• Journal of Industrial Convergence
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• v.20 no.9
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• pp.47-58
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• 2022

Digital content is difficult to distinguish between the original and the replica due to its nature. For this reason, NFT technology using blockchain technology is attracting attention because it can guarantee the proof and scarcity of the original digital content. However, the NFT buyer does not own the copyright to the digital content, but the ownership. In particular, since the minting process of issuing NFTs is possible for anyone, there is a copyright threat to the copyright holder. In this study, we propose a verification protocol based on DID for the process of issuing and transacting NFTs for copyright protection of copyright holders' digital contents. As a research method, the problems of research cases related to digital contents were analyzed and the safety was comparatively analyzed. NFT issuance can only be issued by copyright holders whose identity has been verified through DID, and only users who have completed authentication can participate in the transaction to prevent indiscriminate theft and use of digital content and form a safe and transparent transaction market.

• Membrane Journal
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• v.34 no.2
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• pp.140-145
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• 2024

In modern times, when a change in the energy paradigm is required, hydrogen is an attractive energy source. Among these hydrogen purification technologies, technology using a membrane is attracted attention as a technology that can purify high purity hydrogen at low cost. However, palladium(Pd), which is mostly used because of its excellent hydrogen separation performance, is very expensive, so a replacement material is needed. In this study, a alloy membrane was manufactured from an alloy of niobium (Nb), which has high hydrogen permeability but is weak to hydrogen embrittlement, and nickel (Ni) and zirconium (Zr), which have low hydrogen permeability but are highly durable. Hydrogen permeation characteristics were confirmed under conditions of 350~450 ℃ at 1 to 4 bar. The maximum hydrogen permeation flux was 0.69 ml/cm²/min for the Ni₄₈Nb₃₂Zr₂₀ alloy membrane without Pd coating, and 13.05 ml/cm²/min for the Pd coated alloy membrane.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.708-712
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• 2012

Ionic liquids (ILs) existing as liquid state at room temperature are composed of a immense heterocyclic cation and inorganic anion which is smaller than cation's size. Thus, the species of cation and anion as well as the length of alkyl group on the cation have influence on their physical properties. Their outstanding properties such as non-volatility, thermal stability and wide range of electrochemical stability make these materials excellent candidates for green solvent which can substitute the conventional organic solvents. In this study, ILs based on imidazolium cation have been synthesized such as 1-butyl-3-methylimidazolium bromide ([BMIM][Br]), 1-butyl-3-methylimidazolium chloride ([BMIM] [Cl]), 1-butyl-3-methylimidazolium iodide ([BMIM][I]), and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][$BF_4$]). The density, viscosity, refractive index, heat capacity and ionic conductivity of [BMIM][Br], [BMIM][I], and [BMIM] [$BF_4$] were measured over range of temperature of 293.2 to 323.2 K. The density and refractive index values of [BMIM][I] were the highest among three ILs and the viscosity values of [BMIM][Br] were the highest among three ILs. The heat capacities [BMIM][$BF_4$] were higher than those of [BMIM][Br]. The ionic conductivities of [BMIM][$BF_4$] were higher than those of [BMIM][I].

• Applied Chemistry for Engineering
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• v.26 no.6
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• pp.640-647
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• 2015

As the need for next-generation flexible electronics grows, novel materials and technologies that can replace conventional indium tin oxide (ITO) for transparent electrodes have been of great interest. Among them, a conducting polymer, especially poly(3,4-ethylenedioxythiophene) : poly(styrene sulfonate) (PEDOT : PSS) is one of the most promising candidates because it is mechanically flexible, inexpensive, and capable of being processed in solution. Currently, there are a lot of research efforts on enhancing its electrical conductivity to the level of ITO or metal electrodes through chemical and/or physical processing. In this review article, we present various additives and pre-/post-deposition processing methods for improving the electrical conductivity of PEDOT : PSS. Some of representative reports are also introduced, which demonstrated the use of conductivity-enhanced PEDOT : PSS as transparent electrodes in electronics and energy conversion.

