A multi-objective genetic algorithm for the passenger maritime transportation problem

Over the last years, the transportation demand has continuously increased and a further growth is predicted for the next future especially as regards the maritime sector. As a consequence, shipping companies will be asked to improve the supplied services in order to assure a high quality and time-effective goods and passengers transportation, deriving at the same time their own benefits by minimizing costs. Therefore, the optimization of routes and schedules together with the fleet deployment take a meaningful role on companies profitability and efficiency. In such a perspective, the present paper proposes a multi-objective mathematical programming model to determine a set of routes and sch…

A combined multi-criteria approach to support FMECA analyses: A real-world case

[EN] The paper proposes an approach that combines reliability analyses and multi-criteria decision methods to optimize maintenance activities of complex systems. A failure mode, effects, and criticality analysts (FMECA) is initially performed and the fuzzy TOPSIS (FTOPSIS) method is then applied to rank previously identified failure modes. For prioritization, failure modes are assessed against three evaluation criteria that differ from those traditionally involved in risk priority number (RPN) computation (i.e. severity, occurrence and detection). Two criteria refer to the maintenance management reflecting the operational time taken by the maintenance activity performed after the occurrence…

Optimal Selection of Maintenance Actions on a Multi-Component System

The research aims to single out the maintenance actions to perform on a series arranged components system each one constituted by elements in parallel and maintained only during some planned stops. The considered system has to periodically carry out missions during which the system failure is a critical event for their own success. That being so, the faced problem is here to assure the maximum reliability level up to the next planned stop. For this reason an exact algorithm is proposed in order to individuate the set of components on which performing maintenance actions and for each of them determining the number of elements that must be maintained so as the maximum reliability level is ach…

A dempster-shafer theory-based approach to compute the birnbaum importance measure under epistemic uncertainty

Importance Measures (IMs) aim at quantifying the contribution of components to the system performance. In Process Risk Assessment (PRA), they are commonly used by risk managers to derive information about the risk/safety significance of events. However, IMs are typically calculated without taking into account the uncertainty that inevitably occurs whenever the input reliability data are poor. In literature, uncertainty arising from the lack of knowledge on the system/process parameters is defined as epistemic or subjective uncertainty. The present work aims at investigating on its influence on the Birnbaum IM and on how such an uncertainty could be accounted for in the components ranking. I…

Epistemic uncertainty in fault tree analysis approached by the evidence theory

Abstract Process plants may be subjected to dangerous events. Different methodologies are nowadays employed to identify failure events, that can lead to severe accidents, and to assess the relative probability of occurrence. As for rare events reliability data are generally poor, leading to a partial or incomplete knowledge of the process, the classical probabilistic approach can not be successfully used. Such an uncertainty, called epistemic uncertainty, can be treated by means of different methodologies, alternative to the probabilistic one. In this work, the Evidence Theory or Dempster–Shafer theory (DST) is proposed to deal with this kind of uncertainty. In particular, the classical Fau…

A combined fuzzy-SEM evaluation approach to identify the key drivers of the academic library service quality in the digital technology era: An empirical study

A conceptual model of the Academic Library (AL) service quality is hypothesized in the present article, and then validated and analyzed by a novel evaluation approach. Specifically, the conceptual model integrates the fundamental attributes of the canonical AL service together with those more relevant of the new and widely considered AL Electronic Service (e-services). As concerns the evaluation approach, it incorporates the Fuzzy Sets Theory (FST) so as to deal with the students' uncertainty over their own judgments on the AL service quality and a Structural Equation Model (SEM) to validate the conceptual model and to determine the key drivers of the AL service quality. The effectiveness o…

Structured methodology for selection of maintenance key performance indicators: Application to an oil refinery plant

The novel contribution of the work is the proposal of a structured multi-step methodology that may support the Decision Maker (DM) in the measurement of maintenance performance by means of Maintenance Key Performance Indicators (MKPIs). To this aim, a multi-level hierarchical framework able to synthesize the most meaningful aspects affecting the maintenance results is designed. Then, MKPIs are selected from the literature, assigned to the hierarchical framework and ranked by an Analytic Hierarchy Process-based approach with incomplete comparison matrices. A mathematical model is finally formulated to select the optimal set of MKPIs. The methodology is implemented in an oil refinery plant an…

A simulated annealing-based approach for the joint optimization of production/inventory and preventive maintenance policies

Even if more reliable than the past, the performance of modern manufacturing systems is still affected by machine’s deteriorations and breakdowns. As a consequence, adequate maintenance programs must be implemented to adequately satisfy demands during manufacturing stops due to unexpected failures or preventive maintenance (PM) actions. Despite production and maintenance are closely related issues, their joint optimization has become an important research topic just during the last decade. Therefore, the present paper proposes a model for the combined optimization of production/inventory control and PM policies with the aim of minimizing the total expected cost per unit time. The model is f…

Service quality benchmarking via a novel approach based on fuzzy ELECTRE III and IPA: an empirical case involving the Italian public healthcare context.

