• 도시과학
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• 제7권2호
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• pp.29-36
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• 2018

The demand for reinforcement in accordance with remodeling, seismic retrofit, and change of use of the existing structure is increasing. Originally, shear wall new and extension method has been adopted a lot as seismic retrofit methods. Recently, dry seismic retrofit method that uses structural steel is mostly adopted in order to minimize spatiotemporal aspect and underpinning that occurs when a construct shear wall. We redesigned the form of old and new concrete joint high-shear ring anchor that was developed according to recent reinforcement method and determined construction method. Shear tests were performed on High-Shear Ring Anchor for steel-concrete connection. Comparison with 4 tests shows that the average of test-to-prediction ratios is 1.01.

• 방사성폐기물학회지
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• 제19권4호
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• pp.435-446
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• 2021

This article examines the consequences of a significant spent fuel management decision or event in the United States, South Korea and Taiwan. For the United States, it is the financial impact of the Department of Energy's inability to take possession of spent fuel from commercial nuclear power companies beginning in 1998 as directed by Congress. For South Korea, it is the potential financial and socioeconomic impact of the successful construction, licensing and operation of a low and intermediate level waste disposal facility on the siting of a spent fuel/high level waste repository. For Taiwan, it is the operational impact of the Kuosheng 1 reactor running out of space in its spent fuel pool. From these, it draws six broad lessons other countries new to, or preparing for, nuclear energy production might take from these experiences. These include conservative planning, treating the back-end of the fuel cycle holistically and building trust through a step-by-step approach to waste disposal.

• 한국대기환경학회지
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• 제25권5호
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• pp.402-409
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• 2009

Sodium bicarbonate ($NaHCO_3$) was used as a reactant for the removal of acid gases from a waste incinerator. The removal efficiencies of HCl and $SO_x$ were tested with a reactant mixing apparatus and a distributor installed at the bag filter inlet. It was shown that the stoichiometric ratio of $NaHCO_3$ to the acid gases which allows a removal of over 90% for both HCl and $SO_2$ was about 1.2. When a reactant mixing apparatus was installed on the duct, the removal efficiencies of HCl and $SO_2$ at the end of the duct were increased by approximately 1.5 and 3 times respectively, compared to when the apparatus was not installed. At the end of the bag filter, the removal efficiencies of the both were as high as 98% with a stoichiometric ratio of 1.35. Installing a reactant mixing apparatus on the duct and a distributor at the entrance of the bag filter and using $NaHCO_3$ as a reactant helped overcome the problem of low removal efficiencies of acid gases by dry scrubbing.

• 한국지반공학회논문집
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• 제18권1호
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• pp.113-125
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• 2002

연약 지반개량을 위한 심층혼합처리 공법의 사용은 점차로 증가 추세에 있으며 특히, 일본과 해안가에 인접한 동남아 국가는 물론 스칸디나비아지역에서도 보편화된 개량공법으로 각광을 받고 있다. 시멘트는 지반의 강도를 증가시키고 압축성을 감소시키는 역할을 한다. 따라서 심도가 깊은 퇴적지반이나 해안지역에서 지반의 지지력 증가나 압밀침하를 감소시키기 위해 시멘트를 개량재료로 사용할 수가 있다. 연약지반 처리를 위한 고화제로서 시멘트의 사용이 증가하고 있음에도 불구하고 이에 대한 응력-변형특성이나 혼합처리 흙의 구조적인 특성 등의 역학적인 거동특성을 명확하게 파악하지 못하고 있다. 본 연구에서는 시멘트 고화처리 흙의 역학적 성질을 파악하기 위해 카올린을 이용하여 최대 10%의 시멘트를 첨가하여 7일에서 112일가지 양생기간을 변화시켜 삼축압축시험, 일축압축시험, 등방압밀 및 표준압밀시험등을 수행하였으며 이에 따른 시멘트 고화처리 흙의 역학적인 특성을 파악하고자 하였다. 또한 혼합토의 시료 제조 및 양생방법등 일련의 시험과정에 대한 절차 및 방법에 대하여 기술하였다.

