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        검색결과 209

        121.
        1996.11 KCI 등재 구독 인증기관 무료, 개인회원 유료
        A new one series of chiral schiff's base containing benzylidene aniline moieties was synthesized and characterized by IR, 1H NMR. elementary analysis, and polarized optical microscopy(POM). The yield of these synthetic compounds was in the range of 62~67℃. The results showed that most of the synthetic compounds were monotropic liquid crystal and exhibited chiral smectic C(Sc*) liquid crystal phases, and the range of phase transition temperature was to 71.4℃ from 45.0℃.
        4,000원
        122.
        1996.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The phase separated structure and the electo-optical properties of the polymer /liquid crystal(LC) composite films including a dye were investigated. The phase separated structure of the polymer /LC / dye composite film(GH composite film) including below 2wt% dye against LC was almost same with the composite film which does not include dye. But the electro-optical properties of the GH composite film strongly depended on weight fraction of the dye against the LC. The response time of the GH composite film increased with the increase of the dissolved dye in LC because the dye acts as a registivity for the orientation of LC molecules by the electric filed.
        4,000원
        123.
        1995.11 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The phase separated structure and the electro-optical properties of the (polymer/liquid) crystal : LC) composite film strongly depended on the weight fraction of LC in it. The continuous LC phase was formed in a three-dimensional polymer network when the LC weight fraction was above 40wt%. The aggregation structure of the composite film could be controlled by controlling the solvent evaporation velocity during the film preparation process. The smaller LC domains or channels were formed in the case of the faster solvent evaporation velocity. The composite film exhibited reversible light scattering-light transmission switching upon electric field -OFF and -ON states, respectiverly. The light scattering properties of the composite film strongly depended on the spatial distortion of the nematic directors as well as the mismatch in refractive indices between matrix polymer and LC.
        4,200원
        124.
        1993.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Emission of hazardous and volatile organic chemicals from solid waste landfill site was become to important issue because of environmental pollution and health risk by such chemicals. Laboratory batch and continuous experiments were conducted respectively to elucidate isothermal sorption behaviors and transport phenomena(by gas through unsaturated solid waste layer) in wet solid waste-gas system. Source separated and size reduced refuse(bulky waste) and incinerated ash were used after controlling water content, and trichloroethylene(TCE) was chosen among many such chemicals because of it's generality among those man-created pollutants. Isothermal TCE sorption equilibria wet solid waste-gas system can be described in linear equation and partition coefficient in this system can be estimated approximately by the simple equation derived from schematic structure of the system. Transport equation modified by instantaneous equilibrium sorption fraction and kinetic sorption rate(overall mass transfer capacity coefficient) simulated well the column experiment results.
        4,800원
        132.
        2023.09 KCI 등재 서비스 종료(열람 제한)
        본 연구에서는 고압 환경에서 합성된 결정 입자의 크기에 원시료(starting materials)의 상(phase)이 미치 는 영향을 확인했다. 상이 다른 두 가지 원시료인 비정질 시료와 나노파우더 시료를 이용해 알루미늄이 부화된 고 압의 환원환경에서 삼원계 시스템인 브리지마나이트-페리클레이스-칼슘 페라이트(calcium ferrite)상의 MgAl2O4을 합성했다. 시료는 40 GPa 2000 K의 압력온도 조건에서 20 시간 동안 가열하여 합성했다. 합성된 시료는 비정질 시료를 이용한 경우 입자 크기가 50-200 nm였으며, 나노파우더를 이용한 경우 ~500 nm로 나타났다. 이러한 차이 는 1) 시료가 합성된 2000 K의 온도가 낮아 비정질 시료의 경우 결정 성장보다 결정핵 성장이 더 우세하게 나타 났거나 2) 시료에 존재할 수 있는 산화 환원반응 상태의 차이로 생각된다. 추후 다원계 시스템에 대한 고압 실험을 수행할 때 비정질 시료보다 나노파우더를 원시료로 이용하는 것이 결정 성장에서 더 유리할 것으로 생각된다.
        133.
        2019.04 서비스 종료(열람 제한)
        All over the world, concrete gravity dams have to withstand lots of environmental hazards and time-varying external loading during an earthquake. Therefore, the risk assessment of this structure with time may become an important study for the dam structure, which is related to the chemo-mechanical effect on the aging concrete. The focusing point of this study is to propose an earthquake assessment procedure to determine the failure probability with time of any concrete gravity dam for the future if we consider the material deterioration. This material decay is mainly associated with the modulus of elasticity of the concrete and it is explained briefly in the manuscript.
        134.
        2019.04 서비스 종료(열람 제한)
        The earthquake risk prediction for dam structure has been considered as an important analysis. The dam has to interact with water in its lifetime, which maybe induces the chemo-mechanical phenomenon on the aging concrete and damage the capacity of the structure. The main aim of this research is to suggest a procedure to predict the operant condition of the dam based on Cumulative Absolute Velocity (CAV) values after some decades. CAV is a method ordinarily used in Nuclear Power Plant (NPP) fields, but in case of a concrete gravity dam, it will be the new addition along with the aging effect of concrete material.
        135.
        2019.04 서비스 종료(열람 제한)
        An approach is presented for evaluating the vulnerability of electric cabinet in nuclear power plants. The method is based on the lognormal approach, including the maximum likelihood estimation and linear regression to establish the fragility curves. These procedures are applied for a cabinet considering various boundary conditions, which are expressed by restrained and anchored models at the base. The cabinet models have been built and verified by using the system identification technique. The results show that the fragility curves obtained for the anchored model are found to be closer to each other, compared to the fragility curves for the restrained model.
        136.
