• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1D
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• pp.63-72
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• 2009

This study aims at establishing the decision-making support system for the highway assets, long-term performance presumption and evaluation of asset value, which are appropriate for Korea, and proposing the methods of the optimal engineering method and the timing decision for the preventive maintenance through the project evaluation, the optimization method and life-cycle analysis related to the highways. In order to supplement the current problem of the near-sighted budget management system, which chooses the maintenance place of the highway, depending on the level of the budget with fixed amount, the long-term required budget prediction system and the economy principle were introduced, so that the pavement agency can predict the level of the required budget, and it was aimed to develop the pavement asset evaluation system to maintain the performance of the highway with the minimum of the cost. In the use of the highway pavement asset evaluation system, to maintain the appropriate level of the pavement evaluation index, when the budget was efficiently established in the reference of the required maintenance budget for the chosen section of the highway in the year concerned, it was possible to analyze the most rational pavement maintenance budget. With this result, it is estimated to prevent the unnecessary waste of budget in advance, and through the development of the decision-making system for the long-term performance presumption and the asset value estimation of the pavement, it is expected to able to analyze the previous evaluation of the project related to the highway and the feasibility of introduction.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.2077-2078
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• 2011

Now a days, the induction motor is widely used in industry automation. Without monitoring the motor fault, maintenance cost is increased undesirably high. The slip frequency is included in the feature frequency, so rotating rotor speed is needed. In this paper, a sensorless motor speed estimation method, rotor slot harmonic(RSH) method is suggested and a solution of rotor bar diagnosis is proposed for motor running with light-load. When the rotor is rotating, it shows the harmonic signal of back-emf voltage related with number of rotor slot. So from the power spectrum of current signal, we can find the rotor speed.

• The Journal of Sustainable Design and Educational Environment Research
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• v.12 no.2
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• pp.53-60
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• 2013

BIM(Building Information Modeling) is an indispensable tool to secure global competitiveness in construction sector, as already adapted significantly in European countries and U.S. In particular, as considering School Buildings constructed by BTL Method, using BIM tools are required for the accurate estimation of construction cost in planning stage, exact design and construction, well-judged settlement and performance of maintenance schedule. Therefore, this study investigates the BIM education status and the problems on using BIM tools through a survey of 100 BIM trainees and suggests improvement method of BIM education.

• Proceedings of the KSR Conference
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• 2001.10a
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• pp.235-239
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• 2001

The bogie of high speed freight car running on conventional line is welded bogie modeled on Y25 bogie developed in Europe. Y25 bogie has speed limit of 110km/h. But it has limiting factors to speed-up as increasing maintenance cost and friction parts pedestal. And also it was reported that cracks are found in the parts where center beam meet bolster and endbeam near bracket for braking part. This study includes stress analysis improved structure of welded bogie for strength evaluation by numerical method and experimental method. According to the study, new configuration bogie shows improvement in strength.

• International Journal of Railway
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• v.6 no.2
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• pp.45-52
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• 2013

Railway construction needs vast soil investigation for its infrastructure foundation designs along the planned railway path to identify the design parameters for stability and serviceability checks. The soil investigation data are usually classified and grouped to decide design input parameters per each construction section and budget estimates. Deterministic design method which most civil engineer and practitioner are familiar with has a clear limitation in construction/maintenance budget control, and occasionally produced overdesigned or unsafe design problems. Instead of using a batch type analysis with predetermined input parameters, data population collected from site soil investigation and design load condition can be statistically estimated for the mean and variance to present the feature of data distribution and optimized with a best fitting probability function. Probabilistic approach using entire feature of design input data enables to predict the worst, best and most probable cases based on identified ranges of soil and load data, which will help railway designer select construction method to save the time and cost. This paper introduces two Monte Carlo simulations actually applied on estimation of retaining wall external stability and long term settlement of organic soil in soil investigation area for a recent high speed railway project.

• KIEAE Journal
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• v.16 no.3
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• pp.137-143
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• 2016

Purpose: Apartment housing should conduct a cyclic repair to keep and maintain the building performance since they are constructed. Therefore, the repair plan would be provided for long term period which explains the repair time, items and repair cost. Residents of apartment housing are responsible to pay for the repair activities. For repair cost, residents would reserve the money for repair little by little continuously until the required repair time because the repair cost takes a big burden for residents and lots of money a time. But, there is no systematic approach to provide the long term repair cost because it is no proper forecast of the repair cost to the upcoming repair time. In this study, it aimed at providing the monthly accumulation of the long term repair cost with the survey data in Seoul. Method: For these, the surveyed data are classified into 6 categories and number of data are 1,918. In addition, it developed the repair cost model for the 24 repair works and the cumulation function which is reflected with the each cost model. Result: This study are shown as follows : First, among the various estimation for the repair cost, the power function has a goodness of fit in statistics. Second, the monthly accumulation would be 12,840 won/household in size of $100,000m^2$ management area and $81.7won/m^2$ in size of the 1,000 household number during 40 years.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.10 no.4
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• pp.297-303
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• 1981

