Rolling horizon policies for multi-stage stochastic assemble-to-order problems

Assemble-to-order approaches deal with randomness in demand for end items by producing components under uncertainty, but assembling them only after demand is observed. Such planning problems can be tackled by stochastic programming, but true multistage models are computationally challenging and only a few studies apply them to production planning. Solutions based on two-stage models are often short-sighted and unable to effectively deal with non-stationary demand. A further complication may be the scarcity of available data, especially in the case of correlated and seasonal demand. In this paper, we compare different scenario tree structures. In particular, we enrich a two-stage formulation by introducing a piecewise linear approximation of the value of the terminal inventory, to mitigate the two-stage myopic behavior. We compare the out-of-sample performance of the resulting models by rolling horizon simulations, within a data-driven setting, characterized by seasonality, bimodality, and correlations in the distribution of end item demand. Computational experiments suggest the potential benefit of adding a terminal value function and illustrate interesting patterns arising from demand correlations and the level of available capacity. The proposed approach can provide support to typical MRP/ERP systems, when a two-level approach is pursued, based on master production and final assembly scheduling.Comment: This is an Author's Original Manuscript of an article published by Taylor and Francis in the International Journal of Production Research on 21.11.2023, available online: https://doi.org/10.1080/00207543.2023.228357

Inventory management of vertically differentiated perishable products with stock-out based substitution

The need for optimal inventory control strategies for perishable items is of the utmost importance to reduce the large share of food products that expire before consumption and to achieve responsible food stocking policies. Our study allows for a multi-item setting with substitution between similar goods, deterministic deterioration, delivery lead times and seasonality. Namely, we model demand by a linear discrete choice model to represent a vertical differentiation between products. The verticality assumption is further applied in a novel way within product categories. Specifically, the same product typology is vertically decomposed according to the age of the single stock-keeping unit in a quality-based manner. We compare two different policies to select the daily size of the orders for each product. On the one hand, we apply one of the most classical approaches in inventory management, relying on the Order-Up-To policy, modified to deal with the seasonality. On the other hand, we operate a state-of-the-art actor-critic technique: Soft Actor-Critic (SAC). Although similar in terms of performance, the two policies show diverse replenishment patterns, handling products differently

Data-driven control of a Pendulum Wave Energy Converter: A Gaussian Process Regression approach

The energy coming from the motion of the waves of seas and oceans could be an important component in the solution of the energy problem related to the pursuit of alternatives to fossil fuels. However, wave energy is still technologically immature and it has not reached the economic feasibility required for economy of scale. One of the major technological challenges for the achievement of this goal is the development of control strategies capable of maximizing the extracted energy, adapting to the conditions of the seas and oceans that surround the Wave Energy Converter (WEC) devices. To perform this task, control systems often adopt explicitly control-oriented models, that are by nature affected by uncertainties. On the contrary, to address the problem a data-driven solution is proposed here. The presented strategy applies an optimization approach based on a Gaussian Process Regression (GPR) metamodel to learn the control strategy to be applied. In order to accelerate the learning process, we present a novel method that exploits in the initial phase a previous knowledge given by simulations with the system model and based on the co-kriging concept. To test this approach the Pendulum Wave Energy Converter has been adopted as a case study. To differentiate the previous knowledge and the real system behaviour, a simplified linear model is used to obtain the prior knowledge, while a complex nonlinear one acts as the environment in which simulate the behaviour of the real system. A month-long simulation is used to validate the effectiveness of the proposed strategy, showing the ability of adapting to a real system different from the simplified model on the basis only of data, and overcoming the model-based strategy in terms of performance

Simboli e significati nella cultura locale di una periferia urbana: uno studio di caso

