• Fire Science and Engineering
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• v.18 no.1
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• pp.54-66
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• 2004

In this article, we are to suggest the hazard-assessing method for the underground pipelines, and find out the pipeline-maintenance schemes of high efficiency in cost. Three kinds of methods are applied in order to refer to the approaching methods of listing the hazards for the underground pipelines: the first is RBI(Risk Based Inspection), which firstly assess the effect of the neighboring population, the dimension, thickness of pipe, and working time. It enables us to estimate quantitatively the risk exposure. The second is the scoring system which is based on the environmental factors of the buried pipelines. Last we quantify the frequency of the releases using the present THOMAS' theory. In this work, as a result of assessing the hazard of it using SPC scheme, the hazard score related to how the gas pipelines erodes indicate the numbers from 30 to 70, which means that the assessing criteria define well the relative hazards of actual pipelines. Therefore. even if one pipeline region is relatively low score, it can have the high frequency of leakage due to its longer length. The acceptable limit of the release frequency of pipeline shows 2.50E-2 to 1.00E-l/yr, from which we must take the appropriate actions to have the consequence to be less than the acceptable region. The prediction of total frequency using regression analysis shows the limit operating time of pipeline is the range of 11 to 13 years, which is well consistent with that of the actual pipeline. Concludingly, the hazard-listing scheme suggested in this research will be very effectively applied to maintaining the underground pipelines.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.406-409
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• 2007

This paper proposes an algorithm that predicts current electrostatic charge in a factory. The algorithm based on LSM(Least Square Method) dynamically takes the number of sample while calculating the value of electrostatic charge. The simulation results show that the proposed algorithm gains 73.18161 standard deviation with 95% trust probability and is better than conventional algorithm. We design the electrostatic prediction embedded system based on pxa255 with the proposes algorithm.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.346-353
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• 2002

The risk of bearing failure is evaluated through the seismic response analysis of a bridge considering the probabilistic characteristics of structural properties such as the mass of superstructure, the stiffness of pier, and the translational and rotational stiffness of the foundation as well as seismic loadings during the bridge service lift. The effect of pounding between adjacent vibration units on the risk of bearing failure is also investigated. The probabilistic characteristics of structural properties are obtained by the Monte Carlo simulations based on the probabilistic characteristics of basic random variables included in the structural properties. From the simulation results, the failure probability of fixed bearings attached on the abutment is found to be much higher than those placed on the piers. It is also found that the pounding effect significantly increases the failure probability of bearings. In the simply supported bridges, the risk of bearing failure increases as the number of bridge spans increase. Therefore, the failure probability of fixed bearing due to the effects of pounding phenomena and the number of bridge spans should be considered in the seismic desist of bearings.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.10a
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• pp.24-31
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• 1997

Recently, in Korea, demand for establishment of systematic risk assessment techniques for construction projects has increased, especially after the large construction failures occurred during construction such as New Haengju Bridge construction projects, subway construction projects, gas explosion accidents etc. Most of existing risk analysis modeling techniques such as Event Tree Analysis and Fault Tree Analysis may not be available for realistic risk assessment of construction projects because it is very complex and difficult to estimate occurrence frequency and failure probability precisely due to a lack of data related to the various risks inherent in construction projects like natural disasters, financial and economic risks, political risks, environmental risks as well as design and construction-related risks. Therefor the main objective of this paper is to suggest systematic probabilistic risk assessment model and demonstrate an approach for probabilistic risk assessment using advanced Event Tree Analysis introducing Fuzzy set theory concepts. It may be stated that the Fuzzy Event Tree AnaIysis may be very usefu1 for the systematic and rational risk assessment for real constructions problems because the approach is able to effectively deal with all the related construction risks in terms of the linguistic variables that incorporate systematically expert's experiences and subjective judgement.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.6
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• pp.30-40
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• 2014

The demand of underground structure such as box culvert for electric power transmission is increasing more and more, and the service life extension of these structures is very important. Recent observations in field and experimental evidences show that even steel in concrete can be corroded by carbonation reaction of cover concrete. Carbonation-induced corrosion in concrete may often occur in a high carbon dioxide environment. In this study, the risk of carbonation of box culverts in our nation was evaluated by measuring the carbonation rate and concrete cover depth in field. Then, the service life due to carbonation at the cover depth was calculated by in situ information and the Monte Carlo simulation in a probabilistic way. Additionally, the accelerated carbonation test for the cracked beam specimen was executed and the crack effect owing to the carbonation process on the service life of box culvert was numerically investigated via Monte Carlo simulation based on the experimental results.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.4
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• pp.15-22
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• 2002

