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        검색결과 43

        4.
        2018.05 구독 인증기관·개인회원 무료
        In recent years, pavement distresses have been caused by diverse factors such as spalling, deterioration of repaired sections, blow-up, and alkali aggregate reaction due to changing climate environment of a concrete pavement and its construction and maintenance conditions (supply of materials, increase in use of de-icers, etc,). As a leading repair method for deteriorated concrete pavements, partial-depth repair is implemented in accordance with guidelines of material properties for joints of a concrete pavement and field application evaluation systems, but still some of the repaired sections become deteriorated again at an early stage due to poor construction quality and failure of response to environmental impacts. Distresses that can be corrected with partial-depth repairs are largely divided into those of repair materials and of the existing pavement bonded to repair materials, and combined distress of repair materials and the existing pavement. Although re-repair methods should be different by distress type and scale than conventional pavement repair methods, appropriate repair methods and guidance for re-repairs have not been in place so far, and therefore currently, re-repair practices follow the existing manual of partial depth repairs. Therefore, this study evaluated concrete bond characteristics by removing method and repair scope for an experimental section of frequently distressed pavements to determine a re-repair scope and method for deteriorated partial depth repair sections of concrete pavement, the number of which has increased over time.
        5.
        2018.05 구독 인증기관·개인회원 무료
        Composite pavements are constructed by placing a high functional asphalt surface layer on a high performance concrete rigid base layer and provide a more durable, high functional surface to road users. Service life of composite pavements is dependent on the bonding performance of the lower rigid base and the flexible surface layer. Accordingly, it is necessary to place an impermeability layer between the functional surface layer and the rigid base to enhance bonding performance and to prevent moisture penetration into the rigid base and deterioration of pavement. In order to use optimal composite pavement sections, two types were applied to impermeability layer: highly impermeable water-tight SMA and mastic asphalt currently in use. APT (Accelerated Pavement Testing) and experimental construction were carried out to evaluate bond strengths between the rigid base and the impermeability layer depending on the type of impermeability layers. Composite pavement sections for the APT had a 22 cm concrete rigid base layer and a 5cm functional surface, as well as either 5cm of SMA impermeability layer and 5cm of mastic layer. After applying around 8,574,000 ESALs, pull-off test was conducted, which showed that the mastic section outperformed the SMA section. In the experimental construction, three types of rigid base layers, JCP (Jointed Concrete Pavement), CRCP (Continuously Reinforced Concrete Pavement), and RCCP (Roller Compacted Concrete Pavement), were used for composite pavement sections, and as in the APT, two types of impermeability layers, SMA and mastic, were used per rigid base layer of new and deteriorated concrete pavement. Therefore, seven composite pavement sections in total were constructed. We measured the bond strength over one year or so following the construction of these composite pavement sections and found that regardless of the type of rigid base layer and whether it was new or not, those sections with a mastic impermeability layer had high bond strengths.
        6.
        2016.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study was conducted to investigate the effects of various mulching materials on growth and yield of okra (Abelmoschus esculentus L. Moench). Three kinds of polyethylene (PE) mulching materials were used which are: black (Black), green (Green), and white and black on both sides (White), black non-woven fabric (Fabric), and barley straw (Straw) and the control plot (Control) were also used in this study. The change of soil temperature was observed in various mulching materials with Green showing the highest average temperature of 24.4o, followed by Black > Fabric > Control > White > Straw. The variation of plant length,, aboveground weight, and root weight were constant in the order of Green > Black > White > Fabric > Control > Straw. Total yield (number of fruits) were 281,000 in Green which was the highest yield, and the least was from Straw which was 62.3% of Green. Total weight of fruits in Green was 395 kg which was the heaviest, and in Straw was least with 226 kg Hence, the weight of fruits
        4,000원
        7.
        2014.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study examined relationships among healthy food awareness, behavioral intention toward healthy foods, and actual behavior of Generation Y consumers. This study hypothesized that Generation Y consumers are aware of healthy foods and more likely to eat healthy foods while avoiding junk foods. According to structural equation modeling, all hypothesized paths were statistically significant, meaning that the three constructs in the model showed positive relationships with each other. Results showed that this group of college students is generally aware of healthy foods and have positive intentions toward healthy food choices. Therefore, university foodservice management needs to continue to improve their menus in order to attract this new generation of college student consumers.
        4,000원
        8.
        2014.07 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Amorphous agglomerates of carbon nanospheres (CNS) with a diameter range of 10-50 nm were synthesized using the solution combustion method. High-resolution transmission elec-tron microscopy (HRTEM) revealed a densely packed high surface area of SP2-hybridized carbon; however, there were no crystalline structural components, as can be seen from the scanning electron microscopy, HRTEM, X-ray diffraction, Raman spectroscopy, and ther-mal gravimetric analyses. Electrochemical and thermo catalytic decomposition study results show that the material can be used as a potential electrode candidate for the fabrication of energy storage devices and also for the production of free hydrogen if such devices are used in a fluidized bed reactor loaded with the as-prepared CNS as the catalyst bed.
