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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

New trends for conducting hazard & operability (HAZOP) studies in continuous chemical processes

Dunjó Denti, Jordi 18 February 2010 (has links)
Identifying hazards is fundamental for ensuring the safe design and operation of a system in process plants and other facilities. Several techniques are available to identify hazardous situations, all of which require their rigorous, thorough, and systematic application by a multi-disciplinary team of experts. Success rests upon first identifying and subsequently analyzing possible scenarios that can cause accidents with different degrees of severity. While hazard identification may be the most important stage for risk management, it depends on subjectivity issues (e.g., human observation, good judgment and intuition, creativity, expertise, knowledge) which introduce bias. Without a structured identification system, hazards can be overlooked, thus entailing incomplete risk-evaluations and potential loss. The present Thesis is focused on developing both managerial and technical aspects intended to standardize one of the most used techniques for hazard identification; viz. HAZard & Operability (HAZOP) study. These criteria have been carefully implemented not only to ensure that most of the hazardous scenarios will be identified, but also that US OSHA PSM Rule, EPA RMP, and Seveso Directive requirements will be accomplished. Chapter I pioneers the main research topic; from introducing the process safety concept up to the evidence of more detailed information is required from related regulations. A review of regulations (i.e., US, Europe legislation) focused on Hazard Identification has been conducted, highlighting, there is an absence of specific criteria for performing techniques intended to identify what can go wrong. Chapter II introduces the risk management system required to analyze the risk from chemical process facilities, and justifies that hazard identification stage is the Process Safety foundation. Hereafter, an overview of the key Process Hazard Analyzes (PHA) has been conducted, and the specific HAZOP weaknesses and strengths have been highlighted to establish the first steps to focus on. Chapter III establishes the scope, the purpose and the specific objectives that the research covers. It answers the following questions on the spot: why the present research is performed, which elements are included, and what has been considered for acquiring the final conclusions of the manuscript. Chapter IV gathers HAZOP-related literature from books, guidelines, standards, major journals, and conference proceedings with the purpose of classifying the research conducted over the years and finally define the HAZOP state-of-the-art. Additionally, and according to the information collected, the current HAZOP limitations have been emphasized, and thus, the research needs that should be considered for the HAZOP improvement and advance. Chapter V analyzes the data collected while preparing, organizing, executing and writing HAZOPs in five petroleum-refining processes. A statistical analysis has been performed to extract guidance and conclusions to support the established criteria to conduct effectively HAZOP studies. Chapter VI establishes the whole set of actions that have to be taken into account for ensuring a wellplanned and executed HAZOP study. Both technical and management issues are addressed, criteria supported after considering the previous chapters of the manuscript. Chapter VI itself is the result of the present research, and could be used as a guideline not only for team leaders, but also for any related party interested on performing HAZOPs in continuous chemical processes. Chapter VII states the final conclusions of the research. The interested parties should be released about the hazard identification related-gaps present in current process safety regulations; which are the key limitations of the HAZOP study, and finally, which are the criteria to cover the research needs that have been found Annex I proposes the key tools (tables, figures and checklists "ready-to use'') to be used for conducting HAZOPs in continuous chemical processes. The information layout is structured according to the proposed HAZOP Management System. This information is intended to provide concise and structured documentation to be used as a reference book when conducting HAZOPs. Annex II is intended to overview the most relevant petroleum refining processes by highlighting key factors to take into account in the point of view of process safety and hazard identification, i.e. HAZOP. In this sense, key health and safety information