• Environmental Analysis Health and Toxicology
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• 제14권4호
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• pp.203-216
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• 1999

This paper describes a set of multi-pathway models for estimating health risk to lead. The models link concentrations of an environmental contaminant (lead) in air, water and food to human exposure through inhalation, ingestion, and dietary routes. Exposure is used as the foundation for predicting risk of health detriment within the population. The process of estimating exposure using often limited data and extrapolating to a large diverse population requires many assumption, inferences, and simplification. This paper is divided into four section. The first section provides lead contaminant levels on obtaining environmental concentration of air, tap water, and foods. The second section provides a discussion of exposure parameters and uncertainty associated predicting human health risk of contaminants. The third and fourth section illustrate lifetime average daily exposure (LADE) and excess cancer risk (ECR) based on exposure parameters. The relationship between concentration of lead in an environmental medium and human exposure is determined with pathway exposure factors (PEFs). The calculation of LADE and ECR is carried out using Monte-Carlo simulation with probability density function of exposure parameters. Examination of the result reveals that, for lead exposure, ingestion (food) is the dominant route of exposure rather than inhalation (air), and ingestion (tap eater).

• 한국터널지하공간학회 논문집
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• 제5권3호
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• pp.241-250
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• 2003

암반은 그 특성상 매우 불균질하며, 조사 및 시험을 통하여 얻을 수 있는 자료는 아주 한정적이다. 이러한 이유 때문에 암반 중에 구조물을 구축하는 작업은 많은 불확실성 (uncertainties)을 내포하게 된다. 터널 설계에 있어서 주요 설계 파라미터인 지보패턴, 굴진장 및 굴착방법 등은 최적의 값으로 결정되어야 하나 그 결정이 쉽지 않으며, 결정을 잘못할 경우 원하지 않는 risk, 즉 터널 안정성의 저하 혹은 지보재의 지나친 보강으로 인한 경제적 손실을 발생시킨다. 본 연구에서는 터널설계 시 주요한 설계 파라미터인 지보패턴 및 굴진장을 위험도 분석 기법에 근거하여 결정하는 방법을 소개하였다. 지보량이 증가할수록 신뢰지수가 증가하여 터널의 안정성이 증가함을 정량적으로 확인할 수 있었으며, 터널의 붕괴 등으로 말미암아 발생할 수 있는 손실비용 및 공사비를 고려하여 위험도 분석을 실시함으로서 최적의 지보패턴 및 굴진장을 정량적으로 결정할 수 있었다.

• 대한토목학회논문집
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• 제40권2호
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• pp.167-175
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• 2020

1979년 Herman과 Prigogine에 의해 제안된 Two-fluid Model은 도시부 네트워크의 운영성을 설명하는 거시적인 모형으로서 네트워크 내 정지차량 비율과 평균 주행속도의 관계에 기초하고 있다. 이러한 Two-fluid Model의 파라미터는 교통류 특성에 따라 변화하므로 파라미터를 통한 운영성 분석 시 교통류 상태 변화를 규명하는 단계가 수반되어야 한다. 이에 본 연구는 Two-fluid Model의 파라미터를 활용하여 강우에 따른 교통사고 위험도를 비교하였고, 이로 인한 주행 행태가 도시부 네트워크의 운영성에 영향을 미침을 확인하였다. 먼저 Two-fluid Model 파라미터 추정결과, 맑은 날 대비 비가 온 날의 네트워크 운영성이 저하된 것으로 나타났다. 이후 운전자의 교통사고 위험인지 모형 계수를 산출하고 강우 여부에 따른 교통사고 위험도와 그에 따른 주행 행태 변화를 분석하였다. 오전·오후 시간대 모두 운전자는 맑은 날과 동일한 속도를 유지하였을 때 비가 온 날의 교통사고 위험도가 높을 수 있기 때문에, 위험도를 낮추기 위해 주행속도를 감속하는 경향을 보였다. 그러나 맑은 날 보다 비가 온 날의 위험도는 여전히 높은 것으로 파악되었다. 향후에는 도시부 교통망의 거시적 운영성과 사고 위험도 간의 관계를 보다 다양한 네트워크에서 분석하고 동시에 개선할 수 있는 방안을 연구해볼 필요가 있겠다.

