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        검색결과 5

        3.
        2018.05 구독 인증기관·개인회원 무료
        The ride quality (i.e. smoothness) is a key factor for evaluating the construction quality of expressway asphalt pavement. Conventionally, three paving devices are widely used to control the surface layer thickness: leveling sensor (i.e. LS), short-range-surfacing-contact-ski (i.e. SSCS) and long-range-surfacing-contact-ski (i.e. LSCS). However, each of these levelling tools presents one major drawback. In the case of LS, if the original sub-layer evenness is poor, the final asphalt pavement surface and its smoothness will be negatively affected. The SSCS cannot assure satisfactory smoothness when relatively long paving section (in the order of 10 km) are paved. While the LSCS would reduce the drawback of the SSCS, its weight on the one hand and its length on the other discourage its use in the paving site especially for curved sections. In this paper, a next generation pavement smoothness leveling equipment, known as non-contact-digital-ski (i.e. NCDS) was implemented, evaluated and compared to the conventional equipment leveling device. The international Roughness Index (IRI m/km) was measured on sections paved with and without NCDS and the results visually and statistically compared. In addition, for the same sections, the modulus of the pavement layers was computed and compared by means of Falling Weight Deflectometer (i.e. FWD). It was observed that when NCDS is used for asphalt pavement overlay of existing concrete pavement, significant improvement in IRI (i.e. IRI<1.0m/km) and consistently uniform elastic modulus could be achieved compared to the conventional levelling and paving method.
        4.
        2017.11 구독 인증기관·개인회원 무료
        In plants, starch is the main carbohydrate reserve and an important ingredient in human nutrition. Nutritionally, starch is classified into rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) based on the rate and degree of digestion. RS escapes enzymatic digestion in the small intestine, but in the large intestine microbial flora may ferment some RS. Malic acid is C4 carboxylic acid with two carboxyl groups. It is well known to take from 69% up to 92% of all organic acids in grape berries and leaves and is naturally produced by many organisms without showing any nutritional harm. However, properties of malic acid treated starch has not been clearly reported. The objectives of this study were to investigate the influence of pH value on low-digestible malate starch formation and digestibility in relation to structural properties of corn starch. Different pH values (1.5-8.5) of 2 M malic acid solution were reacted with corn starch in a forced-air oven at temperature of 130°C for 12 hr. Using FT-IR, carbonyl groups were detected in malate starch, indicating the formation of cross-linking by esterification. Increasing pH value of malic acid-treated sample from 1.5 to 8.5 showed an increase in degree of substitution (DS) and resulted in increase in the RS content from 18.2 to 74.8%, which was maintained after gelatinization. The granular structure of malate starches was not destroyed, and the starches maintained birefringence. This malate starch could be utilized in heat processed foods such as bread and cookies as well as in the products with reduced calories.
        5.
        2017.11 구독 인증기관·개인회원 무료
        Starch is classified as fast digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS) depending on digestibility. RS can avoid enzymatic digestion in the small intestine, but microbes in the large intestine can ferment some RSs. The purpose of this study was to investigate the structural characteristics of low digestible starch by malic acid mutation in rice, corn and potato starch. Rice, corn and potato starch were treated with a 2M malic acid solution in a forced air oven at 130 ° C for 12 hr. Using FT-IR, carbonyl groups were detected in malate starch, indicating the formation of cross-linking by esterification. And, Using X-ray, diffractograms of malic acid-treated starch. In the micrographs, malate treated corn and potato starch granules were marked with elliptical or polygonal shapes and starch retained birefringence. Through microscopic observe in morphology of starch granules, Microscopic observation did not reveal any changes in morphology of starch granules. The modified starches had higher RS than the control and native starch. RS content of maltitized rice, corn and potato starch was 87.6%, 89.8% and 64.8%, respectively. Malic acid treated RS was maintained after the cooking process. The RS of substituted starches increased with increasing degree of substitution. These results suggest that the increase in RS content by malic acid treatment is caused by the change in the structure. And the highest resistant starch content (86.7%) was found at pH 1.5, 2M of malic acid treated corn starch. Malic acid-treated starch can be used as heat-stable and low-digestible starch containing food ingredients.