150 mL size with three inlets : a temperature measurement, a sample inlet, and a collection tube connector. We changed the UV lamp used from a 450 W halogen lamp to a 100 W LED, which has a lower temperature and is safer. As a result of the experiment, CO2 bubbles were generated in the collection tube, due to the UV irradiation react, which uses oxidizer and catalysts. The maximum temperature of the solution irradiated with the LED UV lamp was less than 56°C. It confirmed the rate of bubble generation changed depending on the lamp distance, the amount of sample, oxidizer, and catalyst. In an experiment to confirm the reaction caused by heat, it was found that although a reaction occurred due to heat, the reaction was significantly lower than when using a UV lamp. The reproducibility experiment was conducted three times in total under the same conditions. It showed the same pattern. In the future, we plan to select mock samples, collect 14CO2 in Carbo- Sorb, and analyze them using LSC. The results of this research will be used as a technology to recover C-14 more safely and efficiently and will also be used to expand its application to the treatment of other wastes such as waste liquid and waste resin through simulated samples.
        44.
        2023.11 구독 인증기관·개인회원 무료
        During the initial cooling period of spent nuclear fuel, Cs-137 and Sr-90 constitute a large portion of the total decay heat. Therefore, separating cesium and strontium from spent nuclear fuel can significantly decrease decay heat and facilitate disposition. This study presents analytical technique based on the gas pressurized extraction chromatography (GPEC) system with cation exchange resin for the separation of Sr, Cs, and Ba. GPEC is a micro-scaled column chromatography system that allows for faster separation and reduction volume of elution solvent compared to conventional column chromatography by utilizing pressurized nitrogen gas. Here, we demonstrate the comparative study of the conventional column chromatography and the GPEC method. Cation exchange resin AG 50W-X12 (200~400 mesh size) was used. The sample was prepared at a 0.8 M hydrochloric acid solution and gradient elution was applied. In this case, we used the natural isotopes 88Sr, 133Cs, and 138Ba instead of radioactive isotopes for the preliminary test. Usually, cesium is difficult to measure with ICP-OES, because its wavelengths (455.531 nm and 459.320 nm) are less sensitive. So, we used ICP-MS to determine the identification and the recovery of eluate. In this study, optimized experimental conditions and analytical result including reproducibility of the recovery, total analysis time and volume of eluents will be discussed by comparing GPEC and conventional column chromatography.
        45.
        2023.11 구독 인증기관·개인회원 무료
        Heavy metal wastewater containing cobalt (Co2+) has received more attention as an environment issue, which is released from electroplating processes, battery materials industries, nuclear power plants, etc. Especially, cobalt exposed to high-temperature and high-pressure environment during the operation of a nuclear power plant to form corrosion products and forming a chalk river unidentified deposit (CURD) along with radioactive materials generated in cooling water pipes. Cobalt present in the oxide film is mainly Co-60, which emits radiation and causes increased radiation exposure to workers, and efficient management is essential. In this study, we demonstrated the performance of copper hexacyanoferrate (CuHCF) electrodes in a capacitive deionization (CDI) system for Co2+ ions removal. The structure and chemical status of CuHCF used as an electrode material were characterized, and electrochemical properties were evaluated. This study showed that Co2+ ions could be efficiently removed in aqueous solutions using CuHCF electrodes. It has been experimentally shown that the ion removal mechanism is driven by the insertion of Co2+ ions within the CuHCF lattice channels. The deionization capacities in 20 and 50 mg-Co2+ L-1 aqueous solutions were 141.62 and 156.85 mg g-1, respectively, and the corresponding charge efficiencies (Λ) were 0.55 and 0.68, respectively. Thus, we suggest that an electrochemically driven process using CuHCF can usefully remove Co2+ ions from wastewater.
        46.
