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        검색결과 29

        2.
        2024.01 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Curing agents are critical components of aqueous epoxy resin systems. Unfortunately, its uses and applications are restricted because of its low emulsifying yields. Epoxy resins are frequently used in electrical devices, castings, packaging, adhesive, corrosion resistance, and dip coating. In the presence of curing agents, epoxy resins become rigid and infusible. Eco-friendliness and mechanical functionality have emerged as vulcanization properties. Curing agents are used for surface modification, thermodynamic properties, functional approaches to therapeutic procedures, and recent advances in a variety of fields such as commercial and industrial levels. The curing agent has superior construction and mechanical properties when compared to the commercial one, which suggests that it has the potential for use as the architectural and industrial coatings. The thermal stability of cured products is good due to the presence of the imide group and the hydrogenated phenanthrene ring structure. Over the course of the projection period, it is anticipated that the global market for curing agents will continue to expand at a steady rate. The growth of the market is mainly driven by its expanding range in future applications such as adhesives, composites, construction, electrical, electronics, and wind energy. This review focused on the most recent advancements in curing techniques, emphasizing their thermal and mechanical properties. The review also presents a critical discussion of key aspects and bottleneck or research gap of the application of curing agents in the industrial areas.
        5,200원
        3.
        2022.05 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This article presents recent advancements in the development of flexible piezoresistive strain sensors based on carbon nanotubes (CNTs)–polymer composites, with particular attention to their electromechanical properties. Various fabrication approaches and material preparation of CNTs–polymer composites with improved piezoresistive performance are introduced. Moreover, the article presents the working principle of the piezoresistive sensors in terms of the tunneling effect and disconnection-reconnection mechanism. The sensing performances of recently reported applications are studied. This work also reveals that the CNTs–polymer composites have great potential for flexible, skin-mountable, and wearable electronics applications. Finally, possible challenges for the future developments of CNTs–polymer composites are discussed.
        4,600원
        4.
        2020.09 구독 인증기관 무료, 개인회원 유료
        4,000원
        5.
        2020.03 구독 인증기관 무료, 개인회원 유료
        With the growing concern of the international community about the negative spillover effects of SOEs on trade, reaching a consensus among different stakeholders has become increasingly urgent. This paper argues that strengthening a redefined competition policy is a feasible alternative, or at least a complementary option to the existing trade framework. The reasons are as follows: (a) surrounding SOEs is not only trade-related, but also competition-related; (b) the existing SOE disciplines have defects when it comes to dealing with competition distortion effects; and (c) characteristics of competition policy make it easier to reach a “maximum common divisor” among all parties. Accordingly, competition policy needs to be redefined and pursued from an international and domestic level. It is necessary to strengthen the fundamental position of competition policy in China by integrating it into SOE reform measures, advancing the implementation of the Fair Competition Review System, and promoting the construction of the competitive neutrality system.
        8,700원
        6.
        2018.07 구독 인증기관·개인회원 무료
        Since the late 1980s, information communication and technology (ICT) have reshaped the landscape of the tourism industry (Buhalis & Law, 2008). Thanks to the Web 2.0 technology, tourism practitioners have never been this close to their customers over social media platforms. According to Kaplan and Haenlein (2010), social media refers to “a group of Internet-based applications which build on the ideological and technological foundations of Web 2.0 and that allow the creation and exchange of User Generated Content” (p. 61). In line with this definition, electronic social networks, user-generated content aggregators, as well as location-based applications are all typical social media platforms, across which enable customers to create, edit, and share content. The increasingly growing social media platforms have greatly facilitated implementations of customer engagement strategies for organizations. As a psychological state, customer engagement is featured by interactive customer experiences with an organization, which encourage psychological, emotional, and physical investment a customer has in the organization (Harrigan, Evers, Miles, & Daly, 2017). In the tourism and hospitality context, customer engagement strategies are as critical in strengthening customer loyalty, trust, and brand evaluations (So, King, & Sparks, 2016). Useful insights have been gained relating to conceptualization and measurement scale of customer engagement, organizational and cultural obstacles to consumer engagement within hotel organizations (Chathoth et al., 2014), customer engagement in a social media context alongside the process of recognition (Cabiddu et al., 2014). Underlying the practical and theoretical significance of customer engagement lies the subjective nature of views on the social media platforms. Goh, Heng, and Lin (2014) recognized that engagement in social media brand communities positively lead to enhanced purchase expenditures through embedded information and persuasion. Quantitively, the persuasive effect of user generated information is at least 22 times more than that of marketer’s in terms of marginal effect. Although previous research has examined consequences of consumer engagement, there has been less attention paid to its causes. Meanwhile, as far as Brodie et al. (2011) were concerned, the persistency of consumer-brand engagement is contingent on an assessment of tangible and intangible costs against possible benefits such as product news and offers. Therefore, identification of these benefits can offer supplementary insights into current literature of consumer engagement. The current study utilizes the self-determination theory to uncover how engagement in social media activities is facilitated by consumers’ intrinsic motivators and what psychological benefits can consumer obtain from such engagement, as either psychological state or process (Brodie et al., 2011). Research subjects in this study are Chinese social media users. According to eMarketer’s (2017) estimated that more than 80 percent of Internet users in China (i.e., around 626 million people) accessed social networks regularly in 2017. The importance of tapping this massive market can never be overestimated.
