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        검색결과 1,353

        382.
        2016.07 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        A cold roll-bonding process was applied to fabricate an AA1050/AA6061/AA1050 laminate complex sheet. Two AA1050 and one AA6061 sheets of 2 mm thickness, 40 mm width and 300 mm length were stacked up after surface treatment that included degreasing and wire brushing; material was then reduced to a thickness of 3 mm by one-pass cold rolling. The laminate sheet bonded by the rolling was further reduced to 1.2 mm in thickness by conventional rolling. The rolling was performed at ambient temperature without lubricant using a 2-high mill with a roll diameter of 210 mm. The rolling speed was 5.0 m/sec. The AA1050/AA6061/AA1050 laminate complex sheet fabricated by roll bonding was then hardened by natural aging T4) and artificial aging (T6) treatments. The microstructures of the as-roll bonded and the age hardened Al complex sheets were revealed by optical microscope observation; the mechanical properties were investigated by tensile testing and hardness testing. The strength of the as-roll bonded complex sheet was found to increase by 2.9 times compared to that value of the starting material. In addition, the hardness of the complex sheets increased with cold rolling for AA1050 and age-hardening treatment for AA6061, respectively. After heat treatment, both AA1050 and AA6061 showed typical recrystallization structures in which the grains were equiaxed; however, the grain size was smaller in AA6061 than in AA1050.
        4,000원
        383.
        2016.06 구독 인증기관·개인회원 무료
        Ganoderma lucidum, a species of the class Basidiomycetes, attracts international attention due to the wide variety of its biological activities and great potential as cosmetic ingredient, such as skin care cosmetics including ‘skin-whitening’. However, there is little information available regarding the tyrosinase inhibitory activity. Therefore, the objectives of this study were to investigate the chemical composition and tyrosinase inhibitory activity of the G. lucidum. To isolate active single compound from G. lucidum (GASC), we conducted ethanol extraction and chloroform fractionation. In addition, we assayed the inhibitoty effect of tyrosinase activity and melanin biosynthesis in B16F10 mouse melanoma cells. In the present study, we identified a GASC, which exhibited inhibitory effects of cellular tyrosinase activity, the protein expression of cellular tyrosinase and tyrosinase-related protein-1, 2. In additional, microphthalmia-associated transcription factor (MITF), as known as crucial regulator of melanogenesis-related genes, was down-regulated by treatment with GASC in a concentration-dependent manner. GASC exhibited significant inhibition of tyrosinase activity and melanin synthesis in B16F10. The finding that melanogenesis inhibitory effect of GASC will contribute to facilitate various approaches of this mushroom for use in skin whitening products.
        384.
        2016.06 구독 인증기관 무료, 개인회원 유료
        Mammals have 3 pairs of major salivary glands i.e., the parotid, submandibular, and sublingual glands. Saliva secretion of these glands is modulated by taste perception. Salivary glands are composed mainly of acinar and ductal cells. Primary saliva is secreted by acinar cells and modified during ductal flow. Recently, of the murine 35 bitter taste receptors, Tas2r108 was expressed at highest levels in the submandibular gland by qPCR. Further, Tas2r108-transfected cells respond to a range of bitter compounds, such as denatonium, quinine, colchicine, diphenidol, caffeine and dapson. The objective of the present study was to characterize the expression of Tas2r108 mRNA in acinar and/or ductal cells of the submandibular gland using in situ hybridization (ISH). Male 42-60 days old DBA2 mice were used in the study. Messenger RNAs were extracted from the submandibular gland for generating digoxigenin (DIG) labeled-cRNA probes. These probes were transcribed in anti-sense and sense orientation using T7 RNA polymerase. Dot blot hybridization was performed using DIG labeled-cRNA probes, in order to estimate integrity and optimal diluting concentration of these probes. Subsequently, ISH was performed on murine submandibular gland to detect Tas2r108 mRNA. Dot blot hybridization data demonstrated that Tas2r108 DIG labeled-cRNA anti-sense probes specifically detected Tas2r108 cDNA. ISH results showed that the anti-sense probes labeled acinar and ductal cells in the submandibular gland, whereas no staining was visible in sense controls. Interestingly, the Tas2r108 expression levels were higher in acinar than ductal cells. These results suggested that Tas2r108 might be more associated with primary saliva secretion than with ductal modification of saliva composition.
        4,000원
        385.
