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        검색결과 151

        1.
        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.
        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
        8.
        2018.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We present the analysis of KMT-2016-BLG-0212, a low flux-variation (Iflux−var ∼ 20 mag) microlensing event, which is in a high-cadence (Γ = 4hr −1) field of the three-telescope Korea Microlensing Telescope Network (KMTNet) survey. The event shows a short anomaly that is incompletely covered due to the brief visibility intervals that characterize the early microlensing season when the anomaly occurred. We show that the data are consistent with two classes of solutions, characterized respectively by low-mass brown-dwarf (q = 0.037) and sub-Neptune (q < 10−4) companions. Future high-resolution imaging should easily distinguish between these solutions.
        4,000원
        9.
        2018.07 구독 인증기관·개인회원 무료
        Export diversification – the extent to which the firm seizes export sales opportunities across different nations and/or geographic regions – is a critical element of export marketing strategy. Yet, knowledge of the export performance consequences of export diversification is lacking. Underpinned by contingency and resource dependence theories, we examine the export diversification-export performance relationship as well as critical contingencies of this link. Based on a sample of UK exporters we find that firms gain the highest export performance benefits when they simultaneously increase national and regional export diversification. Our results also show that the export diversification-export performance link is weaker when firms operate in markets that are very in dynamism. Additionally, the relationship between export diversification and performance is stronger when both resource sharing and interfunctional coordination are high. Such contextual factors provide a better understanding of the diversification-performance relationship.
        10.
        2018.07 구독 인증기관·개인회원 무료
        Researchers have yet to investigate whether it is beneficial for exporters to engage in greater levels of product adaptation in their export operations, or whether there is some limit to the amount of adaptation exporters should engage in. We posit that customer value creation, a central marketing concept and a mechanism to achieving market and financial goals in business to business markets, is a core outcome of export product adaptation activities. In order to explore the routes by which adaptation may shape export customer value creation, we adopt a multi-faceted conceptualization of firm-level product adaptation, comprising export product adaptation (i) quantity, (ii) intensity and (iii) novelty. Drawing on survey data from 249 Finnish exporters involved in business-to-business activities, we find evidence to support the claim that the impact of export product adaptation on export customer value creation is contingent on various factors, and we identify instances where greater adaptation is beneficial for export customer value creation, and instances where greater export product adaptation is potentially harmful for export customer value creation.
        11.
        2018.07 구독 인증기관·개인회원 무료
        Cause-related marketing is a pervasive, global marketing tactic, and the practice grew by 18.5 percent between 2011 to 2016 (IEG 2017). While considerable academic research has been directed to understanding this practice and its impact on consumers, one aspect has received little attention. Almost nothing is known about the impact on consumer perceptions when a firm withdraws from a partnership. Firms withdraw their support of a charity for many reasons (i.e., the charity no longer resonates with major stakeholders, the sponsorship fails to produce the projected results for the charity or the firm, or the firm faces financial constraints). We conducted three on-line experiments with samples of North American adult consumers to address this knowledge gap. We examined the impact of three types of withdrawal on consumer perceptions: withdrawal from a partnership, replacement of one non-profit partner with another partner, withdrawal from a partnership and a price decrease offered based on the savings resulting from terminating the sponsorship. Given that the extant research established that the alignment of the cause with the core business of the firm is an important factor in the success of CRM strategies, we manipulated this variable along with the various withdrawal scenarios. Our findings reveal that consumers view a divorce negatively despite actions taken by firms to offset consumers’ negative views.
        14.
        2018.05 구독 인증기관·개인회원 무료
        The world-wide need to reduce the energy used and the greenhouse gases emitted during cement manufacture has led to the pursuit of more eco-efficient materials, such as ground granulated blastfurnace slag(GGBS) and fly ash. Especially, GGBS is a by-product generated during the manufacture of pig ions. GGBS can be divided into water-cooled slag(WS) and air-cooled slag(AS). With comparison of WS, the AS is formed by allowing the molten slag to cool relatively slowly under ambient conditions. This study presents experimental findings on the mechanical and durability performance of cement concrete pavement with replacement of cement by WS and/or AS. In order to produce concrete specimens, total replacement of cement by GGBS(WS+AS) was fixed at 40% by mass. Concrete specimens were regularly monitored for the variation of mechanical properties such as flexural strength, compressive strength and initial surface absorption. In addition, in order to assess durability of concrete pavement with WS and/or AS, the chloride ion penetration resistance and scaling resistance tests were adopted, and the corresponding results were compared to those of plain concrete pavement. The test results indicated that the performance of concrete pavement was significantly dependent on the replacement level of WS by AS. Concrete specimens incorporating 20% replacement level of AS showed a poor mechanical performance, while 5% replacement of AS showed a beneficial effect both mechanical and durability performance. Especially, the 5% AS replacement led to the higher resistance of concrete pavement against frost-salt action. Based on the experimental results, the present study would be helpful to design high-performance cement concrete pavement.
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