        7.
        2017.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Graphite fibers are materials with a high specific modulus that have attracted much interest in the aerospace industry, but their high manufacturing cost and low yield are still problems that prevent their wide applications in practice. This paper presents a laser-based process for graphitization of carbon fiber (CF) and explores the effect of laser radiation on the microstructure of CF. The obtained Raman spectra indicate that the outer surface of CF evolves from turbostratic structures into a three-dimensional ordered state after being irradiated by a laser. The X-ray diffraction data revealed that the growth of crystallite was parallel to the fiber axis, and the interlayer spacing d002 decreased from 0.353 to 0.345 nm. The results of scanning electron microscopy revealed that the surface of irradiated CFs was rougher than that of the unirradiated ones and there were scale-like small fragments that had peeled off from the fibers. The tensile modulus increased by 17.51% and the Weibull average tensile strength decreased by 30.53% after being irradiated by a laser. These results demonstrate that the laser irradiation was able to increase the graphitization degree of the CFs, which showed some properties comparable to graphite fibers.
        4,000원
        8.
        2017.10 구독 인증기관·개인회원 무료
        The small brown planthopper (SBPH), Laodelphax striatellus, is one of the most serious pest insects of rice plants.Buprofezin has been used to control SBPH for more than a decade, however, the occurrence of buprofezin resistant SBPHwas reported recently. To develop an alternative pest control an alternative pest control strategy, RNA-seq of buprofezin-treatedSBPH was performed to screen the insecticidal target genes for RNA interference (RNAi). Six genes were selected fordsRNA synthesis, and applied to SBPH to assess the insecticidal efficacy. Two and three of those dsRNAs showed moderatedand substantial insecticidal activity up to 60% of mortality in one week, respectively. These results demonstrated the potentialof gene screening strategy for the development of RNAi-based pest management program.
        9.
        2017.04 구독 인증기관·개인회원 무료
        Rice stripe virus (RSV) is one of the serious plant pathogenic viruses for rice transmitted by small brown planthopper (SBPH), Laodalphax striatellus. RNA interference (RNAi) was recently suggested as a promising strategy for controlling insect pests, including those that serve as important vectors for plant pathogens. To disturb transmission of the RSV in SBPH using RNAi pathway, we chose nine genes highly expressed in RSV-viruliferous SBPH by transcriptome sequencing. These SBPH-derived dsRNAs were applied to the insects indirectly through xylem of rice leaves by irrigation. qPCR result demonstrated that five out of nine SBPH-derived dsRNAs successfully reduced the replication of RSV in viruliferous SBPH in dose-dependent manner, suggesting that these five dsRNAs could suppress replication of RSV and provide a new tool for RSV control strategy.
        10.
        2016.10 구독 인증기관·개인회원 무료
        The small brown planthopper (SBPH), Laodelphax striatellus, is one of the most serious pest insects of rice plants because it can transmit the rice stripe virus (RSV) which often causes significant reduction of yield in the field. Buprofezine is an effective insect growth regular (IGR) pesticide to control planthoppers, however, since the use of buprofezine for more than a decade, it has caused a certain resistance of SBPH. To survey the responses of SBPH to buprofezine, we exposed 4th instar SBPH to 200 ppm buprofezine by dipping method, and extracted total RNA for RNA-seq by Illumina platform. The quality filtered raw reads of cDNA obtained from experimental and control SBPH were subjected to Bowtie2 followed by eXpress computer program to compare the differential gene expression which will be important information for pest control methods using RNAi.