• Journal of Korean Neurosurgical Society
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• 제60권5호
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• pp.567-576
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• 2017

Objective : Preoperative parameters including the T1 slope (T1S) and C2-C7 sagittal vertical axis (SVA) have been recognized as predictors of kyphosis after laminoplasty, which is accompanied by posterior neck muscle damage. The importance of preoperative parameters has been under-estimated in anterior cervical discectomy and fusion (ACDF) because there is no posterior neck muscle damage. We aimed to determine whether postoperative subsidence and pseudarthrosis could be predicted according to specific parameters on preoperative plain radiographs. Methods : We retrospectively analyzed 41 consecutive patients (male : female, 22 : 19; mean age, $51.15{\pm}9.25years$) who underwent ACDF with a stand-alone polyether-ether-ketone (PEEK) cage (>1 year follow-up). Parameters including SVA, T1S, segmental angle and range of motion (ROM), C2-C7 cervical angle and ROM, and segmental inter-spinous distance were measured on preoperative plain radiographs. Risk factors of subsidence and pseudarthrosis were determined using multivariate logistic regression. Results : Fifty-five segments (27 single-segment and 14 two-segment fusions) were included. The subsidence and pseudarthrosis rates based on the number of segments were 36.4% and 29.1%, respectively. Demographic data and fusion level were unrelated to subsidence. A greater T1S was associated with a lower risk of subsidence (p=0.017, odds ratio=0.206). A cutoff value of T1S<$28^{\circ}$ significantly predicted subsidence (sensitivity : 70%, specificity : 68.6%). There were no preoperative predictors of pseudarthrosis except old age. Conclusion : A lower T1S (T1S<$28^{\circ}$) could be a risk factor of subsidence following ACDF. Surgeons need to be aware of this risk factor and should consider various supportive procedures to reduce the subsidence rates for such cases.

• Environmental Engineering Research
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• 제23권1호
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• pp.84-91
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• 2018

The present study deals with the management of groundwater resources of an important agriculture track of north-western part of Saudi Arabia. Due to strategic importance of the area efforts have been made to estimate aquifer proneness to attenuate contamination. This includes determining hydrodynamic behavior of the groundwater system. The important parameters of any vulnerability model are geological formations in the region, depth to water levels, soil, rainfall, topography, vadose zone, the drainage network and hydraulic conductivity, land use, hydrochemical data, water discharge, etc. All these parameters have greater control and helps determining response of groundwater system to a possible contaminant threat. A widely used DRASTIC model helps integrate these data layers to estimate vulnerability indices using GIS environment. DRASTIC parameters were assigned appropriate ratings depending upon existing data range and a constant weight factor. Further, land-use pattern map of study area was integrated with vulnerability map to produce pollution risk map. A comparison of DRASTIC model was done with GOD and AVI vulnerability models. Model validation was done with $NO_3$, $SO_4$ and Cl concentrations. These maps help to assess the zones of potential risk of contamination to the groundwater resources.

• The Journal of Asian Finance, Economics and Business
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• 제8권2호
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• pp.25-39
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• 2021

This purpose of this study is to investigate the association among mutual funds (MFs) risk measures and return parameters, evaluate mutual fund performance and also explore the best appropriate mutual fund performance measure for investment in Pakistan. Therefore, thirty-five mutual funds have been selected for the period 2007-2015. The Sharpe, Treynor, Jensen Alpha, Information ratio and Fama's Net Selectivity measures has been used to analyze MF performance. Our study findings show significant positive relation exist between Sharpe and Jenson alpha & information ratio (IR); Treynor ratio is negatively correlated to Jenson alpha and Jenson alpha is positively allied with IR. Moreover, association among performance measures, Fama's net selectivity is a major driver in leading to other measures but Sharpe and IR lead to Treynor ratio as well. Furthermore, performance measures are ranked in accordance standard deviation with the arrangement of Fama's net selectivity at top, Jenson Alpha at second, Sharpe ratio at third, IR at fourth and Treynor ratio at fifth position according to risk parameters in Pakistan. Overall, Jensen Alpha measure appears to be the best suitable mutual fund performance measure in Pakistan due to its practical nature. Finally, the Pakistani stock market index KSE100 (as benchmark) performs better than MF industry of Pakistan.