Una ricerca psicologico-clinica esplora la Cultura Locale (i significati emozionali condivisi da chi partecipa a un contesto, atti a mantenere stabilità e coesione, a regolare e l’emozionalità dei processi di convivenza) di un quartiere della periferia romana nel momento della pianificazione di servizi per la comunità. La ricerca è fondata sulla analisi del testo computer assistita (Analisi Emozionale del Testo) di interviste somministrate a 8 figure chiave, e sulla analisi delle corrispondenze multiple di 314 questionari sulla percezione soggettiva della qualità di vita e sulla anticipazione dei rapporti sociali, somministrati a cittadini del quartiere. I risultati della analisi di interviste e questionari hanno messo in luce la qualità di vita come soggettivamente percepita dagli abitanti e le caratteristiche della cultura locale del territorio oggetto dello studio. Vengono fornite indicazioni pragmatiche sulla attivazione di servizi coerenti con la cultura locale del territorio esaminato. Viene messo in evidenza il possibile contributo della psicologia clinica alle discipline geografiche, urbanistiche, ambientali.This clinical-psychological research explores the Local Culture (emotional meanings shared by people in a given context aimed at maintaining stability and unity as well as regulating emotions affecting cohabitation) of a suburban neighborhood in Rome in the phase of community service planning. The inquiry is based on a computer-assisted text analysis (Emotional Text Analysis) of interviews of 8 key figures, and on the multiple correspondence analysis of questionnaires on the subjective perception of the quality of life and on the expectation of social relationships. The questionnaires have been administered to 314 inhabitants. The results of the analysis of interviews and questionnaires highlighted the quality of life in terms of subjective perception and the specific features of the local culture of the territory considered for this study. Practical solutions are indicated based on the Local Culture of the neighborhood in question. The possible contribution of clinical psychology to geographic, urban, and environmental disciplines is also highlighted. © 2019 The Author(s

Inclusion is a hard work. A research contribution aimed at supporting teachers

Primary educational systems play a meaningful role in creating an inclusive culture, offering a “basic minimum standard of education for all” (OECD 2007), a prerequisite for the full access to all levels of social life. Inclusive practices solicit high commitment from teachers, make their work harder, presume they are able to cooperate and integrate each other’s action. A critical point is special/support teachers’ subjective perception of being supported (or not) by colleagues and the educational staff altogether. Aim of this paper is to present a validated instrument, the CSIT Scale, and its potential use in school settings helping in monitoring the relational well-being of the school staff

Sense of community and resilience after a natural disaster

The aim of this study is to investigate the role of the sense of community in moderating the impact of a natural disaster on community members. The research project began in Central Italy in the months following a massive earthquake in 2016 that caused human and capital casualties. A previous study (Langher et al. in press) tried to identify possible protective and risk factors affecting community resilience. The present study focuses on the sense of community as a protective factor against the onset of mental health issues on a convenient sample of 100 adults. The subjects are administered the following instruments: Life events checklist for DSM-5 (LEC-5) (Gray, Litz, Hsu, & Lombardo, 2004); Resilience Scale for Adults (RSA) (Bonfiglio, Renati, Hjemdal, & Fribord, 2016); Impact of Event Scale – Revised (IES-R) (Craparo, Faraci, Rotondo, & Gori, 2013); Personal Health Questionnaire Depression Scale (PHQ-8) (Kroenke, Strine, Williams, Berry, & Mokdad, 2009); Generalised Anxiety Disorder Assessment (GAD-7) (Spitzer, Kroenke, Williams, & Lowe, 2006); Warwick-Edinburgh Mental Well-Being Scale (WEMWBS) (Gramigni, Stewart-Brown, 2001); Multidimensional Territorial Sense of Community Scale (MTSOCS) (Prezza, Pacilli, Barbaranelli & Zampatti, 2009); Scala di attaccamento al quartiere di residenza (AQ) (Bonaiuto, Fornara, Aiello, & Bonnes, 2002) [scale on the attachment to the neighbourgh]; Local Unconscious Dynamic Intervention Questionnaire (LUDIQ) (Langher, Caputo, Brandimarte, Giacchetta, Grippo, & Nannini, 2019). An exploratory multidimensional data analysis is carried out in order to identify the possible role of the sense of community on the psychological well-being of the community members

Affective symbolization of the parent-child relationship in italian families: the potential role of gratitude

