• Journal of the Korean Society of Safety
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• v.36 no.3
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• pp.1-6
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• 2021

Hydrogen is considered a cleaner energy source than fossil fuels. As a result, the use of hydrogen in daily life and economic industries is expected to increase. However, the use of hydrogen energy is currently limited because of safety issues. The rate of combustion of the hydrogen mixture is about seven times higher than that of hydrocarbon fuels. The hydrogen mixture is highly flammable and has a low minimum ignition energy. Therefore, it presents considerable risks for fire and explosions in all areas of hydrogen manufacturing, transportation, storage, and use. In this study, the auto-ignition characteristics of hydrogen were investigated numerically for diluted hydrogen mixtures. Auto-ignition temperature, a critical property predicting the fire and explosion risk in hydrogen combustion, was determined in well-stirred reactors. When N₂ and CO₂ were used to dilute the hydrogen/air mixture, the ignition delay time increased with increasing dilution ratios in both cases. The CO₂-diluted mixtures exhibited a longer ignition delay than the N₂-diluted mixtures. We also confirmed that lower initial ignition temperatures increased the ignition delay times at 950 K and above. Overall, the auto-ignition characteristics, such as the concentrations of participating species and ignition delay times, were primarily affected by the initial temperature of the mixture.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.407-408
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• 2023

This article proposes a method to assess construction safety risk during the construction phase based on accident loss costs. Risk assessments for hazardous construction work are required by law, but they lack quantitative criteria. To address this, a survey estimated loss costs due to fatalities in the construction industry, finding labor loss cost and delay reimbursement cost to be the largest factors. The proposed method uses algorithm to calculate expected accidents and risk levels based on project characteristics, work methods, personnel, and environment data. This method is expected to enhance the reliability and usability of risk assessments during the construction phase of construction projects.

• Industrial Engineering and Management Systems
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• v.14 no.4
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• pp.372-378
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• 2015

In labor-intensive enterprise, such as garment factory, assembly line is widely used as a manufacturing process for reducing costs and production time. However, for the sake of the various working capacity of worker, idle or delay may happen and influence the rear processes. If these unforeseeable delay happened continuously, it may influence the whole manufacturing process and a model, which is called limited-cycle model with multiple periods (LCMwMP), is assumed to evaluate the influence risk. In order to minimize the risk, the assignment of the workers is focused on. In this paper, we deal with an assembly line as LCMwMP model when two kinds of workers exist, whose efficiency is assumed to two different groups. We consider an optimization problem for finding an assignment of workers to the line that minimizes total expected risk, which is exchanged to expected cost by reset model of LCMwMP. First, reset model as a simple model of LCMwMP is introduced. Then, some hypotheses of the rules of the optimal worker assignment are proposed and some numerical experiments are researched assuming the processing time as Erlang distribution. Finally, the other rules on other certain conditions are discussed.

• Korean Journal of Construction Engineering and Management
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• v.10 no.1
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• pp.91-101
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• 2009

The factors of uncertainty such as work delay could cause many problems, for example, increase of construction cost and terms of work, and the deterioration of quality. Because of these, the uncertainty risk is regarded as an important management factor to obtain the success of construction project. So, the systematic management plan about the uncertainty factors is needed because it plays an important role in the completion of entire project. And also analysis of some factors which can cause the work delay can be one way of improving construction project's certainty and making it competitive. In this reason, we have to make an effort to set a priority based on analysis of quantitatively numerical value about work delay factors to manage them effectively. Thus, this study aims to suggest the basic data for the effective management and prevention of work delay in steel-frame work which is progressive actively now, along with increasing of demand of high-rise buildings by analyzing each reasons of work delay factors and also by suggesting important management factors that are coded according to each construction work using FMEA method which could give a data about the importance of work delay factors through quantitatively numerical value.

• Biomolecules & Therapeutics
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• v.31 no.6
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• pp.583-598
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• 2023

Dementia is a clinical syndrome characterized by progressive impairment of cognitive and functional abilities. As currently applied treatments for dementia can only delay the progression of dementia and cannot fundamentally cure it, much attention is being paid to reducing its incidence by preventing the associated risk factors. Cardiovascular and metabolic diseases are well-known risk factors for dementia, and many studies have attempted to prevent dementia by treating these risk factors. Growing evidence suggests that sex-based factors may play an important role in the pathogenesis of dementia. Therefore, a deeper understanding of the differences in the effects of drugs based on sex may help improve their effectiveness. In this study, we reviewed sex differences in the impact of therapeutics targeting risk factors for dementia, such as cardiovascular and metabolic diseases, to prevent the incidence and/or progression of dementia.