• Environmental Engineering Research
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• 제13권2호
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• pp.73-78
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• 2008

For a given soil-contaminated site, a level of soil contamination is characterized and decisions on risk may be made from the risk assessment. The study evaluated critical design factors for the determination of sample size in the sampling design plan and the assessment of soil contaminant- leaching to groundwater. Two variables, the minimum relative detectable difference (T) and coefficient of variation (CV) were evaluated for the sample size determination. The minimum number of samples can be appropriately determined by CV under a T value greater than or equal to 0.2. Soil-contaminant leaching to groundwater was evaluated by using the Soil Screening Level equation of U.S. Environmental Protection Agency and the Risk Based Screening Level equation of American Society for Testing and Materials, with the same input parameters. The groundwater concentrations estimated from soil contaminant concentrations were significantly affected by the Darcy velocity of groundwater and the organic content of soil.

• Industrial Engineering and Management Systems
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• 제14권2호
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• pp.183-195
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• 2015

In this paper, we propose a two-stage group acceptance sampling plan for generalized inverted exponential distribution under truncated life test. Median life is considered as a quality parameter. Design parameters are obtained to ensure that true median life is longer than a given specified life at certain level of consumer's risk and producer's risk. We also explore situations under which design parameters based on median lifetime can be used for other percentile points. Tables and specific examples are reported to explain the proposed plans. Finally a real data set is analyzed to implement the plans in practical situations and some suggestions are given.

• Nuclear Engineering and Technology
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• 제35권1호
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• pp.64-79
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• 2003

In the risk and reliability analysis of complex technological systems, the primary concern of formal uncertainty analysis is to understand why uncertainties arise, and to evaluate how they impact the results of the analysis. In recent times, many of the uncertainty analyses have focused on parameters of the risk and reliability analysis models, whose values are uncertain in an aleatory or an epistemic way. As the field of parametric uncertainty analysis matures, however, more attention is being paid to the explicit treatment of uncertainties that are addressed in the predictive model itself as well as the accuracy of the predictive model. The essential steps for evaluating impacts of these model uncertainties in the presence of parameter uncertainties are to determine rigorously various sources of uncertainties to be addressed in an underlying model itself and in turn model parameters, based on our state-of-knowledge and relevant evidence. Answering clearly the question of how to characterize and treat explicitly the forgoing different sources of uncertainty is particularly important for practical aspects such as risk and reliability optimization of systems as well as more transparent risk information and decision-making under various uncertainties. The main purpose of this paper is to provide practical guidance for quantitatively treating various model uncertainties that would often be encountered in the risk and reliability modeling process of complex technological systems.

• 한국경영과학회지
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• 제28권4호
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• pp.115-129
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• 2003

This paper suggests that the profit sharing contract can be Pareto optimal for both supplier and the purchaser. It is shown that Pareto optimal risk sharing contract can be obtained even though the decisions are made in a decentralized manner. The effect of risk attitude of the members of the supply chain is discussed. We examined various aspects of the risk sharing contract such as risk altitude, bargaining power, and cost of information system. The different risk attitude changes the optimal parameters and decision variables. Especially, we proved that, when both the supplier and the purchaser are risk averse, the purchaser orders less quantity than when the one is risk neutral and the other is risk averse. If the fixed cost for the information system is big enough to satisfy a certain condition, it is Pareto optimal not to share the profit and the purchaser takes all the risk even though he is risk averse.