Scientific literature reveals the central role of gratitude in the relationship between children and their parents. Li (2016) suggests that chores may play a key role in gratitude development among children, which leads to a closer parent-child bond. Following on from this suggestion, this study explores the affective symbolization of Italian families about parentchild relationship and the potential role of chores in the experience of gratitude. Fifty-eight adolescents (aged 12 to 19) and ninety-seven parents were administered a semi-structured interview, investigating the following areas: expression of love; moral reasoning; discipline; chores; expression of gratitude. The interviews were audio-recorded, transcribed and analysed through Emotional Text Analysis. The analysis detected six clusters of words (CL). CL1 (17.8%) refers to a relation based on an unspoken agreement: behaving well is traded for family cohesion. In CL2 (25%) parent-child relationship is symmetric; problems are solved by peaceful negotiation. In CL3 (13.3%) parent-child relationship is asymmetric, based on a strong discipline; CL4 (12.4%) refers to self and family care through chores as repetitive and obsessive rituals. In CL5 (18.2%) the support function embodied by adolescents in the family is a way to face the world outside, experienced as hostile and overwhelming. CL6 (13.3%) refers to parents’ feeling of gratitude towards the adolescents, and the transmission of moral values from one generation to the next as a way for living forever. The results highlighted that chores respond to the family’s need to take care of the relationship between parents and children, protecting it from the anguish projected on the world outside. The transmission of moral values responds to the unconscious phantasy of living beyond death. Gratitude seems to be the feeling of relief deriving from the satisfaction of those phantasies

Risk-averse Approaches for a Two-Stage Assembly-to-Order Problem

Assembly to order is a production strategy where components are manufactured under demand uncertainty and end items are assembled only after demand is realized. Risk-neutral approaches aim to maximize the expected profit. However, this approach may fail if heavy-tailed or multi-modal distributions are likely to generate significant disruptions or if the shrinking life of products is considered. Conversely, risk-averse models may tackle these problems. In the paper, we deal with an assembly-to-order problem, modeled as a two-stage stochastic linear programming problem considering the introduction of a classical risk measure from finance: the conditional value-at-risk. We examine the characteristics and the performance of the model by means of a large number of out-of-sample scenarios

Simulation-based inventory management of perishable products via linear discrete choice models

Retail inventory management of perishable items, like fresh food, is a relevant and complex problem. It is relevant in the light of trends towards the reduction of food waste, and because of potential cross-sales interaction with other item categories. It is complex, because of multiple sources of uncertainty in supply, demand, and quality, and other complicating factors like seasonality within the week, FIFO/LIFO consumer behavior, and potential substitutions between items, possibly because of a stockout. Similar items may be vertically differentiated due to intrinsic quality, which is also related with item age, or brand image, as it could be the case when a retail chain stocks both a brand item and a private label one. In the paper, we adapt a simple discrete choice model to represent consumers’ heterogeneity and different tradeoffs between price and quality, and apply simulation-based optimization to learn simple ordering rules for two vertically differentiated items, adapted to a seasonal case, in order to maximize long-term average profit under a lost sales assumption. While well-known constant and base-stock policies need not be optimal, they are simple to communicate and apply. We explore combinations of such rules for the two items, obtaining some useful managerial insights

Il sentimento di gratitudine nelle famiglie italiane. Una prima ricerca esplorativa

