• Geomechanics and Engineering
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• 제16권1호
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• pp.71-83
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• 2018

Compacted bentonites were chosen as the backfill material and buffer in high level nuclear waste disposal due to its high swelling pressure, high ion adsorption capacity and low permeability. It is essential to estimate the swelling pressure in design and considering the safety of the nuclear repositories. The swelling pressure model of expansive clay colloids was developed based on Gouy-Chapman diffuse double layer theory. However, the diffuse double layer model is effective in predicting low compaction dry density (low swelling pressure) for certain bentonites, and invalidation in simulating high compaction dry density (high swelling pressure). In this paper, the new relationship between nondimensional midplane potential function, u, and nondimensional distance function, Kd, were established based on the Gouy-Chapman theory by considering the variation of void ratio. The new developed model was constructed based on the published literature data of compacted Na-bentonite (MX80) and Ca-bentonite (FoCa) for sodium and calcium bentonite respectively. The proposed models were applied to re-compute swelling pressure of other compacted Na-bentonites (Kunigel-V1, Voclay, Neokunibond and GMZ) and Ca-bentonites (FEBEX, Bavaria bentonite, Bentonite S-2, Montigel bentonite) based on the reported experimental data. Results show that the predicted swelling pressure has a good agreement with the experimental swelling pressure in all cases.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.507-514
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• 2005

In this construction case study, Crushed stone under 100mm diameter was carried out a test compacted construction for subgrade in the 3rd. runway of the 2th Incheon International Airport Construction area. Conforming to specification needs a minimum rolling compacted number 10 for upper subgrade 100% compaction degree indicated in Federal Aviation Administration and $K_{30}{\geq}20kgf/cm^3$ in plate bearing test. $K_{30}$ to be acquired 100% compaction degree of upper subgrade is confirmed to about $31kgf/cm^3$ from correlation $K_{30}$ vs relative compaction degree.

• 한국농공학회논문집
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• 제56권6호
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• pp.113-119
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• 2014

This study aims to evaluate the behavior of poorly-compacted raised reservoir levee with water level raising by using centrifugal model test. From the test results, it seems that the hydraulic fracturing at the core of the raised reservoir levee with low degree of compaction possibly occurs due to the drastical increase of pore water pressure by water level raising. Additionally, the continuous infiltration may induce crack and/or sinkhole on the surface of the poorly-compacted raised reservoir levee owing to the increase of the subsidences at the crown and the front side of that. Therefore, reasonable construction management for the compaction of the raised reservoir levee is needed.

• Journal of Electrical Engineering and Technology
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• 제9권4호
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• pp.1411-1417
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• 2014

An MPEG-2 AAC Huffman decoding method based on the fixed length compacted codeword tables, where each codeword can contain multiple number of Huffman codes, was proposed. The proposed method enhances the searching efficiency by finding multiple symbols in a single search, i.e., a direct memory reading of the compacted codeword table. The memory usage is significantly saved by separately handling the Huffman codes that exceed the length of the compacted codewords. The trade-off relation between the computational complexity and the amount of memory usage was analytically derived to find the proper codeword length of the compacted codewords for the design of MPEG-2 AAC decoder. To validate the proposed algorithm, its performance was experimentally evaluated with an implemented MPEG-2 AAC decoder. The results showed that the computational complexity of the proposed method is reduced to 54% of that of the most up-to-date method.

• Nuclear Engineering and Technology
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• 제53권10호
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• pp.3359-3366
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• 2021

An engineered barrier system (EBS) for the deep geological disposal of high-level radioactive waste (HLW) is composed of a disposal canister, buffer material, gap-filling material, and backfill material. As the buffer fills the empty space between the disposal canisters and the near-field rock mass, heat energy from the canisters is released to the surrounding buffer material. It is vital that this heat energy is rapidly dissipated to the near-field rock mass, and thus the thermal conductivity of the buffer is a key parameter to consider when evaluating the safety of the overall disposal system. Therefore, to take into consideration the sizeable amount of heat being released from such canisters, this study investigated the thermal conductivity of Korean compacted bentonites and its variation within a temperature range of 25 ℃ to 80-90 ℃. As a result, thermal conductivity increased by 5-20% as the temperature increased. Furthermore, temperature had a greater effect under higher degrees of saturation and a lower impact under higher dry densities. This study also conducted a regression analysis with 147 sets of data to estimate the thermal conductivity of the compacted bentonite considering the initial dry density, water content, and variations in temperature. Furthermore, the Kriging method was adopted to establish an uncertainty metamodel of thermal conductivity to verify the regression model. The R² value of the regression model was 0.925, and the regression model and metamodel showed similar results.

• Computers and Concrete
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• 제28권5호
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• pp.451-463
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• 2021

Inorganic basalt fiber (BF) is a novel sort of commercial concrete fiber which is made with basalt rocks. Previous studies have not sufficiently handled the behavior of self-compacted concrete, at elevated temperature, containing basalt fiber. Present endeavor covers experimental work to examine the characteristics of this material at high temperature considering different fiber content and applied temperature. Different tests were carried out to measure the mechanical properties such as compressive strength (fc), modulus of elasticity (E), Poisson's ratio, splitting tensile strength (fsplit), flexural strength (fflex), and slant shear strength (fslant) of HSC and hybrid concrete. Gene expression programming (GEP) was employed to propose new constitutive relationships depending on experimental data. It was noticed from the testing records that there is no remarkable effect of BF on the Poisson's ratio and modulus of elasticity of self-compacted concrete. The flexural strength of basalt fiber self-compacted concrete was not sensitive to temperature in comparison to other mechanical properties of concrete. Fiber volume fraction of 0.25% was found to be the optimum to some extend according to degradation of strength. The proposed GEP models were in good matching with the experimental results.

