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      • KCI등재

        The effect of SiO2 on the performance of inorganic sludge-based structural concretes

        Zheng Xun Yang,Na Ra Ha,이종국,Min Sik Jang,황규홍 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.3

        As a relatively new material, geopolymer concrete offers benefits as a construction material for sustainable development. It utilizes waste materials such as recycled concrete sludge, fly ash, etc. It has a very low rate of green house gas emission when compared to ordinary Portland cement. In this study, the components of geopolymer are concrete sludge, metakaolin and water glass. NaOH was used as an alkaline activator. To improve the mechanical properties, silica fume was added as a bonding matrix from 0%-10% to replace part of the concrete sludge, and the specimens were cured in air, then their mechanical properties such as compressive strength and bending strength were measured and their microstructures were investigated.

      • KCI등재

        Provably Secure Aggregate Signcryption Scheme

        Xun-Yi Ren,Zheng-Hua Qi,Yang Geng 한국전자통신연구원 2012 ETRI Journal Vol.34 No.3

        An aggregate signature scheme is a digital signature scheme that allows aggregation of n distinct signatures by n distinct users on n distinct messages. In this paper, we present an aggregate signcryption scheme (ASC) that is useful for reducing the size of certification chains (by aggregating all signatures in the chain) and for reducing message size in secure routing protocols. The new ASC scheme combines identity-based encryption and the aggregation of signatures in a practical way that can simultaneously satisfy the security requirements for confidentiality and authentication. We formally prove the security of the new scheme in a random oracle model with respect to security properties IND-CCA2, AUTH-CMA2,and EUF-CMA.

      • Improvement of the stability of hydroxyapatite through glass ceramic reinforcement.

        Ha, Na Ra,Yang, Zheng Xun,Hwang, Kyu Hong,Kim, Tae Suk,Lee, Jong Kook American Scientific Publishers 2010 Journal of Nanoscience and Nanotechnology Vol.10 No.5

        <P>Hydroxyapatite has achieved significant application in orthopedic and dental implants due to its excellent biocompatibility. Sintered hydroxyapatites showed significant dissolution, however, after their immersion in water or simulated body fluid (SBF). This grain boundary dissolution, even in pure hydroxyapatites, resulted in grain separation at the surfaces, and finally, in fracture. In this study, hydroxyapatite ceramics containing apatite-wollastonite (AW) or calcium silicate (SG) glass ceramics as additives were prepared to prevent the dissolution. AW and SG glass ceramics were added at 0-7 wt% and powder-compacted uniaxially followed by firing at moisture conditions. The glass phase was incorporated into the hydroxyapatite to act as a sintering aid, followed by crystallization, to improve the mechanical properties without reducing the biocompatibility. As seen in the results of the dissolution test, a significant amount of damage was reduced even after more than 14 days. TEM and SEM showed no decomposition of HA to the secondary phase, and the fracture toughness increased, becoming even higher than that of the commercial hydroxyapatite.</P>

      • KCI등재

        MRAS Genetic Variation is Associated with Atherothrombotic Stroke in the Han Chinese Population

        Hua Liu,Xiao Qin Huang,Min Yang,Xun Ming Ji,Xin Du,Jian Zheng 대한신경과학회 2013 Journal of Clinical Neurology Vol.9 No.4

        Background and Purpose Atherothrombotic cerebral infarction [atherothrombotic stroke (ATS)] shares common risk factors and pathophysiological mechanisms with coronary artery disease (CAD), and both diseases appear to have common susceptibility loci. The muscle RAS oncogene homolog gene (MRAS) has been identified as a susceptibility locus for CAD and is implicated in atherosclerosis. The aim of this study was to elucidate whether the single-nucleotide polymorphisms (SNPs) and haplotypes of MRAS are associated with increased risk of ATS in a population of Han Chinese. Methods A case-controlled association study was conducted in which only patients with ATS (identified as a major subtype in the Korean modification of the Trial of Org 10172 in Acute Stroke Treatment classification) were enrolled. Subgroup analyses were carried out to determine whether the effect of the MRAS polymorphism was specific to age and gender among the subjects. Results In total, 194 ATS and 186 control subjects were included in the present study. Two tagging SNPs were identified in MRAS (rs40593 and rs3755751). A multivariate regression analysis revealed a positive association between rs40593 and ATS under dominant and additive models after adjustment for covariates. Subgroup analyses revealed that there were no gender differences with respect to allele or genotype frequencies between the groups. The AG genotype for rs40593(p=0.028), the CT genotype for rs3755751 (p=0.036), and G-allele carriers (AG plus GG) for rs40593 (p=0.015) exhibited a significant protective effect among those aged ≥45 years. For the haplotype analysis, ATS subjects aged ≥45 years had a higher frequency of the ACAC haplotype (76.0%) than the controls (68.1%; p<0.05); that haplotype was associated with an increased risk of ATS. Conclusions The obtained data suggest a positive association between MRAS and ATS among the Han Chinese. Further studies should be performed with larger sample and among different ethnic populations, and gene-gene or gene-environment interactions should be considered.

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