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DAVIDE CASTELLANO

Professore Associato
Dipartimento di Ingegneria "Enzo Ferrari"

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Pubblicazioni

2024 - Economic production quantity for a decaying item with stochastic demand and positive lead time [Articolo su rivista]
Castellano, D; Glock, Ch
abstract

2023 - A single-vendor, multiple-buyer coordinated supply chain model with unequal-sized batch shipments and cycle-dependent safety stocks [Articolo su rivista]
Castellano, D.; Gallo, M.; Glock, C. H.
abstract

This paper investigates a single-vendor, multiple-buyer coordinated supply chain under stochastic demand. Each buyer implements a continuous review policy, and the shortage quantity is fully back-ordered. The lead time for the first shipment includes setup, production, and transportation times, while the lead time for the remaining shipments includes only transportation time. The production time is a function of production lot and production rate, which are both decision variables, and the setup and transportation times are controllable as well. For each buyer, the safety stock in the first replenishment cycle is not necessarily identical to that in the remaining cycles. Two successive shipments from the vendor to a buyer may have different sizes, and their ratio is a decision variable. The problem is finding the production and inventory replenishment policy, production rate, and lead times that minimise the long-run expected total cost per time unit. We demonstrate properties satisfied by the cost function and develop an optimisation algorithm, whose performance is compared to a benchmark algorithm based on a commercial solver in a numerical experiment. The experiments also investigate the benefits stemming from the proposed model when compared to models reproducing situations that leverage some or any of the controlled factors.

2023 - Optimizing production-inventory replenishment and lead time decisions under a fill rate constraint in a two-echelon sustainable supply chain with quality issues [Articolo su rivista]
Castellano, D.; Gabbrielli, R.; Gallo, M.; Giri, B. C.; Sarkar, S.
abstract

This paper considers a single vendor-single buyer coordinated supply chain under stochastic demand. GHG emissions arise from the vendor's production process. A carbon tax and penalties for exceeding multiple emissions limits are considered. A random number of defectives characterises the batch received by the buyer, who performs an inspection activity. Setup and transportation times are controllable through a capital investment, whose outcome is uncertain. An optimisation problem is formulated under the minimax distribution-free approach. The objective is to find the production-inventory replenishment policy and the length of setup and transportation times that minimise the long-run expected total system cost rate considering a fill rate constraint. Several properties of the cost function are demonstrated, and an optimisation method is developed. Finally, numerical experiments are carried out to draw insights on the effect of the model parameters, including different legislation schemes concerning GHG emissions, on the optimal system performance. The novelty of the paper consists into investigating the effect of a controllable lead time on coordinated supply chain decisions in presence of GHG emissions and quality issues, in a stochastic environment. A major finding is that controlling lead time enhances both the overall cost efficiency and the environmental sustainability of the system.

2023 - Stochastic joint replenishment problem under a fill rate constraint with controllable lead times and shared cost allocation [Articolo su rivista]
Castellano, D.; Santillo, L. C.
abstract

In a family of items under coordinated inventory replenishments, some products may be replenished at the same time, which in turn implies that some lead time components and costs may be shared among them. This paper investigates this aspect in the context of the joint replenishment problem under the class of cyclic policies, assuming random demands and controllable lead times, and imposing a fill rate constraint for each item.& COPY; 2023 Elsevier B.V. All rights reserved.

2022 - Deep Reinforcement Learning Approach for Maintenance Planning in a Flow-Shop Scheduling Problem [Relazione in Atti di Convegno]
Marchesano, M. G.; Staiano, L.; Guizzi, G.; Castellano, D.; Popolo, V.
abstract

2022 - Economic production quantity with inventory rationing for a decaying item [Relazione in Atti di Convegno]
Castellano, D.; Glock, C. H.
abstract

In this paper, we develop an economic production quantity (EPQ) model with inventory rationing for a decaying item under deterministic conditions. Two demand classes are considered, and inventory rationing is implemented by introducing a critical level: when stock is below the critical level, low-priority demand is rejected. The cost model is developed considering two situations, depending on whether the critical level is in the inventory build-up phase or in the inventory depletion phase. We then formulate the optimization problem and propose a solution procedure. Numerical experiments are finally carried out to demonstrate the benefits of implementing inventory rationing. Copyright (C) 2022 IFAC. Copyright (C) 2022 The Authors.