A novel fuzzy-based approach which combines ELECTRE III along with the Importance-Performance Analysis (IPA) is proposed in the present work to comparatively evaluate the service quality in the public healthcare context. Specifically, ELECTRE III is firstly considered to compare the service performance of examined hospitals in a noncompensatory manner. Afterwards, IPA is employed to support the service quality management to point out improvement needs and their priorities. The proposed approach also incorporates features of the Fuzzy Set Theory so as to address the possible uncertainty, subjectivity and vagueness of involved experts in evaluating the service quality. The model is applied to…

Multi-objective human resources allocation in R&D projects planning

In a R&D department, several projects may have to be implemented simultaneously within a certain period of time by a limited number of human resources with diverse skills. This paper proposes an optimisation model for the allocation of multi-skilled human resources to R&D projects, considering individual workers as entities having different knowledge, experience and ability. The model focuses on three fundamental aspects of human resources: the different skill levels, the learning process and the social relationships existing in working teams. The resolution approach for the multi-objective problem consists of two steps: firstly, a set of non-dominated solutions is obtained by exploring the…

A hierarchical framework for the measurement of maintenance efficacy and efficiency using performance indicators

Maintenance plays an important role in achieving the organizational goals so that the measurement of its effectiveness and efficiency has become an essential element of industrial strategy. In literature several Maintenance Key Performance Indicators (MKPIs) are proposed but none structured approach is suggested to select the best set of MKPIs able to synthetically describe a specific maintenance context. The paper proposes a structured methodology for the maintenance performance measurement by means of MKPIs. Firstly, a multi-level hierarchical framework able to synthesize the most meaningful perspectives affecting the performance of the maintenance process is designed. Successively, some …

A bottom-up procedure to calculate the Top Event probability in presence of epistemic uncertainty

Industrial plants may be subjected to very dangerous events. Different methodologies are employed to evaluate the probability of their occurrence, as Process Safety Analysis (PSA) or Risk Analysis (RA). However, since for rare events reliability data are poor, the epistemic uncertainty needs to be considered. In this context, the classical probabilistic approach cannot be successfully used and then different approaches must be taken into account. Actually, this paper proposes the use of the Evidence Theory or Dempster-Shafer Theory (DST) to deal with data characterizing rare events in high risk industrial sites. In particular, a classical Fault Tree Analysis (FTA) is considered when the onl…

Life cycle analysis of innovative building materials based on circular coffee ground supply chain

The construction sector is widely recognized as one of the most polluting mainly due to its intensive exploitation of natural resources and large energy consumption to produce traditional building materials. In the last years, alternative building materials have been developed with the aim to reduce the environmental burden of this sector. In particular, the use of geopolymer mortars as alternative cementitious materials is gaining increasing acceptance among scientists. Numerous laboratory studies demonstrate their suitability for construction applications, highlighting the potential environmental benefits that can be obtained from their large-scale production. This study aims to perform a…

Fleet deployment e routing design nel trasporto marittimo veloce dei passeggeri tra la Sicilia e le Isole Minori

A Dempster-Shafer Theory-based approach to the Failure Mode, Effects and Criticality Analysis (FMECA) under epistemic uncertainty: application to the propulsion system of a fishing vessel

Abstract Failure Mode and Effects Analysis (FMEA) is a safety and reliability analysis tool widely used for the identification of system/process potential failures, their causes and consequences. When aimed at the failure modes prioritization, FMEA is named Failure Mode, Effects and Criticality Analysis (FMECA). In the latter case, failure modes are commonly prioritized by means of the Risk Priority Number (RPN) that has been widely criticized to have several shortcomings. Firstly, in the presence of multiple experts supplying different and uncertain judgments on risk parameters, RPN is not able to deal with such a kind of information. Therefore, the present paper proposes the Dempster-Shaf…

A Combined Fuzzy-SEM Evaluation Approach to Identify the Key Drivers of the Academic Library Service Quality in the Digital Technology Era: An Empirical Study