        2023.11 구독 인증기관·개인회원 무료
        In all geodisposal scenarios it is key to understand the interaction of radionuclides with mineral particles during their formation/recrystallisation. Studying processes at the molecular scale provides insight into long-term radionuclide behaviour. Uranium is a significant radionuclide in higher activity wastes destined for geological disposal, and iron (oxyhydr) oxides (e.g. goethite, 􀟙-FeOOH). are ubiquitous in and around these systems, formed via processes including metal corrosion and microbially induced reactions. There are numerous reports of uranium-incorporation into iron (oxyhydr) oxides, therefore it has been suggested that they may be a barrier to uranium migration in geodisposal systems. However, long-term stability of these phases during environmental perturbations are unexplored. Specifically, U-incorporated iron (oxyhydr) oxide phases may interact with Fe(II) and sulphide from biological or geological origin. Firstly, electron transfer occurs between adsorbed Fe(II) and iron oxyhydroxides, with potential for changes in the speciation of incorporated uranium e.g. oxidation state changes and/or release. Secondly, on exposure to aqueous sulfide, iron (oxyhydr) oxides undergo reductive dissolution and recrystallisation to iron sulphides. Understanding the fate of incorporated uranium during these process in key to understanding its long term behaviour in subsurface systems. A series of experimental studies were undertaken where U(VI)-goethite was synthesized then reacted with either aqueous Fe(II) or S(-II), and the system monitored over time using geochemical analysis and X-ray absorption spectroscopy (XAS) techniques e.g. U LIII-edge and MIV-edge HERFD-XANES. Reaction with aqueous Fe(II) resulted in electron transfer between Fe(II) and U(VI)-goethite, with > 50% U(VI) reduced to U(V). XAS analysis revealed that U remained within the goethite structure, and electron transfer only occurred within the outermost atomic layers of goethite. which led to U reduction. Rapid reductive dissolution of U(VI)-goethite occurred on reaction with sulfide at pH7. A transient release of aqueous U was observed during the first day, likely due to uranyl(VI)-persulfide species. However, U was retained in the solid phase in the longer term. In contrast, the sulfidation of U adsorbed to ferrihydrite at pH 12.2 led to the immediate release of U (< 10% Utotal) associated with a colloidal erdite (NaFeS2·2H2O) phase. Moreover, in the bulk phase the surface of ferrihydrite was passivated by sulfide, and U was found to have been trapped within surface associated erdite-like fibres. Overall, these studies further understanding of the long-term behaviour of U-incorporated iron (oxyhydr)oxides supporting the overarching concept of iron (oxyhydr) oxides acting as a barrier to U migration.
        47.
        2023.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This paper evaluates the adsorptive removal of sunset yellow (SY) from aqueous solutions using a new magnetic glycodendrimer (MGD). To synthesize the MGD, chitosan dendrons were cultivated on amine-functionalized magnetic graphene oxide. A number of analytical methods were employed to physicochemically characterize the synthesized MGD. Batch adsorption conditions were optimized using the Box–Behnken design. An optimized initial SY content of 633 mg/L, an optimized contact time of 33.37 min, and an optimized pH of 3.72 maximized the MGD adsorption capacity to 485 mg/g. The Langmuir isotherm was employed to describe adsorption equilibrium, while adsorption kinetics was studied via the Lagergren kinetics model. The SY adsorption onto the MGD was thermodynamically found to be spontaneous (ΔG° < 0) and exothermic (ΔH° = – 19.120 kJ/mol), leading to a decreased disorder (ΔS° = – 54.420 kJ/mol) in the solid–liquid interface. The MGD showed reusability and unique magnetic characteristics. It was concluded that the MGD could be a potential alternative for the adsorptive and magnetic removal of SY from an aqueous solution.
        5,500원
        49.
