• Journal of Korean Society on Water Environment
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• v.25 no.5
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• pp.704-712
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• 2009

Advanced Phase Isolation Ditch (APID) process was studied to develop economic retrofitting technology, for the plants where retrofitting of common activated sludge process is required. In this study, to evaluate and monitor the effluent water quality ($BOD_5$, SS, T-N, and T-P) and operating conditions (Influent, SVI, SRT, and HRT) as process capable and stable parameters for treating municipal wastewater, a demonstration plant was installed and operated in the existing sewage treatment plant of P city. During this study, the average effluent $BOD_5$, SS, T-N, and T-P concentrations were 7.7, 5.6, 10.8, and 1.6 mg/L. Trend analysis of influent $BOD_5$, SS, T-N, and T-P in APID process were illustrated that APID process need for more strong APID process management on the winter session, such as developing new intermediated aeration mode, operating methods, and managements strategy. At the application of control chart, the signal of uncommon effects at APID process was determined much higher existing control chart tntr conventional control chart in this study. These results indicate that conventional control chart has been collected and determined cleary signal at only stable situation. Therefore, newly developed APID process of dynamic control chart can be one of the useful tool for monitoring and management process.

• Journal of the Korea Concrete Institute
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• v.22 no.6
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• pp.817-824
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• 2010

The concrete containment structures have been widely used in nuclear power plants, LNG storage tanks, etc., due to their high safety and economic efficiency. The containment structure consists of a bottom slab, wall, ring beam and dome. The shape of the roof dome has a very significant effect on structural safety, the quantity of materials, and constructability; the thickness and curvature of the dome should therefore be determined to give the optimum design. The ring beam plays the role as supports for the dome, resulting in a minimized deformation of the wall. The main issues in designing the ring beam are the correct dimensions of the section and the prestress level. In this study, an efficient design procedure is proposed that can be used to determine an optimal shape and prestress level of the dome and ring beam. In the preliminary design stage of the procedure, the membrane theory of shells of revolution is adopted to determine several plausible alternatives which can be obtained even by hand calculation. Based on the proposed procedures, domes and ring beams of the existing domestic containment structures are analyzed and some improvements are discussed.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.761-764
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• 2008

Most of ready-mixed concrete plants have the problem of construction waste sludge, which pollutes environment and causes economic loss due to the discard and increasing the cost of concrete. Thus, a recycling of the cement sludge has been strongly desired as one of their solution. This research is to the study on the recycling of the cement sludge, especially the study on the hydration control by the sodium gluconate as a set-retarder. The set-retarder can delay the hydration of the cement included in the sludge water, so that the sludge water can be substituted with some of new cement without the property of the cement. And it invests the effect of the sodium gluconate to the hydration of the cement in suspension. The degree of hydration of cement may be controlled by adding the sodium gliconate. The hydration delay time is observed that depends on the concentration of residual sodium gloconate, not how long the cement has been hydrated before the addition of the sodium gluconate.

• Journal of Families and Better Life
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• v.24 no.4 s.82
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• pp.127-139
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• 2006

The purpose of this research was to find out relation between the attitudes toward work and leisure in later life and intention to move to senior community available to work among 50's in Seoul, Incheon, and Kyunggido. The same research questions would be revealed as the previous one done by Cho & Cho(2006). The data were the part of the survey collected from 556 respondents with questionnaire during November, 2002 by the Hong's research team(2004). The results of this study showed that most respondents were somewhat actively preparing toward work in later life and the level of preparation differed by the individual characteristics such as age, health and occupation. They preferred various work items specially managing facility center, raising animals and plants, and managing educating center, which were different from what current elderly workers were mainly involved in. Similarly to the work, most respondents cared for the kind of leisure activities to continue and saved money for the leisure expenses in later life. The better the economic conditions, the more actively prepared for leisure in later life. They were strongly expected to participate in public leisure facilities and programs for the elderly as a user, volunteer, and/or activist. Over two thirds of the respondents preferred to work and live together in later life and over two out of five had intention to move to the senior community available to work. The more active in work and/or leisure in later life, the higher intention to work together and/or to move to the community. Those results generally supported the previous research showed that the needs of work and leisure in later life would be increased and varied, therefor housing for the elderly should considered work space and program as well as leisure. The further study was suggested to focus on the potential and current residents in the sample case of the comprehensive welfare town for the elderly by local administration.

