• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.391-396
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• 2002

The so called setting is defined as the onset of rigidity in fresh concrete. In the analysis of the early-age concrete behavior, we consider fresh concrete as a structural element immediately after mixing. But for the activation of real structural behavior of fresh concrete, it takes some time after the beginning of hydration reaction. So, the very early age deformations due to hydration heat and shrinkage which occur before the setting do not produce restraint stresses. In this paper, we propose a setting characteristic model based on the so called percolation theory. From the analysis using the model, the influence of curing temperature is investigated and analytical results are compared with experimental results. From the comparison, the validity of proposed model is verified. This model is also applied to evaluate stress development in a temperature-stress test machine (TSTM) specimen and then the effect of setting time on the stress development is discussed.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.6
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• pp.144-152
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• 2003

Laboratory experiments were carried out to investigate the influence of pore water contamination on the treatment effect of sandy soil which was solidified by Portland cement. In the experiments, setting time of hydraulic cement that was mixed with contaminated mixing water was measured using Vicat equipment and observed the tendency of setting process with the kind of contaminants, organic or inorganic components. It was shown that organic contaminants of the mixing water affect largely on the initial setting process of hydraulic cement and inorganics, expecially heavy metals, did not affect on the initial setting process, otherwise it was appeared that setting time of the sandy soil that was contaminated with inorganic components was apparently faster than the sandy soil that did not include inorganic components even though organic concentrations was relatively low level (COD=200∼300) in the mixing water. The results of unconfined compression strength test (UCST) were well consistent with the results of Vicat equipment test.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.1195-1198
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• 2000

In this paper, setting and strength properties of concrete with contents of super retarding agent are discussed. Gluconic acid and sucrose and used for super retarding agent. According to experimental results, as super retarding agent content increases, slump show to be increased, while air content decrease about 1~2%. In case of setting properties, as super retarding agent content increases, setting time delays considerable. When gluconic acid and sucrose is added about 0.3%, it delays more than 10days. Compressive strength of concrete of concrete with super retarding agent shows to be higher than that without it. Retarding of setting time of concrete using gluconic acid is longer than that using sucrose.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.99-102
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• 2003

This study discusses the determination of removal time of forms with early strength development in high strength concrete. According to the results, as W/B increases by 10％, the setting time is shortened by about 2 hours. The time when compressive strength of 8 MPa is gained is about 20 hours. Bond strength between form and concrete is highest around final setting time, but decreases drastically after that. Amount of concrete sticking on the form is large before setting, but after that, it is little. The rebound value of P type schmidt hammer is measured faster by 2-3 hours than compressive strength. It is also confirmed that the removal of forms is possible when the rebound value of P type schmidt hammer is more than 34

• Journal of the Korea Furniture Society
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• v.21 no.2
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• pp.97-110
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• 2010

As the contemporary lifestyle has changed and the time to enjoy hobbies is increased, people prefer the DIY furniture that can be used at homes by manufacturing their own unique furnitures. Especially, the architecture of our country handed down traditionally or the setting-up technique used in furnitures are the techniques to maintain firmness even after long time passes by. Accordingly, in order to supply a firm setting-up technique mostly used by craftsman in the manufacture of DIY furniture and to apply this easily, a web site and 3D program system are required. In order to do so, it is important to prepare the system of setting-up that can be followed easily first by classifying the difficulty of setting-up that the general public can follow easily without having difficulties among the types of setting-up. Therefore, this study has performed a systematic arrangement by the order of difficulty for the types of setting-up that are investigated and arranged to set the purpose as presenting materials that are helpful so the furnitures using setting-up can be manufactured even in the manufacture of general DIY furnitures. Accordingly, the investigated results of setting-up difficulty are applied in the order of difficulty to a 3D program and as users select the suitable setting-up for their own standard, it is expected to be utilized in DIY furnitures that are manufactured directly.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.323-328
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• 2002

Rapid set accelerators are widely used in tunnel construction, however quality criteria of and dosage are not well established. The density and solid content of admixtures, setting time and compressive strength of paste and mortar with admixtures were investigated to establish the quality criteria. While the early strength of mortar with sodium-silicate, sodium-aluminate and calcium aluminate type admixtures that have high alkali content are very high, but long-term strength are low. Aggregates of shotcrete has to be carefully selected. Sodium-silicate type admixture need longer setting time than the others.

