• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.4
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• pp.273-282
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• 2023

Probabilistic safety assessment (PSA) has been widely used to evaluate the seismic risk of nuclear power plants (NPPs). However, studies on seismic PSA for process plants, such as gas plants, oil refineries, and chemical plants, have been scarce. This is because the major disasters to which these process plants are vulnerable include explosions, fires, and release (or dispersion) of toxic chemicals. However, seismic PSA is essential for the plants located in regions with significant earthquake risks. Seismic PSA entails probabilistic seismic hazard analysis (PSHA), event tree analysis (ETA), fault tree analysis (FTA), and fragility analysis for the structures and essential equipment items. Among those analyses, ETA can depict the accident sequence for core damage, which is the worst disaster and top event concerning NPPs. However, there is no general top event with regard to process plants. Therefore, PSA cannot be directly applied to process plants. Moreover, there is a paucity of studies on developing fragility curves for various equipment. This paper introduces PSA for gas plants based on FTA, which is then transformed into Bayesian network, that is, a probabilistic graph model that can aid risk-informed decision-making. Finally, the proposed method is applied to a gas plant, and several decision-making cases are demonstrated.

• Journal of Energy Engineering
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• v.23 no.4
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• pp.88-94
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• 2014

In this paper, Thermal Shock tests were performed varying the composition of the solder and ribbon thickness (A-type:0.2mm/60Sn40Pb, B-type:0.25mm/60Sn40Pb, C-type:0.2 /62Sn36Ag2Pb, D-type:0.25mm/62Sn36Ag2Pb) for evaluating the long-term reliability about Ribbon junction of Silicon solar cells. Thermal Shock test condition was performed during the 600cycles having $-40^{\circ}C{\sim}85^{\circ}C$ temperature range each 15 minutes; One cycle time was 30min. As a result, the initial efficiency of the A-type, B-type, and C, D-type were showed 15.0%, 15.4% and 15.8% respectively. After thermal shock test, the efficiency decreasing-rate of each type were as follow that A-type was 13.8%, B-Type was 15.4%. C-Type and D-Type was 15.3% and 16.2%, respectively. Also, degradation of surface changes and I-V characteristic curves were showed that the series resistance of the A, C-type was increased. Also, current lowering starting point of C-type shown 0.05volt[v] earlier than that of A-type. And B, D-type shown characteristics of composite lowering efficiency such as increase of series resistance, decrease of parallel resistance and cell damage. Therefore Initial solderability and efficiency of specimens using the solder with SnAgPb were superior. But, It has inferior the long-term reliability. The test was confirmed that as the ribbon thickness increases, long-term reliability of solar cell will decrease.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.6
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• pp.455-462
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• 2013

The effects of earthquakes can be devastating especially to existing structures that are not based on earthquake resistant design. This study proposes a steel grid shear wall that can provide a sufficient lateral resistance and can be used as a seismic retrofit method. The pushover analysis was performed on RC structure with and without the proposed steel grid shear wall. Obtain the performance point that the target structure for seismic loads applied to evaluate the response and performance levels. The capacity spectrum at performance point is nearly elastic range, so satisfied the performance objectives(LS level). And response modification factor(R factor) were calculated from the pushover analysis. The R factor approach is currently implemented to reflect inelastic ductile behavior of the structures and to reduce elastic spectral demands from earthquakes to the design level. The R factor increases from 2.17 to 3.25 was higher than the design criteria. As a result, according to reinforcement by steel grid shear wall, strength, stiffness, and ductility of the low-rise RC structure has been appropriately improved.

• Journal of the Korean Geotechnical Society
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• v.39 no.7
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• pp.57-67
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• 2023

Slope failures during rainfall have been observed in mountainous areas of South Korea as a result of the presence of solar power facilities. The seepage behavior and pore pressure distribution differ from typical slopes due to the presence of impermeable solar panels, and the load imposed by the solar power structures also affects the slope behavior. This study aims to develop a method for evaluating the stability of slopes with solar power facilities and to analyze vulnerable points by considering the maximum slope displacement. To assess the slope stability and predict behavior while considering rainfall seepage, a combined seepage analysis and finite difference method numerical analysis were employed. For the selected site, various variables were assumed, including parameters related to the Soil Water Characteristic Curve, strength parameters that satisfy the Mohr-Coulomb failure criterion, soil properties, and topographic factors such as slope angle and bedrock depth. The factors with the most significant influence on the factor of safety (FOS) were identified. The presence of solar power facilities was found to affect the seepage distribution and FOS, resulting in a decreasing trend due to rainfall seepage. The maximum displacement points were concentrated near the upper (crest) and lower (toe) sections of the slope.