In the course of seismic probabilistic risk assessment(SPRA), seismic fragility analysis(SFA) is utilized as a tool to evaluate the actual seismic capacity of structures. This paper introduces a methodology of SFA and its evaluation procedures, especially focusing on the basic fragility variables. A new definition of the response spectrum shape factor as one of the most critical basic variables is suggested. The new factor is expressed as a term of linear algebraic sum using the modal contribution factor. The efficiency of new response spectrum shape factor is evaluated and validated to use in practice through the case study of the nuclear power plant structures. The case study results show that the proposed method can be effectively applicable to multi-mode structures with composite modal damping.

• KDI Journal of Economic Policy
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• v.35 no.3
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• pp.91-124
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• 2013

This paper analyzes a situation where multiple targets are exposed to a potential terrorist attack. The probability of an attack is determined endogenously in a game where a terrorist chooses the target while the targets independently determine the level of deterrence. As each target tries to divert an attack to others, the symmetric equilibrium becomes suboptimal and exhibits dispersion in the level of deterrence. The analysis shows that the first best deterrence level may be achieved when the targets can write a binding risk-sharing contract. Such a contract has limited applicability however as it suffers from a potential verification problem.

• Korean Journal of Psychosomatic Medicine
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• v.27 no.1
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• pp.35-41
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• 2019

Objectives : Although delirium is a common complication among patients hospitalized in intensive care units(ICUs), little is known about the roles that diagnostic and therapeutic procedures play in its development. This study investigates the procedure-related risk factors of delirium in ICU patients. Methods : All the consecutive patients admitted to the ICU between June 2016 and May 2017 were routinely evaluated for delirium by psychiatrists. In total, 1156 patients met the inclusion criteria and were retrospectively analyzed. A multiple logistic regression analysis was conducted to investigate independent risk factors of delirium development while adjusting for other characteristics. Results : The age, Acute Physiology and Chronic Health Evaluation (APACHE II) score, proportion of patients who had undergone an operation, and proportion of patients who were foley catheterized, mechanically ventilated, and physically restrained were higher in the delirium group. The multiple logistic regression analysis confirmed that the use of restraint was an independent risk factor of delirium (odds ratio : 10.006 ; 95% confidence interval : 6.120-16.360 ; p<0.001). The patient factors independently associated with delirium were an advanced age and a higher APACHE II score. The incidence of delirium was 15.3%. Conclusions : There is a high prevalence of delirium influenced by potentially harmful procedures in patients in ICU settings. The use of physical restraint had the strongest association with the development of delirium. These findings advocate the need to target procedure-related risk factors such as the use of restraints as preventive intervention measures for ICU delirium.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.6
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• pp.488-496
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• 2015

This paper proposes a framework to determine the routes of multiple unmanned aerial vehicles (UAVs) to conduct multiple tasks in different locations considering the survivability of the vehicles. The routing problem can be formulated as the vehicle routing problem (VRP) with different cost matrices representing the trade-off between the safety of the UAVs and the mission completion time. The threat level for a UAV at a certain location was modeled considering the detection probability and the shoot-down probability. The minimal-cost path connecting two locations considering the threat level and the flight distance was obtained using the Dijkstra algorithm in hexagonal cells. A case study for determining the optimal routes for a persistent multi-UAVs surveillance and reconnaissance missions given multiple enemy bases was conducted and its results were discussed.

• The KIPS Transactions:PartC
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• v.16C no.5
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• pp.621-628
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• 2009

Wireless sensor networks (WSNs) have been considered as a promising method for reliably monitoring both civil and military environments under hazardous or dangerous conditions. Due to the special property and difference from the traditional wireless network, the lifetime of the whole network is the most important aspect. The bottleneck nodes widely exist in WSNs and lead to decrease the lifetime of the whole network. In order to find out the bottleneck nodes, the traditional centralized bottleneck detection method MINCUT has been proposed as a solution for WSNs. However they are impractical for the networks that have a huge number of nodes. This paper first proposes a distributed algorithm called DBND (Distributed Bottleneck Node detection) that can reduce the time for location information collection, lower the algorithm complexity and find out the bottleneck nodes quickly. We also give two simple suggestions of how to solve the bottleneck problem. The simulation results and analysis show that our algorithm achieves much better performance and our solutions can relax the bottleneck problem, resulting in the prolonging of the network lifetime.