        11.
        2015.10 구독 인증기관·개인회원 무료
        Insect Growth Regulators (IGRs) are insecticides that disrupt the normal development of target insects by inducing symptoms such as premature molting or supernumerary larval stages. Juvenile hormone systems become the targets of two types of IGRs: the Juvenile Hormone Agonists (JHAs) and Juvenile Hormone Antagonists (JHANs). Pyriproxyfen is one of the chemical compounds widely used as JHA to control many kinds of insects while Kanakugiol is a plant-extracted compound which acts as JHAN. The small brown planthopper, Laodelphax striatellus, is one of the most serious pest insects of rice plants because it can transmit the rice stripe virus which often causes significant reduction of yield in the field. In order to analyze the differential gene expressions of L. striatellus upon JHA and JHAN treatment by using next generation sequencing technique, we sprayed Pyriproxyfen and Kanakugiol on 4th instar nymphs of L. striatellus respectively, and extracted total RNA for RNA-seq. The quality-filtered Illumina sequence reads of the control, JHA, and JHAN treated samples were mapped to the reference gene sequences by using the Bowtie2 software. Then the results of mapping by Bowtie2 were analyzed by eXpress software to quantity the differential gene expression.
        12.
        2014.10 구독 인증기관·개인회원 무료
        Crystals of proteinaceous insecticidal proteins, Cry proteins, produced by Bacill us thuringiensis (Bt) have been generally used used to control insect pests. In this st udy, through the 3D structure prediction and accompanying mutagenesis study for the Mod-Cry1Ac, 7 and 16 amino acid residues from domain I and II, respectively, responsible for its insecticidal activity against larvae of Plutella xylostella, Spodopt era exigua and Ostrinia furnacalis were identified. To construct novel cry genes wi th enhanced insecticidal activity, we randomly mutated these 24 amino acid sequen ces by in vitro muti site-directed mutagenesis, resulting in totally 34 mutant cry gen es. For further characterization, these mutant cry genes were expressed as a fusion protein with polyhedrin using baculovirus expression system. SDS-PAGE analysis of the recombinant polyhedra revealed that expressed Cry proteins was occluded in to polyhedra and activated stably to 65 kDa by trypsin. When the insecticidal activit ies of these mutant Cry proteins against to larvae of P. xylostella, S. exigua, and O. furnacalis were assayed, they showed higher or similar insecticidal activity compar ed to those of Cry1Ac and Cry1C. Especially, among them Mutant-N16 showed th e highest insecticidal activity against to both of P. xylostella, S. exigua and Ostrinia furnacalis. Therefore, Mutant-N16 is estimated to have the potential for the efficac ious bioagent.
        13.
        2014.07 구독 인증기관·개인회원 무료
        The Chinese outbound travel market has been one of the fastest-growing international markets for destinations, with Chinese tourist arrivals grown from 10 million to 83 million from 2000 to 2012 and their expenditures abroad reaching US102 billion in 2012 to position China as the world’s largest tourism source market in spending (CTA, 2012; UNWTO, 2013). Investigations into how Chinese tourists behave in comparison to their Western counterparts will have tremendous potential for developing insights into tourism literature, especially if previously developed Western theoretical models can interpret Chinese tourist behaviour. Practically, a better understanding of the Chinese outbound tourism phenomenon benefits destinations, which seek to effectively promote economic and social development associated with the ever-growing Chinese outbound market. The purpose of this paper is to provide a systematic, quantitative review of 118 articles published in 15 top tourism and hospitality journals between 2000 and 2012 to determine the status of research on Chinese outbound tourism. This study adopted a hybrid design that incorporated the characteristics of both the narrative and systematic quantitative review methods. The review outlines current achievements and future directions for Chinese outbound tourism research, and is pertinent to both theory building and professional practice. Based on Weaver and Lawton’s (2009) model of multi-disciplinary linkages, the 118 articles were classified into: psychology (38 articles), marketing (33), business management (16), economics (6), history (4), sociology (3), political science (1), and others (17). Credit shall be given to research efforts manifested in several areas such as travel motivation, expectations, travel barriers, destination image and preference, market segmentation and business management issues. However, much of existing literature focuses on one specific domain of sustainability – economic, reflecting an initial excitement about the development potential of this market, promoting it as an ideal source for economic growth at the destinations. The majority of studies are within the positivistic/post-positivistic paradigm. Few studies take a platform beyond advocacy to dialectically evaluate Chinese outbound tourism phenomena and impacts. In general, these studies applied existing theories to the Chinese market but fall short of making a significant breakthrough beyond the widely adopted Western models. As such, knowledge generated is to some extent fragmented and context-confined. Long-term strategic development requires recognition of the complexity and reality of the Chinese outbound tourism phenomenon as well as a need for sustainable and responsible development. In response, research needs to move toward the sustainable, knowledge-based and ethics platforms that adopt a holistic view of tourism as an integrated and interdependent system.
