• 콘크리트학회논문집
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• 제11권3호
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• pp.193-203
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• 1999

The corrosion of steel reinforcements in concrete is of great concern in recent years. This study is focused on the corrosion behavior of steel bars induced by internal chlorides in concrete at early ages. The main objective of this study is to determine the chloride thresholds causing depassivation and active corrosion of steel reinforcement in concrete. To examine the threshold concentration of chloride ion, the half-cell potential, chemical composition of expressed pore solutions of concrete and the rate of corosion area of the specimens were measured. Major variables include the added amount of chlorides in concrete, types of binders, and water-to-binder ration. From the present comprehensive experimental results, the factors influencing chloride-induced corrosion are investigated, and the chloride thresholds causing active corrosion of steel bars are proposed. The present study will enable to specify the realistic chloride limit in concrete which can be used in the future technical specification.

• Computers and Concrete
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• 제19권4호
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• pp.387-394
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• 2017

To study the effects of water-cement ratio changes and cracks on chloride ion transmission rate in cracked concrete, RCM method was adopted to accelerate the diffusion of chloride ion in cracked concrete, and the changes in chloride ion concentration and around the cracks are inferred by finite-element method. The test results show that as far as prefabricated cracks on concrete components are concerned, the width thresholds of two cracks on the concrete specimens with a water-cement ratio of 0.5 and 0.6 are 0.05 mm and 0.1 mm respectively, the width threshold of two cracks on the concrete specimens with a water-cement ratio of 0.4 is 0.05 mm and 0.2 mm respectively; and the results of numerical simulation show that the smaller the water-cement ratio is, the more significant effects of cracks on chloride ion transmission rate are. As a result, more attention shall be paid to the crack prevention, repairing and strengthening for high-strength concrete.

• 대한지역사회영양학회지
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• 제5권3호
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• pp.484-492
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• 2000

In an attempt to figure out the relationship between zinc status and taste acuity of old and young women, dietary zinc intake, urinary zinc excretion, and taste acuity were determined for 118 women. Zinc intake was measured by 2-day food records and food frequency method. Urinary zinc excretion was measured from urine samples collected for twenty four hours. Body fat, lean body mass (LBM), and total body water were measured by bio-impedence. Average dietary zinc intake by food record was 4.15$\pm$1.33mg (=35% if Korean RDA) for the old women and 5.41$\pm$2.76mg (=25% of RDA) for young women. When zinc intake was measured by a frequency method, the average intakes of the old and young women were 3.5$\pm$1.7mg 4.5$\pm$1.9mg, respectively. It appears that dietary zinc intake of young women was significantly higher than that of the old women. Average urinary zinc excretion of the subjects was 0.27$\pm$0.16mg in the elderly and 0.24$\pm$0.13mg in young women, which indicated a marginal zinc status. However, zinc status was not significantly different between old and young women. Correlation analysis indicated that zinc intake and urinary zinc excretion were positively related to BMI and LBM in young women. The old women (m=49) showed significantly higher taste detection thresholds than young subjects (n=47) for both sweet and salty tastes. Recognition thresholds for sodium chloride and sucrose were not significantly different between old and young women. The lower the taste thresholds for salty taste, the higher the average dietary zinc intake. However, taste perception concentration was not related to the urinary zinc excretion level.

• 한국식품영양과학회지
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• 제15권2호
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• pp.176-180
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• 1986

electrogustometer를 이용한 19세에서 23세의 건강한 한국 여대생의 사원미 미각역치에 대하여 다음과 같은 실험 결과를 얻었다. 1. 혀의 부위별 평균 미각역치는 시료처리 전에 단맛부위 $7.5{\mu}A$, 짠맛부위 $19.6{\mu}A$, 신맛부위 $23.5{\mu}A$, 쓴맛부위 $18.4{\mu}A$, 중앙부위 $50.7{\mu}A$로 보여 주었다. 2. 단일 시료처리 후의 단맛, 신맛, 쓴맛물질은 미뢰감도가 상승했음에 비해 짠맛 물질은 감소했으며, 복합 시료처리후의 경우는 혀의 각 부위의 미뢰감도와 비슷하였으며 단일 시료처리에 비해 중앙 부위가 예민 하였다. 3. 혀의 부위별 좌우차는 통계적으로 유의차가 인정되지 않았다. 4. 전기미각의 미질에는 사원미가 모두 표현되었고, 금속맛, 신맛, 짠맛, 쓴맛등을 느낀 예가 전체의 약 90%을 차지했다.