2022 - Optimizing product assortment, joint replenishments, and storage capacity allocation in a deteriorating inventory system [Relazione in Atti di Convegno]
Castellano, D.; Gallo, M.; Grassi, A.; Santillo, L. C.
abstract

In this paper, we consider a single retailer who sells multiple products subject to decay, and that implements coordinated inventory replenishments among them. The overall available surface at the retailer is limited and is partitioned into two areas: the backroom facility and the display area. The demand rate of each product is a function of displayed quantity and location, and it also depends on the cross-elasticity among items. The objective is to find the product assortment, the replenishment policy of each product, the quantity to be displayed, and the surfaces assigned to the backroom and display areas that maximize the total profit per time unit. We develop the mathematical model and formulate the optimization problem. Finally, we investigate the model response by means of numerical experiments considering several problem instances. Copyright © 2022 IFAC.

2021 - A Revised PFMEA Approach for Reliable Design of Assembly Activities [Articolo su rivista]
Braglia, M.; Castellano, D.; Gabbrielli, R.; Marrazzini, L.
abstract

2021 - A periodic review policy for a coordinated single vendor-multiple buyers supply chain with controllable lead time and distribution-free approach [Articolo su rivista]
Castellano, D.; Gallo, M.; Santillo, L. C.
abstract

In this paper, we study a single vendor-multiple buyer integrated inventory model with controllable lead time and backorders-lost sales mixture. Each buyer adopts a periodic review policy in which the review period is an integer fraction of the production cycle time of the vendor. To reflect the practical circumstance characterized by the lack of complete information about the demand distribution, we assume that only the first two moments of the demand during the protection interval are known. The long-run expected total cost per time unit is derived, which includes stockout costs. The problem is to determine the length of the inventory cycle of the vendor, the produce-up-to level for the vendor, the replenishment policy of each buyer, and the length of lead times that minimize the cost function under the minimax distribution-free approach. Two alternative heuristics are proposed. Numerical experiments have been carried out to investigate the performance of the heuristics and to study the sensitivity of the model.

2021 - Controlling lead times and minor ordering costs in the joint replenishment problem with stochastic demands under the class of cyclic policies [Articolo su rivista]
Braglia, M.; Castellano, D.; Santillo, L.; Song, D.
abstract

In this paper, we consider the periodic review joint replenishment problem under the class of cyclic policies. For each item, the demand in the protection interval is assumed stochastic. Moreover, a fraction of shortage is lost, while the other quota is backordered. We suppose that lead times and minor ordering costs are controllable. The problem concerns determining the cyclic replenishment policy, the lead times, and the minor ordering costs in order to minimize the long-run expected total cost per time unit. We established several properties of the cost function, which permit us to derive a heuristic algorithm. A lower bound on the minimum cost is obtained, which helps us to evaluate the effectiveness of the proposed heuristic. The heuristic is also compared with a hybrid genetic algorithm that is specifically developed for benchmarking purposes. Numerical experiments have been carried out to investigate the performance of the heuristic.

2021 - Dataset of metaheuristics for the flow shop scheduling problem with maintenance activities integrated [Articolo su rivista]
Branda, A.; Castellano, D.; Guizzi, G.; Popolo, V.
abstract

This data article presents a flow shop scheduling problem in which machines are not available during the whole planning horizon and the periods of unavailability are due to random faults. The experimental dataset consists of two problems with different sizes. In the largest one, about 2400 problems were analysed and compared with two diffuse metaheuristics: Genetic Algorithm (GA) and Harmony Search (HS). In the smallest, about 600 problems were analysed comparing the solution obtained with an exhaustive algorithm with those obtained by means of GA and HS. This dataset represents a test-bed for further works, allowing a comparison between the solution quality and the computation time obtained with different optimization methods. The substantial computational effort spent to generate the dataset undoubtedly represents a significant asset for the scientific community.

2021 - Metaheuristics for the flow shop scheduling problem with maintenance activities integrated [Articolo su rivista]
Branda, Antonella; Castellano, Davide; Guizzi, Guido; Popolo, Valentina
abstract

This paper deals with a flow shop scheduling problem in which machines are not available during the whole planning horizon and the periods of unavailability are due to random faults. Since they are subject to failures, both corrective maintenance activities and scheduled maintenance activities are performed to increase their availability. Hence, jobs and maintenance tasks are jointly considered to find the optimal schedule. The objective is to find the optimal integrated job-planned maintenance sequence that minimises the makespan and the earliness-tardiness penalty. To this aim, we propose two novel meta-heuristic algorithms obtained modifying a standard Genetic Algorithm (GA) and Harmony Search (HS). Numerical results obtained from experiments considering different problem sizes and configurations show that the proposed Harmony Search and Genetic Algorithm are efficient to approach the integrated job-maintenance scheduling problem.