        14.
        2013.04 구독 인증기관·개인회원 무료
        Plasmids are crucial for determining the pathogenicity and host range of organisms of the Bacillus thuringiensis strains. In this research, a novel serogroup of B. thuringiensis serovar mogi (H3a3b3d), which showed mosquitocidal activity against Anopheles sinensis and Culex pipiens pallens, was isolated from fallen leaves in Mungyeong city, Republic of Korea. In contrast to the complicated plasmid profiles of B. thuringiensis H3 serotype strains, the B. thuringiensis serovar mogi contained two megaplasmids (> 30 MDa) on which the toxin genes were occasionally located. Sequence analysis using 454-pyrosequencing revealed that there are 7 putative cry genes, cry19Bb1, cry73Aa, cry40orf2, cry20Bb1, cry27Ab1, cry56Ba1 and cry39orf2, distributed on the two different megaplasmids, respectively. These cry genes were cloned to the Escherichia coli-B. thuringiensis shuttle vector, pHT1K under the control of its own promoter and p1KSD, which is a recombinant expression vector containing cyt1Aa promoter combined with the STAB-SD sequence, and then introduced into an acrystalliferous B. thuringiensis Cry-B strain for further molecular characterization. To investigate the role of these genes in crystal production, the expression profiles of these toxin genes were analyzed by quantitative PCR (qPCR) from the wild type strain. These results clearly indicate that the cry39orf2 was the dominant ingredient in the crystal. This novel 3a3b3d type strain, B. thuringiensis serovar mogi, could be used as a good resource for studying unknown mosquitocidal cry genes.
        15.
        2013.04 구독 인증기관·개인회원 무료
        ORF78 (ac78) of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is a baculovirus core gene of unknown function. To determine the role of ac78 in baculovirus life cycle, an ac78-deleted mutant AcMNPV, Ac78KO, was constructed. Quantitative PCR analysis revealed that ac78 is a late gene in the viral life cycle. After transfection into Spodoptera frugiperda cells, Ac78KO produced a single-cell infection phenotype indicating that no infectious budded viruses (BVs) were produced. The defection in BV production was also confirmed by both viral titration and Western blot. However, viral DNA replication is unaffected. Analysis of BV and occlusion derived virus (ODV) revealed that AC78 is associated with both forms of the virions and is a structural protein located to viral envelope. Electron microscopy showed that ac78 also plays an important role in embedding of ODV into occlusion body. This study therefore demonstrates that AC78 is a late virion associated protein and is essential for the viral life cycle.
        16.
        2013.04 구독 인증기관·개인회원 무료
        ORF11 (ac11) of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is a highly conserved gene of unknown function. To determine the role of ac11 in baculovirus life cycle, an ac11-knockout mutant AcMNPV, Ac11KO, was constructed. qPCR analysis revealed that ac11 is an early gene in the life cycle. After transfection into Spodoptera frugiperda cells, Ac11KO produced a single cell infection phenotype indicating that no infectious budded viruses (BVs) were produced. The defection in BV production was confirmed by both viral titration and Western blot. However, viral DNA replication is unaffected. Electron microscopy showed that ac11 is required for nucleocapsids envelopment to form ODV and their subsequent embedding into OB. This study therefore demonstrates that ac11 is an early gene which is essential for the viral life cycle.
        17.
