Supply Lead Time Uncertainty in a Sustainable Order Quantity Inventory Model

Abstract Transport plays a key role in inventory management since it affects logistic costs as well as environmental performance of the supply chain. Expected value and variability of supply lead time depend on the transportation means adopted, and influence the optimal values of order quantity, reorder level, and safety stock to be adopted. Fast transportation means allow reducing expected value of the lead time; they are characterized by the highest costs of externalities (i.e. air pollutant emission, noise, congestion, accidents). On the contrary, slow transportation means require high inventory level due to large order quantity; in this case costs of externalities tend to decrease. The Sustainable Order Quantity (SOQ) [1] allows identifying optimal order quantity, reorder level, safety stock as well as transportation means which minimize the sum of the logistic and environmental costs in case of stochastic variability of product demand. In this paper, the authors propose a new SOQ analytical model considering stochastic variability of supply lead time (LT). A solution procedure is suggested for solving the proposed model. The approach is applied to a real industrial case study in order to evaluate the benefits of applying it if compared with the traditional one

Strategic Energy Planning of Residential Buildings in a Smart City: A System Dynamics Approach

Buildings are the largest urban energy consumers, but their impact can be largely cut back by improving efficiency. Policy-making plays a crucial role in harmonizing national and local incentive schemes. The authors analyse variables related to energy consumption, then propose a simulation model based on System Dynamics applied to a medium- sized Italian city. The model allows the testing of “what-if” scenarios and analysis of the results of implementing energy efficiency policies. Results stress the importance of a holistic view of urban energy processes. Simulation trends provide essential information for the city’s future energy and carbon emission profiles, helping policy-makers to achieve their goal

Supporting Circular Economy through Use-Based Business Models: The Washing Machines Case

Abstract The circular economy paradigm is being widely studied as a possible path to a sustainable development, decoupling economic growth from material consumption and environmental impacts. The introduction of new business models, based on use rather than ownership, has been identified as one of the possible enabling actions for the implementation of circular economy strategies. Thus, product-service systems (PSS) can represent a viable way for companies and customers to switch from a linear to a circular scheme, keeping together the advantages of a customer-oriented offer to those of dematerialization. In this work, an example of innovative, circular business model for the large appliances sector is proposed, based on a PSS and a closed-loop supply chain. A context study, supported by a deep literature analysis, is performed to identify the main changes involved in the transition from a traditional to a circular supply chain in the sector, as well as the main impacts on the actors involved, through causal loop diagrams. The study is a first step for the realization of a system dynamics model, for a further research on impact assessment

The Glassy Potts Model

We introduce a Potts model with quenched, frustrated disorder, that enjoys of a gauge symmetry that forbids spontaneous magnetization, and allows the glassy phase to extend from $T_c$ down to T=0. We study numerical the 4 dimensional model with $q=4$ states. We show the existence of a glassy phase, and we characterize it by studying the probability distributions of an order parameter, the binder cumulant and the divergence of the overlap susceptibility. We show that the dynamical behavior of the system is characterized by aging.Comment: 4 pages including 4 (color) ps figures (all on page 4

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

O-MINIMALITY OF DEFINABLE FIELDS

In questa tesi presentiamo un risultato in cui riusciamo a provare che una famiglia di strutture del primo-ordine sono o-minimali. La classe di strutture considerata è quella di campi definibilmente completi nel linguaggio dei campi ordinati espanso con una famiglia di simboli di operazioni interpretate da funzioni pfaffiane. Il risultato in particolare implica che i modelli della teoria dei campi ordinati con l'esponenziale sono o-minimali del primo ordine. The thesis presents a result that proves that a certain class of first-order structures is first-order o-minimal. This class is made of definably complete fields in a language that expands the one of ordered fields by operation symbols interpreted by pfaffian functions. The results proves as a special case that the real fields expanded with the exponential operation are first-order o-minimal structures

Sistemi di Gestione Ambientale. Casi studio a confronto

Un numero crescente di imprese industriali adotta Sistemi di Gestione Ambientale (SGA) al fine di identificare, valutare e monitorare le prestazioni ambientali dei propri sistemi produttivi. A fronte delle indicazioni generali fornite dagli standard internazionali ISO 1400 I ed EMAS (Eco Management and Audit Scheme), la struttura da conferire ai SGA dipende significativamente dalla specificità dei contesti di produzione nell'ambito dei quali essi devono operare. Nel presente lavoro si analizzano le fasi di progettazione e attuazione di SGA in due insediamenti industriali che si differenziano significativamente per dimensione e tipologia di processo produttivo. Si mostra come le caratteristiche di ciascun insediamento abbiano contribuito a indirizzare in modo differente le scelte progettuali e organizzative dei SGA adottati.An increasing number of industrial firms is adopting Environmentol Management Systems (EMSs in order to identify, evoluote and monitor environmental performonces of production systems. Generol stondards of EMSs ore provided by ISO 14001 guidelines and EMAS (Eco-Monogement and Audit Scheme) regulation; however, the structure of EMSs sìgnificantly depends on the specifìc production environment where EMSs have to be implemented, In this paper design and implementotion of EMSs are analysed with reference to two industrial production sites which differ in terms of size and type of process. It is shown how characteristics of each production site offect desìgn and orgonizational choices adopted in the corresponding EMS