of specific petroleum refining units is provided as a valuable guidance during brainstorming sessions. Annex III illustrates the complete set of data collected during the field work of the present research, and also analyzed in Chapter V of the manuscript. Additionally, it depicts a statistical summary of the key variables treated during the analysis. Finally, the Nomenclature, References, and Abbreviations & Acronyms used and cited during the manuscript have been listed. Additionally, a Glossary of key terms related to the Process Safety field has been illustrated. / La present Tesis doctoral té com a objectiu estandarditzar l'aplicació d'una de les tècniques més utilitzades a la industria de procés per a la identificació de perills; l'anomenat HAZard & OPerability (HAZOP) study, específicament a processos complexes, com per exemple, unitat de refineria del petroli.El capítol I defineix el concepte de Seguretat de Processos, i progressivament analitza les diferents regulacions relacionades amb la temàtica, detallant específicament les mancances i buits d'informació que actualment hi ha presents a la primera etapa de la gestió del risc en industries de procés: la identificació de perills.El capítol II defineix el sistema de gestió del risc tecnològic que aplica a les industries de procés, i es justifica que l'etapa d'identificació de perills és el pilar de tot el sistema. Finalment, es mencionen algunes de les tècniques d'identificació més utilitzades, els anomenats Process Hazard Analysis (PHA), i es detallen les seves mancances i fortaleses, característiques que han acabat definint la temàtica específica de la Tesis. Concretament, es dóna èmfasis a la tècnica anomenada HAZard & OPerability (HAZOP) study, objecte principal de la recerca.El capítol III defineix l'abast, el propòsit i els objectius específics de la recerca. La intenció d'aquest capítol és donar resposta a les següents qüestions: el perquè de la recerca, quins elements han estat inclosos i què s'ha considerat per tal d'assolir les conclusions de la Tesis.El capítol IV descriu l'estat de l'art de la literatura relacionada amb el HAZOP. Aquesta revisió no només permet classificar les diferents línies de recerca relacionades amb el HAZOP, sinó que també permet assolir un coneixement profund de les diferents particularitats de la pròpia tècnica. El capítol finalitza amb un conjunt de mancances tant de gestió com tècniques, així com les necessitats de recerca que poden millorar l'organització i execució dels HAZOPs.El capítol V analitza la informació que ha estat recopilada durant la fase experimental de la tesis. Les dades procedeixen de la participació en cinc estudis HAZOP aplicats a la industria de refineria del petroli.En aquest sentit, el capítol V desenvolupa una anàlisi estadística d'aquestes dades per extreure'n conclusions quant a la preparació, organització i execució dels HAZOPs.El capítol VI estableix el conjunt d'accions que s'ha de tenir en compte per tal d'assegurar que un estudi HAZOP estigui ben organitzat i executat (la metodologia). Es defineix un Sistema de Gestió del HAZOP, i a partir de les seves fases, es desenvolupa una metodologia que pretén donar suport a tots aquells punts febles que han estat identificats en els capítols anteriors. Aquesta metodologia té la intenció de donar suport i guia no només als líders del HAZOP, sinó també a qualsevol part interessada en aquesta temàtica.El capítol VII descriu les conclusions de la recerca. En primera instància s'enumeren les mancances quant a la definició de criteris a seguir de diferents regulacions que apliquen a la Seguretat de Processos.Seguidament, es mencionen les limitacions de la pròpia tècnica HAZOP, i finalment, es descriuen quins són els criteris establerts per donar solució a totes aquestes febleses que han estat identificades.L'Annex I és una recopilació de diferents criteris que han estat desenvolupats al llarg de l'escrit en forma de taules i figures. Aquestes han estat ordenades cronològicament d'acord amb les diferents fases que defineixen el Sistema de Gestió HAZOP. L'annex I es pot utilitzar com a una referència concisa i pràctica, preparada i pensada per ésser utilitzada directament a camp, amb la intenció de donar suport a les parts interessades en liderar estudis HAZOP.L'annex II recopila informació relacionada amb aspectes clau de seguretat i medi ambient en diferents unitats de refineria. Aquest informació és un suport per tal de motivar el "brainstorming" dels diferents membres que conformen l'equip HAZOP.L'Annex III recopila les dades de les diferents variables que han estat considerades a la fase experimental de la recerca, juntament amb un conjunt de figures que mostren la seva estadística bàsica.
82

