Sharif Digital Repository

Oil spills in the marine environment can have serious environmental, social and economic impacts. These impacts may be of transnational nature, and this makes the oil spill problem an international issue. Therefore, it is necessary to develop a common structured methodology for oil spill risk assessment. In this research, a general framework is presented for probabilistic risk assessment of oil spill from offshore oil wells. A case study is also performed in Persian Gulf to quantify the risk posed by 357 offshore wells to the near-shore receptors. First, thousands of hypothetical spill scenarios of different volumes are defined and simulated using a Lagrangian particle tracking model. Then,... 

A Markov model is constructed for studying the counterparty risk in a CDS contract. The "wrong-way risk" in this model is accounted for by the possibility of the common default of the reference name and of the counterparty. A dynamic copula property as well as affine model specifications make pricing and calibration very efficient. We also consider the issue of dynamically hedging the CVA with a rolling CDS written on the counterparty. Numerical results are presented to show the adequacy of the behavior of CVA in the model with stylized features  

Hospitals increasingly use control charts to monitor clinical processes and their outcomes. In medical context, control charts should have stable performance when different patients with different levels of risk enter the hospital. In order to monitor multi-Attribute medical processes, we propose a new control chart with entities having different levels of risk. First, risk-Adjusted multivariate cumulative sum control chart (RA-MCUSUM) is developed. Then, simulation experiences are performed to demonstrate the application and to evaluate its performance in terms of in-control average run length (ARL0) stability with the one of a standard MCUSUM chart. The results show that while the standard... 

The infrastructure provided by a Grid enables researchers to collaboratively solve various research problems through sharing their resources and establishing virtual organizations (VOs). However, the distributed and dynamic nature of a Grid VO is a challenge for access control systems. All users in a VO have responsibilities which correspond to their rights. While they should be able to make use of all VO resources, irresponsibility and permission misuse (insider attack) impose costs and losses on the affected resources. Hence, the history of users' behavior and the possibility of misuse need to be considered in the resource providers' risk management process. In this paper, we propose the... 

Ethylene oxide production units are among the most dangerous plants in the petrochemical industry. A detailed consequence analysis for different accidental scenarios for a storage tanks in a petrochemical complex in Iran is put forward. Credible scenarios were selected and all the effective factors that may influence the mechanism of release and dispersion of toxic materials were surveyed. Simulator software and numerical models were used to simulate the distribution of toxic material around the leak source. The results can be used in risk management and in providing an emergency response plan to counter unwanted situations in the plant. This is an abstract of a paper presented at the 7th... 

A risk-based approach for short term security assessment with voltage stability constraint is presented in this paper. This approach includes voltage-stability considerations in reactive power adequacy assessment of a composite power system. The proposed method is based on probabilistic criteria because deterministic risk criteria do not define consistently the true risk in the system. For risk calculation, in this paper, load and parametric uncertainties and system contingencies are considered. Then the effects of uncertainties and contingencies on bus voltage violation are calculated. The required reactive power is determined based on the calculated voltage violation in order to maintain... 

Risk aversion is a prevalent phenomenon when sufficiently large amounts are at risk. In this paper, we introduce a new prescriptive approach for coping with risk in sequential decision problems with discrete scenario space. We use Conditional Value-at-Risk (CVaR) risk measure as optimization criterion and prove that there is an explicit linear representation of the proposed model for the problem  

In this paper, we address a basic production planning problem with price dependent demand and stochastic yield of production. We use price and target quantity as decision variables to lower the risk of low yield. The value of risk control becomes more important especially for products with short life cycle. This is because, the profit implications of low yield might be unbearable in the short run. We apply Conditional Value at Risk (CVaR) to model the risk. CVaR measure is a coherent risk measure and thereby having nice conceptual and mathematical underpinnings. It is also widely used in practice. We consider the problem under general demand function and general distribution function of... 

Distributed Generation (DG) has received increasing attention during the last decade. Advantage and constraints of DG application are well known to both DG owner and electric utility. Various technologies are available for DG units among them gas GenSet is, in particular, more attractive to the investors as the technology provides the control on DG generation. However, there are various financial risks associated with dispatchable DG units that prohibit wide private investment in such technologies. This paper examines the use of financial tools to manage dispatchable DG economic risks. A comprehensive framework has been proposed to consider various economic risks to DG owner. Suitable models... 

Standard-form contracts facilitate the sophisticated public-private partnership (PPP) procurement process. Special care should be taken during the preparation of these documents since any remaining flaws affect subsequent projects. Reviewing the standard-form contract capabilities after its application help to identify its major flaws and improve the contract clauses. This research proposed a novel structured method to address this need and verified its capability. In the proposed method, a comprehensive list of risks is first created for the PPP projects in the specified project environment. The identified risks are prioritised to highlight the priority of the required adjustments in the... 

