• Journal of the Korean Society for Railway
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• v.10 no.3 s.40
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• pp.327-336
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• 2007

Operation a subway company requires high amount of early construction, operation and maintenance costs. Seoul Metro, one of the public subway companies in Seoul, Korea, has undergone operational deficit from its establishment, and the main reason is that the early construction and operation cost exceed the total revenue. Therefore, detailed researches on current operation system and possible alternatives are conducted to settle down finance trouble of the company. In particular, problems on operation and ticketing systems are analyzed, and based on that, necessity and detailed plan of railroad pass for one day are introduced and analyzed.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.255-261
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• 2008

The importance of maintenance of rail surface defects is increasing according to the KTX operation. That is because during high speed operation of rolling stocks, rail surface defects shorten fatigue life of rail, accelerate track degradation and deteriorate ride comfort. Rail grinding has been applied for effective rail maintenance in Kyeong-Bu HS line. This paper evaluates the effectiveness of rail grinding in term of rail fatigue life. To this end, the stresses of the ground rail are measured under KTX running and the equivalent stress range is calculated by RMC after the frequency analysis done with Rainflow counting method. Also, Pamglen-Miner rule is applied to predict the fatigue life of ground rail. The result of the analysis shows that the fatigue life of ground rail is increased by 15%.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.69-70
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• 2008

Automatic control systems(AVR, Governor, Synchronizer) installed $1970{\sim}1980$ in K-water were considered to be rehabilitated around 2000. Moreover, Korea Power Exchange market system was changed from PPA (Power Purchase Agreement) to a bidding system. Therefore, depending on the power quality, the power provider could achieve additional profits. It is the excitation system and governor that have the functions of enhancing power necessities. During the 20 to 30 years of generator operation, there were many major and minor problems. Examples are SCR burnout (Andong: Excitation system), hunting (Imha: governor), field circuit breaker failure (Chungju 1st: excitation system), the rise of leakage current (Chungju 2nd: excitation system), power supply burnout (Chungju 2nd: governor). These are the typical examples of malfunction which hindered the generator operation and, consequently, diminished the profit of power business. In order to satisfy the needs of the power market and prevent malfunctions mentioned above, the rehabilitation of AVRs and governors were executed. A new system was made to have the flexibility of ancillary service (GF, AGC, etc.), PSS function. With user friendly HMI software, it is more convenient for the operator to fulfill suitable maintenance. It was possible to connect SCADA system by opening protocol of AVR, governor for the efficiency of operation and maintenance.

• Geomechanics and Engineering
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• v.36 no.2
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• pp.167-181
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• 2024

The soil-structure relative stiffness is a key factor affecting the seismic response of underground structures. It is of great significance to study the soil-structure relative stiffness for the soil-structure interaction and the seismic disaster reduction of subway stations. In this paper, the dynamic shear modulus ratio and damping ratio of an inhomogeneous soft soil site under different buried depths which were obtained by a one-dimensional equivalent linearization site response analysis were used as the input parameters in a 2D finite element model. A visco-elasto-plastic constitutive model based on the Mohr-Coulomb shear failure criterion combined with stiffness degradation was used to describe the plastic behavior of soil. The damage plasticity model was used to simulate the plastic behavior of concrete. The horizontal and vertical relative stiffness ratios of soil and structure were defined to study the influence of relative stiffness on the seismic response of subway stations in inhomogeneous soft soil. It is found that the compression damage to the middle columns of a subway station with a higher relative stiffness ratio is more serious while the tensile damage is slighter under the same earthquake motion. The relative stiffness has a significant influence on ground surface deformation, ground acceleration, and station structure deformation. However, the effect of the relative stiffness on the deformation of the bottom slab of the subway station is small. The research results can provide a reference for seismic fortification of subway stations in the soft soil area.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.761-766
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• 2007

A brake disc is one of the key elements of friction brake system. Thermal cracks of discs may shorten the lifetime of a disc and increase maintenance cost. Therefore, prevention of thermal cracks is very important to ensure the safety of the vehicle operation and reduction of maintenance cost. In this study, the influence of parameters on the friction heat of brake disc is examined.