2021 - On Reinforcement Learning in production control and its potentiality in manufacturing [Relazione in Atti di Convegno]
Marchesano, M. G.; Guizzi, G.; Castellano, D.; Di Nardo, M.
abstract

2021 - Revised Overall Labour Effectiveness [Articolo su rivista]
Braglia, M.; Castellano, D.; Frosolini, M.; Gallo, M.; Marrazzini, L.
abstract

2021 - The average-cost formulation of lot sizing models and inventory carrying charges: A technical note [Articolo su rivista]
Castellano, D.; Glock, C. H.
abstract

2020 - An ensemble-learning model for failure rate prediction [Relazione in Atti di Convegno]
Braglia, M; Castellano, D; Frosolini, M; Gabbrielli, R; Marrazzini, L; Padellini, L
abstract

2020 - Energy Cost Deployment (ECD): A novel lean approach to tackling energy losses [Articolo su rivista]
Braglia, M; Castellano, D; Gabbrielli, R; Marrazzini, L
abstract

2019 - A Bernoulli model for the single-vendor single-buyer supply system with (s,S)-inventory policy and stochastic lead time [Abstract in Atti di Convegno]
Castellano, D; Gebennini, E; Grassi, A; Santillo, Lc
abstract

2019 - A continuous review, (Q, r) inventory model for a deteriorating item with random demand and positive lead time [Articolo su rivista]
Braglia, M; Castellano, D; Marrazzini, L; Song, D
abstract

2019 - A novel operational approach to equipment maintenance: TPM and RCM jointly at work [Articolo su rivista]
Braglia, Marcello; Castellano, Davide; Gallo, Mosè
abstract

Purpose: The purpose of this paper is to present a new operational approach to equipment maintenance designed to exploit the complementary nature of total productive maintenance (TPM) and reliability-centered maintenance (RCM). Design/methodology/approach: This paper focuses on the operational aspect of the maintenance practice, proposing an equipment maintenance methodology that can be suitably adopted to define a new maintenance plan or check and improve an existing one. It integrates principles and methods of TPM and RCM and uses different tools to support decision-makers and operators. It proposes several worksheets which facilitate planning and implementing maintenance activities, that range from autonomous maintenance tasks to maintainability improvement actions. Findings: This paper exploits the complementary nature of TPM and RCM to design or improve maintenance plans for a generic system. The tools and worksheets presented can be helpful to practitioners and operators. Originality/value: While the integration of TPM and RCM is evidently a central issue in the maintenance management context, it has received limited attention in literature. To the best of the authors’ knowledge, it lacks a structured practical equipment maintenance methodology that exploits the complementary nature of TPM and RCM. Therefore, the approach presented in this paper would fill the current gap.

2019 - A visual planning solution to streamline the processes of hybrid cross-dockings [Articolo su rivista]
Braglia, Marcello; Castellano, Davide; Gallo, Mosè; Romagnoli, Giovanni
abstract

Cross-docking is a logistic strategy widely adopted both in manufacturing and distribution contexts. Despite the huge number of researches on this topic, most of them remain rather theoretical as they do not pay enough attention to operational aspects and daily functioning patterns of cross-dockings. This article aims at introducing a new focus for cross-docking research by proposing a visual planning solution to manage daily operation of a manufacturing cross-docking. By avoiding complex optimization algorithms and by adopting concepts belonging to the lean management theory, the article shows the potential of visual planning techniques to improve performance of cross-dockings. Starting from a specific industrial context, the shipping warehouse of an Italian company of the oil andand gas sector, a visual management methodology has been proposed to support the operation of cross-dockings. Although developed in a particular context, the proposed methodology and its underlying principles are to be considered general and potentially applicable to a wide range of cross-dockings. The methodology fully exploits an analytical tool, namely, the Safety Margin coefficientthat could be used for capacity planning purposes and to evaluate quantitatively the system performance at a given time instant.

