Sharif Digital Repository

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... 

Safety distance has already been a main easurement for the hazard control of chemical installations interpreted to mean providing space between the hazardous installation and different types of targets. But, the problem is how to determine the enough space. This study considers the application of quantitative risk assessment to evaluating a compressed natural gas station site and to identify nearby land use limitations. In such cases, the most important consideration is to assure that the proposed site would not be incompatible with existing land uses in the vicinity. This scope is possible by categorization of estimated levels of risk imposed by the proposed site. It means that an analysis... 

This research investigates a three dimensional parametric risk assessment model considering the 3rd factor to be the impact on business. In order to represent the 3rd order risk assessment matrix monitoring the impact of safety reports on the continuous economical performance of the airline, the other two factors, probability of safety and severity are redefined. Introducing two quantitative and qualitative assessment methodologies, the overall risk of the organization can be studied by means of Analytical Hierarchy Process (AHP). providing an adequate background to define the safety goals of the organization  

API Publication 2218 is one of the most referred practices for fireproofing of onshore structural supports. Despite the extensive citation, it solely considers the effects of pool fire and rarely addresses jet fire outcomes. This absence of an explicit approach is common among all the other major references. Therefore, the basic objective of this paper is to introduce a new approach for determination of the necessity for fireproofing of structural supports against jet fires. For this purpose, the flame geometry and duration of jet fires are simulated for different leak sizes in identified fire potential sources. Then, following a worst-case analysis, those structures that may be impinged by... 

The uncertainty and the complexity associated with the domino effect is a barrier to assessing the frequency of such accidents analytically. The use of simulation techniques, such as Monte Carlo, to examine the domino effect instead of analytical techniques has shown great promise. In this paper, a new method to assess the frequency of domino accidents is proposed-FREEDOM II-which is an improvement on the recent algorithm proposed by the authors (FREEDOM). The modifications on FREEDOM were carried out to overcome a limitation of the method and to extend its capabilities. A key shortcoming of the earlier method was its inability to handle multiple failure scenarios. This shortcoming has been... 

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,... 

This article is focused on developing an Energy Service Company (ESCO) risk assessment model for use by energy savings certificates (ESC) market regulators. This model enables market regulators to determine the appropriate point in time for ESCOs to sell their certificates with the aim of minimizing risk as well as maximizing economic gain yet remain motivated for reducing the cost of energy efficiency technologies. To this end, the interactions between an ESCO and other parties (such as suppliers) in the market in addition to the principles of the energy efficiency performance contract are taken into consideration. Then, appropriate probability distributions have been fitted to the... 

There is limited research that considers the sustainability aspect of the projects’ schedule. The present study proposes a model to cover this gap by considering sustainable development criteria. A multi-objective model with four objective functions, including minimizing cost, risk, and socio-environmental impacts, has been presented to decrease the project’s delay. Since some of the parameters are considered under conditions of uncertainty for the proximity of problems to real projects, the robust programming method is used to deal with the uncertainty, and the epsilon-constraint method was applied to solve the multi-objective model. Several scenarios are also defined to analyze the... 

Background: We developed transformer-based deep learning models based on natural language processing for early risk assessment of Alzheimer’s disease from the picture description test. Methods: The lack of large datasets poses the most important limitation for using complex models that do not require feature engineering. Transformer-based pre-trained deep language models have recently made a large leap in NLP research and application. These models are pre-trained on available large datasets to understand natural language texts appropriately, and are shown to subsequently perform well on classification tasks with small training sets. The overall classification model is a simple classifier on... 

There are many reported researches considering movement behavior of vehicles. In these studies the two basic types of movement of a vehicle are longitudinal movement, car following, and lateral movement, lane changing. Dependency between car following and lane changing models and the fact that many of drivers does not consider driving lanes, necessitate developing of models that combine the car following and lane changing without considering the driving lanes. Utilizing computer simulation, the work can also be applied to conditions where lane disciplines are strictly observed. Microscopic simulation models considering the movement of individual vehicles in a traffic stream can be... 

Cost overrun risks are declared to be dynamic and interdependent. Ignoring the relationship between cost overrun risks during the risk assessment process is one of the primary reasons construction projects go over budget. Conversely, recent studies have failed to account for potential interrelationships between risk factors in their machine learning (ML) models. Additionally, the presented ML models are not interpretable. Thus, this study contributes to the entire ML process using a Bayesian network (BN) classifier model by considering the possible interactions between predictors, which are cost overrun risks, to predict cost overrun and assess cost overrun risks. Furthermore, this study... 

API Recommended Practice 752 is one of the most referenced practices for evaluating vapor cloud explosion (VCE) impacts to site occupied buildings. This reference introduces generic VCE frequencies for different types of process units that are based on VCE incidents database. Although these reported VCE frequencies are not capable of illustrating all parameters that affect explosion likelihood, they are widely used in risk analysis studies and software packages. This paper delineates the structure of a more realistic method for estimation of local VCE frequencies for independent congested spaces or units as a function of process, site, and meteorological variables. Compared to traditional... 

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... 

Frequency estimation of vapor cloud explosions (VCE) are traditionally based on sparse VCE incidents data analysis while process conditions that generate VCE's have a wide spectrum giving VCE's with different strengths. The present paper is focused on developing a systematic methodology to estimate the frequency of VCEs based on process and plant conditions in order to find optimal location of a control room using quantitative risk assessment (QRA). In the presented approach, after classification of plant areas according to variables likely to generate different release conditions, a comprehensive release study is carried out to determine individual probable leakages. Consequently, only... 

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... 

Recent earthquakes clarified that existing a soft/weak-story in a building could completely invert the failure mechanisms of the structure. Several studies were implemented to evaluate the potential risk subjected to the buildings under the earthquake hazard. However, these researchers discarded the effect of soft/weak-story on the demand parameters of their models. This paper presents a rapid demand estimation framework for generic buildings considering the effect of soft/weak-story. In this regard, the simplified model developed according to the HAZUS approach is rectified to apply the effect of soft/weak-story on the structural behavior of the generic buildings. Artificial neural networks... 

In a deregulated electric power utility industry in which a competitive electricity market can influence system reliability, market risks cannot be ignored. This paper (1) proposes an analytical probabilistic model for reliability evaluation of competitive electricity markets and (2) develops a methodology for incorporating the market reliability problem into HLII reliability studies. A Markov state space diagram is employed to evaluate the market reliability. Since the market is a continuously operated system, the concept of absorbing states is applied to it in order to evaluate the reliability. The market states are identified by using market performance indices and the transition rates... 

This paper outlines a quantitative risk assessment for an 110,000 ton/day ethylene oxide production plant in Iran. After a complete and detailed hazard identification study, done by HAZOP method, the purification column was found to be one of the most hazardous sections in this plant. As ethylene oxide with high concentration and inventory is present there. Fault tree analysis (FTA) technique has been used to identify the basic events responsible for top event occurrence and also calculation of top event frequency of occurrence. Human error has been calculated numerically and probability of human error has been estimated. Failure rate data were collected referring to several sources and... 

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...