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        검색결과 15

        1.
        2022.10 구독 인증기관·개인회원 무료
        The underground environment has an advantage to minimize the external influences because it is isolated space with surrounded rock medium. Therefore, underground rock has been used recently as the target for a disposal system of spent fuel with high-level radioactive. The disposal system mainly consists of natural barrier (i.e., surrounded rock medium) and engineered barrier (i.e., concrete lining, plug, backfill, canister, and buffer). In particular, the engineered barrier is important for long-term storage because it has to preferentially block the leakage of radioactive nuclide. Non-destructive technologies (NDT) have been utilized to monitor the state of disposal system for considering the limitation in deep depth conditions such as limited environment for direct damage inspection. Acoustic emission (AE) monitoring technique is an effective method to monitor the damage (crack) magnitude, history (i.e., crack evolution), and location using high-frequency elastic waves. To apply the AE monitoring method in the disposal system, the characteristics of damaged materials should be considered. The concrete lining has multi-failure behavior (i.e., brittle and ductile) resulted from composition as cement and reinforcing steel bar. Therefore, it important to investigate the AE characteristics according to the failure level of reinforced concrete for damage monitoring of the disposal systems. In this study, the four-point bending tests were carried out to measure the AE signals from the cracking of reinforce concrete specimens in laboratory. The test specimens were prepared with different strength. After the experiment, the AE characteristics were analyzed using the AE parameters with loading and failure state in the curve of time-stress. This study will be helpful for damage monitoring using AE technique in the field of high-level radioactive disposal system.
        4.
        2015.12 구독 인증기관 무료, 개인회원 유료
        This study calculated the overall heat transfer coefficient (U-value) of greenhouse covering materials with thermal screens using a simulation model and then estimated the validity of the calculated results by comparison with measured values. The U-value decreased gradually as the thickness of the air space between the double glazing increased, and then remained essentially constant at thicknesses exceeding 25 mm. The U-value also increased with the difference in temperature between the inside and outside of the hot box. The vigorous convective heat transfer between two plastic films caused unsteady heat flow and then created a nonlinear temperature distribution in the air space. The distance did not affect the U-value at distances of 50~200 mm between the plastic covering and thermal curtain. The numerical calculation results, with and without sky radiation, were in accord with the experimental results for a 30°C temperature difference between the inside and outside of the hot box. In conclusion, a reliable Uvalue can be calculated for a temperature difference of 30°C or more between the inside and outside of the hot box.
        4,000원
        5.
        2006.09 구독 인증기관·개인회원 무료
        Dispersion-strengthened copper with was produced by ball-milling and spark plasma sintering (SPS).Ball-milling was performed at a rotation speed of 300rpm for 30 and 60min in Ar atmosphere by using a planetary ball mill (AGO-2). Spark-plasma sintering was carried out at for 5min under vacuum after mechanical alloying. The hardness of the specimens sintered using powder ball milled for 60min at 300rpm increased from 16.0 to 61.8 HRB than that of specimen using powder mixed with a turbular mixer, while the electrical conductivity varied from 93.40% to 83.34%IACS. In the case of milled powder, hardness increased as milling time increased, while the electrical conductivity decreased. On the other hand, hardness decreased with increasing sintering temperature, but the electrical conductiviey increased slightly
        6.
        2006.09 구독 인증기관·개인회원 무료
        Cu- nanocomposite powders were synthesized by combining high-energy ball-milling of Cu-Ti-B mixtures and subsequent self-propagating high temperature synthesis (SHS). Cu-40wt.% powders were produced by SHS reaction and ball-milled. The milled SHS powder was mixed with Cu powders by ball milling to produce Cu-2.5wt.% composites. particles less than 250nm were formed in the copper matrix after SHS-reaction. The releative density, electrical conductivity and hardness of specimens sintered at were nearly 98%, 83%IACS and 71HRB, respectively. After heat treatment at 850 to for 2 hours under Ar atmosphere, hardness was descedned by 15%. Our Cu- composite showed good thermal stability at eleveated temperature.
        7.