2019 - Batching decisions in multi-item production systems with learning effect [Articolo su rivista]
Castellano, Davide; Gallo, Mosè; Grassi, Andrea; Santillo, Liberatina C.
abstract

The average time in the system (or average throughput time) is recognized as a crucial performance measure of manufacturing systems and, in recent years, has become even more relevant as markets have shifted towards mass-customization scenarios, since it directly affects the average inventory in the system. Modern manufacturing systems design paradigms, Industry 4.0 on top, focus on the need to achieve high responsiveness by shortening throughput time as the main lever to maintain cost efficiency and competitiveness in such market scenarios. In the contexts in which the human impact on production operations is not negligible, the learning phenomenon may reasonably affect the average time in the system. This paper analyses the learning effect on this performance measure through batching policies. Here, batching is considered as the possibility to group customized orders presenting similarities in the production processes, thus making it possible the exploitation of learning effect. Both single- and multi-item systems under Markovian arrivals are studied, also deterministic and stochastic processing times are considered. The problem that we pose consists in determining the batch size for each product that minimizes the average time in the system taking into consideration the learning effect, which is included by means of the Plateau model. A solution procedure for each case is discussed and, through numerical experiments, the sensitivity of the model to variations in parameter values is studied.

2019 - Integrating considerations of uncertainty within the OEE of a manufacturing line [Articolo su rivista]
Braglia, M.; Castellano, D.; Frosolini, M.; Gallo, Mose
abstract

Lean manufacturing has become a paramount production paradigm in many industrial sectors and overall equipment effectiveness (OEE) is a widely accepted and adopted lean metric for any type of machine/equipment. However, the standard OEE formulation presents two important limits: 1) it deals with a single machine; 2) gives a deterministic measure of effectiveness. The objective of this paper is to overcome both of these two shortcomings by proposing a Fuzzy approach for measuring the OEE of a manufacturing line (OEEML). Hence, starting from a possible definition of OEEML, this paper provides a framework to measure its modal value and its variability on an entire manufacturing line. The approach exploits fuzzy triangular numbers instead of burdensome stochastic quantities to measure this variability. Furthermore, it integrates a method which enables us to avoid the annoying 'overestimation effect' of FTNs. The integrated approach has proved to be useful in consistently capturing the OEEML variations, also, both the modal value and the range obtained from its application are good estimators of both the OEEML and its variability. A full case study is finally provided to show the effectiveness of the proposed approach in diagnosing problems and addressing improvement actions.

2019 - The effect of GHG emissions on production, inventory replenishment and routing decisions in a single vendor-multiple buyers supply chain [Articolo su rivista]
Castellano, Davide; Gallo, Mosè; Grassi, Andrea; Santillo, Liberatina C.
abstract

This paper studies a supply chain in which one vendor supplies one item type to multiple buyers. The product is transferred from vendor to buyers according to a collection of delivery routes that specifies the number of routes, the buyers served in each route, and the order with which the buyers are served in each route. A mathematical model is developed to evaluate the long-run expected total cost per time unit of the supply chain. The model includes the transportation cost and the cost for emissions of Greenhouse Gases (GHGs) arising from the production and transportation processes. The objective is to find the production rate of vendor, the order quantity and the reorder point of each buyer, the number of shipments from vendor to buyers, and the collection of delivery routes that minimize the long-run expected total cost per time unit. The properties of the cost function are studied, and a two-phase, heuristic algorithm is proposed to approach the minimization problem. Numerical experiments are finally carried out to investigate model sensitivity in respect to input parameters. Some insights into how production, inventory replenishment, and routing decisions should be adapted in the presence of different legislation schemes concerning GHG emissions are given.

2018 - Efficient near-optimal procedures for some inventory models with backorders-lost sales mixture and controllable lead time, under continuous or periodic review [Articolo su rivista]
Braglia, M; Castellano, D; Song, D
abstract

2018 - Optimising replenishment policy in an integrated supply chain with controllable lead time and backorders-lost sales mixture [Articolo su rivista]
Braglia, M; Castellano, D; Song, D
abstract

2018 - Overall material usage effectiveness (OME): a structured indicator to measure the effective material usage within manufacturing processes [Articolo su rivista]
Braglia, M.; Castellano, D.; Frosolini, M.; Gallo, M.
abstract

A rational use of production resources has been catalysing the attention of researchers and practitioners for several years. A number of indicators have been proposed to assess the effective and efficient use of the various production factors. A widely known example of these metrics is the overall equipment effectiveness (OEE), which applies to machines and equipment. This paper proposes a novel methodology that seizes upon OEE’s straight forward and easy-to-use structure to address the problem of measuring the effective use of materials within a factory. An inclusive structure of material loss and a methodology to calculate a novel performance indicator called overall material usage effectiveness (OME) is given. The proposed set of KPIs not only permits the comprehension of material-related issues but also the identification of viable countermeasures. A real-life application to demonstrate the practical usefulness of the methodology and illustrate the capability of its KPIs is described.

