• 지질공학
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• 제13권3호
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• pp.309-320
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• 2003

ASTM C 227-90에 의한 모르타르봉 팽창의 원인에 대해서 현재까지는 막연히 알칼리-골재 반응에 의한 것으로 알려져 왔으나 본 연구에서는 팽창의 원인을 알칼리-골재 반응에 의한 팽창 외에 겔 공극의 팽창과 골재 자체에 형성된 엽리나 쪼개짐에 물이 침투되어 물리적으로 팽창되는 간극수에 의한 팽창으로 세분하였다. 또한 총 팽창량을 이들 세분된 팽창요인별로 정량적인 계산을 실시한 바 골재에 따라서는 팽창결과가 주로 간극수에 의한 것도 있고, 알칼리-골재 반응에 의한 것도 있으며 이들이 복합적으로 작용한 것도 있음을 알게 되었다. 이러한 방법으로 현무암, 사암 등 몇 몇 골재의 문제점을 분석하였다 콘크리트는 현재 건설구조물의 대부분을 차지하고 있으며, 골재는 콘크리트의 75% 내외를 점유하고 있는 만큼 골재의 올바른 선정은 중요한 의미를 갖는다. 또한 이미 완성된 콘크리트 구조물에 골재와 관련된 문제점이 발생하였을 때 이를 치유하는데 정확한 원인을 알아내는 것이 중요하다고 보며 본연 구는 그러한 면에서 활용면을 찾을 수 있다.

• 한국산학기술학회논문지
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• 제19권4호
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• pp.138-142
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• 2018

본 연구에서는 플랜트 기자재 중 수충격에 매우 취약한 신축관 이음을 대상으로 수충격 발생 시 신축관 이음의 신축량의 변화를 현장에서 취득한 후 HIL 시뮬레이터의 작동데이터로 적용한 HILS 기법을 적용한 진동내구 시험을 수행하였다. 또한 진동내구 시험 시 내구수명의 주요 스트레스 인자로 신축관 내부압력을 가정하였다. 진동내구 시험은 신축관 내부 설정압 따라 진행되었으며 수명데이터를 이용, 수명데이터를 잘 따르는 곡선을 접합하여 수명예측 모델식을 유도하였고 특정 내부 설정압에서의 시험 및 수명결과를 통하여 이를 검증하였다. 한편, 시험 중 발생 된 신축관의 고장모드는 모두 벨로우즈 부 표면에 발생된 크랙과 크랙을 통한 누수 등이 있었다. 본 연구에서 유도한 수명에측 모델식은 설정압력을 스트레스 인자로 따르는 전형적인 역승모형이며 특정환경에서만 적용될 수 있는 한계를 지니고 있다. 이에 본 연구는 진동내구 수명의 가속요인인 압력 외 온도상태 등을 다양한 수명변수가 적용 가능한 복합수명예측 모델식을 개발할 예정이다.

• 한국세라믹학회지
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• 제44권9호
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• pp.529-535
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• 2007

Calcium oxide has been used as a demolition agent in fracturing rocks and old concrete structures, etc. With the agent, demolition work can be done in safety without a noise, vibration and any other pollution, since high expansive pressure is obtained gradually by only mixing the agents with water and pouring the slurry into boreholes. But application of the non-explosive demolition agent is a time-consuming job, especially in winter. Essentially, this problem is related to the reaction rate of calcium oxide with water. This study examines the influence of additives such as cement and anhydrite on expansion pressure of calcium oxide at different curing temperatures. The expansion pressure of calcium oxide began to increase steadily with the rise of the curing temperature. When mixing calcium oxide alone with water, blown-out shot occurred. But as additives were added to calcium oxide, the reaction of calcium oxide delayed and the expansion pressure showed gradual increment. Especially, anhydrite showed a superior delaying effect than cement on the reaction of calcium oxide.

• 한국환경복원기술학회지
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• 제13권5호
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• pp.1-11
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• 2010

It is very difficult to control the expansion of reed at a wetland ecological park due to their aggressive reproduction capability. Therefore, proper topography and wetland hydrology should be provided before the construction of a wetland ecological park. Appropriate measures should be taken at the initial stages to prevent reed expansion. Field experiments were conducted at the newly constructed wetland ecological park for 15 months to develop methods to control the reproduction and expansion of Phragmites communis. A complete shading method had the best effect on the prevention of reed reoccurrence among other methods. Complete removal of the rhizomes controlled the reed growth to a greater extent than cutting the aboveground shoots. Water-level manipulation was also better than a half-shading method for the prevention of reed reproduction. These results indicated that soil properties and edge effects can influence the reed growth. Cutting only the aboveground shoots facilitates the growth of reed. These results suggest that reed control should be implemented repeatedly and an alteration in the wetland topography and hydrology may be more effective in the long term. Combination of treatments such as water-level management with shading should be considered to control the growth of reed. Adoptive management for created or restored ecosystem might be considered for accomplishment of its original purpose.