Giftfri miljö på förskolor – Nulägesanalys och förslag till förbättringsarbete (åtgärder) i Båstads kommun

Sami, Inas, Dakhil, Inas January 2016 (has links)
Products that children get in contact with every day, such as toys, paints, electronics and detergents have recently been discovered that they contain harmful chemicals. Children are more susceptible than adults because of their thin skin and yet not fully developed bodies. The purpose of this work is to identify the risks from chemicals that children in the indoor nursery get in contact with, and how these products affect the health of children, and to describe how these chemicals affect children's health and the environment. The aim is also to find out how great the level of the staff's knowledge is about the harmful chemicals, as well as the preventive measures taken.  This is done through a survey among the staff at nurseries in Båstad municipality. The report consists of three parts, two practical parts in the form of an on-site investigation at nine kindergartens in Båstad municipality and a survey among the staff who worked there. The third theoretical part was in the form of literature.  The results of this study show that the indoor environment in nurseries has important significance for children's health. The inventory of nursery in Båstad municipality showed that today there are goods and products with harmful chemicals among kids at nurseries. The products that have been found in nurseries in Båstad municipality where most contain harmful chemicals such as phthalates, flame retardants, perfluorinated substances and bisphenol A. It was above all the electronic toys such as cell phones, keyboards, computers, and even in the older toys or soft and semi-soft toys.  To reduce the amounts of chemicals found in nurseries one should start to throw away old toys, old electronic toys, avoid toys with batteries or electronics that do not have their batteries covered, stop using cleaning products containing chemicals and also increase the number of times that the nurseries are cleaned thoroughly. The questionnaire study showed that most nurseries were not sufficiently aware of the dangerous chemicals in toys and detergents used. There was a certain part of the staff that was aware of what "green flag" means.  To achieve this is the best way, the municipality, and politicians should help the nurseries. Improvements by the municipality, and politicians should provide important training for both nurseries staff and for the various pictures within the community that directly or indirectly impact. In order to improve knowledge in this area it is needed to train nurseries staff, cleaning staff, parents and others in the business. To get a non-toxic nursery, it is important that the municipality, the nurseries staff, cleaning staff and parents all gain knowledge about chemicals in materials and products.
83

An examination of the snow and avalanche hazard on the Milford Road, Fiordland, New Zealand