2018 - Stochastic modeling of a single-vendor single-buyer supply chain with (s, S)-inventory policy [Relazione in Atti di Convegno]
Castellano, D.; Gebennini, E.; Grassi, A.; Murino, T.; Rimini, B.
abstract

Given the relevance of stochastic modelling in supply chain analysis and the advances in queuing theory in different subject fields (such as in-plant manufacturing systems), the present paper deals with the application of a Bernoulli model to the simple but representative (and frequently cited) case of a single-vendor single-buyer supply chain with (s, S)-inventory policy, where the maximum capacity S has to be restored in the intermediate warehouse whenever the inventory position reaches or drops below the reorder point s. An analytical stochastic model is presented which considers two two sources of uncertainty, supply uncertainty and demand uncertainty. The model is analytically formulated and solved in closed-form in order to compute some significant performance measures and, consequently, support tactical decisions (such as the definition of the design parameters s and S). Then, the model setting up is discussed. Specifically, the problem of relating demand and supply probabilities to the behaviour exhibited by the buyer and (particularly) the vendor is addressed. Finally, some numerical results are provided for illustration.

2018 - The effect of GHG emissions on production, inventory replenishment and routing decisions in a single vendor-multiple buyers supply chain [Abstract in Atti di Convegno]
Castellano, D.; Gallo, M.; Grassi, A.; Santillo, L. C.
abstract

2017 - A periodic review policy with quality improvement, setup cost reduction, backorder price discount, and controllable lead time [Articolo su rivista]
Castellano, Davide; Gallo, Mosè; Santillo, Liberatina Carmela; Song, Dongping
abstract

2017 - Considering greenhouse gas emissions in a single vendormultiple buyer coordinated supply chain [Relazione in Atti di Convegno]
Castellano, D.; Gallo, M.; Santillo, L. C.
abstract

2017 - Distribution-free approach for stochastic Joint-Replenishment Problem with backorders-lost sales mixtures, and controllable major ordering cost and lead times [Articolo su rivista]
Braglia, M; Castellano, D; Song, D
abstract

2016 - A novel approach to safety stock management in a coordinated supply chain with controllable lead time using present value [Articolo su rivista]
Braglia, M; Castellano, D; Frosolini, M
abstract

2016 - An extension of the stochastic Joint-Replenishment Problem under the class of cyclic policies [Articolo su rivista]
Braglia, Marcello; Castellano, Davide; Gallo, Mosè
abstract

2016 - Approximated closed-form minimum-cost solution to the (r, q) policy with complete backordering and further developments [Articolo su rivista]
Braglia, Marcello; Castellano, Davide; Gallo, Mosè
abstract

2016 - Approximated closed-form minimum-cost solutions to the (S - 1, S) policy with complete backordering [Articolo su rivista]
Braglia, M; Castellano, D; Frosolini, M
abstract

2016 - Joint-replenishment problem under stochastic demands with backorders-lost sales mixtures, controllable lead times, and investment to reduce the major ordering cost [Articolo su rivista]
Braglia, M; Castellano, D; Frosolini, M
abstract

2016 - Just-in-time parts feeding policies for paced assembly lines: Possible solutions for highly constrained layouts [Articolo su rivista]
Zammori, F.; Braglia, M.; Castellano, D
abstract

2016 - Stochastic reorder point-lot size (r, Q) inventory model under maximum entropy principle [Articolo su rivista]
Castellano, D
abstract

2015 - A study on the importance of selection rules within unbalanced MTO POLCA-controlled production systems [Articolo su rivista]
Braglia, M.; Castellano, D.; Frosolini, M.
abstract