        2016.06 구독 인증기관·개인회원 무료
        박층 아스팔트 포장공법 적용을 위해 10 ㎜ 밀입도 아스팔트 혼합물의 골재 입도 기준을 제시하고자 하 였다. 골재 입도는 강성, 안정도, 내구성 등 물성뿐 아니라 피로, 마찰, 수분 저항성 등을 포함한 아스팔 트 혼합물의 거의 모든 특성에 영향을 미친다. 기존에 사용하는 밀입도 아스팔트 혼합물 골재 입도의 경 우 Fuller와 Thompson이 제안한 퓰러 모델(Fullerʼs Model)에 기반을 두고 있다. 본 연구에서 적용코자 하는 박층 밀입도 아스팔트 포장의 경우 포장두께가 얇아짐에 따라 균열에 취약해질 수 있으므로 아스팔 트 혼합물 품질에 각별한 주의가 필요하다. 국내 아스팔트 혼합물은 가열 아스팔트 혼합물 기준(SPS-KAI0002-F2349)을 적용하며 13 ㎜와 20 ㎜ 밀입도 아스팔트 혼합물에 대한 기준은 있으나 박층 포장용 10 ㎜ 밀입도 기준은 포함되어 있지 않다. 퓰 러 모델을 이용하여 10 ㎜ 밀입도 아스팔트 혼합물의 골재 입도 산정시 최대밀도선과 근접한 입도곡선을 보였다. 최대밀도선과 근접한 밀입도 아스팔트 혼합물의 경우 골재 최대크기가 작고 좁은 구간에 분포되 어 연약한 혼합물이 되는 경향을 나타내었다. 본 연구에서는 골재 다짐시험을 통ㅎ나 골재 입형 및 입도 특성에 기반한 10 ㎜ 밀입도 아스팔트 혼합물 합성입도를 제시하였다. 제시입도와 최대밀도선 입도에 의 해 제작된 혼합물 비교결과 제시 입도로 제작한 혼합물이 최대밀도선 입도 혼합물 대비 간접인장강도는 약 11%, 터프니스는 약 15% 향상되어 혼합물 안정성 확보에도 효과적임을 확인할 수 있었다.
        387.
        2016.04 구독 인증기관·개인회원 무료
        The initial production scale of wind tower is very few. But recently, the production scale of wind tower structure has increased gradually because it maximizes the efficiency in green energy. Many researchers are studying the wind tower, but there is no study about the difference of allowable buckling stress of the wind tower with and without opening. Guideline of codes and standards are very limited when designing a wind tower with an opening. It is also rarely that a study considers the design of the wind tower to be a tubular shell with or without an opening. ABAQUS, a general purpose finite element program, which provides safety evaluation and economical standards for the design and behavior of the wind tower considering the effect of opening was used in the study. Finally, results from this study can serve as reference for structural engineers, manufacturers and further studies of wind turbine when designing a tubular shell wind tower with an opening.
        392.
        2016.04 구독 인증기관·개인회원 무료
        복숭아순나방은 사과, 배 등 핵과류 과실의 심식류로서 일차해충이다. 따라서 살포 농약과 접촉을 피할 수 있어 화학적 방제에 어려움을 주고 있다. 성페로몬을 이용한 교미교란 기술이 개발되어 방제 가능성을 제시하였다. 그러나 효과적 교미교란제 처리는 광범위한 지역에 비교적 다량의 성페로몬이 투여되기에 이에 따른 막대한 방제 비용은 이 기술의 제약점이다. 이를 해결하기 위한 방향으로 효모를 이용한 성페로몬 생합성 기술이 대안책으로 대두되었다. 본 연구는 이를 위해 복숭아순나방의 성페로몬 생합성에 특이적 △10 desaturase의 유전자 특성을 규명하는 데 목표를 두었다. 성페로몬샘 의 전사체 분석은 최소한 3 종류의 후보 △10 desaturase 유전자를 찾아냈다. 이 가운데 Gm_comp1575 전사체의 유전자 구조를 밝혔다. 추정된 전체 아미노산 길이는 371 개로서 다른 desaturase와 유사한 길이를 나타냈고, 복숭아순나방 성페로몬에 서 발현되었다. 현재 이 유전자의 기능 분석이 이뤄지고 있다.
        393.