Introduzione La letteratura scientifica evidenzia il ruolo centrale del sentimento della gratitudine nella relazione tra genitori e figli, nel momento in cui i figli, ormai divenuti adulti, sono chiamati a prendersi cura dei genitori divenuti anziani. Un buon esempio è la Teoria della gratitudine (Keller, 2005), la quale afferma che la presa in carico dei genitori anziani da parte dei figli è un atto di gratitudine in risposta al buon legame creato nel corso della loro relazione. Tali teorie risultano ancora più interessanti se calate all’interno di contesti culturali particolari, come ad esempio il contesto cinese. In Cina il momento della presa in carico dei genitori anziani da parte dei figli riveste un ruolo fondamentale, a causa di un sistema di welfare che non esaurisce tutte le necessità dei cittadini anziani. I figli, divenuti adulti, sono chiamati dallo stato a adempiere alla cura e al mantenimento dei familiari anziani e in difficoltà. In quel particolare contesto lo sviluppo del sentimento della gratitudine nei figli, e quindi di un legame solido tra loro e i genitori, è essenziale per il corretto funzionamento della società. In particolare, Li (2016) afferma che le faccende domestiche giochino un importante ruolo nella trasmissione dei valori morali e nello sviluppo del sentimento di gratitudine nei giovani cinesi. Sulla scia delle ricerche effettuate in Cina sulla gratitudine e sulla funzione sociale che ricoprono le faccende domestiche in quel particolare contesto, abbiamo pensato di esplorare se e come tali questioni siano presenti nel contesto italiano. Obiettivo della ricerca La ricerca intende esplorare la cultura locale delle famiglie italiane sul tema della gratitudine e delle faccende domestiche. Metodo Sono state costruite due interviste strutturate, una per i figli e una per i genitori, volte a indagare i seguenti temi: l’espressione dell’affetto, la trasmissione dei valori morali, l’educazione alle regole, le faccende domestiche e la gratitudine. La prima intervista è stata somministrata a 56 adolescenti, 27 maschi e 29 femmine, divisi in 3 fasce di età (12-14, 15-16 e 17-19 anni); la seconda è stata somministrata a 50 coppie di genitori. Il numero di coppie e di adolescenti non coincide perché, quando possibile, sono stati intervistati fratelli e sorelle appartenenti allo stesso nucleo famigliare. Tutte le interviste sono state registrate, trascritte e assemblate in un unico corpus. Per l’analisi è stato usato T-LAB, un software costituito da strumenti linguistici e statistici che consente l’esplorazione, la comparazione, la rappresentazione grafica e l’interpretazione dei testi (Lancia, 2004). Il software scompone il testo, estrae le parole più significative in base al criterio statistico della co-occorrenza, consentendo di costruire ed esplorare una rappresentazione del corpus attraverso pochi e significativi cluster tematici. I dati sono stati interpretati tramite l’Analisi Emozionale del Testo (AET) (Carli & Paniccia, 2002), uno strumento psicologico volto ad analizzare la Cultura Locale sia in ambito clinico che psicosociale. Risultati L’analisi ha estratto complessivamente 6 cluster di parole sul piano fattoriale. Nel cluster 1 (17,8%) gli sforzi compiuti dagli adolescenti, come lo «studio», sono merce di scambio nel rapporto con i genitori; tale scambio avviene in incognito in occasioni culturalmente codificate, come il «Natale» e il «compleanno». Nel cluster 2 (25%) genitori e figli sono coinvolti in un rapporto simmetrico, tra pari; in questo particolare assetto i problemi vengono risolti mediante il "parlare" e il "capire". Nel cluster 3 (13,3%) il rapporto tra genitori e figli è asimmetrico, basato su una rigida disciplina; i genitori sono i detentori della verità oggettiva, e si impegnano per limitare gli errori dei figli. Nel cluster 4 (12,4) compaiono le faccende domestiche, simbolizzate come la cura del sé e degli altri cari. Nel cluster 5 (18,2%) gli adolescenti sono attivamente impegnati nel supportare i genitori nella cura della casa; emergono vissuti aggressivi e di angoscia nei confronti di ciò che sta «fuori» dal contesto familiare. Nel cluster 6 (13,3%) emerge il vissuto di gratitudine dei genitori nei confronti dei figli; la trasmissione dei valori e dell’educazione da senso alla vita dei genitori, permette di continuare a vivere nella vita dei figli.  Discussione e conclusioni Il sentimento di gratitudine, nelle famiglie intervistate, sembra essere molto distante da quanto riportato in letteratura rispetto alla cultura cinese. In questo contesto, le faccende domestiche rispondono al bisogno dei figli di curare un rapporto che li protegge dall’angoscia, proiettata verso il mondo esterno, fuori dal contesto familiare. La trasmissione dei valori e dell’educazione, invece, risponde alla fantasia inconscia dei genitori di sopravvivere oltre la morte, attraverso la vita dei figli e quella delle generazioni future. Il sentimento della gratitudine, così come viene riportato dagli intervistati, è il vissuto di sollievo che deriva dal continuo soddisfacimento di queste fantasie all’interno delle relazioni familiari. Dai risultati emersi in questa prima ricerca esplorativa è possibile fare ipotesi sul funzionamento delle famiglie nel contesto italiano rispetto al contesto cinese, e orientare ulteriori approfondimenti futuri in merito