Rainer Leisten - Academia.edu (original) (raw)

Papers by Rainer Leisten

Supply Chain Management und Logistik, 2005

Advanced Planning and Scheduling (APS)-Systeme bilden eine Gruppe von modular aufgebauter Planung... more Advanced Planning and Scheduling (APS)-Systeme bilden eine Gruppe von modular aufgebauter Planungsunterstützungssoftware, die zum einen Erweiterungen zu Enterprise Ressource Planning (ERP)-Systemen darstellen. Zum anderen erfordern veränderte Anforderungen an die Planung zur Unterstützung des Supply Chain Management den Einsatz fortgeschrittener Methoden der Planung und Terminierung von unternehmensübergreifenden Produktionsprozessen. Da die durch die einzelnen Planungsmodule zu lösenden Teilpläne der Produktionsplanung zueinander interdependent

2005 IEEE Intelligent Data Acquisition and Advanced Computing Systems: Technology and Applications, 2005

ABSTRACT This paper presents a simulation based analysis of different coordination mechanisms in ... more ABSTRACT This paper presents a simulation based analysis of different coordination mechanisms in hierarchical production planning. According to the results of the simulations the effects of aggregation and capacity assignments on the overall costs are discussed.

Design Models for Hierarchical Organizations, 1995

The EMBO Journal

The hamster cell line HE5 has been derived from primary hamster embryo cells by transformation wi... more The hamster cell line HE5 has been derived from primary hamster embryo cells by transformation with human adenovirus type 2 (Ad2). Each cell contains 2-3 copies of Ad2 DNA inserted into host DNA at apparently identical sites. The site of the junction between the right terminus of Ad2 DNA and hamster cell DNA was cloned and sequenced. The eight [corrected] right terminal nucleotides of Ad2 DNA were deleted. The unoccupied cellular DNA sequence in cell line HE5 , corresponding to the site of the junction between Ad2 and hamster cell DNA, was also cloned; 120-130 nucleotides in the cellular DNA were found to be identical to the cellular DNA sequence in the cloned junction DNA fragment, up to the site of the junction. The unoccupied and the occupied cellular DNAs and the adjacent viral DNA exhibited a few short nucleotide homologies. Patch homologies ranging in length from dodeca - to octanucleotides were detected by computer analyses at locations more remote from the junction site. Whe...

Operations Research-Spektrum

Comparison of heuristics for flowtime minimisation in permutation flowshops

Computers & Operations Research, 2015

ABSTRACT Homogeneity of a specific indicator in scheduling has been discussed in several referenc... more ABSTRACT Homogeneity of a specific indicator in scheduling has been discussed in several references. Namely, the variance of completion times (completion time variance, CTV) has been addressed by several authors since the 1970ies. However, in contrast to some indications in these papers, CTV does not provide smoothness of jobs׳ completion times but is more aiming at minimizing the deviation from a common finishing date of all jobs. In this paper, a new objective function is proposed which intends to smooth the differences between the completion times of each two consecutively scheduled jobs in a permutation flow shop setting. We discuss the relevance of respective considerations, define an objective function accordingly and compare some solution approaches by means of examples and a numerical study based on the test instances from Taillard [1] and [2]. A main topic of this paper is the discussion of the influence of scheduling decisions on other systems linked to this scheduling system by using our new objective function. This intends to contribute, in a specific and heuristic way, to reduce the gap between the dynamic-stochastic perspective of queuing approaches on one hand and the mostly static-deterministic perspective of job scheduling on the other.

GMS Krankenhaushygiene interdisziplinär, 2011

In Germany, cost calculations on the financial burden of wound treatment are scarce. Studies for ... more In Germany, cost calculations on the financial burden of wound treatment are scarce. Studies for attributable costs in hospitalized patients estimate for pressure ulcer additional costs of € 6,135.50 per patient, a calculation based on the assumption that pressure ulcers will lead to prolonged hospitalization averaging 2 months. The scant data available in this field prompted us to conduct a prospective economical study assessing the direct costs of treatment of chronic ulcers in hospitalized patients. The study was designed and conducted as an observational, prospective, multi-centre economical study over a period of 8 months in three community hospitals in Germany. Direct treatment costs for leg ulcer (n=77) and pressure ulcer (n=35) were determined observing 67 patients (average age: 75±12 years). 109 treatments representing 111 in-ward admissions and 62 outpatient visits were observed. During a total of 3,331 hospitalized and 867 outpatient wound therapies, 4,198 wound dressing ...