• Journal of Adhesion and Interface
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• v.21 no.3
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• pp.81-85
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• 2020

Shaving dust is a collagen fiber that is the leather waste occurred for thickness adjustment during the natural leather manufacturing process, and causes problems such as an environmental contamination because of a chromium (Cr) contained when it comes to reclaiming process. Various studies applying the shaving dust are currently being conducted in many countries across the world with an initiative by the EU. Of those applications, the bonded leather is being highlighted as a substitute for natural leather. Since the bonded leather, however, uses latex as a binder, accordingly it entails a high weight and a poor ventilation, which are deemed as disadvantages due to its dense internal tissues compared to other synthetic leathers. To address such disadvantages, this study employed the thermally expandable micro sphere to improve its air permeability and light weight by alleviating the internal structure. This is a study on the manufacturing of light bonded leather using the shaving dusts. In the study, the shaving dusts were forced to foam under 100~120℃ considering the heat resistance of collagen fiber after applying the thermally expandable micro sphere, and then the tendency was analyzed. In the analysis results, the most excellent foaming rate was exhibited when the shaving dusts were treated under 120℃ for 8 minutes and the variation of internal structure according to a foaming was observed through SEM analysis for the cross-section of the bonded leather.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.6
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• pp.743-749
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• 2005

Estrogen is known to play an important role in maintaining bone mass, since the concentration of serum estrogen decrease after menopause and the estrogen deficiency results in bone loss. Phytoestrogens are plant compounds with estrogen-like biological activity, In this study, to investigate the bioactivities of phytoestrogen, which act on bone metabolism, we examined the effect of selected food-borne phytoestrogens (genistein, daidzein and resveratrol) on osteoblast proliferation and IGF-I production using MC3T3-El cells, a mouse calvaria osteoblast-like cell line. Cells were cultured in a serum free medium for 48 hr in the presence of genistein $(10^{-5}\;M)$, daidzein $(10^{-5}\;M)$ and resveratrol $(10^{-5}\;M)$. The effects of genistein, daidzein and resveratrol on the cell proliferation and growth were evaluated by total cell numbers, MTS assay and cell migration assay. Their effect was compared with the $17\beta-estradiol$. Genistein, daidzein and resveratrol exhibited stimulatory effects on the growth of MC3T3-El cells, and the most pronounced effect was shown with daidzein. In addition, these phytoestrogen increased alkaline phosphatase activity of MC3T3-El cells. These effects were similar to that of $17\beta-estradiol$ effects. Moreover, treatment with genistein, daidzein and resveratrol increased production of insulin like growth factor-I (IGF-I) in conditioned media, indicating that the growth promoting effects of these phytoestrogen were related to the changes in production of IGF-I by MC3T3-El cells. These results show that genistein, daidzein and resveratrol have a stimulatory effect on osteoblast function, and that these findings in a cell model may prove relevant to protecting against the loss of bone mass and the development of osteoporosis in human subjects.

• Korean Journal of Construction Engineering and Management
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• v.11 no.6
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• pp.35-44
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• 2010

For efficient maintenance management of bridges, an establishment of asset management system is necessary which helps prediction of maintenance cost and strategic allocation of budget in consideration of top priority. The main purpose of this study is to suggest asset valuation method, which is practical in conformity with domestic situations, through researches on asset valuation method of bridges. This study has researched asset valuation method of bridge, which is appropriate for domestic situations by finding out advantages and disadvantages through investigating domestic and foreign application examples of asset valuation method for bridge facilities. In this study, asset valuation method by historical cost and replacement cost were suggested and a valuation model for bridges was established. In addition, two suggested valuation methods were applied to actual bridges which is used in Korea. As the result, it was analyzed that bridge asset valuation method in consideration of historical cost is desirable for the accounting purpose. And, it was analyzed that valuation method utilizing depreciated replacement cost(DRC), which could consider various factors, is desirable for the maintenance decision supporting purpose.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.6
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• pp.577-582
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• 2013

