• Proceedings of the KSR Conference
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.855-859
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• 2009

In this paper, we introduce the estimation method by Risk or SIL(Safety Integrity Level) for the criterion of safety assurance and summarize each application method and target. IEC 62278(EN 50126) which is international standard for the specification and verification of the railway system RAMS indicate a criterion of safety assurance. Especially, it recommend the safety verification by continuous verification as the order of requirement establishment, design, manufacture, installation, operation, and maintenance for the equipment not easy to quantify the operation environment. In this paper, we study the SIL requirement allocation method relating to internal new system development and existing system improvement by analysing SIL recommendations which were used to understand SIL for a train control equipment in 1990s in IRSE and theoretically their allocation background. This paper help the safety management of Korea train control system to develope the quantitative management procedure as international level by analyzing the SIL requirement allocation by operation agency and the right SIL verification procedure by manufacture and indicating the example to assure safety because it is necessary for improvement and localization for the Korea train control system having highly dependence on aboard technology.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제11권1호
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• pp.133-146
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• 1999

The charge operation of an ice storage system has been analyzed in this paper. The thermal characteristics of major components of the ice storage system. i.e., the refrigerator and the ice storage tank are evaluated from performance tests on an existing ice storage system. Based on the measured data for thermal characteristics, a simulation is carried out for the charge operation and the effect of the refrigerator size on the system performance is investigated. The results indicate that the larger the refrigerator size for a given storage capacity, the lower the inlet temperature of the ice storage tank so that the lower the efficiency of charge operation. It is also found that there exists an optimal size of the refrigerator with which the ice storage at the end of the charge operation is maximized, but the complete charge is not possible even with the optimally sized refrigerator. This leads to the result that the design capacity of the storage tank should be larger than the required amount of cold energy for the daytime cooling considering the practically chargeable amount of cold energy during the nighttime. Where the cooling load sharing of the storage is 40%, the nominal capacity of an ice storage tank needs to be larger than the required storage amount by 30%.

• Computational Structural Engineering : An International Journal
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• 제3권1호
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• pp.1-7
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• 2003

For system identification of large structures, it is not practical to identify the entire structure due to the prohibitive computational time and difficulty in numerical convergence. This paper explores the possibility of performing system identification at substructure level, taking advantage of reduction in both the number of unknowns and the number of degrees of freedom involved. Another advantage is that different portions (substructures) of a structural system can be identified independently and even concurrently with parallel computing. Two substructural identification methods are formulated on the basis whether substructural approach is used to obtain first-order or second-order model. For substructural first-order model, identification at the substructure level will be performed by means of the Observer/Kalman filter Identification (OKID) and the Eigensystem Realization Algorithm (ERA) whereas identification at the global level will be performed to obtain second-order model in order to evaluate the system's stiffness and mass parameters. In the case of substructural second-order model, identification will be performed at the substructure level throughout the identification process. The efficiency of the proposed technique is shown by numerical examples for multi-storey shear buildings subjected to random forces, taking into consideration the effects of noisy measurement data. The results indicate that both the proposed methods are effective and efficient for damage identification of large structures.

• Journal of Korean Society for Geospatial Information Science
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• 제24권2호
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• pp.37-46
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• 2016

The difference between definition time of GPS (Global Positioning System) position data and actual display time of car positions on a map could reduce the accuracy of car positions displayed in PND (Portable Navigation Device)-type CNS (Car Navigation System). Due to the time difference, the position of the car displayed on the map is not its current position, so an improved method to fix these problems is required. It is expected that a method that uses predicted future positionsto compensate for the delay caused by processing and display of the received GPS signals could mitigate these problems. Therefore, in this study an analysis was conducted to correct late processing problems of map positions by mapmatching using a Kalman filter with only GPS position data and a RRF (Road Reduction Filter) technique in a light-weight CNS. The effects on routing services are examined by analyzing differences that are decomposed into along and across the road elements relative to the direction of advancing car. The results indicate that it is possible to improve the positional accuracy in the along-the-road direction of a light-weight CNS device that uses only GPS position data, by applying a Kalman filter and RRF.

• Journal of Biomedical Engineering Research
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• 제17권3호
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• pp.387-394
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• 1996

This paper presents a Neural Network Identification(NNI) method for modeling of highly complicated nonlinear and time varing human system with a pneumatically driven mock circulatory system of Left Ventricular Assist Device(LVAD). This system consists of electronic circuits and pneumatic driving circuits. The initiation of systole and the pumping duration can be determined by the computer program. The line pressure from a pressure transducer inserted in the pneumatic line was recorded System modeling is completed using the adaptively trained backpropagation learning algorithms with input variables, heart rate(HR), systole-diastole rate(SDR), which can vary state of system. Output parameters are preload, afterload which indicate the systemic dynamic characteristics. Consequently, the neural network shows good approximation of nonlinearity, and characteristics of left Ventricular Assist Device. Our results show that the neural network leads to a significant improvement in the modeling of highly nonlinear Left Ventricular Assist Device.

