A flexible MILP model for multiple-shift workforce planning under annualized hours

Flexibility in workforce planning is one of the best ways to respond to fluctuations of the demand. This paper proposes a flexible mixed integer linear programming (MILP) model to solve a multiple-shift workforce planning problem under annualized working hours. The model takes into account laws and collective agreements that impose constraints on overtime and holidays. We consider possible gradual hiring of full time and partial time workers. Several objectives are pursued such as balancing the workload of the employees or minimizing the workforce size. Computational experiments on a real life problem demonstrate the effectiveness of the model.     

Auxiliary space preconditioning in H 0(curl; Ω)

We adapt the principle of auxiliary space preconditioning as presented in [J. Xu, The auxiliary space method and optimal multigrid preconditioning techniques for unstructured grids, Computing, 56 (1996), pp. 215–235.] to H (curl; ω)-elliptic variational problems discretized by means of edge elements. The focus is on theoretical analysis within the abstract framework of subspace correction. Employing a Helmholtz-type splitting of edge element vector fields we can establish asymptotic h-uniform optimality of the preconditioner defined by our auxiliary space method. This author was fully supported by Hong Kong RGC grant (Project No. 403403) This author acknowledges the support from a Direct Grant of CUHK during his visit at The Chinese University of Hong Kong.     

Mixed Integer Programming to Schedule a Single-Shift Workforce under Annualized Hours

Nowadays flexibility is a strategic concept for firms. Indeed workload has to follow, as close as possible, the development of demand throughout the year. However, firms cannot engage and dismiss employees according to production requirements. Thus, workforce scheduling becomes a delicate task. In this paper, four mixed integer programming models are developed to solve the workforce schedule problem for a single-shift. The annualized hour scenario is considered with respect to a set of Swiss legal constrains. Furthermore, the minimal required workforce is guaranteed and it is assumed that each employee is able to perform each task within the team. All employees are full-time workers.     

Genotyping Cryptosporidium parvum by single-strand conformation polymorphism analysis of ribosomal and heat shock gene regions

Polymerase chain reaction (PCR)-coupled single-strand conformation polymorphism (SSCP) approaches utilizing nuclear DNA regions of the small subunit (SSU) of ribosomal RNA and heat shock protein 70 gene (HSP70) were established for genotyping Cryptosporidium parvum. The regions were amplified (individually or in a multiplex reaction) by PCR from DNA extracted from oocysts from ruminant or human hosts, then denatured and subjected to electrophoresis in a mutation detection enhancement (nondenaturing) gel matrix. Single-strand profiles produced in SSCP allowed the unequivocal identification/differentiation of the two common (human, 1 and cattle, 2) genotypes of C. parvum and the direct display of sequence variability within some samples, reflecting population variation. As these are considered among the most closely related genotypes (based on SSU and HSP70 sequence data), these findings and other preliminary results for C. felis (from cat) C. serpentis (from snake) and C. baileyi (from bird) indicate that the SSCP approaches established could be employed to identify any of the currently recognised genotypes and species of Cryptosporidium.     

Technische Verfahren zur Synthese von Carotinoiden und verwandten Verbindungen aus 6-Oxo-isophoron. III. Ein neues Konzept für die Synthese der enantiomeren Astaxanthine

Technical Procedures for the Synthesis of Carotenoids and Related Compounds from 6-Oxo-isophorone. III. A New Concept for the Synthesis of the Enantiomeric Astaxanthins A new and efficient concept for the total synthesis of (3S, 3'S)- and (3R, 3'R)-astaxanthin ( 1a and 1c , resp.) in high overall yield and up to 99,2% enantiomeric purity is described. Key intermediates are the (S)- and (R)-acetals 10 and 17 , respectively (Scheme 2). These chiral building blocks were synthesized via three different routes: a) functionalization of the enantiomeric 3-hydroxy-6-oxo-isophorons⁴) 2 and 11 , respectively (Scheme 2); b) optical resolution of 3,4-dihydroxy-compound⁴) 19 (Scheme 3), and c) fermentative reductions of 6-oxo-isophorone derivatives (Schemes 4 and 5). - The absolute configurations of the two intermediates 12 and 13 (Scheme 2) have been confirmed by X-ray analysis. - The final steps leading to the enantiomeric astaxanthins are identical with those described for optically inactive astaxanthin [1].     

Stoffwechselprodukte von Mikroorganismen. 101. Mitteilung. Synthese der trans-5-Hydroxy-3-methylpenten-(2)-säure (trans-Δ2-Anhydromevalonsäure)

trans-Δ²-Anhydromevalonic acid (XVII) was prepared by a Wittig reaction, starting from (4-tetrahydro-2-pyranyloxy)-2-butanone. On the other hand, the corresponding 4-acetoxy-2-butanone gave, under similar conditions, the cyclohexene derivative V, explainable by a twofold Michael addition of the Wittig reagent to methyl vinyl ketone, followed by an intramolecular alcol condensation.     

CO2/ SOx-sensors with different β“-aluminas as solid electrolytes

Sensors with solid electrolytes provide the possibility of correct and fast measurements of partial pressures of various gases. By modification of the solid electrolyte, sensors with specific performances may be manufactured. Layers of Na⁺-, Li⁺-, Ca²⁺- and Sr²⁺-β“-alumina on top of polycrystalline α-alumina substrates were produced by an in-situ formation process and were used as solid electrolytes for CO₂ and SO_x sensors. Carbonates and sulphates were applied as measuring electrodes and oxidic mixtures of SiO₂ and silicates were used as reference electrodes. The different performance of these sensors was investigated over a wide temperature range and the results were compared with theoretical data. Different solid electrolyte / electrode combinations were applied, which all showed different characteristic cross sensitivities against water and organic components. Paper presented at the 5th Euroconference on Solid State Ionics, Benalmádena, Spain, Sept. 13–20, 1998.