• International Journal of Highway Engineering
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• v.8 no.2 s.28
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• pp.87-93
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• 2006

To evaluate the deformational characteristics of subgrade soils, four subgrade samples in Korea were tested using the RC and TS tests with various dry unit weight and water content. Both the maximum modulus and normalized modulus reduction curves of subgrade soils were affected by the dry unit weight. The normalized modulus was decreased about 20% with increasing of relative compaction of 5%. It was founded that the variations of modulus of subgrade soils in Korea were over 40% with water content variation of $\pm$2%, and those effects can be estimated by exponential model. However, the normalized modulus reduction curves were almost identical and independent of water content. It was also founded that confining pressure, loading frequency, dry unit weight, and water content have an affect on modulus of subgrade soils independently. Therefore, it can be considered that those effects are independent variables.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.301-310
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• 2006

A series of laboratory tests was carried out for analyzing compaction characteristics of hydraulic fill soils(or hydraulically filled soils). Hydraulic fill soils were settled down by the weight of soil particle itself in water and consolidated by the extraction of water from the soil structures. Water content and dry unit weight were observed as the depth of sedimentation and consolidation soil. It was found from the result that the optimum water content $(W_{cpt})$ of the maximum unit weight$(\gamma_{dmax})$ is higher than that of laboratory compaction test(KS F 2312 A method). It was due to difference in compaction energy and compaction effect between two methods. And the maximum dry unit of hydraulic fill soil is smaller than that of laboratory compaction test. Especially in terms of compaction effect, the maximum relative compaction degrees$(R_{cmax})$ of Seamangum dredged sand, river sand and mixed sand, half and half of dredged and river sands, were 85%, 91% and 86%, respectively. It means that the compaction effect can be $85\sim91%$ of the maximum unit weight in laboratory compaction test.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.61-62
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• 2022

The unit quantity is an important factor influencing the durability, workability, and quality of concrete. Methods for measuring the unit quantity include a high frequency heating method, a unit volume mass method, a capacitance method, and a microwave method. However, these methods have disadvantages of poor measurement method, time required, and accuracy, and a relatively experimental method compensating for these disadvantages was used to measure the unit quantity using a high frequency main sensor (FDR) capable of simple and fast measurement. In addition, the unit quantity was evaluated by analyzing the measurement data through deep learning.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.1
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• pp.46-51
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• 2014

In this study, strength development properties of high volume fly ash concrete was evaluated through compressive strength of concrete with reduction of unit water content. And concrete specimens were prepared according to target strength 3 level and variation of unit water content. As a result, the improved fluidity were obtained as a result of the ball bearing action of the spherical, the electrostatic repulsion and the particle size distribution of fly ash particles in case of using more than 50% fly ash. Through this, the mixture of fly ash has been shown to reduce the amount of water required in concrete. Also, the early strength of high volume fly ash concrete with reduction of unit water content was improved more about 66% than general concrete mixture.

• Proceedings of the Korea Concrete Institute Conference
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• 1991.10a
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• pp.5-10
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• 1991

This study was performed to find out the effect about the spacing factor and durability factor to evaluate the durability of concrete in high-strength concrete with freezing and thawing as following each condition, 1) unit cement content : 500kg/$\textrm{m}^3$, 550kg/$\textrm{m}^3$ 2) water/cement ratio : 25%, 30%, 35% 3) air content : below 1.5%, 1.6~3.5%, 4~6%, over 7% From the results tested, a variation of air content was more effective to the durability of concrete than that of water/cement ratio and unit cement content.

• ALGAE
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• v.18 no.2
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• pp.129-134
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• 2003