• 한국가구학회지
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• 제19권6호
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• pp.411-419
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• 2008

Xylia xylocarpa is fast-growing trees that are currently planted on trial basis in Sabah, Malaysia. The wood quality of trees grown in Sabah may differ from those grown in other places due to the environmental factors. Five 9-year-old trees of each species were extracted from their respective plots at Luasong, Tawau. Wood specimens were prepared from three height levels; bottom, middle and top, at the inner and outer radial positions. The within-tree and between-tree variations of physical properties of these species were analyzed. The basic density, oven-dry density and green moisture content(MC) are 0.72g/$cm^3$, 0.78g/$cm^3$ and 49.8% respectively. The shrinkage from green to oven-dry conditions for the radial and tangential directions were 3.35% and 5.76%, respectively. The trends of within-tree variations for most properties were more consistent in radial rather than vertical direction. This suggests diameter growth to be a more important factor contributing to the variations compared to height. Samples from the outer part of the stem were found to have higher density, shrinkage and mechanical strengths. The between-trees variations of some wood properties were found to be significantly different, probably due to genetic and micro-environmental factors. Significant correlation was recorded among the physical properties of the species. The true potential of X. xylocarpa for end-uses would be enhanced by further research such as the study on properties of wood from different sites and other properties like durability, seasoning, processing and machining characteristics. The characteristics of X. xylocarpa are comparable to a number of local popular hardwood species, indicating its suitability for heavy construction uses.

• KIEAE Journal
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• 제16권1호
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• pp.67-71
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• 2016

Purpose: There is a growing interest in rainwater runoff reduction effect of green roof, as flooding caused by increasing impervious surface is becoming more and more frequent in urban areas. This study was conducted to prove runoff reduction and runoff delay effect of the retentive green roof and to investigate its influencing factors to the rainfall events that occurred in the summer of 2013. Method: The experiment intended to monitor the runoff quantity of the retentive green roof($140m^2$) and normal roof($100m^2$) in #35 building in Seoul National University, Seoul, Korea for 75 days in 2013. Result: On analysis of 9 rainfall events, it showed that the retentive green roof has 24.8~100% of runoff reduction ratio, 21.2~100% of peak flow reduction ratio, 0.5~3.75 hours of peak delay, and $1.8{\sim}7.2m^3$ of retaining capacity in an area of $140m^2$. It shows different results depending on rainfall and antecedent dry days. The results show that runoff reduction effect is effective when the rainfall is less than 50 mm and antecedent dry day is longer than five days on average. By installing retentive green roofs on buildings, it can help mitigate urban floods and rehabilitate urban water cycle.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.453-458
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• 2001

This study was performed to reuse the dyeing wastewater sludge treated by Fenton process through the solidification/stabilization technique. To solidify the dyeing sludge the industrial by-products such as blast furnace slag, fly ash and waste sand with cement were used. The laboratory scale and pilot scale test were conducted at room temperature to make construction brick which has high compressive strength and low leaching of heavy metals. The experimental results showed that blast furnace slag and fly ash could be used instead of cement and the products satisfied the regulation of Korean Standards. The blast furnace slag increased the compressive strength and the optimum ratio of slag/dyeing sludge on dry basis was found 0.4. The solidifying agent of SB series could increase rapidly the compressive strength and the optimum ratio of solidifying agent/sludge on dry basis was 0.26 at which the strength was two times compared with non-added condition. The portion of waste and industrial by-products in matrix was over 80%. From the pilot test the optimum pressure in molding was 100kg/$\textrm{cm}^2$ at which the compressive strength was over 100kg/$\textrm{cm}^2$. And the strength increased continuously to 160kg/$\textrm{cm}^2$ until 120 days curing time due to pozzolanic reaction. When SB-20 as a solidifying agent was used, the unconfined compressive strength of dyeing sludge could be obtained 110kg/$\textrm{cm}^2$ which satisfied the regulation of cement brick in Korea Standard(KS).