A conceptual model of the Academic Library (AL) service quality is hypothesized in the present article, and then validated and analyzed by a novel evaluation approach. Specifically, the conceptual model integrates the fundamental attributes of the canonical AL service together with those more relevant of the new and widely considered AL Electronic Service (e-services). As concerns the evaluation approach, it incorporates the Fuzzy Sets Theory (FST) so as to deal with the students’ uncertainty over their own judgments on the AL service quality and a Structural Equation Model (SEM) to validate the conceptual model and to determine the key drivers of the AL service quality. The effectiveness o…

Human Factor Interrelationships to Improve Worker Reliability: Implementation of MCDM in the Agri-Food Sector

Performance Shaping Factors (PSFs) are contextual, individual, and cognitive factors used in Human Reliability Analysis (HRA) to quantify the worker contribution to errors when performing a generic task. Although the empirical evidence demonstrates the existence of PSF interrelationships, the majority of HRA methods assume their independence. As a consequence, the resulting Human Error Probability (HEP) might be over- or underestimated. To deal with this issue, only a few qualitative guidelines or statistical-based approaches have been proposed so far. While the former are not well structured, the latter require a high computational effort and a proper number of input data. Therefore, the p…

An equation to calculate the availability for the k-out-of-n system

Reliability and availability (R&A) analyses are primary phases in management of complex systems and play a fundamental role in products and services quality. Management of maintenance activities has to be based on optimisation to simultaneously improve the operative conditions of the system. Maintenance optimization can be effeectively pursued by the RCM (Reliability-centered maintenance) approach. The authors demonstrate the global improvement of R&A by applying the RCM to the results derived by the FMECA (Failure Modes Effects and Criticality Analysis). Many efforts have been made to improve traditional methodologies of analysis, mainly tending to reduce the imprecision on data related to…

Food safety risk analysis from the producers' perspective: prioritisation of production process stages by HACCP and TOPSIS

[EN] From the manufacturers perspective, the Hazard Analysis and Critical Control Point (HACCP) system nowadays represents the mainly way to implement the food safety risk management in food industries. Nevertheless, the identification and prioritization of hazards as the outcome of the first principle of HACCP is not sufficient to identify production process stages that more significantly and critically contribute to the consumer¿s risks. With this recognition, the present paper proposes a Quantitative Risk Assessment (QRA) approach based on HACCP and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) to individuate production process phases on which implementing co…

An imprecise Fault Tree Analysis for the estimation of the Rate of OCcurrence Of Failure (ROCOF)

Abstract The paper proposes an imprecise Fault Tree Analysis in order to characterize systems affected by the lack of reliability data. Differently from other research works, the paper introduces a classification of basic events into two categories, namely Initiators and Enablers . Actually, in real industrial systems some events refer to component failures or process parameter deviations from normal operating conditions ( Initiators ), whereas others refer to the functioning of safety barriers to be activated on demand ( Enablers ). As a consequence, the output parameter of interest is not the classical probability of occurrence of the top event, but its Rate of OCcurrence (ROCOF) over a s…

Project manager assignment by fuzzy inference and mathematical programming

Optimal design of k-out-of-n systems

The present paper is aimed at finding the best compromise to design a system k-out-of-n reliability configuration by means of the formulation of a multi-objective mathematical model. The Pareto front, which is the set of non-dominated solutions, is determined by considering the stationary availability and the achievable profit as objectives to be simultaneously optimized. The Pareto front represents a useful tool for the analyst to make the choice related to the analyzed design problem. In addition, the knowledge of the Pareto front permits to consider different design scenarios.

ELECTRE TRI-based approach to the failure modes classification on the basis of risk parameters: An alternative to the risk priority number

Proposing an ELECTRE TRI-based approach for the failure modes classification into predefined and ordered risk classes.Direct identification of failure modes on which performing the corrective actions with priority.Easy definition of risk classes on the basis of DMs expertise and perception of the industrial context considered.Application to dairy manufacturing processes. Failure Mode and Effects Analysis (FMEA) is an engineering technique aimed at the detection of potential failures, their causes and consequences on the system/process under investigation. When used for the failure modes prioritization, FMEA is also referred to as Failure Mode, Effects and Criticality Analysis (FMECA). In tr…

A multi-objective fleet routing optimization for passenger shipping among islands

In the last few years the statistical analysis on maritime freight and passenger transport highlights a positive trend of demand and for the next future, given the stressing congestion characterizing the road transport, a further increase both on the deep-sea-shipping and the short-sea-shipping is predicted. Given that, the navigation companies are called to improve their own services to assure a high quality and efficient customers transport, deriving at the same time their own benefits by minimizing the operating costs. Hence, an efficient and careful routes planning activity plays a meaningful role on navigation company productivity and income. Furthermore, the fleet deployment also cons…