Hendrikx, Jordy January 2005 (has links)
Avalanches pose a significant natural hazard in many parts of the world. Worldwide the hazard is being managed in a number of new and traditional methods. In New Zealand, the Milford Road, Fiordland, has a significant avalanche problem which has been managed by the Transit New Zealand Milford Road Avalanche Programme since 1984. This avalanche programme has generated a database of all avalanche occurrences and associated meteorological parameters for the time period 1985 to 2002. Elsewhere around the world, similar and more extensive data sets have been used to examine a wide variety of aspects in relation to the snow cover, avalanching and avalanche hazard. The availability of the Milford Road database has provided the opportunity use new and traditional approaches to examine many aspects of avalanching including; the trends in and relationships with the snow and avalanche regime, evaluation of the avalanche hazard, statistical forecasting of avalanches and the visualisation of avalanche occurrence information in a GIS. Statistical and graphical examination of the inter-annual variation in the snow and avalanche regime revealed relationships between the snow depth, avalanche occurrences and atmospheric circulation similar to those found elsewhere around the world, but not previously examined in New Zealand. Furthermore, the analysis resulted in strong correlations despite using a database significantly shorter than those used elsewhere. Atmospheric circulation types that bring strong winds and precipitation were found to be highly significantly correlated with avalanche occurrences and snow depth. Avalanche occurrences were more highly correlated with atmospheric circulation than snow depth was, reflecting the strong maritime avalanche climate. Risk evaluation was undertaken using two approaches, the avalanche hazard index (AHI) and the probability of death to individuals (PDI) method. The present avalanche risk was compared to a theoretically uncontrolled avalanche regime, using 2002 traffic volumes for AHI and PDI. The AHI analysis highlighted the reduction in the AHI resulting from the control programme, and the significantly lower AHI when compared to Rogers Pass, B.C., Canada. The PDI analysis using equations modified to allow for a range of consequences indicated that the Milford Road is similar in risk to roads in Switzerland, but is far more accessible, with fewer closed days. A new equation for PDI, which accounted for waiting traffic was derived, and suggested that the calculated risk was high and unacceptable compared to standards applied to other hazards. Statistical forecasting using classification tree analysis has been successfully applied to avalanche forecasting in other climatic settings. This study has applied an extension to this technique through 10-fold cross validation to permit classification of an avalanche day in this direct action maritime climate. Using varying misclassification costs two classification trees were generated. The tree that used only wind speed and wind speed and precipitation combined in a temperature sensitive wind drift parameter obtained an overall accuracy of 78%, with correct prediction for an avalanche day at 86%. These predictor variables are considered to be the fundamental controls on avalanche forecasting in this climate, and coincide with important variables inferred from the atmospheric circulation analysis. Following the investigation of various methods for the creation of a high resolution digital elevation model (DEM), a GIS was used for the visualisation and examination of avalanche occurrences. Similar to other studies, qualitative and quantitative analysis of the spatial distribution in terms of aspect of avalanche occurrences was undertaken using the GIS. Colour coding of occurrences highlighted the influence of two storm directions, while an excess ratio showed the clear influence of aspect on avalanche occurrences in relation to two dominant storm directions, avalanche size and avalanche paths. Furthermore, the GIS has many applications for operational forecasting, teaching and the maintenance of institutional memory for the avalanche programme.
84

Models of tephra dispersal

Bonadonna, Costanza January 2001 (has links)
No description available.
85

Lava flow volume and morphology from ERS synthetic aperture radar interferometry

Stevens, Nicola Frances January 1999 (has links)
No description available.
86

Bayesian nonparametric survival analysis via Markov processes

Nieto-Barajas, Luis E. January 2001 (has links)
No description available.
87

The role of risk analysis in the control of major accidents

Lloyd, David J. January 1988 (has links)
No description available.
88

Hedge Funds' Performance Fees and Investments

Gong, Yuhui 27 April 2017 (has links)
The high-water mark provision in hedge fund managers' compensation raises concerns of investors, because they are worried about that fund managers would take unnecessarily high risk in the fund investment. In this paper, we theoretically analyze the optimal strategies for hedge fund managers who choose to maximize the expected power utility from fees in both discrete-time and continuous- time models. The results show that when approaching the fee payment date, hedge fund managers would take as much risk as they are allowed to in the fund investment. However, if hedge fund managers are given more time, they tend to be more conservative. In the continuous-time model, the optimal allocation of the fund in the risky asset depends on market conditions, which are measured by the state price density.
89