AZO (aluminum-doped zinc oxide) is one of the best candidate materials to replace ITO (indium tin oxide) for TCOs (transparent conductive oxides) used in flat panel displays, organic light-emitting diodes (OLEDs), and organic solar cells (OSCs). In the present study, to apply an AZO thin film to the transparent electrode of an organic solar cell, a low-temperature selective atomic layer deposition (ALD) process was adopted to deposit an AZO thin film on a flexible poly-ethylene-naphthalate (PEN) substrate. The reactive gases for the ALD process were di-ethyl-zinc (DEZ) and tri-methyl-aluminum (TMA) as precursors and H2O as an oxidant. The structural, electrical, and optical characteristics of the AZO thin film were evaluated. From the measured results of the electrical and optical characteristics of the AZO thin films deposited on the PEN substrates by ALD, it was shown that the AZO thin film appeared to be comparable to a commercially used ITO thin film, which confirmed the feasibility of AZO as a TCO for flexible organic solar cells in the near future.

• Journal of the Korea Concrete Institute
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• v.25 no.2
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• pp.187-194
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• 2013

Fiber reinforced polymer (FRP) has been gathering interest from designers and engineers for its possible usage as a replacement reinforcement of a steel reinforcing bar due to its advantageous characteristics such as high tensile strength, non-corrosive material, etc. Since it is manufactured with various contents ratios, fiber types, and shapes without any general specification, test results for concrete members reinforced with these FRP reinforcing bars could not be systematically used. Moreover, since investigations for FRP reinforced members have mainly focused on short-term behavior, the purpose of this study is to evaluate long-term behaviors of glass FRP (GFRP) reinforcing bar and concrete beams reinforced with GFRP. In this paper, test results of tensile and bond performance of GFRP reinforcing bar and creep behavior are presented. In the creep tests, results showed that 100 years of service time can be secured when sustained load level is below 55% of tensile strength of GFRP reinforcing bar. A modification factor of 0.73 used to calculate long-term deflection of GFRP reinforced beams was acquired from the creep tests for GFRP reinforced concrete beams. It is expected that these test results would give more useful information for design of FRP reinforced members.

• Korean journal of communication and information
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• v.27
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• pp.247-282
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• 2004

The purpose of this study is to examine the mobile phone service usage patterns of Korean teenagers and their motivation to use it, and to explore the relationships between the teenagers' social-psychological characteristics and their trails of mobile phone usage. After reviewing prior theoretical studios, three hypotheses regarding the research questions shown above were generated. Questionnaire study was conducted with 400 high school students in Busan and Ulsan metropolitan areas. They were to answer three categories of questions, such as frequencies of voice calls and text messaging services and the other mobile services, questions asking their social-psychological characteristics, and their motivations for using mobile phone services. Findings show that the teenagers more likely to tend to use voice calls when communicating family members. They tend to avoid those services with high rate of use as multimedia, game, and broadcasting services via mobile phones. The teenagers use mobile phone services for the similar purposes to conventional telephone uses. Therefore, the classical theories showing the alternative purposes or motivations to use conventional telephone usage, which divided the main purposes for phone uses in to two; work/instrumental and socializing/entertaining, proved to be reasonable. The cheap messaging services with texts are popular among the teenagers and are used for socializing/entertaining purposes rather than instrumental/functional purposes. In addition, the teenagers' social-psychological characteristicss are significantly associated with the amount of mobile phone uses. A characteristic of "individual-centeredness" is positively related with non-voice service uses, while "group-centeredness" explains heavy amount of using voice calls and text messaging services. Such characteristics as "immediacy," "directness," "innovativeness," and "other-direction" are positively associated with the frequencies and amounts of mobile phone uses, while "inner-direction" and "tradition-direction" are negatively correlated.