• Journal of Ecology and Environment
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• 제38권2호
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• pp.133-143
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• 2015

Freshwater macrophytes improve the structural heterogeneity of microhabitats in water, often providing an important habitat for zooplankton. Some studies have focused on the overall influence of macrophytes on zooplankton, but the effects of macrophyte in relation to different habitat characteristics of zooplankton (e.g., epiphytic and pelagic) have not been intensively studied. We hypothesized that different habitat structures (i.e., macrophyte habitat) would strongly affect zooplankton distribution. We investigated zooplankton density and diversity, macrophyte characteristics (dry weight and species number), and environmental parameters in 40 shallow wetlands in South Korea. Patterns in the data were analyzed using a self-organizing map (SOM), which extracts information through competitive and adaptive properties. A total of 20 variables (11 environmental parameters and 9 zooplankton groups) were patterned onto the SOM. Based on a U-matrix, 3 clusters were identified from the model. Zooplankton assemblages were positively related to macrophyte characteristics (i.e., dry weight and species number). In particular, epiphytic species (i.e., epiphytic rotifers and cladocerans) exhibited a clear relationship with macrophyte characteristics, while large biomass and greater numbers of macrophyte species supported high zooplankton assemblages. Consequently, habitat heterogeneity in the macrophyte bed was recognized as an important factor to determine zooplankton distribution, particularly in epiphytic species. The results indicate that macrophytes are critical for heterogeneity in lentic freshwater ecosystems, and the inclusion of diverse plant species in wetland construction or restoration schemes is expected to generate ecologically healthy food webs.

• 한국해안·해양공학회논문집
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• 제24권4호
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• pp.235-246
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• 2012

연안방재계획 수립을 위한 기초자료 생성의 일환으로 태풍에 의한 해일 범람모의를 수행하였다. 통상적인 침수-노출 처리가 불가한 직립안벽을 갖는 항만역의 특징이 반영되도록 가상의 내부제방 개념을 도입하여 해석하였다. 목포항에 대한 실제해역 적용에 앞서 단순해역에서 다수의 적용성 평가를 통해 내부제방의 폭은 1 m가 적정한 것으로 평가되었다. 해일범람으로 인한 침수면적과 침수심 산정에 민감하게 작용하는 육역의 침수-노출 처리기법에서의 최소침수심은 격자에 의존적이나 10 m 내외의 유한요소 상세격자에서는 0.01 m가 적정한 것으로 판단된다. 기존 태풍경로에 준거한 100년 빈도급 중심기압과 최대풍속을 가지며 비대칭 경도풍과 파랑효과가 고려된 가상태풍의 내습에 따른 목포해역의 침수예상역이 모의되었다. 침수면적은 기존 연구결과와 유사성을 나타내지만 항만권역 일부에서 확대 가능성이 있는 것으로 평가된다.

• Earthquakes and Structures
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• 제11권1호
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• pp.83-107
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• 2016

In this study, the response and behavior of machine foundations resting on dry and saturated sand was investigated experimentally. A physical model was manufactured to simulate steady state harmonic load applied on a footing resting on sandy soil at different operating frequencies. Total of (84) physical models were performed. The parameters that were taken into consideration include loading frequency, size of footing and different soil conditions. The footing parameters are related to the size of the rectangular footing and depth of embedment. Two sizes of rectangular steel model footing were used. The footings were tested by changing all parameters at the surface and at 50 mm depth below model surface. Meanwhile, the investigated parameters of the soil condition include dry and saturated sand for two relative densities; 30 % and 80 %. The dynamic loading was applied at different operating frequencies. The response of the footing was elaborated by measuring the amplitude of displacement using the vibration meter. The response of the soil to dynamic loading includes measuring the stresses inside soil media by using piezoelectric sensors. It was concluded that the final settlement (St) of the foundation increases with increasing the amplitude of dynamic force, operating frequency and degree of saturation. Meanwhile, it decreases with increasing the relative density of sand, modulus of elasticity and embedding inside soils. The maximum displacement amplitude exhibits its maximum value at the resonance frequency, which is found to be about 33.34 to 41.67 Hz. In general, embedment of footing in sandy soils leads to a beneficial reduction in dynamic response (displacement and excess pore water pressure) for all soil types in different percentages accompanied by an increase in soil strength.