        2016.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        PURPOSES: The objective of this study was to determine the optimum ratio of mix design, for a reclaimed asphalt pavement (RAP) content of 100%, for spray injection application. METHODS: A literature review revealed that spray injection is an efficient and cost-effective application for fixing small defective regions of an asphalt pavement. Rapid-setting polymer-modified asphalt mixtures prepared from two types of rapid-setting polymer asphalt emulsion were subjected to Marshall stability and wet track abrasion tests, in order to identify the optimum mix designs. RESULTS and CONCLUSIONS : Different mix designs of type A and type B emulsions were prepared using RAP and virgin aggregates, in order to compare the performance and determine the optimum mix design. The performance of mixtures prepared with RAP was superior to that of mixtures containing virgin aggregates. Moreover, for optimum ratio of the design, the binder content prepared from RAP was set to 1~2% lower than that consisting of virgin aggregates. Compared to their Type A counterparts, type B mixtures consisting of a reactive emulsion performed better in the Marshall stability and wet track abrasion tests. The initial results confirmed the advantages associated with using RAP for spray injection applications. Further studies will be performed to verify the difference in the optimum mix design and performance obtained in the lab-scale test and tests conducted at the job site by using the spray injection machine.
        4,200원
        394.
        2016.03 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        TGS(Tomographic Gamma Scan)분석 기술은 방사성폐기물 드럼을 10×10×16개의 단위부피로 분할하여 분할단위 마다 밀 도 및 방사능 농도를 각각 측정하기 때문에 기존 기술에 비해 높은 분석정확도를 갖는 장점에 비하여 낮은 정밀도를 갖는 단 점이 있다. 이를 보완하기 위해 하나의 에너지를 구별하는 전흡수피크(Full Energy Peak)의 범위(ROI : Region of Interest) 를 넓게 설정하여 정밀도를 최적화한다. 하지만 전흡수피크의 범위 증가는 인접한 에너지를 방출하는 핵종간 상호간섭이 발 생할 확률이 높아진다. 본 연구에서는 TGS분석에서 기준 핵종인 137Cs(661.66 keV 반감기 30.5 년) 정량분석에 간섭을 일으 키는 원인을 규명하였으며 그 원인으로 인접한 110mAg(657.75 keV 반감기 249.76 일)임을 확인하였다. 이러한 간섭을 제거 할 수 있는 방안으로 최적화된 ROI를 결정할 수 있는 새로운 교정기술을 개발하였으며 본 교정기술을 적용 후 정확도 검사 에서 기준핵종 137Cs을 정확히 판정함을 확인하였다.
        4,000원
        395.
        2016.03 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        A roll-bonding process was applied to fabricate an AA1050/AZ91/AA1050 laminate complex sheet. Two AA1050 and one AZ91 magnesium sheets of 2 mm thickness, 30 mm width and 200 mm length were stacked up after surface treatment that included degreasing and wire brushing; material was then reduced to a thickness of 3 mm by one-pass cold rolling. The laminate sheet bonded by the rolling was further reduced to 2 mm in thickness by conventional rolling. The rolling was performed at 623K without lubricant using a 2-high mill with a roll diameter of 210 mm. The rolling speed was 15.9 m/min. The AA1050/AZ91/AA1050 laminate complex sheet fabricated by roll bonding was then annealed at 373~573K for 0.5h. The microstructure of the complex sheets was revealed by electron back scatter diffraction (EBSD) measurement; the mechanical properties were investigated by tensile testing and hardness testing. The strength of the complex sheet was found to increase by 11 % and the tensile elongation decreased by 7%, compared to those values of the starting material. In addition, the hardness of the AZ91 Mg region was slightly higher than those of the AA1050 regions. Both AA1050 and AZ91 showed a typical deformation structure in which the grains were elongated in the
        4,000원
        396.
        2016.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        10 wt.% and 20 wt.%Li-TiO2 composite powders are synthesized by a sol-gel method using titanium isopropoxide and Li2CO3 as precursors. The as-received amorphous 10 wt.%Li-TiO2 composite powders crystallize into the anatase-type crystal structure upon calcination at 450oC, which then changes to the rutile phase at 750oC. The asreceived 20 wt%Li-TiO2 composite powders, on the other hand, crystallize into the anatase-type structure. As the calcination temperature increases, the anatase TiO2 phase gets transformed to the LiTiO2 phase. The peaks for the samples obtained after calcination at 900oC mainly exhibit the LiTiO2 and Li2TiO3 phases. For a comparison of the photocatalytic activity, 10 wt.% and 20 wt.% Li-TiO2 composite powders calcined at 450oC, 600oC, and 750oC are used. The 20 wt.%Li-TiO2 composite powders calcined at 600oC show excellent efficiency for the removal of methylorange
        4,000원
        397.