Optimal design of shell and tube heat exchanger system with the working fluids which may condense outside the tubes has been carried out under specified inlet and outlet conditions. Independent variables such as number of parallel series, tube diameter, distribution pitch, tube side pressure loss, baffle cut and shell side pressure loss as well as dependent variables such as shell diameter, number of tubes, number of serial series and number of baffles were all characterized according to the standard. Exhaustive search method was used to construct a computer program together with the calculation of heat transfer rate by LMTD method. stress analysis of maj or parts was made to examine their dimensions satisfying heat transfer and pressure loss requirements. Cost estimation based on the installation, operation and maintenance was also made, A few representative variables, heat transfer area, shell diameter and pressure loss, were used to express cost function, finally giving the optimal selection of all tentative solutions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.2A
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• pp.98-106
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• 2008

To reduce the outage probability and to increase the transmission capacity, the importance of repeaters in cellular systems keeps increasing. Unlike optical repeaters which require wireline connections, RF repeaters are easy to install, have low limitations in location and also have a reduced operational expense such as the optical fiber maintenance cost. On the other hand, RF repeaters suffer the interference due to the feedback signals between the transmitter and receiver antennas, hence require an extra interference cancellation method when the amount of the feedback signal reduction by using the shielding is not sufficient. In this paper, a channel estimation method for two-path feedback interference signals in the ICS (Interference Cancellation System) repeaters using baseband signal processing is proposed and its performance is evaluated. When compared with the conventional method which estimates each multipath individually, the proposed method achieves 10 dB performance gain in terms of the normalized mean-squared-error.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.2
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• pp.63-72
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• 2016

An expected-discounted cost model based on RRP(Renewal Reward Process), referred to as a stochastic decision model, has been developed to estimate the optimal period of in-depth inspection which is one of critical issues in the life-cycle maintenance management of harbor structures such as rubble-mound breakwaters. A mathematical model, which is a function of the probability distribution of the service-life, has been formulated by simultaneously adopting PIM(Periodic Inspection and Maintenance) and CBIM(Condition-Based Inspection and Maintenance) policies so as to resolve limitations of other models, also all the costs in the model associated with monitoring and repair have been discounted with time. From both an analytical solution derived in this paper under the condition in which a failure rate function is a constant and the sensitivity analyses for the variety of different distribution functions and conditions, it has been confirmed that the present solution is more versatile than the existing solution suggested in a very simplified setting. Additionally, even in that case which the probability distribution of the service-life is estimated through the stochastic process, the present model is of course also well suited to interpret the nonlinearity of deterioration process. In particular, a MCS(Monte-Carlo Simulation)-based sample path method has been used to evaluate the parameters of a damage intensity function in stochastic process. Finally, the present stochastic decision model can satisfactorily be applied to armor units of rubble mound breakwaters. The optimal periods of in-depth inspection of rubble-mound breakwaters can be determined by minimizing the expected total cost rate with respect to the behavioral feature of damage process, the level of serviceability limit, and the consequence of that structure.

• 한국태양에너지학회:학술대회논문집
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• 2009.11a
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• pp.394-399
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• 2009

Since some decades ago, there has been a concern for resource depletion and environmental pollution associated with building properties. In addressing such impact of the built environment, there is a recognition of the existence of alternative building materials, fuels for energy supply as well as technologies for waste handling and disposal. Nevertheless, for long time, the choice between such alternatives was dictated by factors such as differences in prices and aesthetic values. A new important dimension in discriminating between different options is the environmental dimension. This aspect is important since buildings are one of the spatially big new additions to the natural environment that consume a lot of materials and energy during their long lifetime. Thus, with the environmental dimension kept in mind, a existing cost estimation needs to be changed. A new cost assessment method, Life Cycle Cost, should calculate overall costs with dimensional factors: investment and utility costs as well as maintenance costs over the lifetime of the building. Aiming to give an overview of the present status of Building Life Cycle Assessment(LCA) tools as a basis for further research and development including economic performance, this paper describes and compares 3 different tools for Life Cycle Assessment(LCA) and economic analysis of the green buildings. This paper compared these approaches based on various aspects. These include economic analysis method, evaluation duration, data of results(index). Use of the comparison analysis is to produce a better picture and indicate profits and shortcomings for the tools as a group; thus providing important direction improvement of LCA tool as well as further research and development of this group of tools.