        2018.10 서비스 종료(열람 제한)
        When conducting the seismic response analysis on a long elevated structure, if the transmitting boundary is set at both ends of the analysis region, there is a condition that the response becomes larger than in the case of the free boundary. In this research, we studied the influence of the effective duration time of earthquake motion on the maximum displacement amplitude of earthquake response and the response energy of earthquake when carrying out similar analysis using viscous boundary. As a result, it was confirmed that the correlation between the effective duration and the relationship between the viscous boundary and the maximum displacement amplitude ratio of the free boundary is low. On the other hand, for the relationship between the effective duration time and the response energy ratio between the viscous boundary and the free boundary, the variance was small and a certain correlation was confirmed.
        137.
        2018.05 서비스 종료(열람 제한)
        Background : Osteoarthritis is an inflammatory disorder related with oxidative stress and apoptosis leading to cartilage damage. Recently, Cirsium japonicum var. maackii (CJM) was reported to play a protective role in various inflammatory response. However, the role of CJM in cartilage degeneration and osteoarthritis progression is still unknown. Therefore, this study aims to investigate the protective effect of CJM in a animal model of osteoarthritis and cartilage degradation. Methods and Results : First, in order to determine active ingredient contents of CJM, we were carried out total polyphenolic content and total flavonoid content analyses. As a result, dried aerial parts of CJM were found to contain 149.2 ± 24.1 ㎎·GAE/g dry weight and 27.9 ± 2.0 ㎎·NE/g dry weight in boiling water extraction. Also, the HPLC analysis of CJM showed major compounds identified as cirsimarin and cirsimaritin. In addition, CJM protected against osteoarthritic cartilage destruction in an osteoarthritis mouse model induced by destabilization of the medial meniscus, as demonstrated by histopathological analysis. Conclusion : The results of this study demonstrate that CJM may protect against the osteoarthritis and cartilage destruction. Further study is needed to identify the mechanism for their improvement effects of osteoarthritis and cartilage destruction.
        138.
        2018.05 서비스 종료(열람 제한)
        Background : Oxidative stress and inflammatory response are important features of the brain pathology of Alzheimer's disease. Therefore, the purpose of this study was to the antioxidant activity and biochemical characterization of safflower seed. Moreover, we investigated the impact of Safflower seed on scopolamine-induced memory impairment in mice. Methods and Results : First, in order to determine active ingredient contents of safflower seed extract, we were carried out total phenol content and total flavonoid content analyses. As a result, dried safflower seed were found to contain 35.4 ± 0.4 ㎎·GAE/g dry weight and 45.3 ± 7.5 ㎎·NE/g dry weight in boiling water extraction. Also, the major compounds of safflower seed from HPLC analysis were identified as serotonin and serotonin derivatives [N- (p-coumaroyl)serotonin and N-feruloylserotonin]. In addition, the antioxidant activity of safflower seed showed IC50 values of 331.4 and 168.2, respectively, against DPPH and ABTS in vitro. Finally, with regard to the memory improvement activity, the administration of Safflower seed extract significantly restored memory impairments induced by scopolamine in the behavior tests such as novel object recognition and Morris water maze test. Conclusion : The results of our study suggest that the safflower seed extract possess potent memory improvement activity and are also a good source of natural antioxidants. Further study is needed to identify the mechanism responsible for their memory improvement activity.
        139.
        2018.05 서비스 종료(열람 제한)
        Background : Obesity, a global health problem and a chronic diseases, is associated with increased risk of developing type 2 diabetes and coronary heart diseases. A wide variety of natural remedies have been explored for their obesity treatment potential. To elucidate the anti-obesity effect of ginsenoside Rg5 : Rk1 (Rg5 : Rk1), a mixture of protopanaxadiol type ginsenosides isolated from Panax ginseng Meyer in a 3T3-L1 adipocytes. Methods and Results : In order to determinate the anti-obesity effect of Rg5 : Rk1, Oil Red O staining and triglyceride (TG) content was assessed. Furthermore, to elucidate the possible mechanism whether Rg5:Rk1 affects lipid accumulation, mRNA and protein expression analyses of adipocyte markers such as STAT3, PPARγ, CBEPα and ap2 were carried out. Rg5:Rk1 treatment showed an inhibition of lipid droplet accumulation and decrease on TG content. In addition, expression of STAT3, PPARγ, CEBPα and ap2 were decreased in dose dependent manner. Similar to these results, Rg5:Rk1 treatment reduced PPARγ and CEBPα protein expression. Conclusion : Rg5 : Rk1 treatment exhibits anti-adipogenic activity by down-regulation of the STAT3PPARγ/CEBPα pathway in 3T3-L1 adipocyte cell line.
        140.
        2018.05 KCI 등재 서비스 종료(열람 제한)
        본 연구에서는 프리스트레스 긴장력의 위치와 크기에 따른 거더의 횡비틀림 안정성 실험을 수행하였다. 거더를 이용한 횡방향 거동 및 안정성 실험은 재료의 비선형성, 초기 기하학적 불완전성, 긴장력의 변화, 하중조건과 지지조건 등 다양한 변수에 의해 예상치 못한 결과를 발생시킬 수 있다. 따라서, 본 연구에서는 프리스트레스 거더 축소 모형 실험안을 제안하여 긴장력에 의한 횡비틀림 안정성을 실험을 수행 하였다. 하중 가력조건과 면내 및 면외 지지조건을 만족하며 긴장력을 조절할 수 있는 실험장치를 제안하고 제작하였다. 실험결과 하부 플랜지에 긴장력이 작용하는 경우 횡비틀림 안정성을 증가시켰으며, 최종적으로 긴장력의 위치와 크기에 따라 횡비틀림 안정성을 평가할 수 있는 해석식을 제안하였다.