• Journal of Korea Multimedia Society
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• v.23 no.10
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• pp.1307-1317
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• 2020

In recent years, the PV plant is gradually increasing in korea and has begun to focus on PV system O&M(Operation and Management). The legacy PV system can hardly be gathering realtime information. That is why it is difficult for the facility to respond immediately to situations in which problems arise. This leads to economic losses due to reduced power generation. In this study, we implemented an RMC(Remote Maintenance Control) gateway that supports multi-area equipment(inverters, junction boxes, switchboards, environmental sensors) that are not limited to specific manufacturers. It provides a function to visualize the collected data. Users can easily check the power generation and operation status of PV system equipment. In the future, we will develop an algorithm capable of analyzing beta factors that cause equipment performance degradation, parts aging, and deterioration using data collected from facilities. We intend to use this algorithm as a fundamental technology for O&M by transplanting it to the RMC gateway.

• Architectural research
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• v.7 no.1
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• pp.11-18
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• 2005

In today's building industry the emphasis has been geared more towards construction, thus building maintenance and life cycle have been neglected until now. A direct result of this neglect is the rapid aging of building, which leads to more cost-effective decision making methods for the prolongation of building life span. The following study is conducted in the area of Daegu and Seoul in order to develop the estimation analysis method of the annual operation cost of the Korean high-rise condominiums for the cost-effective decision making support through mathematical and statistical analyses including the present value and standardized measurement corrections. Based on the assumption that the life expectancy of the high rise condominium is 50 years, initial cost is ￦421,212/$m^2$, and a total sum of yearly operation cost during life expectancy is ￦2,154,499//$m^2$), yearly accumulated operation cost is shown as below: $AOC=0.7097t^4-38.803t^3+806.95t^2+11045t-496.52$ ($R^2=0.98$) (Here, AOC = Accumulated Operation Cost, t = given years)

• Journal of Information Technology Services
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• v.17 no.2
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• pp.83-100
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• 2018

Demand for stone products used as building materials is increasing. The construction industry, the value of the stone industry is sufficient, but the domestic stone industry is very lag regarding IT utilization. However, the overseas stone industry produces high-quality products using IT. In this study, we want to offer an IT application technology priority fit for the stone industries. We identify the current status and production process of the stone industries, then set the priority of various IT, so that obtain competitiveness in the domestic stone industries, and minimize the gap between the overseas stone industries. Therefore, we used AHP method; stone industry production processes were selected as the Enterprise Operation Management, Quarrying, Manufacturing, Construction and Maintenance of first-tier. The second-tier ones are consisted of 30 factors out of IT elements. Focus group interviews were conducted to confirm the validity of each factor. As a result, most important factors of first-tier was selected as the order of Manufacturing, Quarrying, Enterprise Operation Management, and Construction & Maintenance. The top 5 of 30 factors in the second-tier were selected Smart Sensor, Mobile Device, Robot of manufacturing, GIS of quarrying, and SCM of enterprise operation management. And the factor that relatively less important was GPS of construction and maintenance. If properly applied an IT application technology for stone industry, we expect to provide efficient production lines and increase customer satisfaction, which will ultimately expand the promotion for the industry and thus act as positive factor in promoting the stone industry.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.5
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• pp.325-331
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• 2009

This study was performed to evaluate characteristics of algal occurrence in Lake Paldang. Chlorophyll a concentration was highest during spring, based on weekly measurements from 2006 to 2008, which revealed a different trend compared to the data before 2000 that showed the highest level during summer. Total algae cell quantity was also highest during spring, based on monthly data. Overall, Bacillariophyceae was dominant and represented 87% of total algae cells and occupation was more significant during spring and winter. Cyanophyceae was dominant during summer. 2-MIB and geosmin originating in algae which caused odor problems was high in July 2008, and more research on the relationship between algae and production of odor causing material is needed.

• Journal of Energy Engineering
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• v.24 no.1
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• pp.10-16
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• 2015

Recently, RCM(reliability centered maintenance) process is introduced and applied for the planning and implementing efficient and effective maintenance system in terms of optimal rolling stock maintenance. Particularly, cost-time benefits analysis associated with the implementation of RCM for rolling stock maintenance is necessary and required for railway operator in advance. The RCM process was primarily starting from military, airplane and nuclear industries and is now adapted in railway industry for local railway operators. This paper focuses on suggesting the way of connecting the RCM process with railway maintenance activities in the railway operation field. Thus, in order to introduce and establish reliability activities, it needs to review and evaluate the maintenance environment in the organizational point of view. Based on these reviews and evaluations, various maintenance methodologies are reviewed for customizing local railway field situations and establish specific process in the application of major systems on the reliability technology. In this paper, the railway RCM process is proposed for the establishment and construction of the systematic and optimal maintenance system.