• Journal of the Korea Institute of Building Construction
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• v.21 no.4
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• pp.347-359
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• 2021

Recently, construction projects have emerged in the form of program management, which is complicated by the large-scale of construction, and requires astronomical construction costs. In particular, projects that absolutely require management at the program level, such as large-scale construction projects, require overall control of the planned schedule and cost as a set of various projects, including infrastructure. But in Korea, there is no specific management standard for delays in construction. In order to avoid the risk of cost increase and project delay in the program-level construction project, it is necessary to apply more systematic management standards to prevent delay and to take a more preemptive response in the construction process. Therefore, in this study, a delay management index (DMI) was developed to successfully carry out large-scale construction projects at the program level and prevent delays in advance. In addition, case studies were conducted for large-scale construction projects, and a delay prevention system was established for program-level construction projects.

• Journal of Korean Society of Transportation
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• v.33 no.5
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• pp.478-487
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• 2015

This study proposed a Variable Speed Limits(VSL) algorithm to use traffic information based on Cumulative Demand-Capacity Analysis and evaluated its performance. According to the analysis result, the total of delay consisted of 3 separate parts. There was no change in total travel time although the total of delay decreased. These effects was analysed theoretically and then, evaluated through VISSIM, a microscopic simulator. VISSIM simulation results show almost same as those of theoretical analysis. Furthermore in SSAM analysis with VISSIM simulation log, the number of high risk collisions decreased 36.0 %. However, the total delay decrease effect is not real meaning of decrease effect because the drivers' desired speed is same whether the VSL model is operated or not. Nevertheless this VSL model maintains free flow speed for longer and increases the cycle of traffic speed fluctuation. In other words, this is decrease of delay occurrence and scale. The decrease of speed gap between upstream and downstream stabilizes the traffic flow and leads decrease number of high risk collision. In conclusion, we can expect increase of safety through total delay minimization according to this VSL model.

• Investigative Magnetic Resonance Imaging
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• v.24 no.1
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• pp.30-37
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• 2020

Purpose: Preterm infants are at high risk for adverse neurodevelopmental outcomes. Magnetic resonance imaging (MRI) has been proposed as a means of predicting neurodevelopmental outcomes in this population. It is controversial whether diffuse excessive high signal intensity (DEHSI) represents damage to the white matter or delayed myelination in preterm infants. This study investigated MRI findings for predicting the severity of neurodevelopmental outcomes and assessing whether preterm infants with DEHSI near term-equivalent age have abnormal neurodevelopmental outcomes. Materials and Methods: Preterm infants (n = 64, gestational age at birth < 35 weeks) undergoing brain MRI near term-equivalent age and subsequent neurodevelopmental outcomes were evaluated between 18 and 24 months of age. The associations of MRI findings and the risk of severe cognitive delay, severe psychomotor delay, cerebral palsy (CP), and neurosensory impairment were analyzed. The associations of DEHSI with risks of severe cognitive delay, severe psychomotor delay, CP, and neurosensory impairment (hearing or visual impairment) were analyzed. Outcome data were evaluated by logistic regression and the Fisher's exact test. Results: There were significant associations between abnormal white matter findings and delayed mental development, delayed psychomotor development, neurosensory impairment, and presence of CP. The presence of DEHSI was not correlated with delayed neurodevelopmental outcomes or presence of CP. In multivariate logistic regression analyses, cystic encephalomalacia, punctate lesion, loss of white matter volume and ventricular dilation were significantly associated with CP. Conclusion: Abnormal MRI findings near term-equivalent age in preterm infants predict adverse neurodevelopmental outcomes. No significant association between DEHSI and adverse neurodevelopmental outcomes was demonstrated.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• autumn
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• pp.509-512
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• 2003

The Critical Path Method(CPM) is an effective tool used for planning and scheduling. One of strong point in the CPM is what can calculate float. Float is able to prolong without having an effect on overall schedule of project, however concept and scope about ownership is not definite, because it is a by-product of project. Thus participants have had many dispute in using float because of their interests. In recent years, a few theories have evolved in an attempt to solve this problem. But the prior research did not make a reasonable distribution of float because their criteria of distribution was based on ratio for total project time. Actually, an application of float is achieved by participant's delay risk. Therefore. this paper proposes criteria for float distribution using delay risks, and the framework for the assessment of the delay risks.

• Clinical and Experimental Pediatrics
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• v.52 no.9
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• pp.957-963
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• 2009

Neonatal seizures are the most common and distinctive clinical sign of prenatal and/or neonatal brain disorders. Newborn infants with seizures are at risk of mortality and survivors at risk for neurologic impairment, developmental delay, and subsequent epilepsy. Fifteen reports on neonatal seizures in Korea from 1983 to 2009 were analyzed. A total of 731 neonatal seizure cases were reported. Day of seizure onset, etiology, type of seizures, electroencephalogram findings, and outcomes were analyzed. It is necessary to establish a basic report for a future nationwide study of neonatal seizures.