        2015.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this study, we investigated the concentrations of PM10 and CO2 in public transportation vehicles (express bus, train, KTX, and subway) reported by previous indoor air quality (IAQ) surveys carried out from 2005 to 2013 in Korea. The number of valid data for PM10 was 566 and for CO2 was 579, and all data were classified according to whether it was collected during rush-hour or non rush-hour. PM10 and CO2 concentrations in subway cabin during the rush-hour were 1.3 and 1.45 times higher, respectively, than those of non rush-hour (p<0.05) in terms of geometric mean value. PM10 and CO2 concentration of express bus and train during the rush-hour also were 1.23 times higher than those of non rush-hour with relatively weak correlations (p=0.246). Among all PM10 concentrations, 16.9% and 3.8% of PM10 concentrations exceeded the IAQ guidelines (200 μg/m3 for non-rush hour and 250 μg/m3 for rush-hour), respectively. In terms of CO2 concentrations, 10.5% and 3.0% of them exceeded the IAQ guidelines (2,500 ppm for non rush-hour and 3,000 ppm for rush-hour), respectively. As a result, concentrations of PM10 and CO2 were estimated to be dominantly influenced by the operation characteristics of public transportation, such as degree of congestion and type of vehicle. In order to improve the IAQ of public transportation vehicles, specific air purification and ventilation systems are needed, depending on the characteristics of public transportation vehicles.
        4,000원
        398.
        2015.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The concern of fine particle (PM2.5) management of outdoor environments has been increasing due to its exposure and related health effects in Korea. As a result, PM2.5 standard in atmosphere environment was regulated in 2015. On the other hand, indoor PM2.5 standard has been required because most people spent their times in indoor environments. In this study, we measured the PM2.5 and PM10 concentrations both indoor and outdoor environments of public-use facilities such as underground stations, underground shopping centers, and nurseries for 24 hour with filter-weighing method in Seoul and Daegu. Measurement duration was from March to April in 2014 during the Asian dust period. At all measurements, indoor to outdoor (I/O) concentration ratios exceeded 1 except 1 day nursery in Daegu in spite of Asian dust period. The ratios of PM2.5 to PM10 concentrations ranged from 0.63 to 0.75 in indoor environments, and from 0.63 to 0.82 in outdoor, indicating that PM2.5 should be carefully managed in indoor environments as well as outdoor atmosphere.
        4,000원
        399.
        2015.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        As a part of the short-period variability survey (SPVS) at Bohyunsan Optical Astronomy Observa- tory, we obtained time-series BV CCD images in the region of the open cluster NGC 1039 (M34). The observations were performed for 22 nights from July 29, 2008 to September 26, 2010. We also made LOAO observations for 10 days from September 18, 2009 to October 30, 2010 to confirm the small variabilties of δ Scuti-type variable stars. In this paper we presented the observational properties of 28 variable stars found in the region. They are seven δ Scuti-type variable stars, two Doradus-type variable stars, four- teen eclipsing binary stars and five semi-long periodic or slow irregular variables, respectively. Only three variables were listed in the GCVS and the rest are newly discovered ones. We have performed multiple- frequency analysis to determine pulsation frequencies of the δ Scuti-type and ɤ Doradus-type variable stars, using the discrete Fourier transform and linear least-square fitting methods. We also have derived the periods and amplitudes of 12 eclipsing binaries from the phase fitting method, and presented the light curves of all variable stars.
        4,300원
        400.
        2015.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This research investigated changes in Joseon food culture mainly focusing on acceptance of Western food in the enlightenment period. Joseon intended to learn the advanced technology of the West. Through an exchange with various Western countries, the royal family and upper class of Joseon rapidly accepted foreign food and food culture. As hotels were built in Incheon and Seoul, foreign food became more widely provided, which spread to the public, accordingly, and Western style restaurants were built and spread to the Busan area besides Seoul. As Western food rapidly spread, concerns arose. Particularly, after an attempt to assassinate Gojong by inserting poison into his coffee in 1898, appeals were made concerning Western food “that should not be consumed, because it is not proper for Korean people's intestines and stomach”.
        4,300원