• Proceedings of the KSR Conference
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• 2005.11a
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• pp.1184-1189
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• 2005

Durability of concrete has been currently issued in the engineering societies and a large number of studies on the concrete corrosion in salty environment have been performed. The reinforcement corrosion, which is the primary reason of deterioration of the concrete structure exposed to chloride environment. is caused by the chloride ions infiltration owing to underground water seeping into the concrete. In this study. the endurance periods using the diffusion equation of the concrete specification have been evaluated on the concrete structures with different addictives for the brand new R/C subway structure exposed to seashore underground water. Furthermore. the guidance for proper use of the addictives and the reasonable thickness of concrete cover are derived for concrete mixing. From the result of the evaluation corresponding to salt damage for Inchon subway line I, the endurance periods of the ordinary Portlandcement concretes are represented as $42\~75$ years and fail to achieve the objective period of 100 years. However, the lower water-cement ratio expands the endurance periods and the blast furnace slag concrete with small quantity of the silica fume, which shows the best performance of corrosion resistance in this study, represents more than 170 years of the endurance period. Moreover, the case of use of blast furnace slag and fly ash together shows the endurance period of $134\~171$ years and it means that the result very satisfies the objective endurance period.

• Journal of the Korean Solar Energy Society
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• v.39 no.2
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• pp.45-55
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• 2019

More than 76% of the detached houses in Korea are over 20 years old. These old detached houses have poor energy efficiency. According to the 2017 Housing Census (Statistics Korea), more than 50% of low-income families live in detached houses. Therefore, the improvement of energy efficiency in old detached houses is needed from the viewpoint of energy welfare. The general method of building energy modelling for the verification of energy efficiency is based on the construction year data of "Building Design Criteria for Energy Saving" due to the cost and time involved in collecting the thermal performance data of buildings. There is poor accuracy with the deterioration of long-term aging of building materials. Also, the selection of alternatives for energy performance improvement is based on the items to be applied, not a performance improvement goal. It is difficult to calculate energy performance that reflects variations in various parameters with dynamic energy simulations. In this study, the influence of long-term aging is used to accurately predict the energy performance of old detached houses. The building energy modelling method is called ENERGY#, which is a static analysis method based on ISO13790. Energy performance is evaluated by a combination of input variables including building orientation, insulation of walls and roof, thermal performance of windows and window/wall ratio, and infiltration rate. Finally, this study provides a way to determine alternatives that meet energy performance improvement goals.

• Korean Journal of Remote Sensing
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• v.38 no.6_3
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• pp.1861-1869
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• 2022

Recent climate change can increase the frequency and damage of wildfires worldwide. It can also lead to the deterioration of the forest ecosystem and increase casualties and economic loss. Satellite-based indices for forest damage can facilitate an objective and rapid examination of burned areas and help analyze inaccessible places like North Korea. In this letter, we conducted a detection of burned areas in North Korea using the traditional Normalized Burn Ratio (NBR), the Normalized Difference Vegetation Index (NDVI) to represent vegetation vitality, and the Fire Burn Index (FBI) and Forest Withering Index (FWI) that were recently developed. Also, we suggested a strategy for the satellite-based detection of burned areas in the Korean Peninsula as a result of comparing the four indices. Future work requires the examination of small-size wildfires and the applicability of deep learning technologies.

• Architectural research
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• v.7 no.1
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• pp.49-54
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• 2005

Conventional studies have focused on the reduction in the water-cement ratio, the use of various admixtures, etc., to ensure the durability of reinforced concrete structures against such deterioration factors as carbonation and chloride attack. However, improvement in the concrete quality alone is not considered sufficient or realistic for meeting the recent demand for a service life of over 100 years. This study intends to improve the durability of reinforced concrete structures by improvement in the reinforcing steel, which has remained untouched due to cost problems, through subtle adjustment of the steel components to keep the cost low. As a fundamental study on the performance of Cr-bearing rebars in steel reinforced concrete structures exposed to corrosive environments, The test specimens were made by installing 8 types of rebars in concretes with a chloride ion content of 0.3, 0.6, 1.2, 2.4 and $24kg/m^3$. Corrosion accelerated curing were then conducted with them. The corrosion resistance of Cr-bearing rebars was examined by measuring crack widths, half-cell potential, corrosion area and weight loss after 155 cycles of corrosion-accelerating curing. The results of the study showed that the corrosion resistance increased as the Cr content increased regardless of the content of chloride ions, and that the Cr-bearing rebars with a Cr content of 5% and 9% showed high corrosion resistance in concretes with a chloride ion content of 1.2 and $2.4kg/m^3$, respectively.

