15 research outputs found

    Scatter Search based algorithms for min-max regret task scheduling problems with interval uncertainty

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    Uncertain versions of three task scheduling problems: P║Cmax, F2║Cmax, R║&#931 Cj are investigated. Parametric uncertainty is only considered which is represented by intervals. It is assumed that values of execution times of tasks are not a priori given, and they belong to the intervals of known bounds. No distributions additionally characterizing the uncertain parameters are assumed. The regret is used as the basis for a criterion evaluating the uncertainty. In a consequence, min-max regret combinatorial problems are solved. Heuristic algorithms based on Scatter Search are proposed. They are evaluated via computational experiments and compared to a simple middle intervals heuristics and to exact solutions for small instances of the problems considered

    Towards dedicated decision support tools: CLP-based approach

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    Constraint programming (CP) is an emergent software technology for declarative description and effective solving of large combinatorial problems especially in areas of integrated production planning. In that context, the CP can be considered as a well-suited framework for development of decision making software supporting small and medium size enterprises in the course of Production Process Planning (PPP). The problem considered regards of finding of computationally effective approach aimed at scheduling of a new project subject to constraints imposed by a multi–project environment. In other words, we are looking for an answer whether a given production order specified by its cost and completion time can be accepted in a given manufacturing system specified by available production capability, i.e., the time-constrained resources availability. The problem belongs to a class of multi-mode case project scheduling problems, where the problem of finding a feasible solution is NPcomplete. The aim of the paper is to present the CP modeling framework as well as to illustrate its application to decision making in the case of a new production order evaluation. So, the contribution emphasizes benefits derived from CPbased DSS and focuses on constraint satisfaction driven decision-making rather than on an optimal solution searching

    Routing flow-shop with buffers and ready times - comparison of selected solution algorithms

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    This article extends the former results concerning the routing flow-shop problem to minimize the makespan on the case with buffers, non-zero ready times and different speeds of machines. The corresponding combinatorial optimization problem is formulated. The exact as well as four heuristic solution algorithms are presented. The branch and bound approach is applied for the former one. The heuristic algorithms employ known constructive idea proposed for the former version of the problem as well as the Tabu Search metaheuristics. Moreover, the improvement procedure is proposed to enhance the quality of both heuristic algorithms. The conducted simulation experiments allow evaluating all algorithms. Firstly, the heuristic algorithms are compared with the exact one for small instances of the problem in terms of the criterion and execution times. Then, for larger instances, the heuristic algorithms are mutually compared. The case study regarding the maintenance of software products, given in the final part of the paper, illustrates the possibility to apply the results for real-world manufacturing systems

    First Polish Greenland expedition in the year 1937. Results of meteorological survey conducted by Stanisław Siedlecki and Alfred Jahn

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    W opracowaniu przedstawiono wybrane wyniki (wraz z krótką interpretacją) pomiarów meteo-rologicznych przeprowadzonych przez S. Siedleckiego i A. Jahna w czasie pierwszej polskiej wyprawy naukowej na Grenlandię w 1937 roku. Słowa kluczowe: wyniki pomiarów meteorologicznych, Grenlandia 1937.The paper presents unpublished results of meteorological measurements, which were carried out during the first Polish scientific expedition to Western Greenland in the year 1937. All the materials have been compiled as a graphs and diagrams. The archival daily maps of atmospheric pressure distribution for the northern hemisphere (NCAR Daily Northern Hemisphere SLP grids; 1937) were also used, on the basis of which a short interpretation of the collected materials was made. According to the authors, the main factor influenced the weather conditions and local climate characteristics of the Polonia Glacier and Arfersiorfik Fiord area in the 1937 summer season was the passage of pressure lows through the Davis Strait and Baffin Sea area. When the favourable barometric conditions occurred in the region, the foehn effect was formed on the orographical barrier around the fiord and above the glacier’s plateau. In the analyzed dataset the foehn periods were characterized, among others, by clearly visible positive anomalies of air temperature. In the remaining periods the air temperature, wind direction and wind velocity in the upper part of the fiord were influenced by cold air, which flew downward from the ice sheet, alongside the Polonia Glacier and Arfersiorfik Fiord axis

    An Attempt to Evaluate the Productivity of Ecosystems Under Field Conditions of Wielkopolska

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    The Eddy Covariance technique has been applied for corn field NEE estimation. The Smith, Michaelis-Menten and Misterlich formulas has been used for calculation of net ecosystem exchange (NEE) values between corn canopy and the atmosphere. These approaches have been applied for estimation of temeparture and radiation modification impact on the corn field productivity. The NEE has been evaluated in the first part of this paper and then the relation of NEE runs and elements that influence the NEE values has been summarized. In another part the analysis of NEE under thermal and radiative conditions has been presented. The Michaelis-Menten model has been found as the most distinct one for the measurements of the relationship. This model indicated that the highest NEE value (NEE = 10.0 µmol m-2 s-1) has been found under combination of the low radiation and high temperature conditions. The lowest value of NEE has been estimated under the highest PPFD and lowest Ta amount. The applied models have confirmed relationship between NEE, PPFD and Ta. All three models confirmed the fact that the lowest ecosystem productivity is found under high radiation input. The accumulated NEE values were compared with the real values according to the Smith, Michaelis-Menten and Misterlich equations. The results of the Michaelis-Menten equation and Misterlich were the most similar to the real cumulative NEE values. The theoretical change of thermal (0.5°C increase) and radiation (4% decrease) resulted in tested higher CO2 sequesteration from the atmosphere
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