In order to examine the effects of deep seawater (mesopelagic water in the broad sense) on the growth of macroalgae, the growth and nutrient uptake (nitrate and phosphate) of Ulva sp. (Ulvophyceae, Chlorophyta) were investigated by cultivation in deep seawater (taken from 687 m depth at Yaizu, central Japan, in August 2001), surface seawater (taken from 24 m depth), and a combination of the two. Culture experiments were carried out in a continuous water supply system and an intermittent water supply system, in which aerated 500-mL flasks with 4 discs of Ulva sp. (cut sections of ca. 2 $cm_2$) were cultured at 20$^{\circ}C$ water temperature, 100 $\mu$mol photons $m^{-2}{\cdot}s^{-1}$ light intensity, and a 14:10 light:dark cycle. Nutrient uptake by Ulva sp. was high in all seawater media in both culture systems. The frond area, dry weight, chlorophyll a content, dry weight per unit area, and chlorophyll a content per unit area of Ulva sp. at the end of the experimental period were the highest in deep seawater and the lowest in surface seawater in both culture systems. These values, except for dry weight per unit area and chlorophyll a content per unit area, for each seawater media in the intermittent water supply system were higher than those in the continuous water supply system. We conclude that not only deep seawater as the culture medium but also the seawater supply system is important for effective cultivation of macroalgae.

• 한국해양학회지
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• v.26 no.3
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• pp.193-203
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• 1991

KODOS (Korea Deep ocean Study)-89 sediments, recovered from western part of Clarion-Clipperton fracture zone in north Pacific, show two distinctly colored layer zones: surface yellow brown layer (unit A) and subsurface dark brown layer (unit B), and roughly recognized as Quaternary and Tertiary in age, respectively. Geochemical characteristics are also different in those two units. Smectite, water, micronodule, and heavy metal contents are higher in unit B, while POC content is higher in unit A. High smectite and low POC contents in unit B are due to the longer formation period of smectite, almost decomposition of labile organic matter in unit B relative to unit A. High water content in unit B is caused by coarse fabric which results from higher content of spicules and spines. Additionally, stronger electrostatic repulsion force caused by high smectite content also supports high water content in unit B relative to unit A. Variations in heavy metal contents are closely related to the amount of micronodule, which has higher metal contents than that of sediment. Therefore, we conclude that the differences of geochemical characteristics in unit A and unit B are resulted from the different diagenetic durations of unit A and unit B.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.70-71
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• 2021

The unit quantity that affects the workability, shrinkage cracking, and durability of concrete is an important factor. Methods for measuring the unit quantity include a high frequency heating method, a capacitance method, a unit volume mass method, and a simple method. However, these methods have the disadvantage of poor measurement method, time required, and precision. To solve this problem, a relatively simple and fast measurement method was adopted to compensate for the shortcomings through a Frequency Domain Reflection (FDR) sensor, and the unit quantity was used. In addition, the measurement data was analyzed by deep learning to evaluate the unit quantity of concrete.

• Journal of the Korea Institute of Building Construction
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• v.3 no.3
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• pp.91-97
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• 2003

At present, the antiwashout underwater concretes are used as popular construction materials in European countries, the United States and Japan. The water-soluble polymers in the antiwashout underwater concretes provide excellent segregation or washout resistance, self-compaction and self-leveling property to the concretes. The purpose of this study is to recommend to optimum mix proportions of antiwashout underwater concretes according to compressive strength of 300kgf/$\textrm{cm}^2$ to 500kgf/$\textrm{cm}^2$. The antiwashout underwater concretes are prepared with various unit cement content, unit water content, sand-aggregate ratio, unit antiwashout agent and superplasticizer content. And they are tested for flowability, and compressive strength. From the test results, it is possible to recommend the optimum mix proportions of antiwashout underwater concretes according to compressive strengths within the range of 300kgf/$\textrm{cm}^2$ to 500kgf/$\textrm{cm}^2$.

• Journal of the Korea Institute of Building Construction
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• v.7 no.4
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• pp.139-144
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• 2007

The purpose of this study is to analyze concrete characteristics by admixing agent and additive contents according to the change of unit-water to identify its effect on compressive strength. First of all, as for flesh concrete, overall unit-water showed a tendency to decrease as component inclusion rate of admixing agent was increased. In addition, air content showed a tendency to increase by increasing WR, WB, NP series admixing agent contents, on the other hand, the change of air content was gentle by around $1.5{\pm}0.5%$ for S, T, M series agents. Bulk density showed an inverse proportion to the change of air content. As for hardened concrete, expression rate of 3-day age compressive strength was generally decreased for S, T, WR, WB, NP, M series admixing agent component. Also, expression rate of 7-day age compressive strength showed an excellent record for S, M series agents, and expression rate of 28-day age compressive strength showed a tendency to increase more than plain on the whole.