• Advances in concrete construction
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• v.13 no.2
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• pp.191-198
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• 2022

FIB is introduced as the sole guideline for the design purpose that results in a practical relationship for the torsional capacity of concrete beams strengthened with carbon fiber-reinforced polymer (CFRP). This study applies first-order reliability method to assess the reliability evaluation of the torsional capacity of CFRP-strengthened beams on the basis of FIB guidelines. In terms of steel reinforcement losses, this study applies a corrosion model to investigate the ceaseless deterioration of the existing structure. Hence, the average of reliability indices varies between 2.68 and 2.80, indicating the reliability viewpoint of the design methodologies. The average values are somehow low compared to the target values of reliability (3.0 or 3.5) applied in the calibration stage of the FIB guideline. In this way, the partial safety factors may change in the forthcoming guideline revisions. For this aim, the reliability of strengthening ratio was applied to assess the variation in the average value of the reliability index with different partial safety factors. The performance of parametric study for the factor proved that minimum values of 1.60 and 2.32 are required for target values of reliability (3.0 and 3.5), respectively.

• Korean Journal of Heritage: History & Science
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• v.56 no.2
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• pp.148-169
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• 2023

Hayeob pigment is known as one of the traditional dark green pigments, but the color, raw material, and manufacturing method have not been clearly identified. However, comparing the analysis results of the particle shape and constituent minerals of Hayeob pigments revealed through pigment analysis studies of colored cultural properties such as Dancheong, Gwaebul, and paintings, Hayeob pigments appear to be the same as Dongrok pigments produced by salt corrosion. Therefore, in order to restore Hayeob pigment, the manufacturing method of Dongrok pigment was studied based on the records of old literature. The Dongrok pigment manufacturing method confirmed in the old literature records is a natural corrosion method in which copper powder and a caustic are mixed and then left in a humid condition to corrode. Based on this, artificial corrosion using a corrosion tester was adopted to corrode the copper powder more efficiently, and an appropriate mixing ratio was selected by analyzing the state of corrosion products according to the mixing ratio of the caustic agent. In addition, the manufacturing method of Dongrok pigment was established by adding a salt removal process to remove residual caustic agents and a purification process to increase chroma during pigment coloring. The prepared Dongrok pigments have a bluish green or green color, show an elliptical particle shape and a form in which small particles are aggregated, and a porous surface is observed. The main constituent elements are copper(Cu) and chlorine(Cl), and the main constituent mineral is identified as atacamite [Cu₂Cl(OH)₃]. As a result of an accelerated weathering test to evaluate the stability of the prepared Dongrok pigments, it was found that the greenness partially decreased and the yellowness significantly increased as deterioration progressed. Before deterioration, the Dongrok pigments had lower yellowness compared to the Hayeob pigments of the old Dancheong, but after deterioration, yellowness increased significantly, and it was found to have a similar chromaticity range as Dancheong's Hayeob pigments. As a result, the prepared Dongrok pigments were confirmed to be similar to Dancheong's Hayeob pigments in terms of color as well as particle shape and constituent minerals.