A Multistep Methodology for the Evaluation of Human Resources Using the Evidence Theory

The paper aims at proposing a model for the human resources evaluation as regards to a set of skills. Specifically, it starts sfrom the judgments expressed by a team of experts on the basis of their previous working experiences with the resource to be evaluated. Information arising from experts is successively handled by the analyst and aggregated to determine the resource suitability or unsuitability. The Dempster–Shafer theory is proposed here as an appropriate tool to deal with both the uncertainty of experts due to the incomplete knowledge about resources to be evaluated and that of the analyst to convert expert judgments in terms of resource suitability/unsuitability. Furthermore, the …

Selection of Series System Components to Maximize Reliability

The paper tackles the problem of maximizing the reliability of a series system by an opportune choice of components. Each type of component must be selected among the available alternatives for that component whereas a fixed amount of budget can not be overcome. The problem can be formulated by a binary non linear programming model and it is equivalent to a knapsack problem with multiple-choice constraints, well known to be NP-hard. An exact algorithm is proposed for solving large dimension problems to the optimum in a short time. The algorithm efficiency is finally compared with the recent heuristics proposed in literature to approach the same problem.

Handling epistemic uncertainty in the Fault Tree Analysis using interval valued expert information

Risk Analysis ( RA) is a meaningful process in every industrial context, particularly referring to major hazard plants. In such sites, input reliability data are generally poor so leading to a partial or incomplete knowledge of the failure process. As a consequence, RA is always affected by the so called epistemic uncertainty which presence makes inappropriate the classical probabilistic approach. Therefore, the present work deals with such a kind of uncertainty in the Fault Tree Analysis (FTA) and proposes a new aggregation rule to combine the interval-valued information supplied by a team of experts about each Basic Event ( BE). The aggregation leads to an interval which bounds are modell…

Handling the epistemic uncertainty in the selective maintenance problem

Abstract Nowadays, both continuous and discontinuous operating systems require higher and higher reliability levels in order to avoid the occurrence of dangerous or even disastrous consequences. Accordingly, the definition of appropriate maintenance policies and the identification of components to be maintained during the planned system’s downtimes are fundamental to ensure the reliability maximization. Therefore, the present paper proposes a mathematical programming formulation of the selective maintenance problem with the aim to maximize the system’s reliability under an uncertain environment. Specifically, the aleatory model related to the components’ failure process is well known, where…

Multi-skilled human resources allocation in R&D projects

A multifunctional plant for a sustainable reuse of marble waste toward circular economy

The marble processing cycle involves the production of large quantities of wastes whose disposal represents an economic and environmental concern for marble companies due to the difficulty of identifying suitable landfills and the high transfer costs. In this context, the design of a sustainable industrial plant that allows the reuse of the calcium carbonate (CaCO3) contained in the marble waste is extremely challenging. With this recognition, the main industrial applications of CaCO3 are firstly analyzed in the present work to identify the physical–chemical properties required to CaCO3 in these contexts. Later, different plant solutions are suggested to recover CaCO3 from marble sludge in…

A Multistep Methodology for the Evaluation of Human Resources Using the Evidence Theory

Economic and Environmental Assessment of Biomass Power Plants in Southern Italy

In 2019, Europe adopted the New Green Deal as a strategic plan to become a competitive, resource-efficient, and driven economy by reducing its gas emissions and carbon footprint. Due the COVID-19 pandemic, this strategic plan was recently updated to expedite the green transition of European industries. Therefore, the present paper deals with the problem of deciding an appropriate size for a biomass plant that directly produces electric energy by means of two different conversion processes: combustion and gasification. After an initial estimation of the energy potential in western Sicily, GIS data of biomass growth were used to identify the appropriate size for the power plants under investi…

Project Management Information Systems (PMISs): A Statistical-Based Analysis for the Evaluation of Software Packages Features

Project Managers (PMs) working in competitive markets are finding Project Management Information Systems (PMISs) useful for planning, organizing and controlling projects of varying complexity. A wide variety of PMIS software is available, suitable for projects differing in scope and user needs. This paper identifies the most useful features found in PMISs. An extensive literature review and analysis of commercial software is made to identify the main features of PMISs. Afterwards, the list is reduced by a panel of project management experts, and a statistical analysis is performed on data acquired by means of two different surveys. The relative importance of listed features is properly comp…