        2023.10 구독 인증기관·개인회원 무료
        Natural enemy insects, including predators and parasitoids, are beneficial organisms that feed upon other agricultural pests. Using natural enemy insects to suppress or prevent outbreak of pests is a key component of integrated pest management strategy. It is safe, effective, and environmentally friendly and can be applied easily to the greenhouses, filed crops and orchards. Rearing and application of natural enemy insects in biocontrol in China have a long history. As early as 1700 years ago, the predator Oecophylla smaragdina has been used for controlling many kinds of citrus pests. Up to now, more than 30 species of natural enemies that can be artificially mass produced and widely used for biological control of many kinds of pests, including caterpillars, aphids, whiteflies, thrips, leaf mites and scales in China. The annual average application area of natural enemies is over 11.34 million hectares. However, with the increasing demand of using natural enemies in biological control programs, the development of natural enemy insect industrialization still face many challenges. It is urgent to explore more effective candidate natural enemies, improve the production efficiency, increase the shelf life of products and enhance the colonization of natural enemy insects after release, and thus facilitate the commercially production and application of natural enemies. This is of great significance for comprehensively promoting the use of green prevention and control techniques for crop diseases and pests, reducing the use of chemical pesticides, ensuing the quality and safety of food and agricultural products, and ultimately promoting sustainable agricultural development.
        58.
        2023.09 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        In this study we examine variations in the structure of perovskite compounds of LaBa2Cu2O9, LaBa2CaCu3O12 and LaBa2Ca2Cu5O15 synthesized using the solid state reaction method. The samples’ compositions were assessed using X-ray fluorescence (XRF) analysis. The La: Ba: Ca: Cu ratios for samples LaBa2Cu2O9, LaBa2CaCu3O12 and LaBa2Ca2Cu5O15 were found by XRF analysis to be around 1:2:0:2, 1:2:1:3, and 1:2:2:5, respectively. The samples’ well-known structures were then analyzed using X-ray diffraction. The three samples largely consist of phases 1202, 1213, and 1225, with a trace quantity of an unknown secondary phase, based on the intensities and locations of the diffraction peaks. According to the measured parameters a, b, and c, every sample has a tetragonal symmetry structure. Each sample’s mass density was observed to alter as the lead oxide content rose. Scanning electron microscope (SEM) images of the three phases revealed that different Ca-O and Cu-O layers can cause different grain sizes, characterized by elongated thin grains, without a preferred orientation.
        4,000원
        59.
        2023.09 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        This study focuses on how the partial substitution of copper by nickel nanoparticles affects the electrical and structural properties of the Bi2Ba2Ca2Cu2.9Ni0.1O10+δ, Bi2Ba2Ca2Cu2.8Ni0.2O10+δ and Bi2Ba2Ca2Cu2.6Ni0.4O10+δ compounds. Approximate values of crystallization size and crystallization percentage for the three compounds were calculated using the Scherer, modified Scherer, and Williamson-Hall methods. A great similarity was observed in the crystal size values from the Scherer method, 243.442 nm, and the Williamson-Hall method, 243.794 nm for the second sample. At the same time this sample exhibited the highest crystal size value for the three methods. In the examination of electrical properties, the sample with 0.1 partial substitution, Bi2Ba2Ca2Cu2.9Ni0.1O10+δ was determined to be the best with a critical temperature of 100 K and an energy gap of 6.57639 × 10-21 MeV. Using the SEM technique to analyze the structural morphology of the three phases, it was discovered that the size of the granular forms exceeds 25 nm. It was determined that the samples’ shapes alter when nickel concentration rises. The patterns that reveal the distribution of the crystal structure also exhibit clear homogeneity.
        4,000원
        60.
        2023.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The emergence of Mo2C- based catalysts in recent years has been favored as promising contender within diverse class MXenes. In terms of rapid development in the photocatalytic application, these intriguing compounds exhibit excellent photocatalytic performance because of their superior optical properties and peculiar structure characteristics. Unfortunately, a systematic review of Mo2C- based catalysts is lacking. In this review, we abstract the implication of structure—property relationship of emerging Mo2C- based MXenes materials and their applications toward the photocatalytic hydrogen evolution reaction (HER). Furthermore, synthetic pathways to prepare high-quality, low cost Mo2C- based MXenes materials and their outcomes for high HER applications are systematically described. Finally, several insights are provided into the prospects and future challenges for the development of highly reactive Mo2C- based MXenes materials, which present large range opportunities in this promising 2D materials for green and clean energy in environmental fields. This review provides a comprehensive scientific guide to the preparation, modification, and photocatalytic HER of MXenes-based materials.
        4,600원
        1 2 3 4 5