The present paper is aimed at investigating, through simulation, the behaviour of the POLCA method when a Make-to-Order (MTO) production system is highly unbalanced, in terms of both routings and times. In particular, the study is addressed to verify (i) the effective capability of the POLCA method to improve the uncontrolled system and (ii) the impact of how orders are processed at each workstation, to show that POLCA performance can be further improved in such circumstances by adopting an appropriate selection rule. Germs and Riezebos (2010) proved that POLCA is very effective in reducing the Total Throughput Time (TTT) with respect to the corresponding unconstrained production systems. Owing to this, it appears evident that POLCA represents a valuable and effective Make-to-Order (MTO) production control method. However, they only considered balanced systems, hence some observations must be carefully addressed. In fact, often, in real world applications, the systems to be controlled are designed to process units with very different routings, each with significantly different probability to occur.

2015 - Improving Tool-Life Stochastic Control Through a Tool-Life Model Based on Diffusion Theory [Articolo su rivista]
Braglia, M.; Castellano, D.
abstract

It is known that estimating the wear level at a future time instant and obtaining an updated evaluation of the tool-life density is essential to keeping machined parts at the desired quality level, reducing material waste, increasing machine availability, and guaranteeing the safety requirements. In this regard, the present paper aims at showing that the tool-life model that Braglia and Castellano [23] developed can be successfully adopted to probabilistically predict the future tool wear and to update the tool-life density. Thanks to the peculiarities of a stochastic diffusion process, the approach presented allows deriving the density of the wear level at a future time instant, considering the information on the present tool wear. This makes it therefore possible updating the tool-life density given the information on the current state. The method proposed is then experimentally validated, where its capability to achieve a better exploitation of the tool useful life is also shown. The approach presented is based on a direct wear measurement. However, final considerations give cues for its application under an indirect wear estimate.

2015 - Protection of passive RFID labels by resin doming and encapsulation [Relazione in Atti di Convegno]
Braglia, M; Castellano, D; Frosolini, M; Russo, A
abstract

2014 - A note concerning physical space occupation costs in Vendor Managed Inventory with consignment agreement models [Articolo su rivista]
Braglia, M.; Castellano, D.; Frosolini, M.
abstract

A new analytic formulation of the Vendor Managed Inventory with consignment agreement is proposed. It represents a modified and more realistic version of the model proposed in Braglia and Zavanella (2003). The evaluation of the stockholding related costs is herewith substantially revisited to consider the requirements of a standard VMI relationship with consignment agreement. In particular, the physical space occupation cost held by the buyer is introduced as a component of the overall holding cost and is referred to the maximum stock level, rather than to the average value, as proposed in the past literature. Finally, an implicit analytical solution is given and compared to the original one obtained by Braglia and Zavanella (2003).

2014 - A note on "A Multiple-Vendor Single-Buyer Integrated Inventory Model With a Variable Number of Vendors" [Articolo su rivista]
Braglia, M.; Castellano, D.; Frosolini, M.
abstract

In this technical note, an alternative solution procedure to the model that developed is presented. In particular, we take into account the same assumptions, but the total cost function is reformulated, i.e., the step-type discontinuity is replaced by a logistic approximation and the total costs of the system are computed on the whole set of preselected suppliers. Subsequently, we show that the total cost function possesses some properties in terms of convexity and continuity that allow the exploitation of standard constrained nonlinear minimization algorithms. Finally, tests conducted on the same set of problems that originally considered illustrate the good performances of the solution procedure developed in this note.

2014 - Computer-Aided Activity Planning (CAAP) in Large-Scale Projects With an Application in the Yachting Industry [Articolo su rivista]
Braglia, M.; Castellano, D.; Frosolini, M.
abstract

The present paper provides the schema for an innovative and modular computer-based approach to the planning of activities in largescale projects. Such projects are characterized by tens of thousands of tasks, which are consequently burdensome and difficult to plan manually. This is true to the point that in many shipyards only a low level of detail is used and poor planning is generally performed. The proposed approach is called Computer-Aided Activity Planning (CAAP), and an application in the yachting industry is shown to demonstrate its effectiveness. In particular, the so-called outfitting planning problem is faced. The CAAP system, taking into account the available shipyard resources and the knowledge on the building rules is able to automatically define, sequence, and schedule the activities of the whole outfitting process acting as a "planning configurator". Moreover, it allows the industry-specific knowledge to be stored, maintained and shared within the (extended) organization. Owing to these "building blocks", plans can be defined accurately and in a shorter time starting from pre-defined templates, with particular impact on lead times whenever variations to complex projects are needed. Finally, to verify the actual capabilities of the approach, the CAAP was implemented within a prototypical software called NautiCAAP.