        2019.08 KCI 등재 서비스 종료(열람 제한)
        본 연구의 목적은 여러 가지 하지입식검사에 적용할 수 있는 Multi-Function Device(MFD)를 제작하여 기 존에 사용하던 Weight Bearing Platforms(WBPs)들과 X 선 영상의 비교를 통해 임상 활용을 제안하고자 한 다. MFD는 단상(보조기구)를 이용한 Weight Bearing Foot/Ankle, Hindfoot Alignment View 검사시 X선 장치 의 X선 관구의 최하 조절 높이를 고려하여 제작하였다. 그리고 Foot/Ankle Phantom으로 MFD와 WBPs에서 Weight Bearing Lateral Foot과 Hindfoot Alignment View를 검사하여 X선 영상의 해상력을 Quick MTF(modula tion transfer function)프로그램으로 비교하였다. 연구결과 MFD와 WBPs에서 검사한 두 가지 영상 모두 MTF 50(50% Contrast Spatial Frequency)과 10-90%(10-90% of Maximum Energy Rise Distance) Rise의 C/P(Cycles Pe r Pixel)평균과 LPH(Lines Per Image Height)평균 모두 유의한 차이는 없었다(p>0.05). 연구에서 제작한 MFD 는 환자의 안전과 여러 가지 검사를 복합적으로 수행 할 수 있는 유용한 보조기구로 임상 활용을 제안한 다. 또한 정책적으로 보조기구의 활용을 권장한다면 전문 업체의 활성화를 돕는 길이며 의료의 질도 더욱 향상할 수 있을 것이다.
        8.
        2019.08 KCI 등재 서비스 종료(열람 제한)
        Purpose – This study aims to explore women's beauty industry market and growth development by identifying the main factors of women's perception of skin health care. Research design, data, and methodology – The survey was conducted on women aged 20 to 60 living in Seoul. For the statistical analysis, frequency analysis, t-test and one-way ANOVA were conducted, and significant differences in p<0.05 were tested through the multiple range test of the Scheffe. The factor analysis was conducted to verify the validity of questions, and the reliability was determined by the coefficient of Cronbach's α. Results – The lower the age, the higher the perception of the skin, and women pay a higher price for skin health as a provisional customer. 'Acne care' was the most common skin condition (32.8%), 'life style' (79.8%) was the most important part of skin care. Final education was the highest level of skin care for women with a professional background (M=3.41) (F=4.028, p<.05). Conclusions – The differences in the recognition of health knowledge by age, marital status, and household monthly income were significant, but there was no difference between jobs and final education. Customers who use less skin care than customers who frequently use the skin care center were more aware of skin health, and women who have a high awareness of skin are more interested in aging and regenerating due to the skin care.
        9.
        2012.06 KCI 등재 서비스 종료(열람 제한)
        A new species of Chrysosplenium (Saxifragaceae), C. epigealum J.W.Han & S.H.Kang is described from Mt. Seoraksan, Inje-gun, Gangwon-do, Korea. This new species is distinct from C. flaviflorum Ohwi, its closely relative species, in having calyx 2-2.5 mm long, pistils slightly shorter than calyx, filaments 2-3 times longer than anthers and stolons epigeal.
        10.
        2007.06 KCI 등재 서비스 종료(열람 제한)
        To develop a clinically available saponin- or sapogenin complex from Oriental medicines, the EtOH extract (KPRG-A) was obtained by extracting from the four crude drugs, Kalopanacis Cortex, Platycodi Radix, Rubi Fructus and Glycyrrhizae Radis. The BuOH fraction (KPRG-B), a crude saponin complex, was prepared by fractionating KPRG-A, which were further completely hydrolyzed to afford the sapogenin complex (KPRG-D). In an attempt to find the antinoicpetive effects of the saponin complex and sapogenin complex, KPRG-C, and -D, were assayed by writhing-, hot plate-, and tail-flick tests using mice or rats. The three samples were also subjected to antiiflammatory tests using serotonin-induced and carrageenan-induced hind paw edema mice and rats, respectively. The three samples significantly reduced inflammations and pains of the experimental animal. The potency were found in the order of KPRG-D> KPRG-C> KPRG-B. The most active sample, KPRG-D, caused no death, no body increase or no anatomical pathlogic change even at 2,000 mg/kg dose. These results suggest that a sapogenin complex, KPRG-D, which was found to contain mainly hederagenin, platycodigenin, polygalacic acid, 23-hydroxytormentic acid, glycyrrhetic acid together with minor triterpene acids, could be a potential candidate for antiinflammatory therapeutics.