Simulation Optimization for the Stochastic Economic Lot Scheduling Problem with Sequence-Dependent Setup Times

We consider the stochastic economic lot scheduling problem (SELSP) with lost sales and random demand, where switching between products is subject to sequence-dependent setup times. We propose a solution based on simulation optimization using an iterative two-step procedure which combines global policy search with local search heuristics for the traveling salesman sequencing subproblem. To optimize the production cycle, we compare two criteria: minimizing total setup times and evenly distributing setups to obtain a more regular production cycle. Based on a numerical study, we find that a policy with a balanced production cycle leads to lower cost than other policies with unbalanced cycles. (authors' abstract

Using simulation optimization and genetic algorithms to solve single-machine, multiple-item scheduling problems with sequence-dependent setup times and stochastic demands

Diese Arbeit behandelt die stochastische Version des Economic Lot Sizing Problem (ELSP) mit sequenzabhängigen Setupzeiten. Das Problem entwickelt sich aus der Tatsache, dass es in vielen Fällen günstiger ist, eine teurere Maschine mit höherer Kapazität und breiteren Einsatzmöglichkeiten anzuschaffen, als eine spezialisierte Maschine, die nur für einen spezifischen Vorgang einzusetzen ist. Die deterministische Version des Problems wird seit einigen Jahrzehnten behandelt und es ist eine große Masse an Literatur dazu verfügbar. Auch die sequenzabhängige Version des deterministischen ELSP-Problems ist als Abwandlung des Traveling Salesman Problem (TSP) relativ gut erforscht. Arbeiten, die beide Probleme kombinieren sind hingegen fast nicht vorhanden. Aus diesem Grund versucht die vorliegende Arbeit, Probleme mit beiden Einschränkungen simultan zu lösen. Dazu werden vorhandene Arbeiten aus beiden Bereichen ausgewertet und relevante Teile kombiniert. Metaheuristiken aus dem Gebiet des deterministischen ELSP werden dazu verwendet, um Startparameter für Simulationsoptimierung zu erhalten. Anschließend versucht ein globaler Optimierer die Lösung sukzessive zu verbessern. Zum Setzen der Produktionssequenzen -- welche bei sequenzabhängigen Setupzeiten entscheidend sind -- wird ein genetischer Algorithmus aus dem Bereich der TSP-Forschung verwendet. Im numerischen Teil der Arbeit werden fünf verschiedene Produktionsplanungsregeln verglichen. Zwei davon basieren auf einem gemeinsamen Zyklus, der für alle Produkte gleich sind. Die restlichen drei Regeln implementieren fixe Zyklusfolgen, in denen ausgewählte Produkte mehrfach vorkommen können. Die letztgenannten Regeln werden in Hinsicht auf das Optimierungsziel verglichen. Der Zyklus wird entweder auf Ausgeglichenheit, Kosteneffizienz in Hinsicht auf Setupzeiten oder eine Kombination aus den beiden optimiert.This text deals with the stochastic version of the Economic Lot Sizing Problem (ELSP) with sequence-dependent setup times. The problem arises from the fact that it is often more profitable to invest in a single high-capacity machine that can be used for multiple purposes, than cheaper specialized machines. Deterministic and setup-independent versions of the problem have been researched extensively. Research approaches that combine both are relatively sparse. The paper combines some earlier works, as well as metaheuristic concepts to set better production policies. A genetic algorithm is used to improve the sequence and minimize setup times of the whole cycle. Then a global optimizer evaluates policies in simulation runs and tries to improve the result by adapting base stock levels and product frequencies. The results are evaluated in a numerical study

The Role of Personality in the Adoption of Pro-Environmental Behaviors through the Lens of the Value-Belief-Norm Theory

This article belongs to the Special Issue Urbanization and Environmental Sustainability[Abstract] The present study investigated citizens’ self-reported pro-environmental behaviors by adopting a survey and bootstrapping via structural equation modeling for five different personality traits. Adopting one traditional psycho-social theory, this study investigates how motivations, values, intentions, norms, and behaviors are connected by using different constructs from the value-belief-norm theory extended with external influences and three different pro-environmental behaviors, namely, waste preventer, green consumer, and avoider, and how the connections change between different personality traits from the Big Five personality test, namely, openness, extroversion, neuroticism, agreeableness, and consciousness. According to this study, personal conscience may inspire environmentally beneficial behaviors like green purchasing and waste reduction when appealing to the emotions of the general public. As a result, strengthening the population’s subjective norms requires interventions that concentrate on communication tactics to raise knowledge of penalties and obligations for communal advantages

CAIRT - The changing-atmosphere infra-red tomography explorer

Optics InfoBase Conference Papers2021 Article number FTh4G.6. Fourier Transform Spectroscopy, FTS 2021 - Part of OSA Optical Sensors and Sensing Congress 2021Virtual, Online19 July 2021 through 23 July 2021Code 174136CAIRT, a candidate for ESA’s Earth Explorer 11 mission, will observe the Earth’s limb with an imaging Fourier-transform spectrometer. It will provide global observations of ozone, temperature, water vapour and key halogen and nitrogen compounds.With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709Peer reviewe

