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Michael Zimmermann – One of the best experts on this subject based on the ideXlab platform.

  • On the validity of Aggregate Models in designing supply chain contracts
    International Journal of Production Economics, 2006
    Co-Authors: Mirko Kremer, Christoph Schneeweiß, Michael Zimmermann
    Abstract:

    Abstract The vast majority of the existing papers on supply chain contracts analyse these contracts based on a highly Aggregate Model description of the supply chain. Recognizing the high complexity of real (supply chain) systems, such Models can naturally only be rough approximations of reality. Out of the many possible ways for aggregating a planning Model our study focuses on item aggregation. Here, due to computational, informational, or organizational reasons, a multi-product reality is approximated by a Model representation with fewer products. We explore the aggregation error made when using an Aggregate Model in order to optimize a supply chain contract, which is subsequently applied to a more detailed (real) system. Based on a numerical analysis it is shown that the design of supply chain contracts by means of an Aggregate planning Model may lead to significant suboptimalities.

Mirko Kremer – One of the best experts on this subject based on the ideXlab platform.

  • On the validity of Aggregate Models in designing supply chain contracts
    International Journal of Production Economics, 2006
    Co-Authors: Mirko Kremer, Christoph Schneeweiß, Michael Zimmermann
    Abstract:

    Abstract The vast majority of the existing papers on supply chain contracts analyse these contracts based on a highly Aggregate Model description of the supply chain. Recognizing the high complexity of real (supply chain) systems, such Models can naturally only be rough approximations of reality. Out of the many possible ways for aggregating a planning Model our study focuses on item aggregation. Here, due to computational, informational, or organizational reasons, a multi-product reality is approximated by a Model representation with fewer products. We explore the aggregation error made when using an Aggregate Model in order to optimize a supply chain contract, which is subsequently applied to a more detailed (real) system. Based on a numerical analysis it is shown that the design of supply chain contracts by means of an Aggregate planning Model may lead to significant suboptimalities.

  • Designing Supply Chain Contracts by Means of Aggregate Models
    , 2005
    Co-Authors: Mirko Kremer, Christoph Schneeweiß
    Abstract:

    The vast majority of the existing papers on supply chain c ontracts analyse these contracts based on a highly Aggregate Model description of the supply chain. Recognizing t he high complexity of real (supply chain) sys- tems, such Models can naturally only be rough approximations of reality. We explore the aggregation error made when using an Aggregate Model in order to optimize a supply chain contract which is subsequently applied to a more detailed (real) system. Based on a numerical anal ysis it is shown that the design of supply chain contract s by means of an Aggregate planning Model may lead to significant suboptimalities.

Takaaki Ohishi – One of the best experts on this subject based on the ideXlab platform.

  • an hybrid Aggregate Model applied to the short term bus load forecasting problem
    IEEE PowerTech Conference, 2009
    Co-Authors: Ricardo Menezes Salgado, Rosangela Ballini, Takaaki Ohishi
    Abstract:

    In this paper we present a hybrid methodology built on a combination of clustering and forecasting techniques used to solve the short-term bus load forecasting problem. The proposed method was made in two phases: In the first phase a clustering algorithm is used to identify buses clusters with similar daily load profile and in the second phase is proposed an Aggregate structure for to foresee each bus using a conventional prediction Model. The methodology was applied on bus load data from the Brazilian North/Northeast system and the results showed that the Model was efficient with 2% to 3.6% of the mean percentage error level on the buses.

  • an Aggregate Model applied to the short term bus load forecasting problem
    IEEE PES Power Systems Conference and Exposition, 2009
    Co-Authors: Ricardo Menezes Salgado, Rosangela Ballini, Takaaki Ohishi
    Abstract:

    In this paper we present a methodology based on a combination of clustering and forecasting techniques. The proposed method is built in two phases: In the first phase, a clustering algorithm is used to identify buses clusters with similar daily load profile. In the second phase we introduce an Aggregate structure for to foresee each bus. The methodology was applied on bus load data from the Brazilian North/Northeast system and the results showed that the Model was efficient with 2% to 4% average percentage error level on the buses. The obtained forecasting was compatible with the load safe operating levels of the Brazilian power system.

Christoph Schneeweiß – One of the best experts on this subject based on the ideXlab platform.

  • On the validity of Aggregate Models in designing supply chain contracts
    International Journal of Production Economics, 2006
    Co-Authors: Mirko Kremer, Christoph Schneeweiß, Michael Zimmermann
    Abstract:

    Abstract The vast majority of the existing papers on supply chain contracts analyse these contracts based on a highly Aggregate Model description of the supply chain. Recognizing the high complexity of real (supply chain) systems, such Models can naturally only be rough approximations of reality. Out of the many possible ways for aggregating a planning Model our study focuses on item aggregation. Here, due to computational, informational, or organizational reasons, a multi-product reality is approximated by a Model representation with fewer products. We explore the aggregation error made when using an Aggregate Model in order to optimize a supply chain contract, which is subsequently applied to a more detailed (real) system. Based on a numerical analysis it is shown that the design of supply chain contracts by means of an Aggregate planning Model may lead to significant suboptimalities.

  • Designing Supply Chain Contracts by Means of Aggregate Models
    , 2005
    Co-Authors: Mirko Kremer, Christoph Schneeweiß
    Abstract:

    The vast majority of the existing papers on supply chain c ontracts analyse these contracts based on a highly Aggregate Model description of the supply chain. Recognizing t he high complexity of real (supply chain) sys- tems, such Models can naturally only be rough approximations of reality. We explore the aggregation error made when using an Aggregate Model in order to optimize a supply chain contract which is subsequently applied to a more detailed (real) system. Based on a numerical anal ysis it is shown that the design of supply chain contract s by means of an Aggregate planning Model may lead to significant suboptimalities.

Hans Knudsen – One of the best experts on this subject based on the ideXlab platform.

  • an Aggregate Model of a grid connected large scale offshore wind farm for power stability investigations importance of windmill mechanical system
    International Journal of Electrical Power & Energy Systems, 2002
    Co-Authors: Vladislav Akhmatov, Hans Knudsen
    Abstract:

    Abstract An Aggregate Model of a large-scale offshore wind farm, comprising 72 wind turbturbines of 2 MW rating each, is set up. Representation of the shaft systems of the wind turbturbines shall be taken into account when a simplified Aggregate Model of the wind farm is used in voltage stability investigations. Because the shaft system gives a soft coupling between the rotating wind turbturbine and the induction generator, the large-scale wind farm cannot always be reduced to one-machine equivalent and use of multi-machine equivalents will be necessary for reaching accuracy of the investigation results. This will be in cases with irregular wind distribution over the wind farm area. The torsion mode of the shaft systems of large wind turbturbines is commonly in the range of 1–2 Hz and close to typical values of the electric power grid eigenfrequencies why there is a risk of oscillation between the wind turbturbines and the entire network. All these phenomena are different compared to previous experiences with Modelling of conventional power plants with synchronous generators and stiff shaft systems.