        4,000원
        12.
        2010.12 구독 인증기관 무료, 개인회원 유료
        Oleanolic acid is a natural triterpenoid that exists widely in foods and some medicinal herbs. The purpose of this study was to determine the antimicrobial activity of oleanolic acid against Streptococcus mutans strains isolated from a Korean population. Antimicrobial activity against these bacteria was evaluated by minimal inhibitory concentration (MIC) and time kill curves. The tolerance of human gingival fibroblasts and human periodontal ligaments to oleanolic acid was tested using a methyl thiazolyl tetrazolium (MTT) assay. The MIC90 value of oleanolic acid for both S. mutans and S. sobrinus isolated from Koreans was 8μg/mℓ. Oleanolic acid showed bactericidal effects against S. mutans ATCC 25175T and S. sobrinus ATCC 33478T at 1 × MIC(8μg/mℓ) and had no cytotoxic effects against KB cells at this dose. The results suggest that oleanolic acid could be useful in the future development of oral hygiene products for the prevention of dental caries.
        4,000원
        13.
        2009.08 구독 인증기관·개인회원 무료
        Mycotoxin producing moulds are commonly in contact with forage in the field before harvest, during harvesting, drying and transport and during storage. Therefore, this study was to isolate and identify fungi contaminated rice straw in the earlier spring of Korea. The pure fungi colony was isolated from normal rice straws in the tree dairy farms. The fungi were cultured on MEA and PDA agar plate and confirmed by sequencing the ITS region. Fungal contamination was found in all samples of rice straws and mold counts averaged 4.6×10⁴ per gram. The mycotoxigenic fungi found were Penicillium roqueforti and Fusarium culmorum. Other several fungi were determined Gibberella moniliformis, Ascomycota sp., Myrothecium sp. When the rice straw samples were analyzed mycotoxins by HPLC, it was not found aflatoxins, zearalenone, deoxynivalenol, fumonisin, ochratoxins A and T-2 toxin. The results suggest t㏊t the mold contaminated rice straw is not activated in the spring of cool season but is able to develop in the coming warm and humidly summer, specially mycotoxigenic fungi such ase Penicillium roqueforti and Fusarium culmorum.
        14.
        2009.08 구독 인증기관·개인회원 무료
        Although winter rye is now widely grown as a silage crop in Korea, but silage quality of the winter rye produced from farmer's fields have not been published. Therefore, this experiment was conducted to evaluate forage quality of winter rye which was participated in Forage Quality Contest in 2008. These data were classified by resign, forage production, added inoculants, planting date, and harvest date. Difference on lactic acid of rye silage was detected in forage production (p<0.01), however, there were no significant differences among the rye silage tested. The moisture and lactic acid were significant differences in dry matter yield of rye silage. There is all the difference between silage added inoculants and control. The pH, ash, CP, NDF and ADF of rye added with inoculants were higher t㏊n those of control silage, however, the TDN and lactic acid were increased in silage added with inoculants. The ash and CP were significant differences in planting date, but lactic acid was significant differences in harvest date. This experiment indicates t㏊t lactic acid of silage was good indicator for evaluation of rye silage. Differences in forage quality were also observed among winter rye silage. Therefore, nutritional quality as well as lactic acid is important in silage quality contest of winter rye silage.
        15.
        2009.05 구독 인증기관·개인회원 무료
        The present investigation establishes deltamethrin resistance in the common bed bug, Cimex lectularius, populationcollected from New York City (NY-BB). The mortality resistance ratio indicated that NY-BB population was 264-fold more resistant to 1% deltamethrin in contact bioassay compared to one insecticide- susceptible population collected in Florida (FL-BB). Specific enzyme activities (general esterase, glutathione S-transferase, and 7-ethoxycoumarin O-deethylase) of NY-BB were not statistically different from those of FL-BB, indicating that the metabolic factors are not associated with the deltamethrin resistance in NY-BB. Complementary DNA fragments that encoded the open reading frame of voltage-sensitive sodium channel α-subunit genes from the FL-BB and NY-BB were obtained by homology probing PCR and sequenced. Sequence alignment of the internal and 5’ and 3’ RACE fragments generated a 6500 bp cDNA sequence contig, which was composed of a 6084 bp open reading frame (ORF) encoding 2027 amino acid residues and 186 bp 5’ and 230 bp 3’ untranslated regions (5’ and 3’UTRs, respectively). Sequence comparisons of the complete open reading frames of the sodium channel genes identified two point mutations (V419L and L925I) that were presented only in the NY-BB population. L925I, located the intracellular loop between IIS4 and IIS5, has been previously found in the pyrethroid-resistant populations of whitefly (Bemisia tabaci) that was more than 100-fold resistant to fenpropathrin. V419L, located in the IS6 transmembrane segment, is a novel mutation. This evidence suggests that the two mutations are likely the major resistance-causing mutations in the deltamethrin-resistant NY-BB via a knockdown-type nerve insensitivity mechanism.
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