• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.93-100
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• 2014

Steel reinforcement buried in concrete structure in submerged zone does not easily become corroded due to lack of dissolved oxygen. For that reason, accelerated corrosion test in submerged state is performed with an electrochemical method, which is not suitable for actual corrosion mechanism and makes it difficult to find relevance with long-term behavior. In this study, accelerated corrosion test was performed with the temperature and chloride concentration as main variables in order to establish a method for accelerated corrosion test in submerged zone. Corrosion was determined by the result of reinforcement corrosion monitoring based on galvanic potential measurement and half-cell potential method. The accelerated corrosion test result showed that temperature had the most dominant influence. To determine the chloride content, chloride concentration by depth in the test sample was measured. With the same conditions, chloride penetration interpretation was performed by DuCOM, a FEM durability interpretation program. Also, a test was performed to measure dissolved oxygen according to soaking conditions of artificial seawater, which was used for verifying the validity of the accelerated corrosion test result.

• Atmosphere
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• v.20 no.2
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• pp.131-151
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• 2010

This study establishes a conceptual model to analyze heavy rainfall events in Korea using multi-functional transport satellite-1R satellite images. Three heavy rainfall episodes in two major synoptic types, such as synoptic low (SL) type and synoptic flow convergence (SC) type, are analyzed through a conceptual model procedure which proceeds on two steps: 1) conveyer belt model analysis to detect convective area, and 2) cloud top temperature analysis from black body temperature (TBB) data to distinguish convective cloud from stratiform cloud, and eventually estimate heavy rainfall area and intensity. Major synoptic patterns causing heavy rainfall are Changma, synoptic low approach, upper level low in the SL type, and upper level low, indirect effect of typhoon, convergence of tropical air in the SC type. The relationship between rainfall and TBBs in overall well resolved areas of heavy rainfall. The SC type tended to underestimate the intensity of heavy rainfall, but the analysis with the use of water vapor channel has improved the performance. The conceptual model improved a concrete utilization of images and data of satellite, as summarizing characteristics of major synoptic type causing heavy rainfall and composing an algorism to assess the area and intensity of heavy rainfall. The further assessment with various cases is required for the operational use.

• Journal of the Korean Ceramic Society
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• v.44 no.9
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• pp.529-535
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• 2007

Calcium oxide has been used as a demolition agent in fracturing rocks and old concrete structures, etc. With the agent, demolition work can be done in safety without a noise, vibration and any other pollution, since high expansive pressure is obtained gradually by only mixing the agents with water and pouring the slurry into boreholes. But application of the non-explosive demolition agent is a time-consuming job, especially in winter. Essentially, this problem is related to the reaction rate of calcium oxide with water. This study examines the influence of additives such as cement and anhydrite on expansion pressure of calcium oxide at different curing temperatures. The expansion pressure of calcium oxide began to increase steadily with the rise of the curing temperature. When mixing calcium oxide alone with water, blown-out shot occurred. But as additives were added to calcium oxide, the reaction of calcium oxide delayed and the expansion pressure showed gradual increment. Especially, anhydrite showed a superior delaying effect than cement on the reaction of calcium oxide.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.2
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• pp.55-64
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• 2015

In this study, a 3-D flame cooling analysis is conducted to examine thermal safety for the flame deflector of the 75 tonf class propulsion test facility, and the safe discharge of the exhaust gas is assessed by using numerical results. The Mixture multiphase model is adopted for the simulation of heat transfer and phase exchange process between flame and cooling water, and the computational study using the single species unreacted model for the exhaust plume is carried out for the flame cooling. Numerical analysis predicts maximum temperature on the flame deflector wall for different water flow rates, and evaluates the safe minimum flow rate of water corresponding to the fire-resistant temperature for concrete.

• Journal of the Korean Solar Energy Society
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• v.22 no.3
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• pp.39-46
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• 2002

The results of experiment on the performance of natural ventilation by insulation thickness and height system of solar chimney are described. The 3-inside wall was made of concrete and 1-wall was made of glass. The two kinds of model experiment were performed. One was the varition of the 60cm, 90cm and 120cm of solar chimney, the other was the variation of the insulation thickness 10mm and 50mm and without insulation of outside wall of solar cimney. As the temperature difference between bottom and top expressed $1.7\sim2.9^{\circ}C$, air velocity measured $0.5\sim0.8m/s$ and ventilation rate was $194.4m^3/h$ in the case of the 120cm height of solar chimney, the respect of natural ventilation performance was superior to others cases in the first model experiment. Though the case of 120cm height of solar chimney was attached 50mm insulation the ventilation rate was not so much as the case of solar chimney was attached 10mm insulation. the temperature difference between bottom and top was the largest in the other cases. From this research, the natural ventilation performance of solar chimney was affected by not only height and insulation thickness of solar chimney but also wind velocity and directon.

