Concurrent Importance and Sensitivity Analysis Applied to Multiple Fault Trees

Complex industrial systems may present different potentially dangerous failure states (Top-events). The analysis of system failure states via Fault-tree technique allows determining the failure frequency of potential accidents and the importance measures of components' failure modes. The combination of Importance and Sensitivity Analysis (ISA) constitutes a very powerful tool to improve the design of critical systems or to prove that the design satisfies safety requirements. The present reports describes a novel approach to implement Importance and Sensitivity analysis applied to Fault-trees, which consists of the concurrent analysis of all relevant system's Fault-trees to identify the weakest parts of the system which require further design improvement. This approach aims at overcoming the limitations of the current methods in application for ISA in which Top-events are sequentially analysed. In addition the proposed method extends the ISA application also to 'over-reliable' system functions (if any) on which the reliability/maintainability characteristics of the involved components can be relaxed with consequent cost saving. The result is a uniformly protected system satisfying the predefined design goals.JRC.G.7-Traceability and vulnerability assessmen

Model uncertainty and sensitivity analysis for thermal comfort prediction

Building Performance Simulation (BPS) is poorly used to support informed decision making between different design options nor is it used for building and/ or system optimization. Currently BPS is only used for code compliance during the detailed design [Wilde, 2004]. The approach of this research by using an existing tool as initial prototype is rapid prototyping to make incremental improvement of BPS. This paper elaborates the above in more detail in particular by focusing on an uncertainty and sensitivity analysis for thermal comfort prediction. A case study is described to evaluate the necessity of the use of uncertainty and sensitivity analysis in BPS. For that purpose an in the Netherlands well-known and commonly-used simulation tool for the detailed design is chosen. Furthermore, a range of results reflecting the impact of UA and SA are presented

ASTRA Plus User Manual

This report describes the user interface and the main commands to perform system dependability analysis by means of ASTRA Plus. This package implements the analysis methods developed at the Institute for the Protection and Security of the Citizen from mid-2008. ASTRA Plus is composed of the Fault Tree Analysis (FTA) module and of the Concurrent Importance and Sensitivity Analysis (CISA) module. The FTA module contains three different methods for solving a fault tree; all are based on the state of the art approach of Binary Decision Diagrams (BDD). These three methods allow the user to analyse fault trees of increasing complexity (i.e. increasing number of basic events and gates). In particular the third method, which is based on functional decomposition, allow performing the analysis of fault trees of very high complexity. The CISA module is based on a new methodology for system design improvement. The key operation is the calculation of Global Importance Measures of basic events considering all system fault trees. This allows identifying the weakest part of the system with reference to all top-events. Then the on-line sensitivity analysis allows the user to rapidly identify the set of suitable design improvements from which the best cost-effective one can be selected.JRC.G.6-Security technology assessmen

Risk-informed approach to the safety improvement of the reactor protection system of the AGN-201K research reactor

Periodic safety reviews (PSRs) are conducted on operating nuclear power plants (NPPs) and have been mandated also for research reactors in Korea, in response to the Fukushima accident. One safety review tool, the probabilistic safety assessment (PSA), aims to identify weaknesses in the design and operation of the research reactor, and to evaluate and compare possible safety improvements. However, the PSA for research reactors is difficult due to scarce data availability. An important element in the analysis of research reactors is the reactor protection system (RPS), with its functionality and importance. In this view, we consider that of the AGN-201K, a zero-power reactor without forced decay heat removal systems, to demonstrate a risk-informed safety improvement study. By incorporating risk- and safety-significance importance measures, and sensitivity and uncertainty analyses, the proposed method identifies critical components in the RPS reliability model, systematically proposes potential safety improvements and ranks them to assist in the decision-making process. Keywords: Research reactor, Reactor protection system, Probabilistic safety assessment, Risk-informed design, Unavailability analysis, Sensitivity analysi

Examining Collaboration in Interdisciplinary Product Development Focusing on Dependencies

