24 research outputs found

    Outcomes from elective colorectal cancer surgery during the SARS-CoV-2 pandemic

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    This study aimed to describe the change in surgical practice and the impact of SARS-CoV-2 on mortality after surgical resection of colorectal cancer during the initial phases of the SARS-CoV-2 pandemic

    An enumerative algorithm for two-machine flow shop problems with earliness and tardiness penalties

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    We consider a two-machine flow shop problem with a common due date where the objective is to minimize an arbitrary function of a weighted sum of penalties assigned to early and tardy completion of jobs. Since the problem is NP-hard in the strong sense, we investigate some general properties of optimal schedules for the problem, we develop lower and upper bounds, derive dominance criteria, and propose an enumerative algorithm for finding an optimal schedule. Finally, the performance of the proposed algorithm is evaluated empirically. (orig.)Available from TIB Hannover: RR 4487(1999,33) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

    Heuristics for hybrid flow shops with controllable processing times and assignable due dates

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    We consider a generalization of the permutation flow shop problem of scheduling n jobs on m machine centers which more appropriately represents several production scheduling problems. Each center consists of parallel identical machines, each job consists of ordered operations that have to be processed on machines from different machine centers where the sequence in which the jobs pass through the machine centers is identical for all jobs. The problem is to find an optimal sequence (schedule) in which n jobs pass through each machine center, keeping the sequence same for each center. In addition to the hybrid flow shop problem, we also consider the following generalizations, which enhances its practical use. The processing times of the operations on some machines may vary between a minimum and a maximum value dependent on the use of a continuously-divisable resource. We consider a nonregular criterion based on due dates which are not a priori given but can be fixed by a decision-maker. A due date assignment cost is included into the objective function. For this generalization, we propose a heuristic constructive algorithm based on job insertion techniques and heuristic iterative algorithms. For the latter, we primarily deal with the design of suitable neighbourhoods of a solution. Computational results for problems with up to 20 jobs and 10 machine centers are given. (orig.)Available from TIB Hannover: RR 4487(1998,29) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

    Procedural Retrenchment and the States

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