• ETRI Journal
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• 제38권5호
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• pp.962-971
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• 2016

A wireless power transfer (WPT) system is generally designed with the optimum source and load impedance in order to achieve the maximum power transfer efficiency (PTE) at a specific coupling coefficient. Empirically or intuitively, however, it is well known that a high PTE can be attained by adjusting either the source or load impedance. In this paper, we estimate the maximum achievable PTE of WPT systems with the given load impedance, and propose the condition of source impedance for the maximum PTE. This condition can be reciprocally applied to the load impedance of a WPT system with the given source impedance. First, we review the transducer power gain of a two-port network as the PTE of the WPT system. Next, we derive two candidate conditions, the critical coupling and the optimum conditions, from the transducer power gain. Finally, we compare the two conditions carefully, and the results therefore indicate that the optimum condition is more suitable for a highly efficient WPT system with a given load impedance.

• The Journal of Society for e-Business Studies
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• 제14권3호
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• pp.15-37
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• 2009

This study presents a new retrieval system developed to consider various preferential requirements for buyers in the real estate market. The paper analyses essential factors affecting the price of real estate and then a set of factors are classified by region-related factor and individual-related factor. After endowing the buyer's selected factors with weights in the retrieval system, the optimal solutions have been drawn by comparing with the others through an entropy measure of Multi-attribute Decision Making. This retrieval system is applied to the Busan real estate market to estimate the solutions of retrieval. Evaluation results indicate that the retrieval system can provide useful information to analyse the price determination factors of real estate, as well as to save the searching cost of the buyers.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제21권1호
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• pp.63-70
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• 2009

The air sterilization systems are investigated experimentally in this paper. The goal is to reduce bacteria, mold and viruses in office air by using a UV sterilizer installed inside a partition panel and wall-mounted unit. These systems allow occupants to turn the system on/off and to control the incoming air speed and direction. The partition air sterilization system conditions and sterilizes the air, and then delivers the clean air into the personal task area through the partition panels, which are connected to the pressurized under-floor plenum. Room air exits through the return grills mounted on the ceiling. The wall-mounted air sterilization system sterilizes the air, and then delivers the clean air to the personal task area from the wall. In this study a full-size experimental environment is established to investigate the immunization performance of these air sterilization systems. A typical office space scale is used in this study in order to find an optimal system to achieve a sterilized healthy micro-environment. Multiple system parameters, including volume flow rate and velocity of supplied air, were regulated during the experiments. The more air contact these air sterilization systems had, the better disinfection performance. Over 90% of eradication ratios were obtained by these two air sterilization systems. The results indicate that these systems can efficiently disinfect office air contamination.

• Journal of the Korea Society for Simulation
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• 제20권3호
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• pp.29-39
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• 2011

The appointment system is widely used to facilitate customer access to service in many industries including healthcare and others. Because of its importance, much research has investigated how to build an effective appointment policy under various environments. However, most research has considered a single-server service system. The objective of this work is to evaluate several appointment policies in a two-stage service system in which multiple servers are available and build separate appointments at the second-stage. In such a system, we propose and evaluate the staggering appointment policy. Simulation experiments indicate that the proposed staggering appointment policy outperforms other traditional appointment policies in terms of customer waiting time, server idle time, and the number of customers who are later to scheduled appointments.

• KIEE International Transactions on Power Engineering
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• 제4A권4호
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• pp.221-226
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• 2004

As power systems grow more complex and power demands increase, the fault current tends to gradually increase. In the near future, the fault current will exceed a circuit breaker rating for some substations, which is an especially important issue in the Seoul metropolitan area because of its highly meshed configuration. Currently, the Korean power system is regulated by changing the 154kV system configuration from a loop connection to a radial system, by splitting the bus where load balance can be achieved, and by upgrading the circuit breaker rating. A development project applying a 154kV Superconducting Fault Current Limiter (SFCL) to 154kV transmission systems is proceeding with implementation slated for after 2010. In this paper, SFCL is applied to reduce the fault current in power systems according to two different application schemes and their technical and economic impacts are evaluated. The results indicate that both application schemes can regulate the fault current under the rating of circuit breaker, however, applying SFCL to the bus-tie location is much more appropriate from an economic view point.