• Structural Engineering and Mechanics
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• v.39 no.6
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• pp.795-812
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• 2011

Estimation of damage probability of buildings under a future earthquake is an essential issue to ensure the seismic reliability. Fragility curves are useful tools for showing the probability of structural damage due to earthquakes as a function of ground motion indices. The purpose of this study is to compare the damage probability of R/C buildings with low and high level of strength and ductility through fragility analysis. Two different types of sample buildings have been considered which represent the building types mentioned above. The first one was designed according to TEC-2007 and the latter was designed according to TEC-1975. The pushover curves of sample buildings were obtained via pushover analyses. Using 60 ground motion records, nonlinear time-history analyses of equivalent single degree of freedom systems were performed using bilinear hysteretic model and peak-oriented hysteretic model with stiffness - strength deterioration for each scaled elastic spectral displacement. The damage measure is maximum inter-story drift ratio and each performance level considered in this study has an assumed limit value of damage measure. Discrete damage probabilities were calculated using statistical methods for each considered performance level and elastic spectral displacement. Consequently, continuous fragility curves have been constructed based on the lognormal distribution assumption. Furthermore, the effect of hysteresis model parameters on the damage probability is investigated.

• Journal of the Korea Institute of Building Construction
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• v.2 no.2
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• pp.121-127
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• 2002

The functions and uses of existing buildings are not properly changing as modern life needs. As a result, the frequent reconstruction(construction after removal) of existing buildings have been done but it became more and more difficult because of strengthening of regulations and systems concerning construction. And also it has several disadvantages like lower plot ratio and site coverage than existed buildings, enormous construction cost, production of waste-construction materials and thoughtless consumption of natural resources, which gives rise to environmental pollution. Therefore renovation is brought to the fore. In Korea, many business buildings were constructed in 1960s-1970s, during the period of high growth. Such buildings needs to be repaired in whole. It is caused by the change of social, economic, and cultural conditions and deterioration of equipments. Therefore renovation meets some necessary conditions; recovery of building functions and extension of building life span. In case study, the present state of renovation in business buildings is 1) Basic safety, for example, fire prevention and crime prevention, is great important. 2) Advanced technology, INS(international news service), IBS(Intelligent Building System), and internationalization, is pursued for adapting to multimedia ages. 3) It tries to promote proficiency, and to save the energy using spatial environment and natural energy(light and sound). Also, improving comfortable level of users and installing equipments for physically handicapped person needs to be considered.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.4
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• pp.82-90
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• 2009

Pneumatic cylinder is one of the low cost actuation sources which have been applied in industrial and prosthetic application since it has a high power/weight ratio, a high-tension force and a long durability However, the control problems of pneumatic systems, oscillatory motion and compliance, have prevented their widespread use in advanced robotics. To overcome these shortcomings, a number of newer pneumatic actuators have been developed such as McKibben Muscle, Rubber Actuator and Pneumatic Artificial Muscle (PAM) Manipulators. In this paper, one solution for position control of a robot arm, which is driven by two pneumatic artificial muscles, is presented. However, some limitations still exist, such as a deterioration of the performance of transient response due to the changes in the external load of the robot arm. To overcome this problem, a switching algorithm of the control parameter using a learning vector quantization neural network (LVQNN) is proposed in this paper. This estimates the external load of the pneumatic artificial muscle manipulator. The effectiveness of the proposed control algorithm is demonstrated through experiments with different external working loads.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.1
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• pp.102-108
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• 2006

On the refutation demanded for a control of various toxic substances. PCBs(poly chlorinated biphenyl) has a fatal poisonous matter in the ecosystem and the environmental pollution as it Is a kind of stable chemical substance. Especially, the gross Product of PCBs is estimated at about one million tonnage all over the world. However it is kept on storing in untreated state, then has a deterioration by the Prolonged storage and a risk of overflowing. Therefore, this research examined the fundamental characteristics of combustion and emission for the target of using the IPA (iso-propyl alcohol) solution as a part of PCBs control. IPA was filled to three kinds of Vessel, i.e. Vessel I, II, and III, and then was investigated as follows combustion shape, flame temperature. mass burning velocity, and PM(Particulate matter). A radial thermometer and a C-A thermocouple measured the flame temperature, and the optical extinction method by using He-Ne laser and the filter weight method used in the PM measurement. As a result, with an increasing of L/S ratio, the flame length become shorter and the burning velocity is more rapid, but the particulate matters is higher. It is supposed that the air flow rate is high on Vessel. and then the combustion is Promoted in the surface area of the upstream zone. The future works plan to investigate the characteristics with an using of the mixing of IPA and PCBs