Compiling a homogeneous earthquake catalogue for Southern Africa

Mulabisana, Thifhelimbilu Faith January 2016 (has links)
An accurate seismic hazard assessment can only be carried out if a homogeneous and sufficiently complete catalogue for the study area is available. Since the catalogue for southern Africa was last updated in the early 1990s for the Global Seismic Hazard Assessment Program (GSHAP), it is necessary that a new updated, homogeneous and complete earthquake catalogue be compiled that includes data acquired during the last two decades. The process of compiling the new earthquake catalogue for southern Africa (South Africa, Lesotho, Swaziland, Botswana, and Namibia) was done as part of the Global Earthquake Modelling (GEM) project. The data from published and unpublished sources, and databases from the South African National Seismograph Network (SANSN), Bulawayo (BUL), the Geological Survey of Botswana, the National Earthquake Information Centre (NEIC), the Advanced National Seismic System (ANSS), and the International Seismic Centre (ISC) were retrieved and evaluated. After the data from the different sources were merged, duplicates and induced earthquakes were removed. The catalogue was unified with all magnitude types converted to moment magnitude (MW). Unifying the southern African catalogue to one magnitude scale had multiple challenges, considering that the catalogue is mostly incomplete, and it was therefore not easy to derive relations between different magnitude scales. The question of which method and relations are most suitable for converting all magnitude scales to MW had to be addressed. To ensure that all the events are independent, several procedures were carried out to decluster the catalogue and most suitable method selected. The final catalogue includes all available events, i.e. historical, and instrumental events from 1690 to December 2011, excluding fore- and aftershocks and induced events. This catalogue has 920 events with MW ≥ 4 whereas GSHAP has only 100 events with MS ≥ 4 in the southern African region. The largest event in the final catalogue occurred in 1952 and is located in the Okavango Delta region in Botswana with magnitude MW = 6.7. The maximum likelihood method was used at each point on a grid covering the study area, to estimate the spatial distribution of the b-value and the activity rate. The maximum curvature method was used for estimating the spatial distribution of magnitude of completeness, which was also substantiated with the Gutenberg-Richter, time-scale and spatial-scale magnitude of completeness graphs.
90

GIS-based Assessment of Debris Flow Susceptibility and Hazard in Mountainous Regions of Nepal

Paudel, Bhuwani Prasad 14 February 2019 (has links)
Rainfall-induced landslides that change into debris flows and travel large distances are one of the treacherous natural calamities that can occur in mountainous areas, particularly in Nepal’s mountains. Debris flow was the second highest cause of human death in Nepal after epidemics between 1971 and 2016. Because debris flow is common in mountainous regions, its prediction and remedial measures through land use plans are important factors to consider for saving lives and properties. The spatial distribution of the initial landslides that change into debris flow, on a watershed scale, is still an important area of study in this mountainous region to develop essential land use plan. In this research, hydrologic, slope stability and Flow-R models are applied in GIS modeling to locate potential landslide and debris flow areas for a given threshold rainfall in a mountainous watershed-Kulekhani, Nepal. Soil samples from 73 locations within the watershed and a geotechnical investigation on one old landslide area were considered to determine the Soil Water Characteristics Curve (SWCC), friction angle, cohesion, and infiltration characteristics of the subsurface soils in the study area. This information is applied in an unsaturated slope stability model to find unstable locations in the study watershed in a GIS environment. The model is tested on a recorded 24-hour rainfall of 540 mm in the watershed, and potential landslide locations are obtained. The validation results show that there is a good agreement between the predicted and mapped landslides. For debris flow run out, Flow-R model, which has the capability to analyze debris flow inundation with limited input information, and the model software is readily available in the public domain, was chosen for further analysis. Two recent debris flow events and the study watershed are taken as case studies to identify the appropriate algorithms of Flow-R for runout analysis of the study areas. Landslide-triggering threshold rainfall frequency is related to the frequency of landslides and the debris flow hazard in these mountains. The above validated models are applied in a GIS environment to locate potential debris flow areas in expected threshold rainfall. Rainfall records from 1980 to 2013 are computed for one- to seven-day cumulative annual maximum rainfall. The probable rainfalls for 1 in 10 to 1 in 200 years return periods are identified. The anticipated probable rainfalls are modeled in the GIS environment to identify the factor of safety of mountain slopes for landslide susceptibility in the study watershed. The Flow-R model with user-defined landslide-susceptible areas was chosen for debris flow runout analysis. A relation between the frequency of rainfall and landslide-induced debris flow hazard area is derived for return periods of 25, 50, 100, and 200 years. Also, the debris flow hazard results from the analysis are compared with a known event in the watershed and found to agree. This developed method can be applied to anticipated landslide and landslide-induced debris flow from the live rainfall record to warn hazard-prone communities for saving lives and regulating hazardous transportation corridors in these mountains. In addition to this, this methodology will be a useful tool to help policy makers create appropriate land use plans.

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