• 한국도로학회논문집
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• 제12권3호
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• pp.103-111
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• 2010

에너지 절약과 $CO_2$발생량의 절감을 위해 자전거의 이용을 적극 장려하고 있다. 이를 위해 다량의 신설 자전거 도로 건설 계획을 추진 중에 있다. 현재 국내에서 신설 자전거도로 건설을 위해 아스팔트포장 및 콘크리트 포장을 비롯하여, 반강성포장, 유색포장, 흙포장 등이 적용되고 있다. 하지만 이들 포장형식은 자전거도로의 요구 성능에 비하여 시공비용이 높다. 본 연구에서는 경제적이고 친환경적이며 내구성을 확보한 자전거도로포장으로써 롤러 다짐 콘크리트의 최적 다짐율과 배합비를 기초물성시험을 통해 검토하였다. 도출된 배합비에 대한 동결융해와 제설제 저항성 시험을 통해 환경저항성을 검토하였다. 추가적으로 경제성 및 $CO_2$발생량을 일반콘크리트포장과 비교를 통해 평가했다.

• Computers and Concrete
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• 제19권4호
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• pp.435-442
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• 2017

In recent years, the use of supplementary cementing materials, especially in addition to concrete, has been the subject of many researches. Rice husk ash (RHA) is one of these materials that in this research, is added to the roller compacted concrete as one of the pozzolanic materials. This paper evaluates how different contents of RHA added to the roller compacted concrete pavement specimens, can influence on the strength and permeability. The results are compared to the control samples and determined optimal level of RHA replacement. As it was expected, RHA as supplementary cementitious materials, improved mechanical properties of roller compacted concrete pavement (RCCP). Also, the application of adaptive neuro-fuzzy inference system (ANFIS) in predicting the permeability and compressive strength is investigated. The obtained results shows that the predicted value by this model is in good agreement with the experimental, which shows the proposed ANFIS model is a useful, reliable, fast and cheap tool to predict the permeability and compressive strength. A mean relative error percentage (MRE %) less than 1.1% is obtained for the proposed ANFIS model. Also, the test results and performed modeling show that the optimal value for obtaining the maximum compressive strength and minimum permeability is offered by substituting 9% and 18% of the cement by RHA, respectively.

• 대한토목학회논문집
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• 제3권2호
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• pp.109-117
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• 1983

구속응력(拘束應力), 전단변형율진폭(剪斷變形率振幅), 다짐함수비(含水比), 다짐에너지, 간극비(間隙比) 및 포화도(飽和度)가 다짐점성토(粘性土)의 동적전단탄성계수(動的剪斷彈性係數)에 끼치는 영향(影響)을 연구(硏究)하기 위하여 도주공진시험(圖柱工振試驗)을 하였다. 이들 각각(各各)의 요소(要素)들은 다짐 흙의 동적전단탄성계수(動的剪斷彈性係數)에 큰 영향(影響)을 나타내며 그 원인(原因)은 다짐에 의한 흙의 여러 가지 변화(變化)로서 설명(說明)할 수 있다. 흙의 동적전단탄성계수(動的剪斷彈性係數)는 다짐에 의해서 크게 증가(增加)되며 최적함수비(最適含水比) 건조측(乾燥側)의 함수비(含水比)에서 다지는 것이 훨씬 더 효과적(効果的)이다. 그리고 동적(動的) 전단탄성계수(剪斷彈性係數)와 정적(靜的) 전단탄성도(剪斷彈性度)는 좋은 상관관계(相關關係)를 나타내며 이를 이용(利用)하여 어떤 일정(一定)한 구속응력(拘束應力)에 대한 동적전단탄성계수(動的剪斷彈性係數)를 일축압축강도(一軸壓縮强度)로부터 쉽게 구할 수가 있다.

• 한국분말재료학회지
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• 제21권3호
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• pp.196-201
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• 2014

In this study, nanocrystalline Cu-Ni bulk materials with various compositions were cold compacted by a shock compaction method using a single-stage gas gun system. Since the oxide layers on powder surface disturbs bonding between powder particles during the shock compaction process, each nanopowder was hydrogen-reduced to remove the oxide layers. X-ray peak analysis shows that hydrogen reduction successfully removed the oxide layers from the nano powders. For the shock compaction process, mixed powder samples with various compositions were prepared using a roller mixer. After the shock compaction process, the density of specimens increased up to 95% of the relative density. Longitudinal cross-sections of the shock compacted specimen demonstrates that a boundary between two powders are clearly distinguished and agglomerated powder particles remained in the compacted bulk. Internal crack tended to decrease with an increase in volumetric ratio of nano Cu powders in compacted bulk, showing that nano Cu powders has a higher coherency than nano Ni powders. On the other hand, hardness results are dominated by volume fraction of the nano Ni powder. The crystalline size of the shock compacted bulk materials was greatly reduced from the initial powder crystalline size since the shock wave severely deformed the powders.