• Proceedings of the Korean Institute of Building Construction Conference
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• 2004.05a
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• pp.1-4
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• 2004

In this paper. applicability of high early strength type AE water reducing agent(HESAEWA) developed by the authors is discussed by applying Mock-up test. For fresh concrete properties, concrete using existing AE water reducing agent(EAEWRA) and HESAEW A meets the target slump and air content at jobsite. Setting time of concrete using HESAEWA is shorter than that using EAEWRA. Remarkable variance of bleeding and settlement is not observed with type of AE water reducing agent. For hardened concrete properties, use of HESAEW A results in higher strength development compared with that of EAEWRA at standard curing and in field curing condition. Reaching time to accomplish 5MPa of compressive strength. which is possible to remove side form. is taken using HESAEWA earlier than that of EAEWRA by 1day. Therefore, it is confirmed that use of HESAEWA can meet the requirements of general quality of concrete and achieve high early strength development as well as has a desirable field applicability.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.3
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• pp.359-366
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• 2007

Slow sand filtrations have been widely used for water treatment in small communities, however their capacity is often limited by high turbidity in the raw water. For this reason, several pre-treatment facilities were required for a slow sand filter. Turbidity removal from the highly turbid raw water was investigated in roughing filters as a pre-treatment process. The roughing filters followed by rapid mixing tank were operated in the form of a contact filtration. In several jar tests, the predetermined optimum aluminium sulfate (alum) doses for turbid water of 30 and 120NTU were 30 and 50mg/L, respectively. At the optimum alum dose, physically optimum parameters including G value of $220sec^{-1}$ and rapid mixing time of 3 minutes were applied to the contact filtration system. Without addition of alum, the filtrate turbidity from the roughing filters, packed respectively with different media such as sand, porous diatomite ball and gravel, was in the range of 5~30NTU at filtration velocities of 30 and 50m/day. However, the application of a contact filtration to roughing filters showed stably lower filtrate turbidity below 1.0NTU at filtration velocity of 30 m/day. Although the filtration velocity increased to 50m/day, filtrate turbidity was still below 1.0NTU in both single and double layer roughing filters. At influent turbidity of 120NTU, the filtrate turbidity was over 5 NTU in the triple layer roughing filter, which shortened the filter run time. The flocs larger than $10{\mu}m$, formed in the rapid mixing tank, were almost captured through the roughing filter bed, while the almost flocs smaller than $10{\mu}m$ remained in filtrate.

• The Journal of the Korea Contents Association
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• v.13 no.9
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• pp.410-417
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• 2013

Long-term behavior analysis considering construction sequence should be performed in the design and the actual construction of reinforced tall buildings. Most of the analytical studies on this subject, however, has not been applied directly to the structural design and the construction caused by the simple approach. As the axial force redistribution of shores and columns is time-dependent, the actual construction sequence with the placement of concrete, form removal, reshoring, shore removal, and the additional load application is very important. Object-oriented analysis program considering construction sequence, especially time-dependent deformation in early days, is developed. This system is composed of input module, database module, database store module, analysis module, and result generation module. Linkage interface between the central database and each of the related module is implemented by the visual c# concept. Graphic user interface and the relational database table are supported for user's convenience.

• Journal of Korean Society on Water Environment
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• v.33 no.1
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• pp.8-14
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• 2017

Microcystis aeruginosa (M. aeruginosa) is a cyanobacterium species that can form harmful algal blooms in freshwater bodies worldwide. The use of pine needle extract (PNE) to control nuisance algae by allelopathic inhibition will be environmentally friendly and promising. PNE removed successfully upto 98% of M. aeruginosa at the following optimal conditions: pH 7, $25^{\circ}C$ of temperature, 100 rpm of mixing rate, 5 min of mixing time. These results was indicated that the amount of 1 g/L PNE was removed 1g dryweight/L of M. aeruginosa. The kinetic data showed substrate inhibition kinetics and maximum growth rate was obtained when the M. aeruginosa was grown in medium containing 0.5 g/L of initial concentration of PNE. Different substrate inhibition models were fitted to the kinetic data and found the Luong model was best. The model predicted kinetic parameters were in agreement with the experimental findings. The natural extract, PNE, can be a promising inhibition due to its high efficiency and low dose requirements.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.147-150
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• 1999