• KDI Journal of Economic Policy
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• v.29 no.3
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• pp.75-109
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• 2007

This paper empirically investigates the effects of import tariff on within-plant productivity growth in Korean manufacturing, using the detailed plant-level longitudinal data of the Korea Census of Manufacturers for the period of 1993-2003. Our main findings are as follows: First, the productivity changes of Korean manufacturing for the period under analysis were mostly induced by within-plant productivity gains, rather than within-industry and/or between-industry resource reallocations. Second, after controlling for firm-specific heterogeneity, the estimation results indicate that lowering tariff-barriers has a positive impact on within-plant TFP growth. We interpret the results in a way that trade liberalization through the removal of tariff and non-tariff barriers heightens the competitive pressure, which in turn creates incentives to reduce production and managerial inefficiency and to invest more on innovative activities. Third, we also find that plant productivity growth from reducing tariff barriers is particularly conspicuous within a year after tariff changes, which implies that plants are quickly adjusting to heightened import competition. On the other hand, our results show that the trade effect on employment creation proceeds relatively slow.

• Journal of Ocean Engineering and Technology
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• v.29 no.5
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• pp.366-372
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• 2015

Ocean energy is one of the most promising renewable energy resources. In particular, South Korea is one of the countries where it is economically and technically feasible to develop tidal current power plants to use tidal current energy. In this study, based on the design code for HARP_Opt (Horizontal axis rotor performance optimizer) developed by NREL (National Renewable Energy Laboratory) in the United States, and applying the BEMT (Blade element momentum theory) and GA (Genetic algorithm), the optimal shape design and performance evaluation of the horizontal axis rotor for a 200-kW-class tidal current turbine were performed using different numbers of blades (two or three) and a pitch control method (variable pitch or fixed pitch). As a result, the VSFP (Variable Speed Fixed Pitch) turbine with three blades showed the best performance. However, the performances of four different cases did not show significant differences. Hence, it is necessary when selecting the final design to consider the structural integrity related to the fatigue, along with the economic feasibility of manufacturing the blades.

• Journal of Advanced Navigation Technology
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• v.22 no.3
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• pp.205-212
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• 2018

Spontaneous ignition is not only severe economic damage but also a typical plant damage caused by harmful gases generated during the fire. Because coal is porous, it causes oxygen to be absorbed in the amount of oxygen per unit weight of oxygen, resulting in low humidity and low thermal conductivity. The cause and effect of spontaneous ignition are very complex, so it is difficult to prevent it beforehand and once it is difficult to digest it, it is difficult to digest it. This study examines structural safety by conducting a structural analysis of the cooling ball system to prevent spontaneous combustion of coal stockpile plants and external pressures.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.9
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• pp.1325-1330
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• 2010

The breakdown of any critical component of a turbine results in the outage of power plants. Unexpected failure decreases equipment utilization and causes enormous economic losses. Currently, we conduct conservative preventive maintenance for a maintenance period that is proposed by a vendor. In the rapidly changing business environment, reliability-based maintenance is required in order to remain competitive and reduce maintenance costs while maintaining the reliability of equipment. In order to determine an appropriate maintenance period for guaranteeing reliability, we must determine the failure probability by carefully analyzing the failure history of the equipment. In this study, we created a database of failure history for power-plant turbines, predicted the best repair time using the Weibull function, and investigated how the appropriate maintenance cycle can be determined.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2006.11a
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• pp.408-413
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• 2006

Recently, the economic trend of internal enterprises toward the world market appears to exceedingly associate with industrial plants. Such circumstance would limit the diversity of project items and cause various issues of extreme disproportion of overseas construction market at the same time. Consequently, it seems essential to inspect the present state of bookings in the civil engineering and construction fields including the service corps, regarding the former period (from the year 1990 to 1996), the depressed period (from 1997 to 2000), and the latter period of monetary crisis (from 2001 to July 2006), based on the critical situation in foreign exchange occurred in the late 1990's; also important to look into the shifts of the representative items in such fields by regional groups of principal nations throughout the world. Therefore, the current situation of bookings in overseas construction companies should be clarified, and ultimately, appropriate measures should be established.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.663-670
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• 2019

Corrective thermal performance analysis is required for power plants' turbine cycles to determine the performance status of the cycle and improve the economic operation of the power plant. We developed a sectional classification method for the main feed-water flow to make precise corrections for the performance analysis based on the Performance Test Code (PTC) of the American Society of Mechanical Engineers (ASME). The method was developed for the estimation of the turbine cycle performance in a classified section. The classification is based on feature identification of the correlation status of the main feed-water flow measurements. We also developed predictive algorithms for the corrected main feed-water through a Kernel Regression (KR) model for each classified feature area. The method was compared with estimation using an Artificial Neural Network (ANN). The feature classification and predictive model provided more practical and reliable methods for the corrective thermal performance analysis of a turbine cycle.