• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.59-64
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• 2001

The concrete bridge decks are in need of replacement and rehabilitation due to decreasing load carrying capacity. In this study, to extend life cycle of the concrete bridge decks which are reinforced with the glass fiber sheets, the concrete bridge decks are examined on the strengthen effect and the fatigue behavior. The behavior of strengthened slabs is represented by load-displacement relationship, variation of compliance and total released energy. Owing to result of that, the strengthened slabs is modified the elasticity, the compliance and represents to control the crack elongation, to elevate the total released energy, to modify the fatigue life. When the concrete bridge deck is strengthened, the crack propagation nay be controled efficiently.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.1
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• pp.51-64
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• 1994

Analytical study on the thermodynamical cyclic behabiour and characteristics of HFC-l34a refrigerant for automotive air conditionser system for the replacement of existing CFC-12 has been carried out in this paper through development of system performance simulation program, expecially in the view point of system design considerations. The results indicate that HFC-l34a system will give a greater refrigerating capacity than CFC-12 if appropriate engineering measures such as proper codensers, flow controllers, etc., taken for certain operating conditions. The results, however, also show that the operating power for compression process increases over entire temperature range as a result of decreasing volumetric efficiency due to larger specific volume and increased discharging pressure. The present study results indicate that proper selection of condensing and evaporating temperature plus refrigerant control is very important performance factor to have better COP in the HFC-134a system design.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1216-1216
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• 2015

In this study, the author apply the VLF(Very Low Frequency) tan-delta data that has been measured at each office of the KEPCO 2012 to the Weibull distribution which is the statistical analysis as previous studies for the remaining life prediction through the improvement of the sensitivity and reliability of the degradation state assessment of underground distribution power cables. Also, in this paper, UCD(Used Cable Diagnosis) Matrix proposed by KEPCO was applied to the hierarchy of assessment prioritization. it suggests Aging Index for condition assessment and high reliability of proper economic replacement cycle using the weight according to the assessment prioritization.

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.334-336
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• 1999

Piping systems of the power generating stations have been generally protected by hydraulic and mechanical snubbers which can allow large displacements arising from temperature change while those can reduce or absorb stresses due to vibrations. However these snubbers require amounts of budget for maintenance or replacement because of the leakage, lubrication and finally short life cycle. Recently the snubbers consisted of wire rope have been proved to reduce vibrations of piping systems. While the wire rope snubbers are free of maintenance such as leakage and lubrication imported price are so high. Now it is necessary to design. manufacture and certificate these wire rope snubbers.

• Journal of the Korean Society of Food Science and Nutrition
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• v.19 no.5
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• pp.395-402
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• 1990

The semicontinuous production of blue pigment from gardenia fruit by immobilized cells of Bacillus subtilis KS-380 which excreted $\beta$-glucosidase was investigated in comparison with free cells, . The blue pigment produced higher productivity under the conditions of aeration of 0.2m$\ell$/min and 2mm diameter of gel beads by using 3.5% sodium alginate. Semicontinuous production by immobilized cell showed the highest productivity with replacement of fresh production medium in every 24hr for fourth fermentation cycle following the conditions of blue pigment productivity.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.11 no.2
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• pp.51-60
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• 2015

Local wall thinning and integrity degradation caused by several mechanisms, such as flow accelerated corrosion, cavitation, flashing and/or liquid droplet impingement, is a main concern in secondary steam cycle piping system of nuclear power plants in terms of safety and operability. Thinned pipe management program (TPMP) has being developed and optimized to reduce the possibility of unplanned shutdown and/or power reduction due to pipe failure caused by wall thinning. In this paper, newest technologies, standards and regulations related to the integrity assessment, repair and replacement of thinned pipe component are reviewed. And technical improvement items in TPMP to secure the reliability and effectiveness are also presented.

• International Journal of Aeronautical and Space Sciences
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• v.6 no.2
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• pp.76-83
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• 2005

Thrusters are important actuators where air is rare. Since the maintenance or replacement of thrusters is not easy in such an environment, a thrusting system must be highly reliable. Redundant thrusters are used to meet the reliability requirement. In this paper, a reconfiguration problem for those redundant thrusters is discussed, especially the management or distribution logic of redundant thrusters is focused on. The logic has to be changed if faults occur at thrusters. Reconfiguration is to change the distribution logic to accommodate thrusters' faults. The authors propose a reconfiguration algorithm based on the linear programming method. The authors define the reconfiguration problem as an optimization problem. The performance index is a quantity related with total fuel consumption by thrusters. This algorithm can accommodate multiple faults. Numerical examples are given to show the advantage of the proposed algorithm over existing methods.

• International Journal of Human Ecology
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• v.17 no.2
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• pp.31-42
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• 2016

We examine the self-control problems of U.S households and their effects on households' retirement preparedness based on the Behavioral Life-Cycle Hypothesis. Using the 2010 Survey of Consumer Finances dataset, the level of retirement adequacy was estimated with income replacement ratio (IRR), and only 42% of households were adequately prepared for retirement. Results from logistic regression analysis indicated that households with loan payment and saving self-control problems were less likely to be prepared adequately for retirement compared to those without such problems. Age, education, race/ethnicity, marital status, employment status, retirement plans, expected retirement age and risk tolerance were significantly related to retirement preparedness. This study provides financial educator and researchers with suggestions on how to help household make a better retirement plan.

• Smart Structures and Systems
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• v.15 no.3
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• pp.543-553
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• 2015

The condition of the vehicular bridge network in New York City, as represented by ratings obtained during biennial inspections is reviewed over a period of three decades. Concurrently, the bridges comprising the network are considered as networks of structural elements whose condition defines the overall bridge condition according to New York State assumptions. A knowledge-based matrix of assessments is used in order to determine each element's vulnerability and impact within the network of an individual structure and the network of City bridges. In both networks expansion deck joints emerge as the weak link. Typical joint failures are illustrated. Bridge management options for maintenance, preservation, rehabilitation and replacement are examined in the context of joint performance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.596-598
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• 2000

This paper presents a new accelerating aging test facility for distribution lightning arresters. Aging parameters of lightning arrester are moisture ingress, electrical stress and surge absorption and so on. In this system, we applied 13.2kV to 6 samples and controled temperature and humidity of chamber and measured leakage currents of the all samples. Also we developed accelerating aging cycle which consists of -35$^{\circ}C$∼90$^{\circ}C$ temperature and 40%∼90% humidity. Through the aging test we found out the leakage current of aged sample increases rapidly according to the temperature rising. Hereafter we can determine the replacement guide of leakage current for field operating arresters and condition assessment of aged samples through this aging test.