2014 - Diffusion theory applied to tool-life stochastic modeling under a progressive wear process [Articolo su rivista]
Braglia, M.; Castellano, D.
abstract

In this paper a novel approach to the derivation of the tool-life distribution, when the tool useful life ends after a progressive wear process, is presented. It is based on the diffusion theory and exploits the Fokker-Planck equation. The Fokker-Planck coefficients are derived on the basis of the injury theory assumptions. That is, tool-wear occurs by detachment of small particles from the tool working surface, which are assumed to be identical and time-independent. In addition, they are supposed to be small enough to consider the detachment process as continuous. The tool useful life ends when a specified total volume of material is thus removed. Tool-life distributions are derived in two situations: (i) both Fokker-Planck coefficients are time-dependent only, and (ii) the diffusion coefficient is neglected and the drift is wear-dependent. Theoretical results are finally compared to experimental data concerning flank wear land in continuous turning of a C40 carbon steel bar adopting a P10 type sintered carbide insert. The adherence to the experimental data of the tool-life distributions derived exploiting the Fokker-Planck equation is satisfactory. Moreover, the tool-life distribution obtained when the diffusion coefficient is neglected and the drift is wear-dependent is able to well-represent the wear behavior at intermediate and later times.

2014 - Harmony search algorithm for single machine scheduling problem with planned maintenance [Articolo su rivista]
Zammori, FRANCESCO ALDO; Braglia, Marcello; Castellano, Davide
abstract

This paper focuses on the single machine scheduling problem, with sequence dependent setup times. Both processing and setup times are deterministic and the objective is to minimize total earliness and tardiness penalties. The novelty of the model can be traced in the fact that the single machine is subjected to breakdowns and that, in order to increase its availability, planned maintenance tasks are also performed. Hence, jobs and maintenance tasks are jointly considered to find the optimal schedule. These features make the problem NP-hard and so, a quasi-optimal solution is searched using a recent metaheuristic, which integrates harmony search and genetic algorithms. In order to validate the proposed metaheuristic, a comprehensive set of scheduling problems was fully investigated. Obtained results, compared with those of exhaustive (for small problems) and standard metaheuristics, confirm both the robustness and the speed of the proposed approach.

2014 - Optimization of POLCA-controlled production systems with a simulation-driven Genetic Algorithm [Articolo su rivista]
Braglia, M.; Castellano, D.; Frosolini, M.
abstract

The present work is meant to show the effective capability of optimizing an unbalanced Paired-Cell Overlapping Loops of Cards with Authorization (POLCA)-controlled production system by means of a heuristic algorithm. This objective is suggested by the fact that one of the most significant issues when using card-driven production control systems is represented by the optimized setting of the large number of cards within the control loops. This is particularly true in the case of unbalanced systems, where the number of cards may vary significantly among the different loops. Little law is usually adopted in literature to infer this number from historical data, but the obtained number is usually far from the optimum. Indeed, in real-world applications, the systems to be controlled are designed to process units with very different routings, each with different probability to occur. In all these situations, they result particularly difficult to set correctly. To this aim, in the present work a Genetic Algorithm is used. The objective is that of finding the correct number of cards and to reduce the overall Total Throughput Time and the average Work In Process. The proposed approach may provide a valid support tool to overcome these limitations, making the most of POLCA capabilities in many manufacturing configurations.

2014 - Safety Stock Management in Single Vendor-Single Buyer Problem under VMI with Consignment Stock Agreement [Articolo su rivista]
Braglia, M.; Castellano, D.; Frosolini, M.
abstract

In this paper a new analytical approach to safety stock management, within single buyer–single vendor framework under VMI with consignment agreement, is presented. In particular, the cost of the safety stock is evaluated adopting a logistic approximation of the standard normal cumulative distribution. The service level is put in relation to the dimension of the single shipment, to the average demand on the buyer and to the number of admissible stockouts. Once the mean joint total cost function is defined, on the basis of the model of Braglia and Zavanella, (2003. Int. J. Prod. Res. 41, 3793–3808) modified according to Braglia et al. (2014. Int. J. Logist. Syst. Manage. forthcoming 2014), a minimum cost solution (within a predefined domain) is derived. Moreover, a numerical study is carried out. First, a sensitivity analysis is shown. Then, the model of Braglia and Zavanella, (2003. Int. J. Prod. Res. 41, 3793–3808), in its original expression, is compared with both Hill (1997. Eur. J. Oper. Res. 97, 493–499), Hill (1999. Int. J. Prod. Res. 37, 2463–2475) and Hill and Omar (2006. Int. J. Prod. Res. 44, 791–800). In particular, the comparison considers the equal-sized shipments case without delayed deliveries taking into account different reciprocal values for the stockholding costs.