• Journal of Korean language education
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• v.25 no.1
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• pp.83-113
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• 2014

This study aims to examine the change of strategy use by analyzing the refusal sequence of beginner Japanese Korean learners by time difference of 10 weeks. The results of the study are as follows; First, in the solidarity system of politeness(power-, distance-), learners showed similar ability as native Koreans after 10 weeks. Second, in the deference system(power-, distance+), there was a difference according to the situational burden when using strategies. In the invitational setting, the learners sought justification for their refusal or tried to negotiate by explaining in detail as time passed. However, in the request setting, they showed no will to compromise by refusing directly and leading the listener to give up. Third, similar difference was found in the use of strategies depending on the situational burden in the hierarchical system(power+, distance+). While learners could present their justification for refusal by showing their interest in the invitation as time passed in the invitation setting, they expressed straight refusal and were not willing to negotiate in the request setting.

• Journal of Applied Reliability
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• v.15 no.4
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• pp.248-255
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• 2015

Purpose : The purpose of this research is to develop the optimized method and process in the reliability-growth target setting, especially for complex and repairable system (or products) such as vehicle and airplane, construction equipment. Method : A reliability-growth test plan specifies a scenario to achieve the planned reliability value (or reliability target). The major elements in test planning are reliability-growth starting time and reliability level at that time, reliability-growth rate and reliability-growth target. All of them except a reliability target can be referred to the previous development data and reference researches. The reliability target level is directly influencing to test period (or time) which is related to test and warranty cost together. There are a few researches about the reliability target setting method and but showing the limitations to consider the views of engineering, business and customer together. There is no research how to handle the target setting process in detail. Result : We develop the optimized method and systematic process in reliability target setting with considering such views. This research also establish the new concept as production capability which means company (or supplier) capability to product its products. Conclusion : In this research result, we apply the new method to a few projects and can set the reasonable test planning. The developing results is showing the good balance between the developing cost and warranty cost at market.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.7 s.172
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• pp.155-163
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• 2005

Pressure heating rollers with temperature control were mounted to a flat cable laminating machine (FCLM). Pressure heating rollers should be heated up to the setting temperature $(175^{\circ}C)$ and kept on to producing good quality flexible flat cables (FFC). Existing Pressure heating rollers took more than 70minutes to the setting temperature and did not keep on the setting temperature in production. Temperature controller, electric power controller, material and diameter of rollers and heat capacities were changed to improve the temperature control of the pressure heat rollers for better production of the FFC. Thus, the reaching time to the setting temperature (RT), temperature stability time (TST) and temperature hunting (TH) were measured and compared with the existing pressure rollers case. The RT of A roller was shortened by 50minutes, and B roller was shortened by 15minutes. The TST of A roller was shortened by 13minutes, and B roller was shortened by 15minutes. The THs of both A and B rollers were settled up to ${\pm}5^{\circ}C$. Finally, the productivity of the FCLM and the quality of the FFC were increased.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.87-88
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• 2020

The purpose of this study is to explore the possibility of estimating optimum surface finish time of the fresh concrete placed at the job site by applying a surface hardness test meter(Durometer). Tests are carried out by measuring and comparing the Penetration resistance test and hardness test by Durometer. Penetration resistance tester and improved Durometer are similar, but the higher the temperature, the higher the setting time, and the higher the correlation was shown. When the hardness value of the improved Durometer is about 50 HD, it is found that the initial and 80 HD represent the end. It is expected that this will be useful in determining the finish time of the surface at the actual site.