Shift rostering using decomposition: assign weekend shifts first

This paper introduces a shift rostering problem that surprisingly has not been studied in literature: the weekend shift rostering problem. It is motivated by our experience that employees’ shift preferences predominantly focus on the weekends, since many social activities happen during weekends. The Weekend Rostering Problem (WRP) addresses the rostering of weekend shifts, for which we design a problem specific heuristic. We consider the WRP as the first phase of the shift rostering problem. To complete the shift roster, the second phase assigns the weekday shifts using an existing algorithm. We discuss effects of this two-phase approach both on the weekend shift roster and on the roster as a whole. We demonstrate that our first-phase heuristic is effective both on generated instances and real-life instances. For situations where the weekend shift roster is one of the key determinants of the quality of the complete roster, our two-phase approach shows to be effective when incorporated in a commercially implemented algorithm

Eerst weekend! Wiskunde in dienst van een sociaal leven

Het sociale leven - sportactiviteiten, verjaardagsbezoeken, het ontmoeten van vrienden - vindt vooral in de weekeinden plaats. Dit maakt werken in het weekend voor veel mensen onaantrekkelijk. In sectoren waar de dienstverlening 7 dagen in de week en 24 uur per dag beschikbaar moet zijn, zoals in de gezondheidszorg en de beveiligingssector, dienen medewerkers wel in het weekend te werken. Het maken van goede dienstroosters voor het weekend is een uitdaging: medewerkers hebben vaak heel specifieke voorkeuren terwijl de werkgever moet zorgen dat er voldoende mensen worden ingezet. Het maken van goede dienstroosters wordt verder bemoeilijkt doordat er rekening moet worden gehouden met de Arbeidstijdenwetgeving (ATW) en omdat werkgevers de diensten 'eerlijk' over de medewerkers willen verdelen

Plant responses to flooding stress

Most plant species cannot survive prolonged submergence or soil waterlogging. Crops are particularly intolerant to the lack of oxygen arising from submergence. Rice can instead germinate and grow even if submerged. The molecular basis for rice tolerance was recently unveiled and will contribute to the development of better rice varieties, well adapted to flooding. The oxygen sensing mechanism was also recently discovered. This system likely operates in all plant species and relies on the oxygen-dependent destabilization of the group VII ethylene response factors (ERFVIIs), a cluster of ethylene responsive transcription factors. An homeostatic mechanism that controls gene expression in plants subjected to hypoxia prevents excessive activation of the anaerobic metabolism that could be detrimental to surviving the stress

Cost-efficient staffing under annualized hours

We study how flexibility in workforce capacity can be used to efficiently match capacity and demand. Flexibility in workforce capacity is introduced by the annualized hours regime. Annualized hours allow organizations to measure working time per year, instead of per month or per week. An additional source of flexibility is hiring employees with different contract types, like full-time, part-time, and min-max, and by hiring subcontractors. We propose a mathematical programming formulation that incorporates annualized hours and shows to be very flexible with regard to modeling various contract types. The objective of our model is to minimize salary cost, thereby covering workforce demand, and using annualized hours. Our model is able to address various business questions regarding tactical workforce planning problems, e.g., with regard to annualized hours, subcontracting, and vacation planning. In a case study for a Dutch hospital two of these business questions are addressed, and we demonstrate that applying annualized hours potentially saves up to 5.2% in personnel wages annually

Informatienet 2003 in zicht: Totstandkoming en kwaliteit van de steekproef land- en tuinbouwbedrijven van het Bedrijven- Informatienet

The EU Farm Accountancy Data Network (FADN) requires the Netherlands to yearly sent bookkeeping data of 1,500 farms to Brussels. This task is carried out by LEI and CEI. The data send to Brussels mainly involves technical and financial economic information. For national policy purposes additional data is collected, such as pesticide use, manure production, nature management, non-farm income and rural development. This report explains the background of the farm sample for the year 2003. The report mainly focuses on the Dutch contribution to the European Farm Accountancy Data Network. All phases from the determination of the selection plan, the recruitment of farms to the quality control of the final sample are described in this report. Mede voor de Europese Unie organiseren het CEI en het LEI jaarlijks de verzameling van technische en financieel-economische gegevens van circa 1.500 bedrijven in de akkerbouw, tuinbouw en veehouderij. Voor nationaal beleidsgericht onderzoek wordt die informatie aangevuld met gegevens over bijvoorbeeld milieubelasting, natuurbeheer en plattelandsontwikkeling. Alle gegevens worden vastgelegd in het Bedrijven-Informatienet. In dit rapport wordt verantwoording afgelegd over de steekproef 2003, toegespitst op de Nederlandse bijdrage aan het Farm Accountancy Data Network van de Europese Unie. De diverse fasen, van het opstellen van het selectieplan, het werven van de bedrijven tot het beoordelen van de kwaliteit van de resulterende steekproef worden beschreven.Agricultural Finance,

Functional Balancing of the Hypoxia Regulators RAP2.12 and HRA1 Takes Place in vivo in Arabidopsis thaliana Plants

Plants are known to respond to variations in cellular oxygen availability and distribution by quickly adapting the transcription rate of a number of genes, generally associated to improved energy usage pathways, oxygen homeostasis and protection from harmful products of anaerobic metabolism. In terrestrial plants, such coordinated gene expression program is promoted by a conserved subfamily of ethylene responsive transcription factors called ERF-VII, which act as master activators of hypoxic gene transcription. Their abundance is directly regulated by oxygen through a mechanism of targeted proteolysis present under aerobic conditions, which is triggered by ERF-VII protein oxidation. Beside this, in Arabidopsis thaliana, the activity of the ERF-VII factor RAP2.12 has been shown to be restrained and made transient by the hypoxia-inducible transcription factor HRA1. This feedback mechanism has been proposed to modulate ERF-VII activity in the plant under fluctuating hypoxia, thereby enhancing the flexibility of the response. So far, functional balancing between RAP2.12 and HRA1 has been assessed in isolated leaf protoplasts, resulting in an inverse relationship between HRA1 amount and activation of RAP2.12 target promoters. In the present work, we showed that HRA1 is effective in balancing RAP2.12 activity in whole arabidopsis plants. Examination of a segregating population, generated from RAP2.12 and HRA1 over-expressing plants, led to the first quantitative proof that, over a range of either transgene expression levels, HRA1 counteracts the phenotypic and transcriptional effects of RAP2.12. This report supports the occurrence of fine-tuned regulation of the hypoxic response under physiological growth conditions

Uitdagend gedifferentieerd vakonderwijs:Praktisch gereedschap om je onderwijsrepertoire te blijven uitbreiden

Teaching and Teacher Learning (ICLON