2014 - Stochastic Theory of Tool-Life - Theoretical developments on the injury theory [Articolo su rivista]
Braglia, M.; Castellano, D.; Frosolini, M.
abstract

This paper aims at presenting a revisited and extended version of the injury theory, originally developed by Ramalingam and Watson (1977) and Ramalingam (1977). This theory allows deriving tool-life distributions when either a single catastrophic event or a gradual and cumulative wear process terminates the tool useful life. Since these models cover great importance in tool-life modelling, this paper would contribute in this direction with further observations and results, giving special attention to the mathematical formulation. In particular, besides deriving known results following a different approach, we extend the theory to the case of multiple machines with both single- and multi-tool configurations. Moreover, as examples we derive different expressions of the tool-life distribution in the cases studied related to particular formulations of the injury rate.

2013 - A novel game theory based exit selection model in emergency conditions [Articolo su rivista]
Braglia, M; Castellano, D; Gabbrielli, R
abstract

In this paper, a new game theory based approach for the evacuees exit selection in emergency conditions is presented. It is founded on the theoretical concepts of multi-stage games with perfect information. In particular, an evacuee is a player and the available actions for a generic player are the accessible emergency exits. The developed mathematical model involves several psychological parameters, in order to make the emergency exit choice also affected by the individual character. Moreover, an evacuation simulation model incorporating this novel approach is shown. The model involves many other parameters and aspects attempting to obtain a satisfactory representation of the actual evacuation process and of the human behavior in emergency conditions. Finally, the effectiveness of the model is demonstrated with a simulative study.

2013 - An Integer Linear Programming Approach to Maintenance Strategies Selection [Articolo su rivista]
Braglia, M; Castellano, D; Frosolini, M
abstract

Purpose - The paper presents a RCM embedded integer linear programming approach (suited to the budget monetary resources allocation task) to the maintenance strategies mix selection for an industrial plant equipments. Design/methodology/approach - The developed approach allows to determine the optimal maintenance strategies mix for a set of equipments in a more quantitative way than the classic RCM approach. The proposed model takes into account, for each potential failure determined using the FMECA and for each admissible strategy, the costs and the potential RPN reduction. Finally, an industrial case concerning an Italian paper-mill plant is reported to demonstrate the effectiveness of the approach presented. Findings - The paper finds that the application of the proposed approach allows to optimally allocate the budget monetary resources, determining which suitable maintenance practice apply to each failure, taking into account the costs of each strategy and the potential reduction of the RPN. Practical implications - The proposed model permits to assign (during the budget monetary resources allocation task) to each failure the optimal strategy, among a set of suitable maintenance practices, considering the costs and the estimated RPN reduction. Originality/value - The paper proposes a completely new RCM embedded approach to the maintenance strategies selection, in order to optimally allocate the budget monetary resources. This model overcomes the limits of the traditional RCM approach, taking into account quantitative aspects, i.e. the compatibility constraint between failures and policies, the maintenance strategies costs, and the RPN estimated reduction.

2012 - Application of the QFD methodology to plant layout evaluation [Relazione in Atti di Convegno]
Braglia, M; Castellano, D; Frosolini, M
abstract

This paper presents a QFD based methodology allowing the assessment of different plant layout proposals. Facilities layout is a key factor affecting a firm’s profitability and productivity. Such a decision is a strategic one. In literature several works deal with this aspect, and in particular concerning the design task. Meanwhile, along the plant layout life cycle, other ac-tivities have to be carried out that are equally important. This makes the evaluation phase necessarily subsequent. With respect to other assessing techniques, that are often too vague, the one here presented attempts to face the problem in a more rigorous fashion. On the basis of the QFD concept, the most important aspects concerning a plant layout evalua-tion are considered. In particular, customer needs are first derived, technical requirements are identified, and finally a comparison method is presented.