• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.96-97
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• 2017

Performances such as retention, setting time and strength generation of mortar with phosphate-introduced chemical admixture, domestic and foreign admixtures are evaluated to find one that meets over 3 hours retention in extremly hot weather condition in this study.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4602-4609
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• 2013

In summer and winter, the difference between the temperature during the day and that during the night is high, which leads to various problems during concrete placement, such as cracks and defects in the concrete as well as low durability and strength. Although nuclear power plant concrete is widely used for placement in all seasons, particular attention must be paid to its quality during the summer. Therefore, we evaluated the effects of a cooling method for mixing water, which is a commonly used hot weather precooling method, and the use of a retarder, on the characteristics of Nuclear Power Plant concrete. In the cooling method for mixing water, cold water at 5 was used, with 50% of the water content consisting of ice flakes. The effects of using a retarder were evaluated by reviewing the characteristics of the cement at the unset stage and after hardening. To evaluate the characteristics of the unset cement, we measured the slump, air volumes, setting times, and pressure strengths after hardening. Furthermore, we measured the heat of hydration at different temperatures; the loss of heat was minimized using insulation. Both the slump time and the complete ageing time of the air volume were found to be 120 min at $20^{\circ}C$ and 40 min at $40^{\circ}C$. In the case when the cooling method for mixing water was used and in the case when a retarder was used, the initial and final sets by penetration resistance were delayed, and the delay decreased with increasing air temperature. For the heat of hydration, the cooling method for mixing water not only lowered the maximum temperature but also delayed its attainment. However, the use of a retarder had no effect on the maximum temperature. Moreover, in the early ages (e.g., 3 and 7 days), the pressure strength of the concrete was lower than that of plain cement. However, the strength of 28-day concrete met the standard construction specifications.

• Journal of Information Technology Application
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• v.1 no.3_4
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• pp.25-45
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• 1999

과거 재료가공 위주의 산업시대에는 에너지가 산업의 가장 중요한 열쇠였으나 현대 산업사회에서는 부가가치를 지식과 정보로부터 창출해낸다. 그러므로 21세기에는 지식정보와 커뮤니케이션이 산업의 가장 중요한 열쇠가 될 것이다. 현대 기업환경의 변화는 과거와 다른 양상으로 나타나고 있고 한편 경영자들에게는 기업경영과 기업의 의미에 대해 새로운 패러다임을 요구하는 상황에 이르렀다. 이러한 변화 추세로 21세기를 예측해 본 학자들은 대표적인 조직모델로 소위 '가상기업을 내세우고 있다. 가상기업이란 특정 프로젝트가 끝나면 해체할 수 있는 전략적 제휴에 의해 임시로 형성되는 조직체이다. 이 논고에서는 현대 기업환경과 기업조직의 변화로 인한 가상기업 개념의 출현배경을 알아보고, 아직까지 애매 모호한 이 개념을 정의하고 그 모델을 제시한다. 그리고 정보기술의 응용과 공용 인터페이스의 활용으로 어떻게 이러한 형태의 가상공동체를 형성하고 관리할 수 있는지 고찰해보고, 21세기 지식경영시대에 가상기업형 조직의 경영을 위한 지식정보시스템 구축의 예로서 재단법인 충청지역정보원의 통합정보시스템을 소개한다.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.128-129
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• 2018

The high performace water reducing agent with three-hours-fluidity-retention performance is developed for the purpose of entering into the global market belonging to extreme environment such as Southeast Asia and the Middle East. In this study, the fresh and mechanical properties of the concrete with three-hours-fluidity-retention performance are presented.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.201-202
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• 2019

The high performace water reducing agent with three-hours-fluidity-retention performance is developed for the purpose of entering into the global market belonging to extreme environment such as Southeast Asia and the Middle East. In this study, the fresh and mechanical properties of the high strength concrete with three-hours-fluidity-retention performance are evaluated by making mock-up members in Vietnam.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6A
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• pp.881-891
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• 2008

The purpose of the present study is to investigate the influence of seasonal temperature variation on the thermal stresses in roller compacted concrete dam(RCD) structures. Using the finite element code, DIANA performs 2-D transient temperature and resultant stress analysis for RCD. Time variability of the mesh geometry is considered in order to simulate successive phases of the structure's construction. The main analysis variables are construction sequence, concrete temperature and ambient temperature. The results show principal tensile stress of hot-weathering concrete is higher than that of cold-weathering concrete. In some case the index of thermal cracking excesses 1.0, RCD also needs thermal management on placing temperature according to weather condition.

• Journal of the Korean GEO-environmental Society
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• v.13 no.9
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• pp.83-89
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• 2012

Anchor, soil nail and micropile have been widely used for slope reinforcement and foundation. These all methods need grouting work after placing reinforcing member. The pressure injection-grouting techniques helps to increase the bearing capacity of reinforcing member by enhancing larger effective pile diameter and increasing the radial stresses acting on the grout body and causing irregular surface. However, the pressure reinjection-grouting techniques is not commonly used because grouting equipment and practical application example are short and the verification of reinforcing effect is difficult. In this study, the laboratory test was performed to evaluate the reinforcing effect with variation of grouting methods in clay. As a result of the test, the pressure reinjection-grouting techniques showed that the pullout capacity of reinforcing member increased up to 1.22~2.61 times comparing to the gravity fill techniques.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.4
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• pp.289-299
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• 2019

Attitude control modeling and simulation (M&S) can be extensively applied in overall development process, from simple algorithm design to on-board software verification. This paper introduces CMG-based attitude control M&S software, which consists of 6-DOF modeling (CMG and space environments modeling), and attitude control algorithm. The M&S software is divided into three modules, from an inner CMG motor control module to an outer earth observation mission module. While an application of this developed software is currently limited to the initial-phase attitude controller development, its application area can be extended to the later-phases by considering sophisticated model information in future.

• KIPS Transactions on Computer and Communication Systems
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• v.11 no.2
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• pp.51-58
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• 2022

Blockchain technology is a system in which data from users participating in blockchain networks is distributed and stored. Bitcoin and Ethereum are attracting global attention, and the utilization of blockchain is expected to be endless. However, the need for blockchain data privacy protection is emerging in various financial, medical, and real estate sectors that process personal information due to the transparency of disclosing all data in the blockchain to network participants. Although studies using smart contracts, homomorphic encryption, and cryptographic key methods have been mainly conducted to protect existing blockchain data privacy, this paper proposes data privacy using matrix character relocation techniques differentiated from existing papers. The approach proposed in this paper consists largely of two methods: how to relocate the original data to matrix characters, how to return the deployed data to the original. Through qualitative experiments, we evaluate the safety of the approach proposed in this paper, and demonstrate that matrix character relocation will be sufficiently applicable in private blockchain environments by measuring the time it takes to revert applied data to original data.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.10-18
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• 2014

Mechanically fastening FRP (MF-FRP) strips using nails and anchors, has been shown to provide a more ductile behavior to the strengthened structural element than using bonded FRP. To further advance the state of the knowledge on this strengthening method, the current study examined environmental effects for six months on MF-FRP beams. Reinforced concrete beams strengthened with mechanically fastened FRP strips and subjected to sustained loads for six months were exposed to outdoor weather and constant high temperatures ($40^{\circ}C$). For comparison, the behavior of RC beam with and without sustained loads was evaluated. Results from flexural tests did not show any significant degradation or change of failure mode as a result of sustained load and of environmental effects such as high temperatures and outdoor weather over a period of six months. Failure of the beams was governed by FRP delamination followed by concrete crushing as not much load applied to the nail and anchors because of slip effects.