        2013.04 구독 인증기관·개인회원 무료
        Crystals of proteinaceous insecticidal proteins, Cry proteins, produced by Bacillus thuringiensis (Bt) have been generally used to control insect pests. In this study, through the 3D structure prediction and accompanying mutagenesis study for the Mod-Cry1Ac, 7 and 16 amino acid residues from domain I and II, respectively, responsible for its insecticidal activity against larvae of Spodoptera exigua and Ostrinia furnacalis were identified. To construct novel cry genes with enhanced insecticidal activity, we randomly mutated these 23 amino acid sequences by in vitro muti site-directed mutagenesis, resulting in totally 24 mutant cry genes. For further characterization, these mutant cry genes were expressed as a fusion protein with polyhedrin using baculovirus expression system. SDS-PAGE analysis of the recombinant polyhedra revealed that expressed Cry proteins was occluded into polyhedra and activated stably to 65 kDa by trypsin. When the insecticidal activities of these mutant Cry proteins against to larvae of P. xylostella and S. exigua were assayed, they showed higher or similar insecticidal activity compared to those of Cry1Ac and Cry1C. Especially, among them Mutant-N16 showed the highest insecticidal activity against to both of P. xylostella and S. exigua. Therefore, Mutant-N16 is considered to have the potential for the efficacious biological insecticide.
        18.
        2012.10 구독 인증기관·개인회원 무료
        The baculovirus expression system is one of the most popular methods used for the production of recombinant proteins but has several complex steps which have proved inherently difficult to meet a multi-parellel process. We have developed a novel recombinant bacmid, bEasyBm that enabling easy and fast generation of pure recombinant virus without any purification step. In the bEasyBm, attR recombination sites were introduced to facilitate the generation of recombinant viral genome by in vitro transposition. Moreover, extracellular RNase gene from bacillus amyloliquefaciens, barnase, was expressed under the control of Cotesia plutellae bracovirus early promoter. Therefore, only when the barnase gene was replaced to gene of interest, the bEasyBm could replicate in host insect cells. When the bEasyBm was transposed with pDualBac-EGFP and pDualBac-LUC respectively, there were no non-recombinant backgrounds were detected from unpurified BmEasy-EGFP or BmEasy-LUC stocks. In addition, the resulting recombinant virus, BmEasy-EGFP, showed comparable level of EGFP expression efficiency with the plaque-purified recombinant virus, BmEGFP, which was constructed using bBmGOZA system. Based on these results, high-throughput condition for generation of multiple recombinant viruses in a time was established.
        19.
        2012.10 구독 인증기관·개인회원 무료
        Varieties of Bacillus thuringiensis (Bt) crystal proteins, Cry proteins, have so far been found as one of the most successful biological control agents which are safe to natural environments for a long time. Recently, cry genes encoding these Cry proteins have been widely applied for construction of transgenic crops resistant to pest insects. In this study, through the 3D structure prediction and accompanying mutagenesis study for the Mod-Cry1Ac, 7 and 16 amino acid residues from domain I and II, respectively, responsible for its insecticidal activity against larvae of Spodoptera exigua and Ostrinia furnacalis were identified. To construct novel cry genes with improved insecticidal activity, we randomly mutated these 23 amino acid sequences by in vitro muti site-directed mutagenesis, resulting in totally 24 mutant cry genes. For further characterization, these mutant cry genes were expressed as a fusion protein with polyhedrin using baculovirus expression system. SDS-PAGE analysis of the recombinant polyhedra revealed that expressed Cry proteins was occluded into polyhedra and activated stably to 65 kDa by trypsin. In the further study, we plan to investigate their insecticidal activity against Plutella xylostella, S. exigua and O. furnacalis larvae.
        20.
        2011.10 구독 인증기관·개인회원 무료
        Although baculoviruses have a long history of safe use as specific, environmentally benign insect control agents, their use has been limited by several factors, especially their slow speed of action. In this study, we intended to improve the insecticidal activities of Autographa californica nucleopolyhedrovirus (AcMNPV) by expressing Kunitz-type toxin isolated from venoms of Bombus ignitus or Araneus ventricosus. For this, recombinant AcMNPVs, AcBi-KTT, AcAv-Tox1 and AcAv-Tox2 expressing Bi-KTT, Av-Tox1 and Av-Tox2, respectively, under the control of p10 gene promoter were constructed. While polyhedra produced by these recombinant viruses were identical to those of the wild-type AcMNPV in shape, their sizes were relatively smaller than those of the AcMNPV. Among recombinant viruses, AcBi-KTT and AcAv-Tox2 showed significant reduction in median lethal time (LT50) against Spodoptera exigua larvae. Especiaaly, these two viruses showed about 6.2~10-folds higher polyhedra production rate compared to that of the AcMNPV. These results suggested that Kunitz-type toxins from insect venom could be successfully applied to improve insecticidal activity of baculoviruses.
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