• Computers and Concrete
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• v.16 no.3
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• pp.343-356
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• 2015

1078 sets of mixtures in total that include fly ash, slag, and/or silica fume have been collected for prediction on concrete properties. A new database platform (Compos) has been developed, by which the stepwise multiple linear regression (SMLR) and BP artificial neural networks (BP ANNs) programs have been applied respectively to identify correlations between the concrete properties (strength, workability, and durability) and the dosage and/or quality of raw materials'. The results showed obvious nonlinear relations so that forecasting by using nonlinear method has clearly higher accuracy than using linear method. The forecasting accuracy rises along with the increasing of age and the prediction on cubic compressive strength have the best results, because the minimum average relative error (MARE) for 60-day cubic compressive strength was less than 8%. The precision for forecasting of concrete workability takes the second place in which the MARE is less than 15%. Forecasting on concrete durability has the lowest accuracy as its MARE has even reached 30%. These conclusions have been certified in a ready-mixed concrete plant that the synthesized MARE of 7-day/28-day strength and initial slump is less than 8%. The parameters of BP ANNs and its conformation have been discussed as well in this study.

• Journal of the Korean institute of surface engineering
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• v.51 no.5
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• pp.316-324
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• 2018

Harsh seawater environment is subdivided into marine atmosphere, splash zone, tidal zone, submerged zone and bottom of sea depending on the exposed part. Since corrosion rate depends on the conditions of the exposed parts, proper protection and maintenance for each parts are essential for long-term use of steel structures in seawater environment. For steel structures which were installed in Shiwha Lake, a special maintenance system is required to guarantee its long-term durability and safety. As the tidal power plant has recently been operated, the salinity has risen due to the rapid influx of seawater upstream into Sihwa Lake and the corrosion tendency of the structure is variable according to the water level fluctuation. In this study, corrosion properties of steel structures under water level fluctuation was evaluated by corrosion rate measurement, visual inspection and natural potential measurement and their durability and life management were discussed in view of the effect of variation in of seawater level fluctuations in Shihwa Lake.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.1
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• pp.52-60
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• 2018

The winding of the motor stator coil is broken due to external stress and various factors. If the proper current is not injected when interturn fault(ITF) occurs, the fault can easily be expanded and the motor can be finally destroyed, resulting in many problems with time costs and safety. In this paper, the power loss limit concept, which is the inherent durability of each motor, is applied to secure safety by controlling the total power loss of the motor within the limits. So, we propose an algorithm that can control maximum torque per minimum power loss based on constant torque curve and power loss limit. To verify the proposed method, the simulation and experimental results with an Interior permanent magnet synchronous motor(IPMSM) having an ITF are shown.

• Tribology and Lubricants
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• v.29 no.1
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• pp.7-12
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• 2013

Turbine power control devices at a nuclear / thermoelectric power plant lead to failure by creating mechanical shocks and strong vibrations that are due to the strong elasticity of a spring and the inertia of the valve face during its rapid movement to block steam. To ensure durability of the turbine power control device, which is the main component in the power plant, it is necessary to develop a device that can prevent such vibrations. In this study, a cushion mechanism is added to the head of the hydraulic servo actuator, which is a turbine power control device. Moreover, the cushion mechanism, which includes various modifies shapes and orifices is investigated dynamically through modeling and simulations.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.57-64
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• 2008

Generally, organic paint on steel towers can guarantee durability in normal condition but occasionally shows its deterioration on the power line tower and electric power facilities, exposed to light(ultra violet) or heat. The objective of this study is to develope the inorganic paint material based on fluid silicic acid for steel electric power facilities. For the purpose, optimal mixture proportion is derived through 6 preliminary test and, additionally physical and durability performance test are carried out for selected specimens. The performances of developed organic paint material is similar to those of organic paint material. If resistance to chemical attack is improved, the developed inorganic paint is evaluated to replace the organic paint and obtain wide application.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.637-642
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• 1998

This study was performed to develop effective management system of concrete structures in Nuclear Power Plants. This D/B system includes three kinds of data : 1)visual inspection data(cracking, spalling, etc.) 2) durability data carbonation, chloride attack, etc. 3) in-service inspection data(prestressing force. material properties, etc. ) By using the life management D/B System, the field engineers can easily acquire the information about the various inspection data. repair and accidental histories of structures. This system, will contribute to the efficient life management of concrete structures.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.2
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• pp.110-116
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• 2013

A concrete structure has become bigger and higher because of development of construction technology and a change in construction environment. Also it tends to focus on repairing, reinforcement and exterior in harmony with environment for structure maintenance and performance improvement. The research is about eco friendly durable painting applicable to concrete structure using civil and architecture. it purpose to improve external beauties and durable problems due to flexibility by variation of temperature, adhesion of exterior wall, crack and delamination in existing organic and mineral painting. For those problems, we made a eco friendly pre-paint that is made with preliminary treatment mixture as a highly enriched waterproof agent and adhesive increasing agent in preprocessing mixture. Then we performed an experiment on durability of prevention neutralization of concrete, durability abrasion, hiding power, adhesion, temperature resistance and resistance to chemical attack. The result of an experiment shows that hiding power is over 0.96 in standard test, durability abrasion test got higher value 1mg than water paint 75mg and tensile strength is 6 times higher than standard waterproof specification.

• Journal of the Korea Concrete Institute
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• v.23 no.3
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• pp.311-320
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• 2011

Fly ash (FA), byproduct from power plant has been actively used as mineral admixture for concrete. However, since bottom ash (BA) is usually used for land reclaim or subbase material, more active reuse plan is needed. Pond ash (PA) obtained from reclaimed land is mixed with both FA and BA. In this study, 6 PA from different domestic power plant are prepared and 5 different replacement ratios (10%, 20%, 30%, 50%, and 70%) for fine aggregate substitutes are considered to evaluate engineering properties of PA as fine aggregate and durability performance of PA concrete. Tests for fine aggregate of PA for fineness modulus, density and absorption, soundness, chloride and toxicity content, and alkali aggregate reaction are performed. For PA concrete, durability tests for compressive strength, drying shrinkage, chloride penetration/diffusion, accelerated carbonation, and freezing/thawing are performed. Also, basic tests for fresh concrete like slump and air content are performed. Although PA has lower density and higher absorption, its potential as a replacement material for fine aggregate is promising. PA concrete shows a reasonable durability performance with higher strength with higher replacement ratio. Finally, best PA among 6 samples is selected through quantitative classification, and limitation of PA concrete application is understood based on the test results. Various tests for engineering properties of PA and PA concrete are discussed in this paper to evaluate its application to concrete structure.

• Fire Protection Technology
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• s.16
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• pp.13-19
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• 1994

An Experimental study on the relation between responsiveness and elapse of years This experiment study is to appraise a fire detector's durability & reliability. Fire detector is located in office, temp range 10-27 고 65 15%, installed in the ceiling with power on. This is the experiment report of elapsed 5 years.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.110-112
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• 1998

Some recomendations for the manufacturing, operation and maintanance of amorphous alloy core transformer are presented through the operation experiance. Transformers on trouble was taken to pieces and tested from a viewpoint of durability, and low loss characteristics.