ABSTRACT Multi-level production planning systems often suppose a top level which anticipates alow... more ABSTRACT Multi-level production planning systems often suppose a top level which anticipates alower level in terms of coarsened, i.e. aggregate information. Aggregation can occur withrespect to products, capacities, time and/or (sub-)projects. Since many of the underlyingmodels are constructed on the conceptual basis of linear programming, results from linearprogramming aggregation have to be regarded when generating and evaluating such asystem. A review of LP-aggregation is presented. Results are then transferred to productand resource aggregation with respect to the coordination of aggregate production planningand master production scheduling. In contrast to many other publications, the analysis doesnot interpret aggregation in production planning heuristically or as black-box, but explicatesaggregation in production planning in terms of LP-aggregation. Results can be transferredto several other aggregation approaches in production planning.

ABSTRACT In this paper we present an application of the scenario aggregation approach proposed by... more ABSTRACT In this paper we present an application of the scenario aggregation approach proposed by Rockafellar and Wets to a simple standard multi-product multi-period production planning problem with uncertain demand and setup cost modelled by logical zero-one variables. The uncertainty in demand is expressed by a number of demand scenarios. As compared with more traditional approaches that require distributional assumptions and/or estimates of parameters from historical demand data, the scenario approach offers greater flexibility and makes it possible to take subjective information into account. The scenario aggregation principle and the corresponding progressive hedging algorithm offer a theoretically sound basis for generating consistent solutions for production planning models with uncertain demand. Since the production planning problem studied in this paper is of mixed-integer type the original scenario aggregation approach cannot be applied directly. However, since the integer variables in the production planning model are indirectly coupled to the continuous production decisions an alternative method in which only the production quantities are used to couple the different realizations can be used. This paper is a first attempt to perform this form of coupling. We illustrate the ideas on a small example and use this example to demonstrate how the solution can be evaluated in terms of flexibility measures.

ABSTRACT We present an aggregation/disaggregation approach to hierarchical production planning. W... more ABSTRACT We present an aggregation/disaggregation approach to hierarchical production planning. We start off with a disaggregate mixed-integer linear programming model which follows a monolithic approach. Based on this disaggregate model we use the theory of aggregation in mathematical programming to derive an aggregate production planning model. Through an iterative aggregation/disaggregation procedure we derive models which could be interpreted as planning models in a hierarchical production planning approach. We point out the similarities and differences between our approach and the approach given by Graves (1982).

ABSTRACT In this paper, we tackle the problem of total flowtime and makespan minimisation in a pe... more ABSTRACT In this paper, we tackle the problem of total flowtime and makespan minimisation in a permutation flowshop. For this, we introduce a multi-criteria iterated greedy search algorithm. This algorithm iterates over a multicriteria constructive heuristic approach to yield a set of Pareto-efficient solutions (a posteriori approach). The proposed algorithm is compared against the best-so-far heuristic for the problem under consideration. The comparison shows the proposal to be very efficient for a wide number of multicriteria performance measures. Aside, an extensive computational experience is carried out in order to analyse the different parameters of the algorithm. The analysis shows the algorithm to be robust for most of the considered performance measures.

Total Quality Management & Business Excellence, 2006

Software measurement is a challenging as well as an essential element of a wholesome and highly e... more Software measurement is a challenging as well as an essential element of a wholesome and highly efficient software engineering culture. ‘Software metrics’ refers to the collective term underlying the wide range of activities associated with measurement in software engineering. There are numerous taxonomies to organize software metrics (based on entities, type of measure etc), but all of them fundamentally fit

Optimization, 1994

Large-scale linear programming problems can be solved approximately with less effort by iterative... more Large-scale linear programming problems can be solved approximately with less effort by iterative aggregation procedures. We present several iterative (variable) aggregation and disaggregation strategies based on gradient considerations. The strategies are tested with some numerical examples