• 한국농공학회:학술대회논문집
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• 한국농공학회 1999년도 Proceedings of the 1999 Annual Conference The Korean Society of Agricutural Engineers
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• pp.283-288
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• 1999

This study is performed to evaluate slump , air content, compressive strength and length change ratio of non-shrinkage high strength ocncrete is achieved by 10% expansive additive contained. The length change ration of non-shrinkage high strength concrete which is in water curing, shows 0.055% expansion in 10% expansive additive contained concrete and 0.308 expansion in 20% expansion additive contained concrete when it is curing 28 days.

• Journal of applied mathematics & informatics
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• 제28권1_2호
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• pp.383-395
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• 2010

In the present paper, we construct the traveling wave solutions involving parameters of nonlinear evolution equations in the mathematical physics via the (3+1)- dimensional potential- YTSF equation, the (3+1)- dimensional generalized shallow water equation, the (3+1)- dimensional Kadomtsev- Petviashvili equation, the (3+1)- dimensional modified KdV-Zakharov- Kuznetsev equation and the (3+1)- dimensional Jimbo-Miwa equation by using a simple method which is called the ($\frac{G'}{G}$)- expansion method, where $G\;=\;G(\xi)$ satisfies a second order linear ordinary differential equation. When the parameters are taken special values, the solitary waves are derived from the travelling waves. The travelling wave solutions are expressed by hyperbolic, trigonometric and rational functions.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.181-186
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• 1999

When the expansive additives are used in concrete to reduce the shrinkage cracking, it shows variable properties with the curing method and curing temperature. Therefore, in this study, the experiments are perfomed to present the expansion of cement mortar by varying the unit additions of expansive additives and the curing method. According to the test results, the order of expansion by curing method, which is caused by hydration heat of cement, is follows ; curing at water > curing at air after curing at water for 7 days > curing at air. Cement mortar using expansive additives shows that high expansion is place with rise of temperature.

• 대한치과의사협회지
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• 제12권1호
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• pp.37-42
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• 1974

To ascertain if the ultrasonic cleaning technique caused any dimensional changes in heat and cold curing and fluid resin denture bases and in addition to evaluate the dimensional changes of the resin denture bases stored in water and air, the author measured the distance between the outsides of two pins embedded in methyl methacrylate test denture bases by mean of 12 inch vernier caliper, accurate to 0.02mm. The results were as follows; (1) Ultrasonic cleaning didn't cause any permanent dimensional changes, but only affected temporary dimensional expansion in 16 test denture bases. (2) Temporary expansion rate caused by 10 minutes' ultrasonic cleaning was 0.29% and at the maximal temperature of the cleaning solution it was 0.64%. (3) The half of the denture bases stored in water showed the dimensional expansion rate of 0.47% while the others stored in air showed the dimensional shrinkage rate of 0.15% after 4 months.

• 한국표면공학회지
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• 제17권1호
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• pp.1-6
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• 1984

The fluidized bed electrode reactor(FBER) with conducting particles has been made use of the removal of metals from dilute electroplating rinse water. The electrolysis was carried out under the conditions of diaphragm current density with 2~28A/$dm^2$ and bed expansion with 20~50%. Recirculating batch operations have been shown that the metal concentration dropped exponentially and may be taken down to 10 ppm. And then, the current efficiency at a concentration of 10 ppm copper was 37% under the conditions of 30% bed expansion and 6 A/$dm^2$, and at concentrated electrolyte (2000ppm copper) was over 80% in the range of 8~28A/$dm^2$ and 20~50% bed expansion. One of the technical possibilities of fluidized bed electrolysis is the separation of copper and nickel from a mixed solution of copper and nickel.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2009년도 학술발표회 초록집
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• pp.2179-2183
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• 2009

As urbanization is progressed, the network for distributing water in a basin become complex due to the spatial expansion and parameter uncertainties of water supply systems. When a long range water supply plan is determined, the total construction and operation cost has to be evaluated with the system components and parameter uncertainties as many as possible. In this paper, the robust optimization approach of Bertsimas and Sim is applied in a hypothetical system to find a solution which remains feasible under the possible parameter uncertainties having the correlation effect between the uncertain coefficients. The system components to supply, treatment, and transport water are included in the developed water supply system and construction and expansion of the system is allowed for a long-range period. In this approach, the tradeoff between system robustness and total cost of the system is evaluated in terms of the degree of conservatism which can be converted to the probability of constraint violation. As a result, the degree of conservatism increases, the total cost is increased due to the installation of large capacity of treatment and transportation systems. The applied robust optimization technique can be used to determine a long-range water supply plan with the consideration of system failure.