• Journal of Pharmacopuncture
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• v.14 no.3
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• pp.19-45
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• 2011

Objectives: This study was performed to analyse the effects of Sweet Bee Venom(Sweet BV-pure melittin, the major component of honey bee venom) on the central nervous system in rats. Methods: All experiments were conducted at Biotoxtech Company, a non-clinical studies authorized institution, under the regulations of Good Laboratory Practice (GLP). Male rats of 5 weeks old were chosen for this study and after confirming condition of rats was stable, Sweet BV was administered in thigh muscle of rats. And checked the effects of Sweet BV on the central nervous system using the functional observational battery (FOB), which is a neuro-toxicity screening assay composed of 30 descriptive, scalar, binary, and continuous endpoints. And home cage observations, home cage removal and handling, open field activity, sensorimotor reflex test/physiological measurements were conducted. Results: 1. In the home cage observation, there was not observed any abnormal signs in rats. 2. In the observation of open field activity, the reduction of number of unit areas crossed and rearing count was observed caused by Sweet BV treatment. 3. In the observation of handling reactivity, there was not observed any abnormal signs in rats. 4. In the observation of sensorimotor reflex tests/physiological measurements, there was not observed any neurotoxic signs in rats. 5. In the measurement of rectal temperature, treatment of Sweet BV did not showed great influences in the body temperature of rats. Conclusions: Above findings suggest that Sweet BV is relatively safe treatment in the central nervous system. But in the using of over dose, Sweet BV may the cause of local pain and disturbance of movement. Further studies on the subject should be conducted to yield more concrete evidences.

• International Journal of Highway Engineering
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• v.2 no.2
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• pp.129-138
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• 2000

This study presents the mechanical characteristics, such as the permanent deformation and the crack, of the large stone asphalt mixtures. The large stone mixture was studied by Kandhal at NCAT(National Center for Asphalt Technology) in 1989. Japan and Arabian countries adopted the large stone mixture for the pavement construction. The experience and the study results showed that the interlocking of the aggregate system of the large stone mixtures is stable and less dependent on the binder characteristics in high temperature. These properties are known as the rutting resistant parameters. However, the mechanical test results should be supported to prove the benefits of the large stone mixtures. The creep test, resilient modulus tests on three different temperature, wheel tracking test and ravelling tests were conducted to evaluate the performance of the large stone mixtures in this study. The test results were compared with the conventional mixtures and modified asphalt concrete mixtures. The large stone mixtures showed better rutting resistance performance.

• Steel and Composite Structures
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• v.33 no.3
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• pp.319-332
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• 2019

This study is aimed to predict the behaviour of channel shear connectors in composite floor systems at different temperatures. For this purpose, a soft computing approach is adopted. Two novel intelligence methods, including an Extreme Learning Machine (ELM) and a Genetic Programming (GP), are developed. In order to generate the required data for the intelligence methods, several push-out tests were conducted on various channel connectors at different temperatures. The dimension of the channel connectors, temperature, and slip are considered as the inputs of the models, and the strength of the connector is predicted as the output. Next, the performance of the ELM and GP is evaluated by developing an Artificial Neural Network (ANN). Finally, the performance of the ELM, GP, and ANN is compared with each other. Results show that ELM is capable of achieving superior performance indices in comparison with GP and ANN in the case of load prediction. Also, it is found that ELM is not only a very fast algorithm but also a more reliable model.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.283-288
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• 2018

Since the crack self-healing materials are activated according to the exposure environmental conditions from the time of crack occurrence, it is very important to clarify the relationship between the healing performance and the exposure environmental conditions of the crack surface. In this paper, the influence of the exposure environmental conditions on the crack healing performance of self-healing repair mortar was investigated through the water permeability test. The influence of temperature and humidity on the crack width of cracked specimens was evaluated. As a result of measuring the change of the crack width, the effect of curing temperature was negligible but it was confirmed that crack-closing occurred due to the change of dry-wet condition. The healing materials produced on the crack surface of the specimens was identified as calcite minerals. Since the minerals with high density are precipitated under the influence of gravity, the healing performance is somewhat different according to the direction of the crack surface, and the healing performance was significantly improved in the wet exposure condition than the air exposure condition.

• Journal of Korean Society on Water Environment
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• v.35 no.5
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• pp.432-438
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• 2019

The purpose of this study is to predict Trophic Diatom Index (TDI) in tributaries of the Han River watershed using the random forest algorithm. The one year (2017) and supplied aquatic ecology health data were used. The data includes water quality(BOD, T-N, $NH_3-N$, T-P, $PO_4-P$, water temperature, DO, pH, conductivity, turbidity), hydraulic factors(water width, average water depth, average velocity of water), and TDI score. Seven factors including water temperature, BOD, T-N, $NH_3-N$, T-P, $PO_4-P$, and average water depth are selected by the Correlation Feature Selection. A TDI prediction model was generated by random forest using the seven factors. To evaluate this model, 2017 data set was used first. As a result of the evaluation, $R^2$, % Difference, NSE(Nash-Sutcliffe Efficiency), RMSE(Root Mean Square Error) and accuracy rate show that this model is compatible with predicting TDI. To be more concrete, $R^2$ is 0.93, % Difference is -0.37, NSE is 0.89, RMSE is 8.22 and accuracy rate is 70.4%. Also, additional evaluation using data set more than 17 times the measured point was performed. The results were similar when the 2017 data set were used. The Wilcoxon Signed Ranks Test shows there was no statistically significant difference between actual and predicted data for the 2017 data set. These results can specify the elements which probably affect aquatic ecology health. Also, these will provide direction relative to water quality management for a watershed that must be continuously preserved.