Glossing Exposure Concrete is a high quality architectural concrete, i.e., appearance of natural stone and a marbling effect concrete to achieve high quality glassy reflective surface for outer wall of the building. In this study to obtain the conservation and durability of gloss of the "glossing exposure concrete" we developed a from practice and the best mix proportion and derived the optimistic removal time of form to bring out the durable glassy reflective surface and durable concrete. Hereby with the "glossing exposure concrete" obtained, we investigate the accelerate carbonation and accelerate durability test to evaluate the durability factor of this type of concrete.is type of concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.668-671
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• 2004

Recently, the concern for mechanical properties at early age concrete are increasing because of the importance of the thermal stress and the determination of removal time of form work and prestressing work. In this study, an estimation for the development of compressive strength and elastic modulus with age in concretes isothermally cured $(10^{\circ}C,\;20^{\circ}C)$ and having W/C ratio of 30, 40, and $50\%$ were investigated. According to experiment results, the development of compressive strength and elastic modulus shows higher values at early ages as the W/C ratio decreases and curing temperature increases. When the maturity concept, for estimation of the strength, is adopted, a modification for W/C ratio is required at early ages.

• Carbon letters
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• v.12 no.2
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• pp.85-89
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• 2011

Coloured wastewater is released as a direct result of the production of dyes as well as from various other chemical industries. Many dyes and their breakdown products may be toxic for living organisms. Activated carbon is one of the best materials for removal of dyes from aqueous solutions. The present study describes the adsorption behaviour of methylene blue dye on three microporous activated carbons, where two samples (AC-1 and AC-2) were prepared by a polymer blend technique and the other is a microporous activated carbon (ARY-3) sample from viscose rayon yarn prepared by chemical-physical activation. The effects of contact time and activated carbon dosage on decolourisation capacity have been studied. The results show that activated carbon having mixed microporosity and mesoporosity show tremendous decolourisation capacity for methylene blue. In addition, the activated carbon in the powder form prepared by the polymer blend technique shows better decolourisation capacity for methylene blue than the activated rayon yarn sample.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.551-554
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• 2002

The paper discusses new approach for machining operation simulation using enhanced Z map algorithm. To extract the required geometric information from NC code, suggested algorithm uses supersampling method to enhance the efficiency of a simulation process. By executing redundant Boolean operations in a grid cell and averaging down calculated data, presented algorithm can accurately represent material removal volume though tool swept volume is negligibly small. Supersampling method is the most common form of antialiasing and usually used with polygon mesh rendering in computer graphics. The key advantage of enhanced Z map model is that the data structure is same with conventional Z map model, though it can acquire higher accuracy and reliability with same or lower computation time. By simulating machining operation efficiently, this system can be used to improve the reliability and efficiency of NC machining process as well as the quality of the final product.

• Tribology and Lubricants
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• v.11 no.2
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• pp.34-43
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• 1995

The boundary films formed in sliding on steel surfaces were characterized using various lubricants. The mechanism of boundary film formation and loss was investigated over a range of temperature. The thickness of the boundary films was monitored in-situ by an ellipsometer, and the composition of the films was analyzed by XPS. The performance of the lubricants is closely associated with boundary film forming ability. In order to achieve high load carrying capacity, a boundary film must be formed on the surface. Sliding is necessary to form the films and some time is also required. As temperature increases, chemical reactivity increases the film formation rate, while the film removal rate increases due to thg decrease of durability of the boundary film material. There is a balance between these two competing mechanisms and this balance is reflected in the boundary film thickness.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.421-422
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• 2010

The decision of the form removal time which leads the early assuring strength of the concrete from apartment construction is the fact which is important from reducing the period of works and the economical efficiency side. This study investigates practical application of early strength concrete for reduction of working preiod in apartment construction.