The SMARTSEA Education Approach to Leveraging the Internet of Things in the Maritime Industry

International audienc

Measurements of Phase Dynamics in Planar Josephson Junctions and SQUIDs

We experimentally investigate the stochastic phase dynamics of planar Josephson junctions (JJs) and superconducting quantum interference devices (SQUIDs) defined in epitaxial InAs/Al heterostructures, and characterized by a large ratio of Josephson energy to charging energy. We observe a crossover from a regime of macroscopic quantum tunneling to one of phase diffusion as a function of temperature, where the transition temperature T∗ is gate-tunable. The switching probability distributions are shown to be consistent with a small shunt capacitance and moderate damping, resulting in a switching current which is a small fraction of the critical current. Phase locking between two JJs leads to a difference in switching current between that of a JJ measured in isolation and that of the same JJ measured in an asymmetric SQUID loop. In the case of the loop, T∗ is also tuned by a magnetic flux.ISSN:0031-9007ISSN:1079-711

The Changing-Atmosphere Infra-Red Tomography Explorer CAIRT – a proposal for an innovative whole-atmosphere infra-red limb imaging satellite instrument

To improve our knowledge of the coupling of atmospheric circulation, composition and regional climate change, and to provide the urgently needed observations of the on-going changes and processes involved, we have recently proposed the Changing-Atmosphere Infra-Red Tomography Explorer (CAIRT) to ESA as Earth Explorer 11 candidate. CAIRT will be the first limb-sounder with imaging Fourier-transform infrared technology in space. By observing simultaneously the atmosphere from the troposphere to the lower thermosphere (about 5 to 115 km altitude), CAIRT will provide global observations of temperature, ozone, water vapour, as well as key halogen and nitrogen compounds. The latter will help to better constrain coupling with the upper atmosphere, solar variability and space weather. Observation of long-lived tracers (such as N2O, CH4, SF6, CF4) will provide information on transport, mixing and circulation changes. CAIRT will deliver essentially a complete budget of stratospheric sulfur (by observations of OCS, SO2, and H2SO4-aerosols), as well as observations of ammonia and ammonium nitrate aerosols. Biomass burning and other pollution plumes, and their impact on ozone chemistry in the UTLS region, will be detected from observations of HCN, CO and a further wealth of volatile organic compounds. The potential to measure water vapour isotopologues will help to constrain water vapour and cloud processes and interactions at the Earth&#8217;s surface. The high-resolution measurements of temperature will provide the momentum flux, phase speed and direction of atmospheric gravity waves. CAIRT thus will provide comprehensive information on the driving of the large-scale circulation by different types of waves. Tomographic retrievals will provide temperature and trace gas profiles at a much higher horizontal resolution and coverage than achieved from space so far. Flying in formation with the Second Generation Meteorological Operational Satellite (MetOp-SG) will enable combined retrievals with observations by the New Generation Infrared Atmospheric Sounding Interferometer (IASI-NG) and Sentinel-5, resulting in consistent atmospheric profile information from the surface up to the lower thermosphere. Our presentation will give an overview of the proposed CAIRT mission, its objectives and synergies with other sensors.</p

Bladder cancer index: cross-cultural adaptation into Spanish and psychometric evaluation

Background: The Bladder Cancer Index (BCI) is so far the only instrument applicable across all bladder cancer patients, independent of tumor infiltration or treatment applied. We developed a Spanish version of the BCI, and assessed its acceptability and metric properties. Methods: For the adaptation into Spanish we used the forward and back-translation method, expert panels, and cognitive debriefing patient interviews. For the assessment of metric properties we used data from 197 bladder cancer patients from a multi-center prospective study. The Spanish BCI and the SF-36 Health Survey were self-administered before and 12 months after treatment. Reliability was estimated by Cronbach’s alpha. Construct validity was assessed through the multi-trait multi-method matrix. The magnitude of change was quantified by effect sizes to assess responsiveness./nResults: Reliability coefficients ranged 0.75-0.97. The validity analysis confirmed moderate associations between the BCI function and bother subscales for urinary (r = 0.61) and bowel (r = 0.53) domains; conceptual independence among all BCI domains (r ≤ 0.3); and low correlation coefficients with the SF-36 scores, ranging 0.14-0.48. Among patients reporting global improvement at follow-up, pre-post treatment changes were statistically significant for the urinary domain and urinary bother subscale, with effect sizes of 0.38 and 0.53. Conclusions: The Spanish BCI is well accepted, reliable, valid, responsive, and similar in performance compared to the original instrument. These findings support its use, both in Spanish and international studies, as a valuable and comprehensive tool for assessing quality of life across a wide range of bladder cancer patients.This work was supported by grants from Instituto de Salud Carlos III FEDER(PS09/02139; PS09/01204; PS09/01619; PS09/02555; PI12/00772) and from AGAUR (2012FI_B1 00177; 2009 SGR 1095)