Background/Purpose: To prevent falling, a common incident with debilitating health consequences among stroke survivors, it is important to identify significant fall risk factors (FRFs) towards developing and implementing predictive and preventive strategies and guidelines. This review provides a systematic approach for identifying the relevant FRFs and shedding light on future directions of research. Methods: A systematic search was conducted in 5 popular research databases. Studies investigating the FRFs in the stroke community were evaluated to identify the commonality and trend of FRFs in the relevant literature. Results: twenty-seven relevant articles were reviewed and analyzed spanning... 

Numerical calculation of Value-at-Risk (VaR) for large-scale portfolios poses great challenges to financial institutions. The problem is even more daunting for large fixed-income portfolios as their underlying instruments have exposure to higher dimensions of risk factors. This article provides an efficient algorithm for calculating VaR using a historical grid-based approach with volatility updating and shows its efficiency in computational cost and accuracy. Our VaR computation algorithm is flexible and simple, while one can easily extend it to cover other nonlinear portfolios such as derivative portfolios on equities and FX securities. © 2022  

In this paper a new approach to risk based seismic assessment of structures is proposed based on acceptable risk levels. In this approach, the probabilistic seismic vulnerability, predicted lifetime of structure, importance and knowledge factors are considered in the evaluation process. Park & Ang damage index is used to quantify damage states of structure. By performing several incremental dynamic analyses, all damage states of structure from minor to heavy and collapse are considered under all possible ground motions. The structural risk level and the necessity of seismic retrofit measures are specified by seismic risk index of structure. This probabilistic performance based method is... 

The safety of hydrogen generation process is a major concern. This paper discusses the quantitative analyzes of the risk imposed on neighborhood from the operation of a hydrogen generator using natural gas reforming process. For this purpose, after hazard identification, the frequency of scenarios was estimated using generic data. Quantitative risk assessment was applied for consequence modeling and risk estimation. The results revealed that, jet fire caused by a full bore rupture in Desulphurization reactor has the highest fatality (26person) and affects the largest area of 5102 m2. The lethality radius, maximum radiation and safe distance of this incident were 140 m, 370 kW/m2 and 225 m... 

This study considers the application of quantitative risk assessment (QRA) on the siting of compressed natural gas (CNG) stations and determining nearby land use limitations. In such cases the most important consideration is to be assured that the proposed site would not be incompatible with existing land uses in the vicinity. It is possible by the categorization of the estimated levels of individual risk (IR) which the proposed site would impose upon them. An analysis of the consequences and likelihood of credible accident scenarios coupled with acceptable risk criteria is then undertaken. This enables the IR aspects of the proposed site to be considered at an early stage to allow prompt... 

This paper puts forward a framework for optimal mitigation of regional risk to enhance the resilience of civil infrastructure. To meet this objective, probabilistic models, methods, and software are developed and applied. The work is conducted within a new reliability-based approach, in which reliability methods compute risk. This contrasts several contemporary approaches for risk analysis. Risk, in this context, denotes the probability of exceeding monetary loss. Evaluating such probabilities requires probabilistic models for hazards, response, damage, and loss. This motivates the following contributions in this paper. First, a new computer program is developed that is tailored to conduct... 

Engineering, procurement and construction (EPC) contracts are commonly used for the construction of oil and gas production facilities. These projects are subjected to many uncertainties. EPC contractors often assume most of the project risks. Several studies have focused on the identification and analysis of EPC project risks. However, they generally fail to define appropriate and effective risk management strategies. The objective of this study is to define efficient risk mitigation strategies that can be utilized in EPC oil and gas projects. A comprehensive review of literature was conducted to identify the risks in EPC projects. Experts' opinion were used to analyze and categorize these... 

In this paper, we propose a sampling policy considering Bayesian risks. Various definitions of producer's risk and consumer's risk have been made. Bayesian risks for both producer and consumer are proven to give better information to decision-makers than classical definitions of the risks. So considering the Bayesian risk constraints, we seek to find optimal acceptance sampling policy by minimizing total cost, including the cost of rejecting the batch, the cost of inspection, and the cost of defective items detected during the operation. Proper distributions to construct the objective function of the model are specified. In order to demonstrate the application of the proposed model, we... 

Using survey data, public awareness of and attitudes toward nanotechnology are examined in Iran (N ≥ 759). Iran is a developing country with a national nanotechnology action plan for a ten year period starting from 2003 and has been active in the field of research and development of nanotechnology meanwhile. First, the results show that majority of people are still not familiar with nanotechnology and perceived risks posed by this technology are not considered to be a lot and most people feel its benefits outweigh the risks. The emotions toward this technology are of a hopeful and positive nature and this technology is looked upon favorably in Iran. In particular, our results reveals that...