• Journal of the Korea Society for Simulation
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• v.15 no.4
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• pp.119-128
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• 2006

A turnout system which permits trains to pass from one track to another is a combination of the switch, the crossing, lead rails which are necessary to connect the switch and the crossing, two guard rails and a switch machine for operating the switch. A turnout is the sole moving part among the railway components and has complex configuration, so the safety has always been raised an issue. In Korea, it is planned to adopt the high speed tilting train, which operates at the maximum speed of 200km/h, at conventional lines by the year of 2010. However, for the application of the tilting train to conventional lines, it is prerequisite to establish a stable turnout system allowing the tilting train to pass through it without reducing speed. Therefore, the improved turnout system for the speed-up of conventional lines has been developed and the prototype of the turnout system has been constructed. In this study, simulation of noise and vibration around the improved turnout system was performed in order to predict the generation level of noise and vibration due to passing of the tilting train through the turnout system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.12C
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• pp.1692-1706
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• 2004

Recently, there are rapid development of information and communication and rapid growth of e-business users. Therefore we try to solve security problem on the internet environment which charges from wire internet to wireless internet or wire/wireless internet. Since the wireless mobile environment is limited, researches such as small size, end-to-end and privacy security are performed by many people. Wireless e-business adopts credit card WPP protocol and AIP protocol proposed by ASPeCT. WAP, one of the protocol used by WPP has weakness of leaking out information from WG which conned wire and wireless communication. certification chain based AIP protocol requires a lot of computation time and user IDs are known to others. We propose a Micro-Payment protocol based on credit card. Our protocol use the encryption techniques of the public key with ID to ensure the secret of transaction in the step of session key generation. IDs are generated using ECC based Weil Paring. We also use the certification with hidden electronic sign to transmit the payment result. The proposed protocol solves the privacy protection and Non-repudiation p개blem. We solve not only the safety and efficiency problem but also independent of specific wireless platform. The protocol requires the certification organization attent the certification process of payment. Therefore, other domain provide also receive an efficient and safe service.

• Journal of the Korean Society for Railway
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• v.20 no.3
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• pp.311-319
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• 2017

The primary suspension system of a railway vehicle restrains the wheelset and the bogie, which greatly affects the dynamic characteristics of the vehicle depending on the stiffness in each direction. In order to improve the dynamic characteristics, different stiffness in each direction is required. However, designing different stiffness in each direction is difficult in the case of a general suspension device. To address this, in this paper, an optimization technique is applied to design different stiffness in each direction by using a conical rubber spring. The optimization is performed by using target and analysis RMS values. Lastly, the final model is proposed by complementing the shape of the weak part of the model. An actual model is developed and the reliability of the optimization model is proved on the basis of a deviation average of about 7.7% compared to the target stiffness through a static load test. In addition, the stiffness value is applied to a multibody dynamics model to analyze the stability and curve performance. The critical speed of the improved model was 190km/h, which was faster than the maximum speed of 110km/h. In addition, the steering performance is improved by 34% compared with the conventional model.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1A
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• pp.71-80
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• 2010

Bridge deck is directly influenced by environment and vehicle load, it is easily damaged so that it requires an appropriate repair and retrofit. Therefore, developing a bridge deck with high durability is necessary in order to minimize the maintenance of bridge deck and use it to its design life. In this study, static test was carried out to evaluate a fatigue capacity of steel-concrete composite deck, which was newly developed by supplementing problems of existing reinforced concrete deck. Based on results from the static test, fatigue load was decided, and fatigue test was conducted under the constant amplitude repeated load. From the fatigue tests, the S-N curve regarding principle structural details of composite deck was made, and characteristics of fatigue behavior was estimated by comparing and evaluating it with fatigue design criteria. In addition, fatigue design guideline was presented. As a result, it is found that each structural details of composite deck proposed by this study, such as upper flange of corrugated steel plate and middle section of it, shear connector and lower flange of corrugated steel plate, is satisfying the fatigue strength.