Product development in manufacturing industry is characterized by intense collaboration need of various stakeholders. Increasing integration of disciplines in modern products makes it more and more a challenge to arrange collaboration efficiently and effectively. Process and product characteristics as well as the architecture of information systems used in product development have to be considered. This paper introduces a methodology for the design of collaboration situations based on principles of system analysis. First, a collaboration situation is defined and modelled regarding constituent elements in the domains process, product and system. Second, a description model for dependencies in these domains is developed. Morphological analysis was applied to derive features and characteristics of the model. Third, an improvement approach to optimize a given collaboration situation is depicted. The improvement approach comprises a sensitivity model, which explicates causal relations between the dependency features. The methodology is applied to a case study from manufacturing industry

Investigating organizational quality improvement systems, patient empowerment, organizational culture, professional involvement and the quality of care in European hospitals: the 'Deepening our Understanding of Quality Improvement in Europe (DUQuE)' project

BACKGROUND: Hospitals in European countries apply a wide range of quality improvement strategies. Knowledge of the effectiveness of these strategies, implemented as part of an overall hospital quality improvement system, is limited. METHODS/DESIGN: We propose to study the relationships among organisational quality improvement systems, patient empowerment, organisational culture, professionals' involvement with the quality of hospital care, including clinical effectiveness, patient safety and patient involvement. We will employ a cross-sectional, multi-level study design in which patient-level measurements are nested in hospital departments, which are in turn nested in hospitals in different EU countries. Mixed methods will be used for data collection, measurement and analysis. Hospital/care pathway level constructs that will be assessed include external pressure, hospital governance, quality improvement system, patient empowerment in quality improvement, organisational culture and professional involvement. These constructs will be assessed using questionnaires. Patient-level constructs include clinical effectiveness, patient safety and patient involvement, and will be assessed using audit of patient records, routine data and patient surveys. For the assessment of hospital and pathway level constructs we will collect data from randomly selected hospitals in eight countries. For a sample of hospitals in each country we will carry out additional data collection at patient-level related to four conditions (stroke, acute myocardial infarction, hip fracture and delivery). In addition, structural components of quality improvement systems will be assessed using visits by experienced external assessors. Data analysis will include descriptive statistics and graphical representations and methods for data reduction, classification techniques and psychometric analysis, before moving to bi-variate and multivariate analysis. The latter will be conducted at hospital and multilevel. In addition, we will apply sophisticated methodological elements such as the use of causal diagrams, outcome modelling, double robust estimation and detailed sensitivity analysis or multiple bias analyses to assess the impact of the various sources of bias. DISCUSSION: Products of the project will include a catalogue of instruments and tools that can be used to build departmental or hospital quality and safety programme and an appraisal scheme to assess the maturity of the quality improvement system for use by hospitals and by purchasers to contract hospitals

Optimised thermosyphon solar hot water heater — simulation, design and experimental analysis

Thermosyphon systems represent 70–80 % of the solar-thermal capacity installed world-wide. Outside of China — the world’s largest thermosyphon system market — thermosyphon systems using flat-plate collectors are the dominant configuration. In Southern Europe conventionally-designed thermosyphon systems with a collector area of about 2.0 m² and a storage tank of 180 l are able to deliver about 70 % of the annually needed hot water of a four person household. However, research into the performance of thermosyphon systems has stagnated in recent years, hence the primary objective of this research was to evaluate in detail the physical factors affecting the performance of flat plate thermosyphon systems hence pointing the way towards improved performance. The investigation consisted of the implementation of a detailed dynamic system simulation, which included the development of new component models, the validation of the new component models via laboratory testing, the use of the system model in a sensitivity analysis of the significance of individual component performance and finally the testing of an improved prototype thermosyphon system. Eighteen different geometrical and physical parameters were investigated in the sensitivity analysis to find the most significant design factors. The sensitivity analysis incorporated three different European locations, but the dependency of the optimal thermosyphon system configuration on the location was found to be rather weak. The research concluded that a performance improvement from 70 % to 85 % of the hot water demand of a four-person household could be achieved with an improved system configuration. The improved system prototype addressed cost reduction by the material selection for the storage tank and its built-in components as well as the selection of aluminium for the solar absorber and the use of prefabricated parts for the system support. Reverse thermosyphoning was prevented by adjusting the tank and collector inlet/outlet co-locations, while the availability of hot water was enhanced by improved hydraulic design of the storage tank. Suggestions for further work included the development of more detailed component models and long-term testing of improved system configurations