Scheduling and lot-sizing in the dairy industry: the yoghurt production case

In this work, a continuous-time Mixed-Integer Linear Programming model (MILP) is developed for the short-term scheduling and lot-sizing problem in a multi-product yoghurt production line of a real-life dairy plant. The problem under question is mainly focused on the packaging stage considering though accurate timing and capacity constraints with respect to the fermentation stage. Packaging units are operating in parallel and share common resources. Sequence-dependent times and costs are explicitly taken into account and optimized by the proposed framework. Daily production line shut-down and setup times are also introduced, as a production policy to guarantee high quality of final products. To the best of our knowledge, the proposed approach is the first systematic attempt to explicitly address all the aforementioned issues in tandem. Several cases of a large-scale Greek dairy plant have been considered using the proposed model. Solutions obtained are presented, criticized and assessed in a real industrial environment. A number of benefits due to the use of optimization-based techniques are revealed. Finally, concluding remarks are drawn.Peer ReviewedPostprint (published version

A captured room temperature stable Wheland intermediate as a key structure for the orthogonal decoration of 4-amino-pyrido[2,3-d]pyrimidin-7 (8H)-ones

Wheland intermediates are usually unstable compounds and only a few have been isolated at very low temperatures. During our work on tyrosine kinase inhibitors, we studied the bromination of 7 in order to obtain a dibromo substituted pyrido[2,3-d]pyrimidin-7(8H)-one which could be orthogonally decorated. Surprisingly, treatment of 7 with 3 equiv. of Br2 in acetic acid (AcOH) afforded 12, a captured room temperature stable Wheland bromination intermediate stabilized by the bromination of the imino tautomer of the amino group at C4 of the pyridopyrimidine skeleton. The structure was confirmed by crystal structure determination from powder X-ray diffraction data. Treatment of 12 with DMSO afforded the dibromo substituted compound 13 presenting a bromine atom at C6 and C5-C6 unsaturation. 13 was directly accessed by treating 7 with N-bromosuccinimide (NBS), a protocol extended to other compounds using NBS or N-iodosuccinimide (NIS) to afford 6-halo substituted systems. 26, bearing an iodine at C6 and a p-bromophenylamino at C2, allows the orthogonal decoration of pyridopyrimidines

Direct, stereodivergent, and catalytic Michael additions of thioimides to α,β-unsaturated aldehydes – Total synthesis of Tapentadol

Direct and stereodivergent Michael additions of N-acyl 1,3-thiazinane-2-thiones to α,β-unsaturated aldehydes catalyzed by chiral nickel(II) complexes are reported. The reactions proceed with a remarkable regio-, diastereo-, and enantioselectivity, so access to any of the four potential Michael stereoisomers is granted through the appropriate choice of the chiral ligand of the nickel(II) complex. Simple removal of the heterocyclic scaffold furnishes a wide array of either syn or anti enantiomerically pure derivatives, which can be exploited for the asymmetric synthesis of biologically active compounds, as demonstrated in a new approach to tapentadol. In turn, a mechanism, based on theoretical calculations, is proposed to account for the stereochemical outcome of these transformations

Analytic signals and zero-locus in multiplexing systems

The theory of analytic functions is used as a new approach to the study of conventional multiplexing schemes. The multiplexing process involves double and triple modulation techniques. The most general form of modulated waves exhibit simultaneous phase and envelope fluctuation. Phase and envelope relationships described in mathematical formulation have a strong dependence on the real and complex zeroes of the actual wave. The properties of analytic signals are studied, yielding a general theory of zero-representation of the original signal that contains its informational attributes. The mathematical representation of zeroes of a periodic real signal has physical significance when related to the spectra, phase, and envelope fluctuations. The zero-pattern representation offers the advantage of showing the phase envelope fluctuation in the time domain, and a frequency domain representation can be based on the frequency spectrum given by the Fourier series coefficient. [...]Electrical and Computer Engineering, Department o

Trace gas detection using diode lasers

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Efficient mathematical frameworks for detailed production scheduling in food processing industries

The production scheduling of a real-world multistage food process is considered in this work. An efficient mixed integer programming (MIP) continuous-time model is proposed to address the production problem under study. The overall mathematical framework relies on an efficient modeling approach of the sequencing decisions, the integrated modeling of all production stages, and the inclusion of a set of strong tightening constraints. The simultaneous optimization of all processing stages aims at facilitating the interaction among the different departments of the production facility. Moreover, an alternative MIP-based solution strategy is proposed for dealing with large-scale food processing scheduling problems. Although this method may no guarantee global optimality, it favors low computational requirements and solutions of very good quality. Several problem instances are solved to reveal the salient computational performance and the practical benefits of the proposed MIP formulation and solution strategy.Peer ReviewedPostprint (published version

The use of unidirectional carbon fibre rods in high loaded joints for a composite large civil aircraft wing structure

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